Partnership for Sustainable
Annual Load Totals
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DENVER, COLORADO
South Lincoln Redevelopment Project Energy Charrette
FINAL REPORT
April 20 11
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Prepared Under:
Contract No. EP-W-07-023
Prepared for:
U.S. Environmental Protection Agency
Office of Solid Waste and Emergency Response
Office of Brownfields and Land Revitalization
Washington, DC 20460
Prepared by:
SRA
IHIIHNMIUNAL INL
www.sra.com/environment
www.yrgsustainability.com
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Table of Contents
1.
Executive Summary
1.1. Energy Priorities
1.2. Summary of Key Findings.
,1
.2
.3
2. Introduction 5
2.1. Framing the Problem 5
2.2. Charrette Process 5
2.3. Energy Charrette Goal 6
2.4. Defining Net-Zero 6
3. Priority Strategy Overview 7
3.1. District Scale Strategies 8
3.2. District Scale Priority Strategies 9
3.3. Building Scale Strategies 10
3.4. Building Scale Priority Strategies 11
3.5. Occupant Scale Strategies 12
3.6. Occupant Scale Priority Strategies 13
4. NREL Analysis and Results 14
4.1. Summary of Analysis 14
4.2. NREL Conclusions and Recommendations 14
5. Report Conclusions and Recommendations 16
5.1. Funding and Incentive Opportunities 17
5.2. Strategic Partnerships 17
6. Appendix 18
6.1. Charrette Photos 18
6.2. Charrette Agenda, Presentation and Handouts 18
6.3. Charrette Notes 39
6.4. Charrette Attendees 49
6.5. Acronyms List 50
6.6. NREL Report and Analysis 51
Annual Load Totals
Electricity
• Space Heating
a Space Cooling
• Domestic Hot Water
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO iii
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iv Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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1. Executive Summary
The Denver Partnership for Sustainable Communities Brownfield Pilot is led by the U.S. Environmental Protection Agency (EPA)
Office of Brownfields and Land Revitalization (OBLR) and the Office of Sustainable Communities (OSC), and is comprised of the
EPA, Department of Housing and Urban Development (HUD), and Department of Transportation (DOT). These agencies are
working together to ensure federal resources and policies support the development of sustainable communities. The partnership
is based on "liability principles" that guide inter-agency collaboration and support the integration of safe, reliable and economical
transportation; affordable, energy-efficient housing; and sustainable reuse of unoccupied or underutilized land. Pilot communities
were selected by EPA's Brownfields Program with input from HUD and DOT, and receive technical assistance and support from
these agencies to build on past investments, identify opportunities to connect housing, transit and brownfields within the
development, and to coordinate resources that can further the integration of sustainability.
The Denver Housing Authority (DHA) is an affordable housing provider whose South Lincoln Redevelopment Project (SoLi) was
selected as a Partnership for Sustainable Communities Pilot in 2010. In recent years, the SoLi project has received much
collaborative support from state, local and community stakeholders and leaders in defining and establishing its concept and goals.
In 2008, prior to being selected as a Pilot project, a 3-acre portion of the SoLi site (at 10th and Osage, included as part of Phase 1
of the project) received funding from the EPA's Brownfield Cleanup grant program to cleanup the area to unrestricted residential
use cleanup standards. In addition, Phase 1 of the project received $10 million in American Recovery and Reinvestment Act
(ARRA) funding from HUD to support its development. In September 2009, the DHA and key project team members finalized a
Master Plan for SoLi focusing on land use, energy, transportation and public health. In addition, this Master Plan identifies
sustainability goals as integral to the project vision (to view the SoLi Master Plan, go to:
http://www.denverhousing.org/development/SouthLincoln/MasterPlan/Pages/default.aspx).
SoLi is a transit-oriented development that strives to be as energy efficient as possible in order to decrease utility bills for its units
and reduce the project's carbon footprint. Since the cost of housing and transportation has a direct impact to household budget,
one goal of the project is to incorporate strategies that emphasize energy use reduction in order to decrease the cost of living for
residents. In addition, as SoLi is a 5-phase project, the phasing of housing and development will need to be carefully evaluated in
order to determine an approach that minimizes the displacement of current residents, maintains affordability and culture of the
neighborhood and community, and effectively incorporates strategies that can be implemented as part of a phased-project.
Developers, designers, policy makers, and residents participated in an EPA sponsored Energy Charrette to identify opportunities
and constraints of a district energy solution, specific building and occupant scale energy strategies, key partnerships and financial
resources, and develop an implementation plan with DHA with a goal to create a net-zero energy development for South Lincoln
residents. As part of the Pilot and charrette process, technical assistance was provided under contract by SRA International, Inc.,
and YRG sustainability. In addition, National Renewable Energy Laboratory (NREL) provided energy analysis based on building
scale modeling to evaluate the energy impacts and feasibility of district-wide systems.
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 1
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"Single-scale problem-solving leads
to solutions that don't always make
sense."
Net Zero vs. Carbon Neutral
1.1 Energy Priorities
The overarching goal of the South Lincoln energy charrette was to evaluate and provide recommendations for a series of
solutions that could create a net-zero energy balance for the development. This, of course, meant a discussion regarding what
definition of net-zero was appropriate and what the appropriate metrics for measuring this should be.
STANDARD PRACTICE
SOUTH LINCOLN DEVELOPMENT
Use
Use
Fundamental to this discussion was a need to identify a solution that was economically realistic - from both a first cost and life
cycle cost perspective. Therefore, the metrics and priorities that eventually emerged as the driving factors were:
• Occupant comfort, health and wellness, including elements such as access to the outdoors and daylight via operable
windows, natural ventilation, etc.
• First cost and net-present value
• Greenhouse gas (GHG) and fossil fuel reductions per $ spent
• Logistically and operationally manageable (shifting the operational costs from fuel to labor, in the form of job creation,
was viewed as acceptable and even attractive in some cases, so long as the increase in operations didn't represent an
undue burden or level of risk for failure)
• Flexibility and adaptability to future technologies, fuel prices, etc.
Much of the effort, therefore, was aimed at (a) reducing demand and (b) using less energy and GHG emission intensive modes of
energy delivery. Additionally, since SoLi is a 5-phase project, strategies will need to be evaluated based on how well they can be
integrated into each project phase. The electricity grid serving the project, it should be noted, represents a fairly high energy and
GHG emission intensity because much of Colorado's electricity is generated by coal-fired power plants; this meant that producing
as much of the project's electricity needs on-site became of paramount importance. It also meant that shifting to electric forms of
heat, such as a ground source heat pump (GSHP) system, would likely not be as attractive (given the higher emissions per
kilowatt of electricity) as other options, unless that electricity could be produced on-site via renewable sources. With these
considerations and circumstances, the order of operations for a solution became as follows:
1. Reduce design demand as much as possible by emphasizing:
a. Lighting reductions, including the Energy Star Advanced Lighting Package
b. Plug Load reductions, by installing high efficiency Energy Star appliances
c. Cooling reductions, by switching to non-compressor based alternatives such as evaporative cooling (which is an
option given Denver's dry climate), or passive cooling using strategies such as shading, thermal mass, and
orientation
d. Heating reductions, by specifying advanced envelopes and allowing for passive solar heat during winter
2. Accommodate as much of the non-HVAC electrical loads, i.e. lighting, plug, and auxiliary load electricity demands from
on-site sources, namely either on-site photovoltaic (PV) collectors or cogeneration (an on-site generator producing
both heat and electricity)
3. Provide as much heat as possible from highly efficient boilers or cogeneration systems, or
4. To reach true on-site net-zero energy, use either biomass or solar-based heating, or shift the heat to ground source
heat pumps with the electricity supplied from on-site solar.
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To reach the true net-zero goal would require that either the biomass option was cost and logistically acceptable (daily truck load
deliveries of fuel during the winter season and weekly deliveries throughout the rest of the year), or that the on-site solar potential
was enough to accommodate (a) the lighting, plug, and auxiliary loads and (b) still have enough to accommodate the electricity
requirements for the GSHP or solar thermal production. Because it was later determined via a site-wide energy balance that the
on-site, rooftop, solar capacity could only accommodate the lighting, plug, and auxiliary loads, the highly efficient boilers (Option
3) also became a reasonable target; i.e. not achieving net-zero, but targeting a reduction in overall GHG emissions, including
those produced at the upstream power plant, on the order of 80-90%.
1.2 Summary of Key Findings
The results of this analysis represent a mix of economic and technical feasibility at both the building level and the district-wide
level. Much of the discussion that follows deals with the supply side options at the district level, but it should be noted that this
supply is intended to meet a dramatically reduced demand due to efficiency measures undertaken at the building level (see
Framing the Problem, below). One of the main conclusions of this analysis is that because electricity represents the highest
intensity of GHG emissions for the project's demand profile, finding ways to economically offset this becomes the top priority.
Further, because electricity rates are relatively cheap in Colorado, installing expensive equipment to produce electricity on-site is
generally a poor investment from a financial perspective. With this mind, we can draw the following conclusions about each of the
supply side alternatives:
PV: Given the incentive structure that is in place in Colorado for PV (yielding between $2.50 and $3.50 per installed Watt), PV
fares relatively well from a financial perspective. More importantly, because PV is an emissions-free means of producing
electricity on-site, it has by far the greatest potential to reduce overall GHG emissions and fossil fuel use. It should be noted that
PV may compete with other rooftop uses such as rooftop patio areas with planters for additional amenity space and potential for
habitat and heat island reduction, green roof for habitat and stormwater management, or greenhouse for food production. The PV
solution should support, rather than compromise, these other important rooftop uses, such as by creating shade, for example.
Cogeneration: Cogeneration - the production of on-site electricity and the capture and use of the resulting waste heat -
generally does well when (a) electricity prices are high, (b) there is a consistent use for as much of the electricity and heat as
possible (i.e. from an economic perspective, the ideal is to run the Cogeneration system at 100% capacity, 24 hours / day, 365
days / yr, but in reality, the electric and heat load profiles vary throughout the day and year). The latter is usually achieved where
there exists a diverse mix of demand profiles within a development, such as residential, commercial, and industrial, because in
those cases, there is a more consistent and continual demand for both electricity and heat.
Because the South Lincoln project is primarily residential and will also include a variety of mixed-used developments, a diverse
mix of load profiles doesn't exist and the resulting economics are less favorable. Further, one can either size the system to offset
as much of the electricity as possible (yet this would result in a huge surplus of waste heat, reducing the economic viability of
such a system), or they can size the system to offset as much of the heat as possible, generally resulting in a much smaller
system, since the heat output makes up 60-70 percent of the useful energy. However, a smaller system will offset a lower
percentage of the project's electricity needs, resulting in a much smaller overall impact at reducing GHG emissions.
Trigeneration: The discussion of trigeneration is very similar to that of Cogeneration, except that for an increase in capital cost,
one can add an absorption chiller which can produce cooling from the system's waste heat in the summertime where there is no
demand for that heat. This could prove to be an attractive option if there was significant cooling demand to justify the increase in
first cost. However, because the cooling demand is relatively small, and it is envisioned that the buildings should be able to
accommodate cooling through passive and evaporative means, there is little justification for a trigen system.
Photovoltaic panels
Unused Waste Heat
&-. NH ii., OUtpm
Fuc-l Input
Cogeneration and trigeneration systems use waste heat.
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 3
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Wood chips being delivered to a biomass energy facility
Ground source heat pumps use energy drawn from the ground
Biomass: As was discussed above, the use of a biomass system is one of only three ways to achieve net-zero on-site (the others
being the use of solar PV with GSHPs and PV with solar thermal for 100% of the electrical and heating load). The use of biomass
in a district heating system represents a lower order priority, because it is displacing on-site natural gas combustion, which has a
much lower overall GHG and fossil fuel impact than electricity production. Therefore, a biomass district system should only be
employed after a solution for electricity production has been implemented. Further, the economics of biomass-based district heat
is among the worst performers of the systems considered. However, there may be a role for a biomass based district heating
system, either now or in the future, in the following scenario: If PV can be used to offset 100% of the lighting, plug, and auxiliary
loads, and it is determined that a district heating scheme is the best option for meeting the remaining heat demand, then a
biomass-based system might be attractive in-lieu of a natural gas fired boiler approach.
Solar Thermal: Along with biomass, solar thermal had the worst financial performance of the strategies considered. In part, this is
due to the financial incentives that favor PV (utilities are more inclined to support on-site electrical production, especially peak
production, as it helps avoid the need to build additional power plants). The economics of solar thermal are even worse when one
sizes the systems to accommodate for both space heat and domestic hot water (DHW), as opposed to just DHW as the current
analysis has done. The reason for this is that there is a fairly consistent demand for DHW throughout the year, whereas the
demand for space heat is seasonal, and a system that is sized to produce enough heat to supply both space heat and DHW will
have a very large surplus of waste heat in the summer.
There is also a competition for roofspace between PV and solar thermal, and given that PV displaces the higher GHG emissions
intense electricity and has more favorable economics, PV would generally be the winner. The only exception to this would be if PV
were able to accommodate the on-site electrical loads with additional roofspace to spare. In this case, solar thermal could be used
to offset some of the heating load. However, it is expected that in reality, it would be unlikely there would be much rooftop to spare
as the PV required to offset the on-site electrical loads would occupy the majority if not all of the available roofspace because
higher density buildings (e.g., high rise buildings) have less roofspace per unit for PV.
District Ground Source Heat Pumps (GSHPs): As was discussed above, GSHP systems shift the supply of heat from gas to
electric, or from a lower emissions fuel source to a higher one. Granted, the efficiency savings for GSHP systems is significant,
but the overall benefit from the savings is nearly erased by the increase in emissions intensity at the power plant. Further, GSHP
systems are generally economically beneficial when there is a year-round demand for space heating or cooling. Given that there
is relatively little cooling demand (and it is envisioned that this demand can be accommodated by evaporative means), the
economics are relatively poor for very little net gain. It should be noted, however, that if there was a surplus of roofspace for PV
(after lighting, plug loads, and auxiliary equipment were accounted for), then a GSHP system coupled with PV would be one of the
three ways to achieve true net-zero for the project.
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2. Introduction
The South Lincoln Redevelopment Project is a 17.5 acre development that seeks to revitalize South Lincoln homes by
enabling residents the opportunity to enjoy the unique advantages of a holistic, transit-oriented development realized
through the core attributes established during the design process: a highly green mixed-use community, focused on a
healthy lifestyle, increased non-auto mobility, an integration of the resource conservation and management systems, and a
diverse mix of new and existing residents. The redevelopment will include new residential units and a mix of retail,
commercial and community services at the ground floor to encourage and promote activity along the streets. The project
also includes planned outdoor amenities, including a new plaza and promenade, and a variety of open spaces, to enrich the
neighborhood.
SoLi is a large multi-phase development project that is currently constructing the Phase 1 building and site plan in the
Northwest corner of the development. Active and continuous community involvement and support has contributed to the
development of the Master Plan that was created in September 2009 and the Neighborhood Plan that was approved in
September 2010. An ongoing group of committed stakeholders have focused on defining the project goals and vision, and
have begun to identify the design elements of the project. As the SoLi project has been selected to receive support by the
Partnership agencies (HUD, DOT, and EPA), DMA plans to utilize this interagency support to execute the vision and ideals
for the project. Although future phases of the project included in the SoLi Master Plan are awaiting funding and have not
been designed, the scope of the Energy Charrette focused on the full development of all future phases of the SoLi
development and surrounding neighborhood areas. The charrette utilized the efforts and progress to date, and allowed
opportunity to further define the project's vision and next steps. Results from the charrette influenced the RFP requirements
for Phase 2, and has also shifted how DMA and the project team view energy consumption by considering the strategy's
C02 emissions intensity and impact in addition to its output and efficiency.
2.1 Framing the Problem
Residential development energy reduction strategies are almost always developed at the building scale on a project-by-
project basis yet most options for efficient on-site energy generation do not work well, if at all, at the building scale, and are
better optimized at a district scale. In addition, building energy end uses are heavily influenced by how the residents actually
live in and operate the buildings. Most development projects consist of just one or two buildings and the developers do not
know who will live in them. At SoLi, there is a rare opportunity to incorporate energy generation at a district scale and
energy savings at the occupant scale, along with high performance strategies at the building scale.
2.2 Charrette Process
DMA is committed to making the redeveloped South Lincoln Homes project as energy efficient as possible in order to
decrease utility bills and reduce the project's carbon footprint. The purpose of the charrette was to discuss the opportunities
and constraints of a campus-wide energy solution and to outline key next steps such as how to leverage partnerships and
identify financial resources.
The "Leadership Team" below was responsible for planning the charrette. This effort included defining the overall charrette
goals, identifying the scope of any analysis needed, and ensuring that charrette outcomes and lessons learned are
distributed throughout the Partnership agencies to support implementation on the SoLi project. This team included
representatives from each of the Partnership agencies as well as the design and technical assistance team. The members
of this team included the following:
Working group presentation during charrette
Metrics and Benchmarks
LIVING
BUILDING
CHALLENGE
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 5
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Devon Bertram, YRG sustainability
Cindy Cody, EPA Region 8
Kimball Crangle, DMA
Jesse Dean, NREL
Stacey Eriksen, EPA Region 8
Rebecca Fox, SRA International
Narada Golden, YRG sustainability
Christian Kaitreider, NREL
Aleka Pappas, Group 14 Engineering, Inc.
Josh Radoff, YRG sustainability
Tim Rehder, EPA Region 8
Otto VanGeet, NREL
The Energy Charrette was an 8-hour session that occurred on August 10th and 11th of 2010 at the La Alma Recreation Center in
the heart of the neighborhood. A charrette is an interactive meeting with a large group of stakeholders that is intended to generate
innovative design ideas, identify barriers to and strategies for implementation, and build key partnerships. Energy Charrette
participants were asked to focus on DESIGN and TECHNICAL solutions in the working groups and discussions by first identifying
priority strategies from a full list of possible strategies (Day 1), then exploring means to achieving those priority strategies (Day 2).
The following report is a summary of these discussions and working groups.
- Nadav Malin, EBN Article
"Getting to net-zero is extremely difficult for
buildings of more than 4 stories."
However,
"In a community, density allows for greater
walk-ability and many other attributes
desired in a sustainable community."
-"Definition of a 'Zero Net Energy' Community ", NREL
2.3 Energy Charrette Goal
The Energy Charrette goal was developed to guide the charrette agenda, discussions, and working groups. Charrette participants
discussed and agreed to this goal at the beginning of the charrette.
To explore the goal of a net-zero energy neighborhood through an interactive dialogue on concept
feasibility, strategies, and actions needed in order to develop an action plan that guides
implementation through all phases of the project.
2.4 Defining Net-Zero
The goal of the Energy Charrette was to explore the concepts, strategies, and feasibility of creating a net-zero energy
development at South Lincoln. Before charrette participants were able to explore the details of this challenge, it was important for
the group to develop a shared definition of "Net-Zero".
Representatives from the NREL presented four commonly accepted definitions for Net-Zero Energy Communities (NZEC) and
Net-Zero Energy Buildings (NZEB) for the group to discuss. These definitions are shown below. Charrette facilitators then led a full
group discussion to better understand the differences between these definitions and decide on one definition of "Net-Zero" for the
South Lincoln Redevelopment project.
Net-Zero Energy Communities
Net-Zero Energy Buildings
NZEC: B
Least-rigorous energy source allowed
Within building footprint or built enviroment or on
unbufldable brownfield sites within the community
Can include some generation on greenfjpjd sites within the
community or usin_g_bjgfy_gj_s imported from off site.
NZEC: C
NZECiD
Can include some off-site renewable energy credits or green
power
No onsite generation; all off-site renewable energy credits or
green power
NZEB dan
NZEB: A
NZEB: B
NZEB: C
NZEB: D
Least-rigorous energy source allowed
Within building footprint
Within building site
Generated onsite using imported faiofiipls
Off-site renewable energy credits for green power
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During the group discussion, participants identified the following key issues:
• All of the electric loads could potentially be offset with PVs, but the space heating loads for the buildings will likely
require a non-electric fuel type which eliminates the possibility of achieving the NZEC-A definition.
• On-site biofuels and/or off-site carbon offsets will likely be required to achieve any definition of net-zero.
• A net-zero definition for the entire Soil Redevelopment Project is more appropriate because there will be a number of
varying building types and it would be very difficult to develop a unified net-zero definition for all of these building types.
• Further analysis of the other project loads and possible energy generation systems will be required to determine
whether the project can achieve any definition of net-zero.
After a full discussion, the charrette participants agreed that NZEC-B was the most appropriate definition of "Net-Zero" for Soli.
This definition states the following:
Can include some generation on greenfield sites within the community or using biofuels imported from
off-site.
3. Priority Strategy Overview
Energy Strategies at Different Scales
Charrette participants divided into the following three self-selected working groups to identify and discuss priority strategies, major
barriers for each of those strategies, and develop an implementation plan focused on addressing the major barriers and
partnership opportunities for each priority strategy. Below are the priority strategies, barriers, actions, and partnerships identified
by each working group.
• District Scale
• Building Scale
• Occupant Scale
District Scale Building Scale Occupant Scale
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3.1 District Scale Strategies
Two working groups developed a list of district scale strategies along with a series of pros and cons, feasibility challenges, and
recommended next steps for implementation. The fourteen strategies below were identified as a comprehensive list of district
energy strategies during the report-out for both working groups. After the report-out, all charrette participants voted for the two
strategies they thought were the most important for achieving the charrette goal. The following is a tally of that vote.
We have elaborated on the three strategies that received the most votes. There is a full set of notes from the working groups in
the Charrette Notes section of the Appendix.
1. Design for multiple systems and hybrid
System diversity
Adapts to various seasons/use patterns
2. Design for Flex Fuel
Complimentary fuel systems
Adapt future
3. Reduce energy use - Orientation
4. Energy use feedback
5. Complete energy analysis
6. Design for the baseline
Don't design district system for peak
Allow for growth
7. Balance loads within district
8. Tax increment financing
New financing
9. District use of right-of-way
Ground source
Earth tubes
Denver Public Works
10. Load optimization
Analysis to look at load balance
11. Solar garden
12. Recognize biggest "User/Loser"
Feedback of individual use
13. Optimizing infrastructure
Eliminate redundant systems
14. Virtual central plant
A system that incorporates various energy generation options would allow for flexibility and
adaptability, especially in response to future fuel costs, maintenance requirements, and site
limitations.
Similar to a hybrid system, designing a solution that utilizes various fuel types that work
together or can substitute one another. This can allow for flexibility to adjust and adapt to
future needs and costs.
Designing Soli utilizing passive design and optimal orientation across the development can
ensure reduced loads and energy demands on the development, leading to reduced size
and costs of both the district-scale and building-scale energy systems.
Providing a vehicle for occupant energy use feedback can allow residents to actively track
and manage their energy use, and operators to more easily troubleshoot problem areas.
Performing a comprehensive energy use study for the development can help identify where
a district system makes sense, evaluate potential synergies, and estimate anticipated
energy demand and design requirements for the system.
Sizing a district system using the baseline demand and allowing for future growth can save
first costs and reduce the risk of over-sizing the system. Alternate systems or fuel sources
may be used to meet peak demands.
District energy systems are most cost and energy efficient when they are supplying a
consistent amount of energy. At Soli, it may make sense to supply energy to buildings
outside the development to make the energy demand more consistent throughout the day.
Identifying a financing mechanism that involves tax increment payments can support upfront
and ongoing district system costs.
Utilizing the public right-of-way (ROW) can allow for strategies such as ground source heat
pump and earth tubes. District system design may require collaboration and partnership with
Denver Public Works if ROW is utilized.
Completing a load analysis can provide information on energy demands within the
development and allow the design team to match strategies to the anticipated loads.
A solar garden is a cooperative ownership investment in a solar electric array. Solar gardens
are typically built off-site when a project needs more land area for solar panels.
Identifying major energy savers and users within development can help promote a culture of
energy efficiency.
Developing a district energy system may require some system redundancy. It will be
important to minimize the unwanted redundancy due to phasing and future flexibility.
Some district systems can be made up of smaller distributed energy production systems.
This can provide system diversity and flexibility but it is important that all of these distributed
systems operate together as a "virtual central plant".
.
" 1
11
8
7
7
5
5
5
4
3
2
1
0
0
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3.2 District Scale Priority Strategies
1. & 2. Design for Multiple or Hybrid, Flex Fuel District Energy Systems
Building a district energy system that relies on a single system type or fuel could create additional risk of future cost increases, system limitations, or comprehensive system maintenance
challenges. One way to hedge against this future risk is to develop a district heating system that allows for various energy generation components and fuel types. One example of this would be a
district hot water loop that can receive hot water from a ground source heat pump, a biofuel combustion engine, and solar hot water collectors. The following is a list of benefits, feasibility
questions, and recommended next steps for this strategy*.
Needs
Heating
Cooling
Plug Loads
Lighting
Hot water
Gas
Easy, cheap now.
Volatility in cost.
Greater
environmental
impact than other
options.
X
Combined Heat
and Power (CHP)
CHP
X
Solar Thermal
Highly efficient
for larger scale.
X
Concentrated Solar
Needs a lot of real
estate.
Railyard roof area as a
resource?
X
X
X
Biomass
Needs storage, unclear on operations and
maintenance requirements and who will
manage this.
Need to determine training and associated
costs.
Not cost-effective without tax credits.
Biomass gasification could be used.
X
Ground Source Heat Pump (GSHP)
Awesome, very efficient, high first
cost, low maintenance
X
Photovoltaics (PV)
May not be best
option unless
heating is electric.
X
X
X
To better convey the strategies and break-out group ideas, some text in the chart above has been revised or added to in order to clarify notes taken during the break-out group discussions.
3. Reduce Energy Use by Optimizing Building Orientation
The size and cost of a district energy system will need to be based on the predicted heating, cooling, and electricity load of the SoLi development. Because a district energy system will likely
require an additional upfront investment in energy infrastructure to work effectively, it will be important to "right size" the district energy system. If DHA can ensure that future development teams
will design and construct highly energy efficient buildings, this could allow for significant reductions in the size and upfront costs of a district energy system. Thus, a feasible and cost efficient
district energy system will likely be coupled with comprehensive building scale and occupant scale energy strategies.
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3.3 Building Scale Strategies
Two working groups developed a list of building scale strategies along with a series of pros and cons, feasibility challenges, and
recommended next steps for implementation. The five strategies below were identified as a consolidated list of building energy
strategies during the report-out for both working groups. After the report-out, all charrette participants voted for the two strategies
they thought were the most important for achieving the charrette goal. The following is a tally of that vote.
We have elaborated on the three strategies that received the most votes. There is a full set of notes from the working groups in
the Charrette Notes section of the Appendix.
Buildina Strat
Super efficient envelope
Structured Insulated Panels (SIPs)
Passive/Evaporative cooling
No compressor based coolants
Ceiling fans
Indirect/direct cooling (would need to be centralized)
Thermal mass construction
Need good orientation
Passive design
Ground coupled systems
Thermal walls on four-stories-or greater high rise
Model building with passive systems
A super efficient envelope can significantly reduce the
external heating and cooling loads that pass through the
building exterior by increasing insulation, reducing solar heat
gain, and reducing air infiltration.
Passive and evaporative cooling use natural airflow,
evaporation, and other low energy cooling strategies to
eliminate the need for compressor based cooling while
greatly reducing the space cooling demands.
Thermal mass construction increases the amount of heavy
materials within the building to passively regulate and
stabilize internal temperatures.
Modeling So Li buildings with passive designs strategies can
inform the impact of these systems and overall influence on
energy demand.
21
17
14
10
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3.4 Building Scale Priority Strategies
1. Super Efficient Building Envelope
Significant reductions in the building energy use will be required if the project is to achieve the goal of net-zero. One of the best
ways to ensure large energy savings is to reduce the amount of energy that is required to operate the buildings. Two of the
largest building loads at Soli are space heating and cooling. Both of these loads can be significantly reduced through increased
efficiencies in the exterior envelope of future projects. These improvements, which include increased insulation, tighter wall
construction to reduce air infiltration, high performance windows, and windows that are appropriately sized and located, will
reduce the transfer of heat from the inside of the building to the outside in the winter, and vice versa in the summer.
2. Passive / Evaporative Cooling
The third largest energy load at Soli, slightly larger than domestic hot water heating, is space cooling. There are several
decisions that could significantly reduce or even eliminate the space cooling load at Soli. Two possible choices are utilizing
passive cooling and/or evaporative cooling. Passive cooling would require the buildings to have an optimized building envelope
(see Strategy 1 above) and be designed for natural ventilation. Evaporative cooling, which relies on the evaporation of water to
provide the cooling required, could also reduce overall cooling loads beyond a traditional air conditioning system.
3. Thermal Mass Construction
The third most popular building scale strategy identified was thermal mass construction. Although the notes and discussions from
the charrette did not clearly define thermal mass construction, several key points were emphasized.
• Design building with exposed concrete or masonry inside the units for thermal mass. This mass will help regulate
internal temperatures.
• Thermal mass is important for optimizing passive solar heating. In order to take advantage of this strategy, the mass
should be exposed to direct sunlight for most of the day during the heating season. Dark concrete floors near windows
on the south side of the building would achieve this goal.
• Thermal mass can also help optimize natural ventilation strategies. Concrete ceilings in particular, can support passive
cooling in the winter and "night flushing" where occupants could open windows to cool down the units at night.
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 11
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y
±M:
3.5 Occupant Scale Strategies
Two working groups developed a list of occupant scale strategies along with a series of pros and cons, feasibility challenges, and
recommended next steps for implementation. The thirteen strategies below were identified as a comprehensive list of occupant
scale energy strategies during the report-out for both working groups. After the report-out, all charrette participants voted for the
two strategies they thought were the most important for achieving the charrette goal. The following is a tally of that vote.
We have elaborated on the three strategies that received the most votes. There is a 1
the Charrette Notes section of the Appendix.
I set of notes from the working groups in
1. Energy Use Transparency and Incentives
Vouchers for green store
2. Green store/resource room
3. Identify benefits for residents
Comfort
Marketing/messaging
Cultural relevance
4. Resident champions
Support/engage/represent residents
DMA to Support leaders
5. Focus on engagement
Education
Residents
External partners
6. Involve kids!
Future leaders, they get it
Help engage others
New "paper boy route"
7. Internships/job opportunities
Work with community colleges
8. Fund ($ pool) for distributing $ from savings
9. Non-computer energy use feedback
10. Energy incentives for market rate housing
11. Establish fair energy budgets/benchmarks
12. Building tours/education
13. Identify strategies within HUD to incentivize savings
Considering a strategy that allows residents to see their individual utility usage can
encourage energy savings. Additionally, providing incentives for reduced energy
usage can encourage residents to incorporate habits that use less energy.
This added amenity for the neighborhood can be a space to sell small sustainability
related products and materials, as well as a community gathering point for
workshops, trainings, and discussions related to energy efficiency, water savings,
low-toxic building materials, and indoor health.
Identifying the clear benefits of living a sustainable lifestyle can increase resident
support for related efforts focused on energy efficiency, cost savings, comfort, and
safety.
A community member identified as the "Resident Champion" can be the point person
to maintain momentum around Soli's sustainability efforts and goals by encouraging
action from the residents, and a central resource and guide for the community.
Involving residents through active engagement can increase their investment in the
community and understanding of the sustainability initiatives. These efforts can
involve educational opportunities such as workshops and discussions and identifying
partners that can support the community goals.
Engaging kids and younger generations can help to push sustainability efforts and
initiatives forward. This can involve workshops or games around sustainability and
energy use reduction, or programs around communicating community goals (creating
murals, signage, etc.).
Identifying internship or job opportunities can encourage relationships with
neighboring academic institutions, support Soli programs such as the green
store/resource room, and resolve the need for ongoing maintenance required for
some of the strategies.
Collecting money saved from energy efficiency strategies and resident energy use
reduction can be used for a money pool that supports community programs and
efforts around sustainability.
In order for all residents to have access to feedback regarding the impact of their
behavior, Soli can provide a system that is easily and readily accessible to occupants
and does not require a computer.
Since some of the Soli development will be market-rate housing, it will be important
to consider how energy related efforts support these residents too.
Target energy budgets will need to be established in order to create incentives for
reduction. Because each resident and family is different, it will be important to create
fair, flexible energy budget criteria.
Regular building tours to highlight energy efficiency strategies and ongoing education
opportunities can support and maintain ongoing discussion about the sustainability
initiatives atSoLi.
Developing a system within HUD that allows residents to receive incentives for their
energy usage savings can encourage energy reduction habits.
14
12
9
9
7
6
6
4
3
2
0
0
0
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3.6 Occupant Scale Priority Strategies
1. Energy Use Transparency and Incentives
Occupants' day-to-day activities will contribute a great deal to the overall energy usage of the Soli development, and yet this
energy usage can vary drastically from household to household. Soli should consider a strategy that includes transparency or
resident-payment of utilities in order for the residents to 'see' their individual utility usage. In addition, incentivizing energy-saving
actions and habits can not only allow for opportunity around education regarding energy efficiency and energy use reduction, but
can also encourage occupants to reduce their overall energy usage within their home. A rewards or incentives program for
reduced energy usage can link to neighborhood amenities and resources such as offering a reduced fee or free hours for
childcare, free or discounted car share hours, discounted transit passes, access to a bike share program, entertainment coupons,
or vouchers to a community green store. These rewards could be purchased in part with savings from the reduced energy use.
2. Green Store / Resource Room
A centrally located Resource Room / Green Store can provide residents access to sustainability related products and materials
(such as low VOC paints, green cleaning products, energy efficient light bulbs, guides and books related to green building, etc.).
This space can also be an area where residents can rent or borrow tools related to small-scale home improvement and
maintenance projects as well as be a resource for guidance and contacts to support these upgrades or improvements.
Additionally, the Green Store can provide an opportunity for community building and education by hosting events, classes,
workshops, and trainings around sustainability. This gathering point can generate enthusiasm and culture around the
sustainability goals of the project, as well as provide jobs or volunteer opportunities for community residents.
3. Identify Clear Benefits for Residents
Education is an ongoing theme within the community and a clear goal of DMA, particularly when around sustainability and the
environmental goals of the project. Educating occupants on the benefits of the community and its amenities and services, as well
as identifying the benefits to living a sustainable lifestyle is crucial to the success of the project. Focusing on energy efficiency and
cost savings, comfort and safety, and cultural relevance, this education can be demonstrated through tracking and monitoring
occupant behavior, and sharing results; hosting community events and discussions around actions and benefits related to
sustainability; displaying signage within resident homes and around the neighborhood that highlights key facts and figures; and
providing ongoing communication of benefits and opportunities through postings and mailings.
4. Resident Energy Champions
In order for the project to excel in regards to sustainability action within the community, a Resident Energy Champion (or
Champions) will need to lead the charge in order to support, engage and represent the community and resident goals. This
resident champion can focus on and prioritize the energy-related initiatives and actions, as well as market and message the
initiatives taking place within the community. DMA (or other partner) will need to support these leaders and provide them the
resources to effectively engage and educate the community and residents.
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Annual Load Totals
6000
Electricity
•Space Heating
- Space Cooling
• Domestic Hot Water
Annual loads above are based on the total demand for electricity, space heating, space
cooling, and domestic hot water across the entire SoLi development.
South Lincoln Annual Demand Profiles
Electric Load
•^Heating Load
(including DHW)
Cooling Load
1000 2000 3000 4000 5000
700D 8000
This demand profile graph above shows the hour demand for electricity, heating, and cooling
for an entire year.
Category
District Heating/DHW
District Heating and Cooling
Cogen
Trigen
Electricity Only
DHW Only
Potential Systems to Analyze
Wood Chip Boiler
GSHP
NG Gas Turbine
NG 1C Engine
NG Fuel Cell
Same generation systems as Cogen
PV
SHW
District systems identified for further analysis.
4. NREL Analysis and Results
The following is a summary of the South Lincoln Redevelopment District Systems Analysis
Report developed by the National Renewable Energy Laboratory. See the Appendix for the full
report.
4.1 Summary of Analysis
Providing heating and cooling for homes and businesses is typically done at the building level,
meaning there is one system dedicated specifically to a single building. However, in many situations
it may be economically and environmentally beneficial to provide these services at the community
scale, in which case many buildings are served by one large district system designed for the entire
community. The advantages of district systems stem from their larger scale, their ability to capitalize
on load diversity within the community, their reliability and maintainability, the possibility to attain high
efficiencies by combining electrical generation with heating and/or cooling, and the autonomy given
to the community concerning the operation of the system and the fuel source it uses. For these
reasons, it has been deemed worthwhile to analyze potential district systems for SoLi.
NREL and Group 14 Engineering, Inc. provided energy analysis for the SoLi development. Group 14
Engineering, Inc. developed building scale energy models for several typical building types using
load assumptions from the Phase 1 project and additional assumptions determined by the
Leadership Team. NREL used this building scale modeling to create annual demand profiles for the
entire development and evaluate the energy impacts and feasibility of district-wide systems.
NREL's analysis of the potential for district systems involves estimating the hourly heating, cooling,
DHW, and electric loads required by the community, investigating potential district system
technologies to meet those needs, and researching available fuel sources to power such systems.
The metrics used to evaluate the economic and environmental viability of each system are simple
payback period (SPP), Net Present Value (NPV), and greenhouse gas (GHG) reductions.
4.2 NREL Conclusions and Recommendations
Although none of the district systems investigated for this analysis show favorable economics, some
options may well make sense as integral parts of the final solution. However, it is highly
recommended that other measures be maximized before implementing any district system.
Specifically, it is vital that electrical loads, heating and DHW loads, and cooling loads in the
community, are reduced as much as possible. Electrical loads can be reduced by a combination of
building system design (high efficiency pumps and fans, timers on bathroom vents, daylighting
design), appliance efficiency standards, occupant education, and any number of occupant incentives.
Heating loads can be reduced primarily by building design, including insulation levels and window
specifications. DHW loads can be reduced by educating the occupants and using low-flow fixtures.
Perhaps the greatest improvements in the baseline energy use can be found in the reduction of
cooling energy use. The Denver climate is ideal for natural ventilation, direct cooling with outdoor air,
night- time pre- cooling, and evaporative cooling. It is conceivable that these technologies could
virtually eliminate conventional cooling methods in the South Lincoln community and significantly
reduce the electricity used for cooling.
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In regards to district systems for this community, the most drastic reductions in GHG emissions will best be achieved using a combination of PV for electricity and biomass for heating and
domestic hot water. If cooling and other electrical loads are reduced based on the recommendations above, it may be possible for the community to reach net zero GHG emissions by installing
19% efficient solar panels on rooftops and carports and installing a biomass heating system sized to 40% of peak heating and DHW demand. In this scenario, heating and DHW will require some
natural gas input. However, with the reductions in cooling and other electrical energy, the PV system is projected to produce enough of a surplus of electrical power to offset the greenhouse gas
emissions from the site's natural gas usage. Although the economics of buying and owning a PV system may be prohibitive, entering into a power purchase agreement (PPA) could make such a
system viable. A PPA is a legal contract between an electricity generator (provider) and a power purchaser (buyer).
An alternative to the scenario above is to install PV to offset electricity, concentrate on reducing heating/DHW loads, and utilize high efficiency natural gas systems at the building level in lieu of
a central biomass plant. While the community is not expected to reach net zero GHG emissions in this scenario, emissions savings of about 80% or higher are achievable.
Furthermore, upfront costs as well as operations and maintenance costs will be significantly lower. This approach would be much simpler and less costly to design and
implement phase by phase, with a relatively small loss of environmental benefit. Considering both economics and environmental benefits, this may be the most reasonable option for
South Lincoln.
A third possibility would be to use a cogeneration or tri-generation plant driven by an 1C engine or a fuel cell to provide a portion of the community's heating and electricity needs. These
systems show the most attractive economics of any of the systems analyzed. It would be possible to supplement a cogeneration plant with PV as a path to net zero emissions. However,
implementation of a cogeneration or tri- generation strategy will require more planning and ongoing operations and maintenance effort by DHA than a PV strategy. Furthermore, while a PV
system can be installed under a PPA, a cogeneration plant would require the consent of the
utility for such an arrangement. Because the utility has little incentive to agree to this type of
arrangement, a PPA for a cogeneration plant is very unlikely.
System Priorities
• Efficiency and Conservation First
o Electric Loads: Building System Design, Occupant Education,
Incentives, Appliance Standards, Lighting Standards
o Heating Loads: Insulation Levels, Window Specs, Duct/Piping Design
o Cooling Loads: Insulation Levels, Window Specs
o DHW Loads: Low-Flow Fixtures, Distribution Design, Occupant
Education
• Drastically Reduce Cooling Energy
o Natural Ventilation, Direct Outdoor Air Cooling, Nighttime Pre-cooling
o Evaporative Cooling
System Recommendations
4. Net Zero GHG
a. High Efficiency PV on Rooftops and Carports (Enter into a PPA to
capture government incentives)
b. Biomass Heating and DHW
5. Significant Reduction in GHG
a. PV
b. High Efficiency Natural Gas Boilers (Condensing)
6. Other Options
a. Internal Combustion (1C) Engine Cogeneration
For a full copy of the NREL South Lincoln Community District Assessment, see the Appendix
to this report or go to the following link.
http://vrgsustainabilitv.centraldesktop.com/denverscpcharrettesexternal/
Results Summary
Technology
Size
SPP (yrs)
NPV($)
Percent
Total COZ
Equivalent
Saved
Cogeneration
NG Gas Turbine
1C Engine
Fuel Cell
250/409
300/300
600/269
85.0
33.1
46.6
-$673,339
-$282,627
-$1,917,016
8%
12%
28%
Trigeneration
NG Gas Turbine
1C Engine
Fuel Cell
250/409
350/350
700/313
83.0
36.4
48.2
-$873,275
-$440,141
-$2,399,469
9%
14%
33%
District GSHP
GSHP
100% of Load
83.2
-$4,642,113
4%
Biomass District Heat
Wood Chip Boiler
40% of Heating Demand
111.5
-$1,545,443
21%
Photovoltaics
Solar Panels (19%
efficient; Rooftops
and Carports)
Solar Panels (15%
efficient; Rooftops
Only)
252,455ftz(as multiple smaller
systems)
188,848ft2(as multiple smaller
systems)
66.4
58.0
-$17,720,053
-$9,019,400
76%
57%
Solar Hot Water
Flat Plate Panels
80% of DHW Load
126.8
-$12,265,323
6%
This table summarizes results for selected systems and technologies. Results here were selected based
on simple payback and feasibility of size. See full NREL report for a complete list of systems analyzed.
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Summary of Building Systems
5. Report Conclusions and Recommendations
Based on the analysis presented herein, the most economic means of achieving near-net-zero energy for the project is to
maximize the production of on-site PV to offset the electrical demand, namely the lighting, plug, and auxiliary loads. If cooling is
assumed to be provided by passive and/or evaporative means, the only remaining load is space heat and DHW. This can be
produced either through a high efficiency boiler (building or district level), or through a cogeneration system. If the latter is used,
then the PV capacity can be reduced in proportion to the expected electricity production from the cogen unit. These system
combinations have the capacity to reduce the overall GHG emissions by 80-90% or more, depending on the degree to which
passive design measures can be employed at the building level.
Reaching True Net-Zero: To address the remaining 10-20% of emissions and fossil fuel use on site, the project would need to
either:
4. Use a biomass district heating system, despite the poor economics and logistical challenges.
5. Shift the heat to a GSHP system and add additional solar to compensate for the increased electrical load for the
GSHP system.
6. Use solar thermal for DHW and space heat, despite the poor economics and lack of roof space to accommodate both
the PV and solar thermal collectors (this would require either off-site PV production, or non-rooftop PV production
such as collectors on the south facades).
While this is technically feasible, the marginal returns are significantly diminishing - that is, the additional costs are harder and
harder to justify given the resulting benefits.
It should be noted that the results of this analysis are heavily dependent on the following factors:
3. Technical solutions, need to match the specific load profiles of the development, thus will be dictated by the Colorado
climate which is heavily heating dominated, as well as building efficiency and plug load assumptions. Different
climates such as Atlanta's, have a greater need for cooling and cannot easily utilize evaporative cooling.
4. The cost and rate structures of electricity and gas: The financial viability of the systems discussed would be markedly
improved if the was project located in a region with higher energy prices, or if the assumptions for energy price
escalation were increased from the current level of 3% annually, or even if there was a more favorable rate structure,
such as a time of use structure.
Lastly, the charrette working groups and discussions identified several other general energy recommendations.
• Soli residents are not currently incentivized to save energy because they do not pay for their own utilities. HUD and
DHA should make this usage transparent to residents and develop an incentive structure that encourages residents to
save energy and share their efforts with others.
• There is a tension between building higher density developments and providing adequate solar access to all buildings
and most units. Planning decisions for energy savings related to solar access should also take into account
transportation impacts of lower density developments.
• District energy systems will likely require a dedicated maintenance staff. DHA will need to hire and train this staff or
hire contractors to provide this service.
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• There could be a number of ownership options for all of the district energy system mentioned above. DMA will need to I ncentlVGS to Save - Cost
explore and negotiate an ownership structure before these systems can be built.
• District systems that include district water loops will require coordination with Denver Public Works (DPW) and other
local agencies in order to be approved.
5.1 Funding and Incentive Opportunities
DHA will need to acquire additional funding to implement many of the strategies outline in this report. The following funding
sources were identified to help support these strategies.
Paid by
• Governor's Energy Office (GEO) Resident
• State and federal tax incentives
• Xcel Energy
5.2 Strategic Partnerships
DHA will need to develop active working relationships with the following strategic partners in order to successfully implement the
transportation strategies recommended in this report.
Housing and Urban Development (HUD) - HUD can provide support for resident programs and facilities that support
energy efficiency strategies.
National Renewable Energy Laboratory (NREL) - NREL completed a district energy analysis for the Soil project
and can continue to be a technical partner as the team explores the logistics and payback of aggressive energy
strategies.
Denver Community Planning and Development (CPD) - Denver CPD has developed a comprehensive
neighborhood plan for La Alma / Lincoln Park and will need to be involved in many of the major decisions moving
forward.
Denver Public Works (DPW) - Denver Public Works plays a critical role in the approval and development of the
public right-of-way in the SoLi development and La Alma / Lincoln Park neighborhood, and may need to be involved for
district-wide energy strategy decisions if these influence neighborhood transit during construction and/or operations.
La Alma / Lincoln Park Neighborhood Association (LPNA) (formally known as La Alma / Lincoln Park Planning
Group (LLPPG)) - Many of the energy efficiency programs and strategies included in this report will not be successful
without engaging and developing support within the LA / LP resident community.
Xcel Energy - Xcel can provide resources for the SoLi development such as building modeling analysis and incentive
programs, and will need to be a partner in the design, approval, and ownership of a district energy system.
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_
6. Appendix
6.1 Charrette Photos
Go to the following link to see photos taken during the Energy Charrette.
http://picasaweb.google.com/yrgconsultants/PSCCharrettes?feat=directlink
6.2 Charrette Agenda, Presentations, and Handouts
The following pages include the Charrette Agenda and presentation slides in handouts format. In addition, the agenda, a PDF
of the PowerPoint presentations, and all handouts for the Energy Charrette have been posted on a public website for
participants and the general public to access. Go to the following website to access those documents.
http://yrgsustainability.centraldesktop.com/denverscpcharrettesexternal/
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Charrette Agenda (Day 1):
Tuesday, August 10,1:00 - 5:30 pm
Welcome and Introductions (1:00-1:15)
• Goals of the charrette (EPA/DHA/YRG)
• Attendee introductions
S. Lincoln Redevelopment Project Overview (1:15 -1:45) (DMA)
• General goals and objectives for the project
• Brief overview of how Master Plan was developed, cultural context, phasing approach, funding implications
• Energy information included in the Master Plan
o Why energy improvements are important to DMA and stakeholders and associated challenges
o Overview of Master Plan's energy goals, metrics, and guidelines
Guiding Principles and Metrics (1:45 - 2:30) (YRG)
• Overview of project's energy design guiding principles (e.g., concepts and strategies for getting to net-zero)
• Overview of project's overarching energy goals and metrics
o Energy metrics (net-zero, carbon neutral, EUI, reductions below code)
o Green Building metrics (LEED NC and ND, Green Communities)
• Lessons learned from Phase I (e.g., specific Phase I energy goals, strategies used, lessons learned, and implications for future energy planning)
• Project challenges and opportunities
Stakeholder Presentations (2:30 - 3:00)
• HUD
• Governor's Energy Office
• Denver Greenprint
• NREL
• Xcel
Break and Site Walk (3:00-3:30)
Concepts and Strategies (3:30-4:30) (NREL/YRG presentation and facilitated discussion)
• Overview of potential energy strategies, including case study examples and pre-charrette energy analysis information
o District scale (e.g., centralized ground source heat pumps, co-generation and district heat and solar gardens)
o Building scale (e.g., orientation, window to wall ratio, shell features, lighting and hvac)
o Occupant/behavioral (e.g., occupant feedback and information, ongoing challenges and reminders to participate in the projects intent)
Goals and Outcomes Working Groups (4:30 - 5:20)
• Break out into groups to and discuss the top 3 desired outcomes for the charrette
Day Wrap-Up (5:20-5:30)
Social at the Buckhorn Exchange at 10th and Osage (not hosted)
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Charrette Agenda (Day 2):
Wednesday, August 11,8:00 am -12:00 pm
Welcome / Recap (8:00 - 8:15)
• Brief review of Day 1
• Goals for day and working groups
Sustainability Working Groups (8:15 - 9:45)
• Break out into three groups to develop concepts, strategies, and metrics
o Topic 1: Building scale energy
o Topic 2: District scale energy
o Topic 3: Occupant / behavior energy impacts
Break (9:45-10:00)
Plenary to Discuss / Evaluate Working Group Ideas (10:00 -11:15) (YRG/SRA to facilitate)
• Each group to select one member to report out to the larger plenary
• Group to discuss ideas, further brainstorm, and identify 3-5 priority concepts/strategies to move forward with
Implementation and Next Steps (11:15-12:00) (YRG/SRA to facilitate)
• For each of the 3-5 priority concept/strategies, the full group will discuss:
o Next steps (e.g., additional analysis needed, partners to engage)
o Estimated timeline
o Funding/technical assistance opportunities
• Review any action items/next steps
• Charrette wrap up
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Presentation Slides
South Lincoln Redevelopment Project
ENERGY CHARflETTE
"*• IT*
T;^ '
Energy Charrette Goal
To explore the goal of a net-zero energy
neighborhood...
,. through an interactive dialogue on concept
feasibility, strategies and actions needed...
,. .in order to develop an action plan that guides
implementation through all phases of the project-
South Lincoln Project
Overview
South Lincoln Master Plan
KAC iii
Project Goals Refinement
South Lincoln Master Plan
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South Lincoln Master Plan
Sustainable strategies
NT)**'
Energy Story
% ^
-
f nerp, Source!
-------
"Net-zero energy is an ambitious goal for any
building - one that can't be achieved without
scrupulous attention to every aspect of a
building's design, construction, and
operation.'"
-NutavMalirvEINArtidc
Achieving Energy Balance
Achieving Energy Balance
s
*
iT
Source
Use
Getting to Zero
et* and Cer«" oa Zero £rn:ssiort: >::
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 23
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Net Zero vs. Carbon Neutral
Net-Zero Energy Buildings
Net-Zero Energy Communities
UfC.t.
Oil IfWufc HUM (nmlUti i» <1 ur/WM mm MBIfa Hi*
IMxn* ..I U S hulVllny. h> 'toot ««. ihM c
nf t-r^foai •function of number or floor*
. of rer-irrD ponmnT in oufi*npf
"Getting to net-zero is extremely difficult for
buildings of more than 4 stories."
- tadav Mahn. CUM Article
However,
"In a community, density allows for greater
walk-ability and many other attributes
desired in a sustainable community."
-•Definition of a "Zero Net InefB/ Cwnmun/tv '. NMl
24 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Projected Energy Use
• Electricity1 Use
• Elsctricity1 Demand
5.453 MWh/yr
1.4 MW
Natural Gas Use (DHWt: 25.337 MMBtu/yr
Heating and Cooling Requirements
• Cumulative armus! heating load' 4.705 Mfctu
• Peak heating load: 3.49 MMBtu/hr
(366 Tons fc
Peak cootirtg load 506 Tons
Solar Energy Potential: Rooftop PV
• Rooftop PV Annual Production
-j Star dard Practice:
- annul' citTfY prodaeboo: Z.119 MW n/yr
Best Practice:
- Annul
Solar Energy Potential: Carport PV
• Carport PV Annual Production
• Standard Practice:
• Annual ti-ftfff production: 1,07V MWWfr
• SvEtm size. 7S1 4W
Best Practice:
• Arcrau
1.&2I M « - • > •
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 25
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Electricity Use and Production Summary
Electricity Use.
Total PV Production
• Standard Practice
• Best Practice:
5.458 MWh/yr
3,189 MWh/yr
5,401 MWri/yr
"Single-scale problem-solving leads
to solutions that don't always make
sense"
Energy Strategies at Different Scales
,. -
-
District Scale Bulking Scale Resident Scale
Metrics and Benchmarks
Lessons Learned - Phase 1
OH*- IOUKI Uncoci tenn
- Goal = 50^ reduction
ASHRAE 90.1. 5iS xhieved
t554l
-------
Inn M 25 strateates modeled
Lessons Learned
* 8-sset appmanatel>
• Design 'c- -• en or-entstjon and let
EEMs drive aesthecc
• Carry cor ;-oer?ror of renewable
and passvve catxa-T ji Mrs with
energy, shading and massing
Soutn L-r«Mn Ogdevriaormgn frafcct
Concepts and Strategies
District Scale Strategies
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 27
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District Energy Systems
Electric Only Options
Renewable Energy Options
• Wind (not viadfe based on resource)
Photovoltaic Opportunities:
• Roof Mounted
• Carpor:
• Community Solar (Solar Ganders |
Photovoltaic Issues
• Purchasing- Agency AppropnaOons/ Power
Purchase Aj^eemert [PPflt
Northeast Denver Housing Center
Project Description
* Installing PV systems on 20 Low Income
Housing Uric* (W 7S kW,
• GEO Grart Loaned to De«e ooe-
- NOHC Pays SO 08,VWrt PPA {30V reduclx>n
* NOHC Recedes loan ImDenest Payment
• Cunomers rtcewe pree surety and rate
Heating or Cooling
Technology Options.
-Central Chilled Wa»<- Plant
KI*fttral Heatfng Want
- B«omus Combustton
• fl.o-T-as: Gauficatior
• fiotlcT * . Renetfrsbie Methane
Centnl Plant tsn^s
* tfcreTeirS' ' nf rairructur*
Devetopment
avsMabfoty /
Renewable Fuel Heating Plant (RFHP)
28 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Green Acres Public Housing Complex
• SO Unit Affordable Housing
• Residential District Woodchip
Heating System
Heating Capacity (output): 06
MW (2.2 MMBtu/hr)
• Year Installed: 1992
• Thermal Output: Hot water
Heating and Cooling
• Central Ground Source Heat Pump
- Sub-mctenng/btHmg
- ICC Bfectivcnexs
re Development
Boulder County Housing Authority
Boulder County Housing Authority
Combined Heat and Power and Tri-Gen
CHP Technology Optowu:
• Kamas Cofnbus&ort or Gasxfkabon
•K Engine
• Gu Turbine
• Fuel Cell
Tri-Cn Coalinf Opti
* Abxorption Chiller
Tcchnotogy Uiuer
• Fuel SuppJy (GHG ravings or net z
• Uniterm utility rater
Range of Bioenergy Concepts
. w.u
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 29
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Integrated Solid Waste Management Hierarchy
Source Reduction
Reuse
Donation
Recycling
Composting/Mulching
Waste to E/ietgv I'«VTEI
Other forms of volume
reduction
Fuel Types and Technologies
Must meet regulations for solid waste (ash) and air
quality
Ch.4le.gr,
-tabor costs for small ptams nearly same as
large
•Higher per unit capital ants
Hfifihci heat rates (lower efficienoes
cnmpired to large)
•No commercial operating history tn U -S
Building Scale Strategies
Optimizing Building Performance
m
30 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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il.lTmi Tirf
office, mai and
l«t* induariai span
Oocksde Grni n one of 16
Qrrnatt fnibatwe's Oinale Posrtwc
Dcvwtjpment Program
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 31
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UXn at sewage treated on-«tr
treaecd xsrttr liiad ter taien
f&St vatp launcs ompvcd
BIOMASS GASIRCATION
residual i such as bark, sawdust
and shawigs irao IV^?* ( Nertctra
peak toad aippticd by thr backup/
OKE conp*t-*. project will cut
COlemiisiara by 1WO tans per
year (ISO can off the mad|
DBjpncri to be 4TM imnr
than the ASHRAE 2007
Mottmacd octerior -Jiidc:
l£D in buddng comdon
mnvoY vcntibton t»
imude 100\ fretft air ID all uniti
" Individual mrterafcr hot
cold
Ventilation Strategy - Typical
Ventilation Strategy • Design
E
32 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 33
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34 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Resident Scale Strategies
Occupant Scale Energy Strategies
• Engaging occupants and operators
o Mandates and Policies
- Information and Feedback
o Fostering Community and Identity
o Incentives for saving enetfy
• COR
• -Doinc the right thine"
* Peer pressure / imn petition
Incentives to Save - Cost
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 35
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Incentives to Save - Cost
Paid by
DHA
rh
Paid by
Resident
Energy Audit Summary
"A major problem with low-income individually
heated apartments, consistent with our
experience with the otnef housing authorities, is
that energy will be wasted as long as someone
else is paying the bills. Open windows,
apartments set to 75°F, and televisions and
computers left on when tenants are gone are
typical."
Range of Energy
Performance
Outcome
• SCHEDULE AND USE
• OCOJRftMT BEHAVIOR
• ACTUAL SYSTEM OPERATION (CxJ
• MODELED SYSTEM OPERATION
Savings From Feedback
I I
—
Electric Bill Example
Energy used Last Month: 1,137 kwn
EledrJcily Bil: 567.12
Your Energy Use compared to your neighbor*.
Electric Bill Example
EnegV Used Last McnUi
Efectnnty nil: 522.82
Your Energy Use compafEd to your ntif t>bo-rs:
36 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Occupant Feedback and Control
Summary of Building Systems
Building llalih»i t
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 37
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Hourty L-Mflo profllu
Energy Strategies at Different Scales
District Scale BuiSdrng ScaJe Resident Scale
Goals and Outcomes
Working Groups
38 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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6.3 Charrette Notes
The following pages contain all of the notes that were recorded on flip charts and taken during the discussions and working groups during the Energy Charrette.
Charrette Goals and Outcomes
Net-Zero Definition
Suggested Outcomes
Energy Strategies
District Scale
Building Scale
Occupant Scale
Summary
Voting on Strategies
Questions / Ideas / Holding Tank
Suggestions
Charrette Goals and Outcomes
Net Zero Definition
Community net zero building be reviewed separately
What PV rebates go away—rely on this
Focus on more than just electricity—don't have all electric load
Zero flow through community
District wide—100% (NCECRE) within footprint
-Plan B—off-site source e.g. solar garden on brownfield (NZEC-B)
NZEC-B: Can include some off-site renewable energy credits or green power
Occupant educational important
Lifetime—not just five-year period
Try offset—BTU/BTU match even if different resources
Electrical diversity vs. contained project
OK to have natural gas input?
-Do through geothermal exchange and passive solar
-Could have geothermal ground source with or without central plant
Remember to focus on minimizing load
Really important to map loads over time
Suggested Outcomes
Determine fuel sources in nearby area
Set goals and keep buildings accountable
Energy budgets?
Look for partnerships and continue them long-term
Fund to pay for first cost appliances to ensure long-term operation?
Decision strategy—what drives decision on central plant
Have building envelope toolbox
How to train people
-Out and within (e.g. occupant behaviors)
Model for other communities
-What decision making did you use
Match funding with phases
Occupant resp. of uses
-Motivation and incentives
Ensure holistic approach (e.g. don't focus just on photovoltaics)
Economic impact—sustainable jobs
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 39
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District Scale Energy Strategies
District Group A (1)
1. DISTRICT energy strategies needed to achieve the goal of a net-zero development?
1. Community Involvement
2. Infrastructure optimization and energy use
3. Solar garden with neighborhood resources (Auraria and Denver Health)
4. Load equalization ("Big Sexy Graphs")
a. Block by block, phase by phase, Soli to neighborhood
5. Sharing opportunities with "neighbors"
a. Auraria Campus roofs for solar garden, same with Denver Health
2. Emphasis on creating energy—instead of using (electric/natural gas)
2. Pros and Cons of these strategies?
Pros
ID inefficiencies and avoid
District-wide approach
Cost savings
Lends to a phased approach (scaling)
Neighborhood approach
Using resources elsewhere that may not be available on our site
Cons
• Planning needs ($) - more costly near term?
• Need to co-operate
• Working among bureaucratic agencies with varying needs
• Joint funding
3. Technical and political feasibility
Must be flexible to market/program changes
Politically—TIP, metro district (to solidify standards)
Next Steps
Colorado Carbon Fund
Inventory energy audits: Xcel energy demand model for Master Plan/Neighborhood
Energy Tax Increment Financing (TIFs)/energy conservation district
Analyze rooftops available
Interest at Denver Health or Auraria?
MOU
ID % "allowances"
Other
Occupant behavior groups affect this strategy
District A (2)
Occupant
Building
Smart switch
-do some things automatically/take out the 'human' factor
Net metering (awareness)
Education (culturally sensitive)
Community buy-in (everyone)
Design—window direction for wind direction
PV canopy/parking lot
BMPs—make it simple
Building orientation/solar access
Minimum threshold of energy
Future assets/needs
Political—work with three large organizations
Phasing—need to further define solar garden
Issue—how big can the garden be? Big enough? DHA using others' roofs
o ID "now" need vs. "unknown" of future needs
40 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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District Group B & C (1)
Strategy
Design for flexfuel (central plant)
-* Ground Source Heat Pump (GSHP)
•> Biomass
-* Solar
•> Denver Water
Pros/Cons
(Pro) Hedges against volatility and allows options towards net-zero
(Con) Land/real estate
Feasibility
Residential use, real estate, financing are barriers
Distribution costs are high
Next Steps
Complete analysis to evaluate needs and feasibility—should this be balanced with
what other strategies?
Partnerships—GEOtool, NREL, Xcel, Denver Water, adjacent landowners, Energy
Outreach Co., Enterprise, Denver Public Schools, HUD, EPA, DOE, Colorado Higher
Education Association (CHEA)
Challenges—need to expand only residential/consider beyond boundaries to
South for industrial, other uses
-N. Lincoln Park
-Railroad
-Denver Health
-Auraria Campus
Strategy
Energy analysis working with building strategies
Identify where district makes sense and how many
Identify synergies
Next Steps
Evaluate energy profiles
Identify opportunities to optimize—building orientation
(Where do savings go?)
What we need from buildings
Optimal orientation, submetering, pay attention to future building code,
understanding how owned properties and rental properties work together for sharing costs
and savings, how to avoid energy use before systems are built (windows, passive, trees),
what type of mechanical systems, will they have—needs to be hydronic or heat pump with
coil, adjacent property plans, roof space
What we need from occupants
Awareness/paying own bills, develop and show incentives, education on lowering
energy usage, rules and policies, financial incentives, peer pressure, start with the kids-
through school
Needs
Heating
Cooling
Plug Loads
Lighting
Hot water
Gas
Easy, cheap now.
Volatility in cost.
Greater
environmental
impact than other
options.
X
Combined Heat
and Power (CHP)
CHP
X
Solar Thermal
Highly efficient
for larger scale.
X
Concentrated Solar
Needs a lot of real
estate.
Railyard roof area as a
resource?
X
X
X
Biomass
Needs storage, unclear on operations and
maintenance requirements and who will
manage this.
Need to determine training and associated
costs.
Not cost-effective without tax credits.
Biomass gasification could be used.
X
Ground Source Heat Pump (GSHP)
Awesome, very efficient, high first
cost, low maintenance
X
Photovoltaics (PV)
May not be best
option unless
heating is electric.
X
X
X
To better convey the strategies and break-out group ideas, some text in the chart above has been revised or added to in order to clarify notes taken during the break-out group discussions.
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 41
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District Group Drawings
*J
?0> ^Hf
'if'ii ski
2e-f *?e 3xp
•'m"'ii ^«»o
ijd?
«^
£
*
District A Drawing
District B Drawing
42 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Building Scale Energy Strategies
Building A (1 & 2)
Strategy
Efficient/alternative HVAC system
Envelope—less than .2 air changes per hour
Passive house standard as potential goal
Passive system
Reorientation of buildings
Frieberg model for some buildings
Window shading—high efficiency
Proven products—most bang for buck
Alternate materials strategies
Thermal mass
Alternative construction strategies (e.g. SIPS)
Building A (3)
Strategy
Thermal mass/construction/earth coupled passive solar heating and cooling
Pros/Cons
Current orientation does not lend to passive
Takes up space, costs more or perception of cost
Energy efficiency, proven strategies, avoid temperature swings
High environmental quality—natural light/fresh air
Pros/Cons
(Con) Cost—upfront cost
No thermal breaks
Lower embodied energy
Reduced infiltration
Lack of familiarity
Feasibility
Construction faster
Highly feasible
Building codes—educating city staff
Need more lead time
Next Steps
Evaluate alternatives
Look at case studies/examples
Feasibility
Unsure can reorient—perception
Unsure codes/regulations
Off-the-shelf systems
Next Steps
More discussion on orientation
Modeling
Other
Occupant behavior important
Other
Reduces load for district-wide system
Building A (4)
Occupant Behavior
Handbook/manual, intro class
Real-time dashboard
Incentives for compliance
Block pricing (positive and negative)
District Scale
Feasible/Affordable design
Two-way system (sell book to district)
Meter individual unit basis
District-wide water conservation solution
Flexibility to interact with passive systems
Landscape/site planning issues for conservation
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Building B (1)
Strategy
Building B (3)
Natural and low-energy cooling and high performance envelopes
Pros/Cons
Low energy usage, minimizes operating costs
Low upfront and maintenance costs
Incentives? (Xcel)
Better indoor air quality
Potential occupant thermal comfort issues
Education campaign to tenants will be time-, cost-intensive
Next Steps
Investigate incentive opportunities
Bring in expertise (if not available in-house)
District
-Passive design at district scale
-Integrate with existing and emerging
neighborhood plans
-Data collection at district scale
-Engage local, proximate businesses,
education institutions, community
members, etc.
Occupant
-Education and communication regarding
energy usage (carrot and stick approach)
-Engage residents in interior design process
-"Tell us what you want" and how you learn
via Resident Committee
Building B (2)
Strategy
Passive design—community and buildings
Pros/Cons
Low cost/rapid payback
Opportunity for significantly reduced loads (system optimization)
Potential code variances/issues
Feasibility
Existing, established process
Next Steps
Look into zoning and land use regulations
Use Building A as a demonstration project with ongoing data (recognize that senior
population is unique to rest of project)
44 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Occupant Scale Energy Strategies
Occupant A (1)
Pros/Cons
Strategy
Provide ownership & sense of pride
Engage residence as early as possible
Identify champions (train the trainer)
Involve community colleges & other partners
Job creation
Get children involved
Education part of cornerstone
Cost
Access to computer/computer labs
Technology/market
Pros/Cons
Culturally relevant
Ongoing training/high turnover/burnout
Quickly evolving technology
Literacy/education issues
Young engineer group
Feasibility
Must keep it fun
Provide incentives (hours for zipcar, childcare, vouchers for green store)
Next Steps
Create teams for buildings
Start engagement
Find the champion (resident to be paid)
Feasibility
Need to engage funders/donators (Honeywell?)
Technology
Next Steps
Research technology
Engage funders
Other
Occupant A (3)
Strategy
Building as teaching tool
Continual commissioning
Use clothesline instead of dryer
Green cornerstone/resource room
Pros/Cons
Other
cost?
Will cornerstone be self-sustaining— can it generate profit if things are provided at
Occupant/community connection with Environment and Earth
Cultural relevance
Education
Resident-driven
Occupant A (2)
Strategy
Energy management system—or other low-tech option—by
unit/floor/building/community
Provide feedback in unit
Provide incentives if they don't pay bills (childcare, zipcar hours, transit passes,
entertainment, bike share)
Children to help teach/educate
Provide incentive voucher to spend at green store— others to pay full cost
Training center
Feasibility
Depends on building type—you need different strategies for different building types
Next Steps
Partners for cornerstone
Retail tenants to leverage cost
Other
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 45
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Occupant B (1)
Strategy
Information & Feedback
Individual and building usage statistics
Rewarding/identifying best practice users -> trip
Social feedback: resident meetings
Non-computer based feedback: lights, flag, ice cream, letter from
Obama, mayor, truck to be powered by alternative energy
Pay-as-you-go metering
Next Steps
Building Program focused on Net-Zero
Occupant B (3)
Strategy
Mandate/Policy: benchmark—rewarding occupants below benchmark/outreach to
occupants with "bad" consumption behavior. Reports given. Benchmark = Sft + # of
occupants
Pros/Cons
Pros/Cons
(Con) Participation/Turnout
(Con) Turnover/Reeducation
(Pro) Community building/Cost effective
Promotes community buy-in/resistance
Undermining behavior patterns
Feasibility
Getting right data
Organize meetings/leadership
Next Steps
Identifying current meetings
Identify strategy/system for data collection
Occupant B (2)
Next Step
Research HUD funding capabilities/30%
Feasibility
Market rate vs. Affordable
Utilities included in all rent?
Occupant B (4)
Strategy
Energy Careers
Job shadows for monitoring/administrative/ops
Internships
Job training
Pros/Cons
Building Group
"Catchy" Display Panel/Lobby Units
Meters at Unit Level
Educational Display
District Group
Energy Flags
District-scale Feedback
-Newsletter
-Lights
-Community Board
Policy for Non-DHA Developers for Energy
Monitoring
(Pro) Skills building
(Pro) More in-depth knowledge of systems
(Pro) Community Building
(Con) Participation
Feasibility
Existing program/Wage subsidies/Training funding
Need buy-in from staff
46 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Occupant Group Drawings:
s
I C^vtj
II
\
ft"fi:rrS±fti
/
^
4
Occupant A Drawing
Occupant B Drawing
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 47
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Summary
Voting on Strategies
See Strategy sections above.
Questions
How will ownership be structured for a district system? What are the ownership options and
possible partners?
What strategies enable DMA to obtain tax credit?
Will it be possible to dictate appliance selection across all income levels?
What is the budget for insulation and air sealing?
To what degree can we control occupancy behavior?
Has any thought been given to installing smart grid technology to allow homeowners energy
use monitoring capabilities?
Ideas
Property Assessed Community Energy (PACE)
Recognition from President every year net-zero is achieved
& Ice cream truck to be powered by alternative energy - symbol of net-zero efforts
and successes
& Street party
Anonymous feedback at occupant level
Building scale feedback
Street lights turn colors to indicate use (Red, White, Green)
Payback for (Soli bucks?)
Energy Cop?
Control of occupant behavior more feasible with long-term leasing, not sales?
Scaled rate thresholds for KWh usage (like current water billing)
Suggestions
Pros
-Everyone's' comments were respected
-Like 2-day format
Cons
-Add glossary of key terms
-Make clear how it will feed into
development process
-Talk more about financing (more time?)
-Add homework before
Miscellaneous Page
No central gas/coal power plant
On/off site solar for electricity
Geothermal
Effective insulation/appliance/windows
Pros
-Low to no carbon
-Decrease residents' utilities
Cons
-Expensive
-Space— roof to building area ratio
Certain permits are needed
Multiple fuel sources:
Different usage times
Heating vs. electricity
Could be put in single plant
Decide fuel service from usage needs
Using surrounding buildings for additional solar area or additional DHA-owned
Housing
Using extra energy at night to freeze ice to use for cooling during the day
Heating
Domestic water
Solar hot water—high efficiency
48 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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6.4 Charrette Attendees:
First Name
Fred
Joel
Devon
Cindy
Shayne
Matt
Cindy
Hope
Kimball
Jesse
Steven
Stacey
Laura
Rebecca
Leslie
Dana
Abby
Elaine
Narada
Dave
Shannon
Elizabeth
Jack
Doug
Abby
Peter
Ron
Christian
Paul
Dan
Stephen
Karly
Last Name
Andreas
Asreal
Bertram
Bosco
Brady
Brady
Cody
Connors
Crangle
Dean
Egglestond
Eriksen
Farris
Fox
Fraley
Fulenwider
Fulton
Gallagher Adams
Golden
Goldenberg
Gray
Gundlach Neufeld
Hidinger
Houdson
Hugill
Hynes
Johnson
Kaltreider
Kriescher
LeBlanc
Loppnow
Malpiede
Organization
UNIT Design Studio
Governor's Energy Office (GEO)
YRG sustainability
Denver Greenprint
HUD
South Lincoln Steering Committee
EPA Region 8
Green Home Denver
Denver Housing Authority (DHA)
National Renewable Energy Lab
HUD
EPA Region 8
EPA Region 8
SRA International
Xcel
Urban Venture
EPA Region 8
Rocky Mountain Institute
YRG sustainability
Conundrum Energy
YRG sustainability
Aurora Housing
EPA Region 8
Metro West Housing Solutions
HUD
South Lincoln Steering Committee
Xcel
National Renewable Energy Lab
Lightly Treading
YRG sustainability
YRG sustainability
Representative Diana DeGette's Office
First Name
Matthew
Joe
Ryan
Conor
Nat
Melissa
Jason
Steve
April
Christopher
Chuck
John
Susan
Josh
Barret
Tim
Sue
Peter
Cathy
Phillip
Eddie
Joan
Laura
Chris
Tami
Ryan
Mike Vail
Michael
Otto
Jonathon
Jaronam
Last Name
Marshall
McCabe
McCaw
Merrigan
Miullo
Nelson
Newcomer
Nowack
Nowak
Parr
Perry
Plakorus
Powers
Radoff
Ramey
Rehder
Reilly
Riedo
Rock
Saieg
Sierra
Smith
Sneeringer
Spelke
Thomas-Burton
Tobin
Vail
Van Dalsem
Van Geet
Walker
Organization
Denver Environmental Health (DEH)
Sentech
Metro West Housing Solutions
Governor's Energy Office (GEO)
EPA Region 8
Coldwell Banker Residential
Diversified Consulting Solutions
Colorado State University (CSU)
EPA Region 8
Denver Housing Authority (DHA)
Perry Rose LLC
CO Housing and Finance Authority
Urban Venture
YRG sustainability
Conundrum Energy
EPA Region 8
Enermodal Engineering, Inc
EPA Region 8
Red Rocks Community College
Alliance for Sustainable Colorado
EPA Region 8
Red Rocks Community College
SRA International
Denver Housing Authority (DHA)
EPA Region 8
Denver Housing Authority (DHA)
Water Legacy
CSU
National Renewable Energy Lab
CSU
Roman Remodel and Restoration
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 49
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6.5 Acronyms List:
Acronym
CPD
CHEA
CHP
DMA
DHW
DOE
DOT
DPW
EPA
GEO
GHG
GSHP
HUD
1C
LA/LP
LPNA
NPV
NREL
NZEB
NZEC
OBLR
OSC
PPA
PV
SIPs
Soli
SPP
TIP
Denver Community Planning and Development
Colorado Higher Education Association
Combined Heat and Power
Denver Housing Authority
Domestic Hot Water
Department of Energy
Department of Transportation
Denver Public Works
Environmental Protection Agency
Governor's Energy's Office
Greenhouse Gas
Ground Source Heat Pump
U.S. Department of Housing and Urban Development
Internal Combustion
La Alma /Lincoln Park
La Alma Lincoln Park Neighborhood Association
Net Present Value
National Renwable Energy Laboratory
Net Zero Energy Buildings
Net Zero Energy Communities
EPA Office of Brownfields and Land Revitalization
Office of Sustainable Communities (formally the Office of Smart Growth)
Power Purchase Agreement
Photovoltaics
Structured Insultated Panels
South Lincoln Redevelopment Project
Simple Payback Period
Tax Increment Financing
50 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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6.6 NREL Report and Analysis
South Lincoln Redevelopment District Systems Analysis Report
National Renewable Energy Laboratory
February?, 2011
Background
Providing heating and cooling for homes and businesses is typically done at the building level, meaning there is one system dedicated specifically to a single
building. However, in many situations it may be economically and environmentally beneficial to provide these services at the community scale, in which case
many buildings are served by one large district system designed for the entire community. The advantages of district systems stem from their larger scale, their
ability to capitalize on load diversity within the community, their reliability and maintainability, the possibility to attain high efficiencies by combining electrical
generation with heating and/or cooling, and the autonomy given to the community concerning the operation of the system and the fuel source it uses. For these
reasons, it has been deemed worthwhile to perform an analysis of district systems for use in the South Lincoln community development in Denver, CO.
The analysis of the potential for district systems involves estimating the hourly heating, cooling, domestic hot water (DHW), and electric loads required by the
community, investigating potential district system technologies to meet those needs, and researching available fuel sources to power such systems. The metrics
used to evaluate the economic and environmental viability of each system are simple payback period (SPP), Net Present Value (NPV), and greenhouse gas (GHG)
reductions.
Energy Sources
The source of energy used in buildings and district systems affects the economics, environmental impact, and feasibility of any proposed project. Several options
are discussed here to address local availability, economic implications, environmental considerations, and any pros or cons specific to this project.
Utility-Supplied Electricity
The utility grid is ubiquitous as a consistent source of energy and will almost certainly play a part in the South Lincoln redevelopment. Though very attractive
based on its convenience and relatively stable costs, electricity from the local utility carries with it significant environmental impacts.
The electricity costs incurred at the building level are highly dependent on the rate structure imposed by the local utility. Residential rates tend to have a fairly
high electricity consumption ($/kWh) charge, and typically no demand charge ($/kW). Commercial rates in the state of Colorado, on the other hand, typically
have low charges for electricity consumption and significant demand charges. The current rates for the South Lincoln Community are discussed more in the
'Economic Analysis' section of this report.
Because most of the electricity in Colorado is generated by coal-fired power plants, the emissions associated with electricity are high. Of the typical fuel sources
for generating electricity, coal has the most significant GHG emissions. Furthermore, the efficiency of a power plant and its distribution lines is typically around
35%. As a result, one kWh of electricity used in a building requires about three kWh of energy from coal. The CO2 emissions from electricity must take this
multiplying effect into account. More information GHG emissions is provided in the 'Emissions Analysis' section of this report.
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 51
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Natural Gas
Natural gas is the conventional fuel source for heating in the Denver area, but it can also be effectively used for electrical power generation. It is in ready supply
and many of the systems that it can fuel are well-established, off-the-shelf technologies.
Current natural gas rates are relatively low by historical standards. Furthermore, Colorado has some of the lowest natural gas rates in the nation, as can be seen
in Figure 1. The cost of natural gas for the South Lincoln community in the past year averaged to about $0.673/therm. Natural gas prices however, are very
volatile. Figure 2 shows prices tripling between the years 2000 and 2006. Use of natural gas in this project would expose the neighborhood to potentially high
fuel prices in the future.
Burning natural gas releases significantly less CO2 than burning coal. Thus, producing electricity using natural gas will generally show sizeable savings in CO2
emissions. However, like coal, natural gas is a non-renewable resource and it is not a carbon neutral fuel source.
U.S. Residential Natural Gas
Prices by State, 2009 (dollars per
thousand cubic feet)
S8.45-S9.81 • $14.09 -$15.22
$11.97-310.24 • $16.43-$36.37
$12.66-$13.98 O Data unavailable
Figure 1: U.S. Residential Natural Gas Rate
(Source: http://www.eia.doe.gov/energyexplained/index.cfm?page=natuml_gas_prices)
52 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Biomass
Monthly Colorado Price of Natural Gas Sold to Commercial Consumers
!
u
_Q
•o
c
=3
VI
.=
I—
s
Q.
14 "
2000
2005
2010
Source: U.S Energy lrfomat)or AAruw
Figure 2: Historic Natural Gas Rates in Colorado
(Source: http://www. eia. doe. gov/dnav/ng/hist/n3020us3M.htm)
Biomass fuel is produced from organic materials such as plants, agricultural residues, forestry by-products, and municipal or industrial wastes. In the Denver
area, the most viable biomass options for the purposes of the South Lincoln community are coarse-ground wood, wood chips, and wood pellets. The primary
source for all three of these is beetle-killed pine, but standard forest thinning, forest fire mitigation, and urban wood waste can provide sources for these fuels as
well. Beetle killed pine is a plentiful biomass source and is projected to be a stable resource for decades (Source: Chris Gaul, NREL biomass plant operator).
Figure 3 shows the forest residue biomass resource in and around Denver. The Denver area currently has a handful of biomass suppliers which could be relied
upon for a consistent fuel supply.
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 53
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_=
HP I
~B
M-
S?
©
!r*. vm
-I (BJ Qg)
Figure 3: Forest Residue Resource (shown in light green) in the Denver Area
(Source: http://rpm.nrel.gov/biopower/biopower/launch)
Wood pellets are the most expensive of these options, followed by wood chips and then coarse-ground wood. Table 1 gives approximate current costs for each
of these fuels. The primary driver for cost is the amount of processing required. Consequently, the most consistent and easiest to use fuels are also the most
expensive options. While coarse-ground wood is attractive from a cost standpoint, any equipment chosen must be capable of processing the relatively larger and
less consistent wood pieces.
Table 1: Approximate Costs of Biomass Fuels
(Source: Chris Gaul, NREL biomass plant operator)
Biomass Fuel Type
Pellets
Wood Chips
Ground Wood2.3
Approximate Cost ($/MMbtu)
12.2
4.4
2.3
In contrast to natural gas and other fossil fuels, biomass is a renewable fuel source. It is also generally considered to be 'carbon neutral', meaning the fuel has no
net CO2 emissions. This is because the organism that the fuel is derived from absorbs approximately the same amount of CO2 while it is living as it will release
during combustion or decomposition. Assuming that the resource is being replaced at the same rate as it is being consumed, the rates of CO2 emission and
absorption will be approximately equal, resulting in near net zero carbon emissions. However, the transportation used energy to move the fuel from the source
to the point of use results in a minor carbon emission. This is not accounted for in this analysis.
54 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Solar
Colorado has a particularly abundant solar resource. As seen in Figure 4, only the southwest has a better solar resource in the continental U.S. There are
generally few overcast days in Colorado and the higher elevation reduces the amount of solar radiation lost while filtering through the atmosphere. A benefit of
using the sun for power is that there is no monetary or environmental cost associated with fuel use throughout the life of the system.
Photovoltaic Solar Resource
United States
Figure 4: U.S. Solar Resource
(Source: http://www. nrel. gov/gis/solar.html)
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 55
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Community Energy Requirements
In order to investigate potential district systems, it is vital to predict the hourly heating, cooling, DHW, and electric energy load and demand for the South Lincoln
community once redevelopment is complete. Heating, cooling, DHW, and electrical load refers to the total annual energy needed by the community for space
heating and cooling of the buildings, hot water for domestic use, and electricity used in the buildings. For the purposes of this analysis the electric load includes
all building level uses except for those associated directly with heating and cooling. This includes lighting, plug loads, and HVAC fans and pumps. Estimating the
load of the community allows a prediction of the amount of fuel expected to be used in a typical year. Load is expressed in units of energy, such as kWh or MWh.
Heating, cooling, DHW, and electric demand refers to the amount of heating, cooling, DHW, or electricity needed by the community at any one instant in time.
Peak demand is the maximum demand experienced on an hourly basis for the entire year. For instance, peak heating demand would be determined by the
amount of heating required to meet the needs of the community on the coldest night of the year. Demand is expressed as a rate of energy production such as
kW or Btu/hr. Estimating the maximum demand of the community allows a prediction of how large a district system has to be so that it is capable of keeping up
with the community's needs during periods of peak demand.
To estimate the energy requirements of the proposed community, building energy models were created to simulate the expected energy usage of each type of
building in the community. These simulations predict hourly energy load and demand for each building type. Simulation results were scaled up to represent the
usage of the entire community.
All of the building areas on the campus were represented with three models: One of the high-rise residential spaces (1099 Osage), one of the low and mid-rise
flats, and one of the townhouse units. The Table 2 gives details of these models; information on floor area by space use, number of residential units, and number
of bedrooms for the campus was taken from the Block-by-Block Analysis from DHA.
56 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Table 2: Building Energy Model Details
Model
A
B
C
Number of Number of Bedrooms per Unit
Residential
Space Use SF Units One Two Three Four
High Rise Flats
(1099 Osage)
Townhouses
(Stand-alone
and Modular)
Low & Mid Rise
Flats
(3-6 stories)
Retail
Community
Lobby
Other
Totals
97,000
183,400
657,731 SF
residential units
+
144,500 SF
circulation/
support
24,700
25,000
10,850
5,000
1,003,681
100
109
680
-
-
-
-
889
70
4
439
-
-
-
-
513
30
16
241
-
-
-
-
287
0
76
0
-
-
-
-
76
0
13
0
-
-
-
-
13
Total
Bdrms
130
316
921
-
-
-
-
1,367
Model Description
Model was completed for Phase 1 of redevelopment.
One model of a strip of two-story townhouses with 8
units @ 1,683 SF each with 23 total bedrooms
(occupants). 8 is the average length of a strip of units
shown in drawings; this will let us model ratio of end
units/ interior units accurately. This model accurately
represents the building SF, number of residential units,
and number of bedrooms.
All of this building area is represented with one model.
The model consists of a 'mid-rise' with 5 stories of flats
above a ground level of retail, community, and lobby
space. Each residential level contains 20 residential
units (& 27 bedrooms) configured in an 'L' shape
around a central corridor: 19,350 SF of residential +
4,250 SF corridor/circulation (18% of floor plan
assumed) = 23,600 SF footprint. The ground level
consists of 3,630 SF of retail space, 3,680 SF of
community space, 1,600 SF of lobby space, and 735 SF
of 'other' space to make the multiplier consistent.
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Figure 5: High Rise Building Energy Model 3D View and Floor Plan
Figure 6: Mid Rise Building Energy Model 3D View and Floor Plan
58 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Figure 7: Townhouse Building Energy Model 3D View and Floor Plan
The results of the models indicate that electricity and space heating are the largest community loads, each requiring approximately 5000 MWh/yr. Cooling and
domestic hot water require approximately 2500 MWh/yr apiece. Figure 8 compares these annual loads.
6000
Annual Load Totals
Electricity
I Space Heating
I Space Cooling
I Domestic Hot Water
Figure 8: Predicted Annual Energy Load Requirements
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Space heating and domestic hot water are often lumped together as one thermal load when served by a tri-generation, cogeneration, or district heating system.
Table 2 shows the annual energy requirements of the site when space heating and domestic hot water are considered together. As can be seen, heating/DHW is
the dominant load. Table 3 gives the peak demand for each of these three loads. Again, heating/DHW is dominant. Figure 9 shows the load profiles over the
course of a typical year.
Table 2: Predicted Annual Energy Load Requirements
Annual Energy Requirements (MWh)
Electricity
5446
Heating (including DHW)
7582
Space Cooling
2491
Table 3: Predicted Peak Energy Demand
Peak Demand (kW)
Electricity
994
Heating (including DHW)
4,636
Space Cooling
1,839
South Lincoln Annual Demand Profiles
8000
Electric Load
•Heating Load
(including
DHW)
•Cooling Load
Figure 9: Predicted Annual Energy Demand Profiles
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Economic and Emissions Assumptions
Economic Analysis
An economic analysis was performed that follows the federal life cycle costing requirements developed by the National Institute of Standards and Technology
(MIST), using federal guidelines for discount rate, electricity escalation rate, and fuel escalation rates. The discount rates for 2010 are valid from April 1, 2010 to
March 31, 2011.
The appropriate escalation rates from the Energy Escalation Rate Calculator were applied to natural gas and electricity rates. The values given in the Energy
Escalation Rate Calculator are based on projections from the Energy Information Administration. The escalation rates were calculated assuming the project came
online in 2012 and had an overall lifetime of 25 years.
The electricity and natural gas rates for this analysis were calculated based on a sampling of energy bills for the existing South Lincoln community. DMA typically
uses a commercial utility rate structure for its larger buildings and a residential utility rate for its smaller units. Because the South Lincoln redevelopment is
expected to have buildings on both structures, average rates were calculated to apply to the entire site. Table 4 lists the parameters used for all energy use and
economic analyses.
Table 4: Economic Parameters Used in This Analysis
Parameters Used in Economic Analysis
Project Lifetime
Real Discount Rate
Electricity Escalation Rate
Natural Gas Escalation Rate
Blended Residential Electricity Rate
Commercial Electricity Rate (Energy only)
Summer Commercial Electricity Demand Rate
Winter Commercial Electricity Demand Rate
Natural Gas Rate
25yrs
3%
0.50%
0.40%
0.104 $/kWh
0.033 $/kWh
20.24$/kW
27.24$/kW
0.673 $/therm
A Federal Investment Tax Credit (ITC) is available for photovoltaics, solar hot water, biomass, cogeneration and tri-generation, and ground-source heat pump
installations. For photovoltaics, solar hot water, and systems powered by fuel cells, the credit is worth 30% of the initial cost of the system. For ground-source
heat pumps, biomass, and cogeneration or tri-generation systems not powered by fuel cells, the credit is worth 10% of the initial cost of the system. Results for
cases including these incentives as well as cases without the incentives are given for each analysis in this report.
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Green House Gas Emissions
Electricity emissions data were taken directly from the U.S. Energy Information Administration's publication of Colorado's electricity profile. Natural gas
emissions data are from the EPA's Climate Leaders program. Table 5 summarizes this data. Notice that CO2 is by far the dominant GHG emission for both
electricity and natural gas. Note also that the emissions associated with utility-supplied electricity are nearly 5 times greater than those from natural gas. This
fact plays a major role in the final results of this analysis.
Table 5: Greenhouse Gas Emissions of Electricity and Natural Gas
Energy Source
Electricity (Generated in Colorado)
Natural Gas
Emission Compound
Carbon Dioxide
Methane
Nitrogen Oxide
Carbon Dioxide
Methane
Nitrogen Oxide
Equivalent CO2 Emissions (Ibs/MWh)
1,883
0.0228
0.02875
399
0.0376
0.0008
(Sources:
Electricity: US Energy Information Administration, 2008 Colorado Electricity Profile Statistics, http://www.eia.doe.gov/cneaf/electricity/st_profiles/colorado.html;
Natural Gas: Natural Gas Emissions Data, Environmental Protection Agency, http://www.epa.gov/climateleaders/documents/resources/comm_boiler_proto.pdf)
District Systems Analysis
Base Case
It is necessary to create a base case for the community in order to generate a baseline energy usage profile for the South Lincoln community. This baseline is
used as the starting point for each energy, economic, and emissions analysis. It is important to note that the base case chosen has a large impact on the analysis
results.
The base case used here assumes that heating is supplied by natural gas boilers with an overall thermal efficiency of 85%. Cooling is assumed to be provided by
chillers with an overall coefficient of performance (COP) of 3.1. Table 6 gives the efficiencies and total costs assumed. Electricity is assumed to be provided by
the local utility. These efficiencies were applied to the energy requirements predicted by the building energy models to determine the baseline energy usage of
the community. The annual energy costs and GHG emissions were based on this baseline energy usage. Figure 10 shows the annual energy usage profile for the
base case. Figure 11 shows the annual GHG emissions profile for this case. Note the disproportionate role that electrical energy usage, including that used for
cooling, plays in the overall emissions profile.
62 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Table 6: Base Case Heating and Cooling Efficiencies and Total Costs
Parameter
Overall Boiler Efficiency
Total Boiler Costs
Overall A/C Efficiency
Total A/C Costs
Value
85%
$491,129
3.1 (COP)
$2,581,907
Base Case Annual Energy Usage Profiles
8000
Electricity
•Heating
(Including
DHW)
•Cooling
Figure 10: Predicted Annual Base Case Energy Usage Profiles
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Base Case Annual GHG Emissions Profiles
Electricity
•Heating
(Including
DHW)
•Cooling
8000
Figure 11: Predicted Annual Base Case GHG Emissions Profiles
District Heating
Clean district heating can be achieved using a central biomass boiler. The heat from a central plant can be applied to both space heating and domestic hot water.
Figure 12: Central Biomass Heating Plant on the NREL Campus
(Source: NREL Pix Photo Library)
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A central biomass plant will require infrastructure such as a building to house the boiler and the fuel. A road must be built to allow easy access for fuel delivery
trucks. Furthermore, a natural gas fueled back-up system should be installed. This significantly increases the upfront cost as well as the simple payback of such a
system. A central biomass plant will also typically require an operator much of the time, resulting in high operation and maintenance costs and further increasing
the payback period of the system.
Because a district biomass system will require the delivery of large volumes of fuel on a regular basis, the site must be prepared for this increased traffic. An
initial analysis was performed to determine the approximate number of tractor-trailer loads of wood chips required per week to meet the South Lincoln
community's heating and DHW loads. During the peak heating season, it was found that about 6 tractor-trailer loads per week would be sufficient. During other
times of the year, the number of loads needed would be less. Table 7 shows the results of this analysis.
Table 7: Approximate Quantities of Wood Chip Fuel Required for Heating and DHW
(MMBtu/month)
(Ib/month)
(Trailerloads/month)
(Trailerloads/week)
Base load
Heating
Month
938
137,940
3
1
Average
Heating
Month
3,423
503,372
11
3
Peak
Heating
Month
6,971
1,025,118
23
6
The analysis for a central system using biomass fuel was performed for three system sizes based on the heating demand of the community. An optimal system
size was determined based on simple payback period. Note that, although the system sizes range from 80% to 30% of the community's maximum demand, the
percent of annual heating energy needs met by each system only vary from about 100% to 80%. This is because the community heating demand only rarely
reaches levels close to its peak demand. The majority of heating energy needed by the community occurs during times when the demand is at a small fraction of
the peak. Thus, smaller systems are capable of meeting these needs most of the time. Wood chips were assumed to be the fuel used for the entire analysis.
Table 8 gives the results of this analysis.
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Table 8: Analysis Results for District Heating with Biomass
Biomass District Heat (Wood Chip Boiler)
Percent Heating
and DHW
Capacity
80%
80% (with 10%
ITC*)
40%
40% (with 10%
ITC*)
30%
(lowest spp)
30%
(lowest spp with
10% ITC*)
Initial Cost ($)
$3,399,489
$3,048,395
$1,831,518
$1,637,221
$1,439,525
$1,284,428
Annual Cost
Savings ($)
$16,976
$16,976
$16,429
$16,429
$13,734
$13,734
SPP (yrs)
200.3
179.6
111.5
99.7
104.8
93.5
NPV ($)
-$3,103,881
-$2,752,786
-$1,545,443
-$1,351,146
-$1,200,373
-$1,045,275
Percent Total
Heating and DHW
Supplied
99.8%
99.8%
91.4%
91.4%
81.8%
81.8%
Percent Total CO2
Equivalent Saved
23%
23%
21%
21%
19%
19%
Initial Investment per
Ton CO2 Equivalent
Saved ($/Ton)
$2,101
$1,884
$1,238
$1,106
$1,085
$968
*Federal Investment Tax Credit. See the 'Economic Analysis'section of this report
Cogeneration
Cogeneration refers to a system which performs two functions simultaneously. The most common cogeneration system is combined heat and power (CHP), in
which the waste heat created during electricity generation is used to meet space heating, domestic hot water, or industrial needs. All systems analyzed here are
CHP systems. The main benefit of cogeneration is that waste heat can be recovered and made useful, greatly increasing to total efficiency of the system. Figure
13 shows a diagram of a CHP system.
Cooling/Heating
Figure 13: Schematic of a Cogeneration or Tri-generation Plant
(Source: http://www. epa. gov/chp/basic/index.html)
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A cogeneration plant can be driven by gas turbines, Internal Combustion (1C) engines, or fuel cells. For the South Lincoln site, natural gas is the most appropriate
fuel for all of these technologies.
The size, or capacity, of a system can have a high impact on its economic viability. If a system is too large then it will likely produce more thermal energy or
electricity than the community can consume at a given time. This results in wasted energy and money. However, smaller systems suffer from economies of scale.
This is because the upfront cost of the distribution system will be virtually the same for large and small cogeneration plants. This cost becomes significant in
relation to the smaller savings seen with smaller systems. For these reasons, each technology is analyzed based on three different capacities: A larger size which
is projected to meet most of the community's thermal loads, a smaller size based on the lower size limits of most technologies, and an optimal size based on the
simple payback analysis. Note that the optimal size based on simple payback may be smaller than is commonly available.
The monetary and environmental savings seen with cogeneration systems are mostly tied to the production of electricity. This is because electricity from the
utility tends to be fairly expensive and is primarily generated using a high-emissions fuel such as coal. Thus, the efficiency with which a cogeneration system can
produce electricity is very important. Overall efficiencies, which include the useful thermal energy produced, are generally of secondary importance. A summary
of the efficiencies and upfront costs used in this analysis is given in Table 9.
Table 9: Efficiency and Cost Assumptions Used in this Analysis
Electrical Efficiency
Thermal Efficiency
Overall Efficiency
Cost ($/kWelec)
(CoGeneration)
Cost ($/kWelec)
(TriGeneration)
Gas
Turbine
28%
47%
75%
$2,500
$3,550
1C Engine
35%
35%
70%
$1,500
$2,020
Fuel Cell
45%
20%
65%
$5,000
$5,320
Gas Turbine: A gas turbine uses the combustion of a gaseous fuel, such as natural gas, to drive a high pressure flow of air through a turbine. The turbine then
generates electricity.
The primary advantage of a gas turbine is its high overall efficiency. Of the three technologies considered, the gas turbine will generally have the highest
efficiency when considering both electricity and useful thermal energy. However, gas turbines have relatively low efficiencies when considering only electric
production at smaller capacities (less than 5 MW). This is a severe disadvantage. Furthermore, gas turbines have fairly high upfront costs at smaller capacities.
The analysis results for cogeneration using a natural gas turbine are given in Table 10.
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Table 10: Analysis Results for Gas Turbine Cogeneration
Cogeneration (Gas Turbine)
Capacity
(kWelec/
kWtherm)
800/1310
800/1310
(with 10%
ITC*)
250 / 409
250 / 409
(with 10%
ITC*)
150 / 246
(lowest
spp)
150 / 246
(lowest
spp with
10% ITC*)
Initial
Cost($)
$2,263,5
47
$2,026,0
47
$888,547
$788,547
$638,547
$563,547
Annual
Cost
Savings ($)
-$24,969
-$24,969
$10,454
$10,454
$8,929
$8,929
SPP
(yrs)
85.0
75.4
71.5
63.1
NPV ($)
$2,636,0
44
$2,398,5
44
$673,33
9
$573,33
9
$461,16
0
$386,16
0
Percent Total
Electricity Supplied
74%
74%
23%
23%
14%
14%
Percent Total
Heating and DHW
Supplied
66%
66%
29%
29%
19%
19%
Percent Total CO2
Equivalent Saved
20%
20%
8%
8%
5%
5%
Initial Investment per Ton
CO2 Equivalent Saved
($/Ton)
$1,617
$1,447
$1,528
$1,356
$1,726
$1,523
*'Federal Investment Tax Credit. See the 'Economic Analysis' section of this report
1C Engine: Internal combustion refers to the method in which electricity is generated by the system. An 1C technology relies on the combustion of a fuel such as
natural gas to power an engine or generator. Although the fuel is combusted, an 1C engine uses a different thermodynamic cycle than a gas turbine. Internal
combustion is a common and well established technology with well understood maintenance and performance issues.
The two main advantages of the internal combustion engine are its relatively low initial cost and high electrical efficiency. Furthermore, this technology tends to
have the lowest operation and maintenance costs of the three technologies considered. The analysis results for Cogeneration using a natural gas 1C engine are
given in Table 11.
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Table 11: Analysis Results for 1C Cogeneration
Cogeneration (Internal Combustion)
Capacity
(kWelec/
kWtherm)
800 / 800
800 / 800
(with 10%
ITC*)
250/250
250/250
(with 10%
ITC*)
300/300
(lowest
spp)
300/300
(lowest
spp with
10% ITC*)
Initial
Cost ($)
$1,463,5
48
$1,306,0
48
$638,548
$563,548
$713,548
$631,048
Annual
Cost
Savings ($)
$28,174
$28,174
$18,954
$18,954
$21,579
$21,579
SPP
(yrs)
51.9
46.4
33.7
29.7
33.1
29.2
NPV ($)
$847,89
5
$690,39
5
$261,80
4
$186,80
4
$282,62
7
$200,12
7
Percent Total
Electricity Supplied
89%
89%
28%
28%
33%
33%
Percent Total
Heating and DHW
Supplied
51%
51%
21%
21%
24%
24%
Percent Total CO2
Equivalent Saved
28%
28%
10%
10%
12%
12%
Initial Investment per Ton
CO2 Equivalent Saved ($/Ton)
$758
$677
$934
$825
$880
$778
*'Federal Investment Tax Credit. See the 'Economic Analysis' section of this report
Fuel Cell: A fuel cell utilizes an electrochemical cycle to produce electricity. The mechanism used to produce power is similar to that for a typical battery, but a
fuel cell uses an open cycle in which the fuel can be continuously supplied. Fuel cells can use hydrocarbon fuels such as natural gas, but the fuel is not burned as
in an 1C generator or gas turbine.
Fuel cells generally have the highest electrical efficiencies of the technologies considered. However, they typically have the highest upfront cost as well. Overall
efficiencies are on par with 1C engines. The analysis results for Cogeneration using a natural gas fuel cell are given in Table 12.
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 69
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Table 12: Analysis Results for Fuel Cell Cogeneration
Cogeneration (Fuel Cell)
Capacity
(kWelec/
kWtherm)
800 / 358
800 / 358
(with 30%
ITC*)
250/112
250/112
(with 30%
ITC*)
600 / 269
(lowest
spp)
700/311
(lowest
spp with
30% ITC*)
Initial
Cost($)
$4,238,5
48
$3,063,5
48
$1,488,5
48
$1,138,5
48
$3,238,5
48
$2,713,5
48
Annual
Cost
Savings ($)
$90,250
$90,250
$29,978
$29,978
$69,532
$69,532
SPP
(yrs)
47.0
34.0
49.7
38.0
46.6
33.9
NPV ($)
$2,521,
175
-
$1,346,
175
$919,62
4
-
$569,62
4
-
$1,917,
016
$1,190,
616
Percent Total
Electricity Supplied
84%
84%
26%
26%
63%
63%
Percent Total
Heating and DHW
Supplied
26%
26%
9%
9%
21%
21%
Percent Total CO2
Equivalent Saved
37%
37%
12%
12%
28%
33%
Initial Investment per Ton
CO2 Equivalent Saved ($/Ton)
$1,629
$1,177
$1,799
$1,376
$1,405
$1,177
*Federal Investment Tax Credit. See the 'Economic Analysis'section of this report
Tri-generation
A tri-generation plant provides electricity, heating, and cooling. The cooling from a tri-generation plant is typically provided by an absorption chiller, which
utilizes heat as its energy source rather than electricity. A tri-generation system will typically be able to use more waste heat than a Cogeneration system, but the
upfront costs will be higher.
Similar to Cogeneration, a tri-generation plant can be driven by gas turbines, 1C engines, or fuel cells. Again, natural gas is the most appropriate fuel for all of
these technologies.
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Like cogeneration, system size and efficiency of electricity production have a large effect on the economics of a given installation. However, tri-generation
systems have a greater ability to use the thermal energy provided by a system. Furthermore, when a tri-generation system is using thermal energy to provide
cooling, it is effectively replacing the electricity that would otherwise have been used for that purpose. Thus, larger system sizes become more feasible.
The same advantages and disadvantages listed above for gas turbines, 1C engines, and fuel cells apply when these technologies are used for tri-generation.
Tables 13, 14, and 15 give the results of the analysis for each technology.
Table 13: Analysis Results for Gas Turbine Tri-generation
Tri-generation (Gas Turbine)
Capacity
(kWelec/
kWtherm)
800/1310
800/1310
(with 10%
ITC*)
250 / 409
250 / 409
(with 10%
ITC*)
200/328
(optimal)
200/328
(lowest
spp with
10% ITC*)
Initial
Cost($)
$3,103,5
47
$2,782,0
47
$1,151,0
47
$1,024,7
97
$973,547
$865,047
Annual
Cost
Savings ($)
-$1,555
-$1,555
$13,861
$13,861
$12,331
$12,331
SPP
(yrs)
—
83.0
73.9
79.0
70.2
NPV ($)
$3,046,
196
-
$2,724,
696
$873,27
5
-
$747,02
5
$728,90
8
-
$620,40
8
Percent Total
Electricity Supplied
83%
83%
24%
24%
19%
19%
Percent Total
Heating and DHW
Supplied
66%
66%
29%
29%
24%
24%
Percent Total CO2
Equivalent Saved
27%
27%
9%
9%
8%
8%
Initial Investment per Ton CO2
Equivalent Saved ($/Ton)
$1,638
$1,468
$1,761
$1,568
$1,858
$1,651
*Federal Investment Tax Credit. See the 'Economic Analysis'section of this report
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Table 14: Analysis Results for 1C Tri-generation
Tri-generation (Internal Combustion)
Capacity
(kWelec/
kWtherm)
800 / 800
800 / 800
(with 10%
ITC*)
250/250
250/250
(with 10%
ITC*)
350/350
(lowest
spp)
350/350
(lowest
spp with
10% ITC*)
Initial
Cost ($)
$1,879,5
48
$1,680,4
48
$768,548
$680,548
$970,548
$862,348
Annual
Cost
Savings
($)
$42,908
$42,908
$20,370
$20,370
$26,666
$26,666
SPP
(yrs)
43.8
39.2
37.7
33.4
36.4
32.3
NPV ($)
$993,39
7
-
$794,29
7
$365,80
6
-
$277,80
6
-
$440,14
1
-
$331,94
1
Percent Total
Electricity Supplied
95%
95%
28%
28%
40%
40%
Percent Total
Heating and DHW
Supplied
51%
51%
21%
21%
28%
28%
Percent Total CO2
Equivalent Saved
32%
32%
10%
10%
14%
14%
Initial Investment per Ton
CO2 Equivalent Saved ($/Ton)
$838
$750
$1,077
$954
$973
$865
*Federal Investment Tax Credit. See the 'Economic Analysis'section of this report
72 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Table 15: Analysis Results for Fuel Cell Tri-generation
Tri-generation (Fuel Cell)
Capacity
(kWelec/
kWtherm)
800 / 358
800 / 358
(with 30%
ITC*)
250/112
250/112
(with 30%
ITC*)
700/313
(lowest
spp)
850 / 378
(lowest
spp with
30% ITC*)
Initial
Cost($)
$4,494,5
48
$3,242,7
48
$1,568,5
48
$1,194,5
48
$3,962,5
48
$3,428,9
48
Annual
Cost
Savings ($)
$93,205
$93,205
$30,231
$30,231
$82,269
$98,586
SPP
(yrs)
48.2
34.8
51.9
39.5
48.2
34.8
NPV ($)
$2,722,
930
-
$1,471,
130
$994,99
3
-
$620,99
3
$2,399,
469
-
$1,554,
614
Percent Total
Electricity Supplied
86%
86%
26%
26%
75%
75%
Percent Total
Heating and DHW
Supplied
26%
26%
9%
9%
24%
24%
Percent Tola 1 CO2
Equivalent Saved
38%
38%
12%
12%
33%
41%
Initial Investment per Ton CO2
Equivalent Saved ($/Ton)
$1,687
$1,217
$1,884
$1,435
$1,400
$1,211
*'Federal Investment Tax Credit. See the 'Economic Analysis' section of this report
District Ground Source Heat Pump
A Ground Source Heat Pump (GSHP) uses the stable temperatures of the ground or ground water to extract heating or cooling for space conditioning. It pulls
heat out of the ground when in heating mode, and dumps heat into the ground when in cooling mode. GSHPs typically have high efficiencies for both heating
and cooling, and use electricity as the only fuel source. Closed loop GSHP systems circulate a fluid through tubes which are buried in the ground, typically in
holes drilled 100 to 500 feet deep. Open loop GSHP systems exchange heat directly with ground water by pumping it through the above-ground heat pump and
then discharging the water back down to the water table from which it came. See Figure 14 for schematics of closed and open loop systems. GSHPs are
sometimes referred to as geothermal heat pumps; the two terms are synonymous.
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 73
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In order to accurately assess the thermal potential of the soil at a project site, test boreholes have to be drilled and thermal testing performed. This was done for
Phase 1 of the South Lincoln redevelopment, and the results may be able to be used for the rest of the site. Also, boreholes were drilled to determine the
structural characteristics of the subsurface for the high rise project at 1099 Osage, and it was found that groundwater can be reached at about 25 ft below
grade. This relatively easily accessible groundwater may make an open loop GSHP system a viable option for heating and cooling. Local laws on groundwater use
could prevent this as a possibility, however.
Closed Loop Systems
Vertical
Open Loop Systems
Figure 14: Closed Loop and Open Loop GSHP Systems
(Source: h ttp://www.energysavers.gov/your_home/space_heating_cooling/index.cfm/mytopic=12650)
GSHP systems are most effective when the heating and cooling needs of the community are well balanced over the course of a year. This allows the ground to
'recharge' and avoid a slow increase or decrease in soil temperature over time. The South Lincoln site presents a challenge in that the heating needs of the
community are far greater than the cooling needs.
Although GSHP systems are highly efficient, the fact that they use electricity as the fuel source for both heating and cooling can often result in marginal
greenhouse gas reductions. While CO2 emissions are typically reduced when the heat pump is being used for cooling, in heating mode the emissions can actually
increase. This is due to the fact that, in the absence of a GSHP, heating is typically provided using natural gas as the fuel. Because the emissions associated with
electricity are so much higher than those for natural gas, heating with electricity, even at the high efficiencies seen from GSHPs, will often result in increased CO2
emissions. Because South Lincoln will require significantly more heating than cooling, the net greenhouse gas savings from using a district GSHP will be marginal.
The results from the district GSHP analysis are given in Table 16.
74 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Table 16: Analysis Results for a District Ground-Source Heat Pump
District Ground-Source Heat Pump
Percent Heating and
Cooling Loads Met
100%
100% (with 10% ITC*)
Initial Cost ($)
$5,904,672
$5,006,901
Annual $ Savings
$70,945
$70,945
SPP (yrs)
83.2
70.6
NPV ($)
-$4,642,113
-$3,744,342
Percent Total CO2
Equivalent Saved
4%
4%
Initial Investment per Ton
CO2 Equivalent Saved
($/Ton)
$22,282
$18,894
*'Federal Investment Tax Credit. See the 'Economic Analysis' section of this report
Photovoltaics
Photovoltaic (PV) systems use only sunlight as a fuel source and produce only electricity. A residential community rooftop PV installation is shown in Figure 15. PV is
a well-established and reliable source of electricity which tends to have fairly high upfront costs and low operation and maintenance costs. However, installed costs
for photovoltaics have dropped dramatically in the last decade, and the trend is continuing. Table 17 gives approximate values for current costs based on actual
installations. Successful implementation of PV at South Lincoln will require thoughtful design of rooftops and parking areas to maximize solar access.
Figure 15: Rooftop Solar PV Installation at the Solar Siedlung in Freiburg, Germany
Table 17: Approximate Current Costs of PV
System Type
Standard Efficiency Panels
High Efficiency Panels
Carport System
Approximate Cost ($/W)
5
5.25
6.50
(Source: Xcel Energy Solar Rewards Program http://www.xcelenergy.com/Colorado/Residential/RenewableEnergy/Solar_Rewards/Pages/home.aspx)
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In addition to federal and state incentive programs, utility incentives for installing PV systems play an important role in a system's economic viability. The
available incentives from Xcel Energy's Solar Rewards Program depend on the size of the system. The program offers a rebate of $2/W with a maximum rebate
of $200,000. In addition, for systems between 10 kW and 500 kW, the system owner will receive a production credit of 2.5 cents for every kWh produced over a
20 year period. For systems above 500 kW, the incentives are the same except that the amount of the production credit is determined through an RFP process.
There are a number of possible models for funding PV installations. For this analysis, it is assumed that DMA will purchase and own the system. In this scenario,
DMA could take advantage of Xcel Energy's Solar Rewards incentive program as well as the 30% ITC on the upfront cost of the system.
As an alternative to purchasing the PV system, the site could host the system under a third-party power purchase agreement (PPA) structure. In this structure, a
private entity (or entities) installs, operates, maintains, and owns the PV system installed on the site property. The site would sign a PPA and commit to
purchasing electricity from this third party for a fixed amount of time - usually 10 to 25 years. The PPA could include a price escalator that will increase the cost
of the electricity at a fixed rate each year over the life of the contract - this rate is usually between 0% - 4%.
The contract would be set up such that the DMA would sign a 20-year contract with the third party, and the third party would in-turn sell the electricity to the
site. DMA would have the option to "buy out" the PPA and become the system owner at any point after year 6. The third party would benefit from the 30%
federal investment tax credit as well as any state and utility incentives. The impact of these tax benefits and incentives is a reduction in the installed cost of the
PV system which will translate into competitive electricity rates for DMA.
This PV analysis investigates two primary scenarios: One in which all suitable rooftop area is used for PV and carports are built for the purpose of mounting solar
panels, and one in which only the suitable rooftop area is used. Each of these options was investigated for both 15% efficient panels and 19% efficient panels.
Furthermore, analyses were done to investigate the effect of installing the photovoltaics as one large project versus multiple smaller projects. The advantage to
dividing the installations into several smaller projects comes from the ability to enter a lower tier in the Solar Rewards Program and to take greater advantage of
the program's upfront rebates. The results of the analysis are given in Table 18.
76 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Table 18: Analysis Results for PV Systems
Photovoltaics
Project
Description
Efficiency
Percent Electric
Load Met
Initial Cost
($)
Annual Cost
Savings ($)
SPP (yrs)
NPV ($)
Percent Total CO2
Equivalent Saved
Initial Investment per Ton CO2
Equivalent Saved ($/Ton)
Rooftop and Carport Systems (252,455 ft2)
One Large
System
One Large
System (w/
30% ITC*)
8 Smaller
Systems
8 Smaller
Systems
(w/ 30%
ITC*)
One Large
System
One Large
System (w/
30% ITC*)
8 Smaller
Systems
8 Smaller
Systems
(w/ 30%
ITC*)
15%
15%
15%
15%
19%
19%
19%
19%
93%
93%
93%
93%
113%
113%
113%
113%
$19,343,324
$13,492,114
$18,343,324
$12,092,114
$24,635,993
$17,185,195
$23,235,993
$15,800,817
330,949
$330,949
330,949
$330,949
405,154
$405,154
405,154
$405,154
67.7
47.2
64.2
42.3
70.4
49.1
66.4
45.2
-$14,837,727
-$8,986,800
-$13,837,727
-$7,586,800
-$19,120,053
-$11,669,255
-$17,720,053
-$10,284,877
62%
62%
62%
62%
76%
76%
76%
76%
$4,466
$3,115
$4,235
$2,792
$4,647
$3,241
$4,383
$2,980
Rooftop Systems Only (188,848 ft2)
One Large
System
One Large
System (w/
30% ITC*)
15%
15%
69%
69%
$13,386,714
$9,318,904
247,566
$247,566
62.7
43.6
-$10,019,400
-$5,948,721
46%
46%
$4,132
$2,876
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Photovoltaics
Project
Description
6 Smaller
Systems
6 Smaller
Systems
(w/ 30%
ITC*)
One Large
System
One Large
System (w/
30% ITC*)
6 Smaller
Systems
6 Smaller
Systems
(w/ 30%
ITC*)
Efficiency
15%
15%
19%
19%
19%
19%
Percent Electric
Load Met
69%
69%
85%
85%
85%
85%
Initial Cost
($)
$12,386,714
$8,318,904
$17,326,870
$12,068,809
$16,326,870
$11,068,809
Annual Cost
Savings ($)
247,566
$247,566
303,074
$303,074
303,074
$303,074
SPP (yrs)
58.0
38.9
66.2
46.1
62.4
42.3
NPV ($)
-$9,019,400
-$4,948,721
-$13,200,692
-$7,942,631
-$12,200,692
-$6,942,631
Percent Total CO2
Equivalent Saved
46%
46%
57%
57%
57%
57%
Initial Investment per Ton CO2
Equivalent Saved ($/Ton)
$3,823
$2,568
$4,369
$3,043
$4,117
$2,791
*Federal Investment Tax Credit. See the 'Economic Analysis'section of this report
Solar Hot Water
Solar hot water (SHW) systems are designed to produce useful thermal energy using only the sun as the energy source. An auxiliary heat source is typically
needed for a consistent supply of hot water for domestic use. An SHW system requires rooftop space to mount the solar collectors, as does a PV system. Thus,
any area which is used for SHW cannot be used for PV, and vice versa. An analysis was done to determine the optimal mix of SHW and PV under the assumption
that all viable rooftop area with solar access would be utilized. Figure 16 shows the total energy production and greenhouse gas reduction of every combination
of systems, from 100% of the roof being covered with PV (on the left of graph) to 100% of the roof being used for SHW (on the right of the graph). It was found
that using 100% PV and 0% SHW gave the highest net present value and the highest greenhouse gas savings. However, the economics of these technologies are
highly dependent on incentives and methods of funding.
78 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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SolOpt Simulation Results
—SHWEnei'sv
/ X /
System Size Percent Allocation
Figure 16: Rooftop PV/SHW Optimization Results based on Greenhouse Gas Reduction
As a SHW system increases in size, its overall effectiveness generally diminishes because it begins producing more hot water than the building can use at certain
times in the year. For this reason, SHW systems are typically sized to meet 70%-80% of the total domestic hot water load for the building they are serving. An
energy and economic analysis was performed assuming a SHW system sized to meet 80% of the South Lincoln community's annual domestic hot water load. This
system would require about 90% of the total roof area deemed suitable for solar panels. The results of this analysis are given in Table 19.
Table 19: Analysis Results for a Solar Hot Water System
Solar Hot Water
Percent DHW
Load Met
80%
80% (with 30%
ITC*)
Initial Cost ($)
$10,647,000
$7,452,900
Annual Cost Savings ($)
$83,949
$83,949
SPP (yrs)
126.8
88.8
NPV ($)
-$12,265,323
-$8,196,679
Percent Tola ICO2
Equivalent Saved
6%
6%
Initial Investment per Ton CO2
Equivalent Saved ($/Ton)
$26,354
$18,448
*Federal Investment Tax Credit. See the 'Economic Analysis'section of this report
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 79
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Conclusions and Recommendations
Table 20 summarizes
and feasibility of size.
the results for selected systems from each of the technologies analyzed. The results shown here were selected based on simple payback
While all results are not reported in this table, it gives a representative comparison of the various district systems.
Table 20: Summary of Analysis Results for Selected District Systems (all results shown include the ITC)
Selected Results Summary (All Results Include the ITC)
Technology
Size
SPP (yrs)
NPV ($)
Percent Tola 1 CO2
Equivalent Saved
Initial Investment per Ton CO2 Equivalent
Saved ($/Ton)
Cogeneration
NG Gas Turbine
1C Engine
Fuel Cell
250 / 409
300/300
700/311
75.4
29.2
33.9
-$573,339
-$200,127
-$1,190,616
8%
12%
33%
$1,356
$778
$1,177
Trigeneration
NG Gas Turbine
1C Engine
Fuel Cell
250 / 409
350/350
850 / 378
73.9
32.3
34.8
-$747,025
-$331,941
-$1,554,614
9%
14%
41%
$1,568
$865
$1,211
District GSHP
GSHP
100% of Load
70.6
-$3,744,342
4%
$18,894
Biomass District Heat
Wood Chip Boiler
40% of Heating Demand
99.7
-$1,351,146
21%
$1,106
Photovoltaics
Solar Panels (19%
efficient; Rooftops
and Carports)
Solar Panels (15%
efficient; Rooftops
Only)
252,455 ft2 (as multiple
smaller systems)
188,848 ft2 (as multiple
smaller systems)
45.2
38.9
$10,284,877
$4,948,721
76%
46%
$2,980
$2,568
Solar Hot Water
Flat Plate Panels
80% of DHW Load
88.8
$12,265,323
6%
$18,448
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Although none of the district systems investigated for this analysis show favorable economics, some options may well make sense as integral parts of the final
solution. However, it is highly recommended that other measures be maximized before implementing any district system. Specifically, it is vital that electrical
loads, heating and DHW loads, and cooling loads in the community are reduced as much as possible. Electrical loads can be reduced by a combination of building
system design (high efficiency pumps and fans, timers on bathroom vents, daylighting design), appliance efficiency standards, occupant education, and any
number of occupant incentives. Heating loads can be reduced primarily by building design, including insulation levels and window specifications. DHW loads can
be reduced by educating the occupants and using low-flow fixtures.
Perhaps the greatest improvements in the baseline energy use can be found in the reduction of cooling energy use. The Denver climate is ideal for natural
ventilation, direct cooling with outdoor air, night-time pre-cooling, and evaporative cooling. It is conceivable that these technologies could virtually eliminate
conventional cooling methods in the South Lincoln community and significantly reduce the electricity used for cooling.
In regards to district systems for this community, the most drastic reductions in GHG emissions will best be achieved using a combination of PV for electricity and
biomass for heating and domestic hot water. If cooling and other electrical loads are reduced based on the recommendations above, it may be possible for the
community to reach net zero GHG emissions by installing 19% efficient solar panels on rooftops and carports and installing a biomass heating system sized to
40% of peak heating and DHW demand. In this scenario, heating and DHW will require some natural gas input. However, with the reductions in cooling and
other electrical energy, the PV system is projected to produce enough of a surplus of electrical power to offset the greenhouse gas emissions from the site's
natural gas usage. Although the economics of buying and owning a PV system may be prohibitive, entering into a PPA could make such a system viable.
An alternative to the scenario above is to install PV to offset electricity, concentrate on reducing heating/DHW loads, and utilize high-efficiency natural gas
systems at the building level in lieu of a central biomass plant. While the community is not expected to reach net zero GHG emissions in this scenario, emissions
savings of about 80% or higher are achievable. Furthermore, upfront costs as well as operations and maintenance costs will be significantly lower. This approach
would be much simpler and less costly to design and implement phase by phase, with a relatively small loss of environmental benefit. Considering both
economics and environmental benefits, this may be the most reasonable option for South Lincoln.
A third possibility would be to use a cogeneration or tri-generation plant driven by an 1C engine or a fuel cell to provide a portion of the community's heating and
electricity needs. These systems show the most attractive economics of any of the systems analyzed. It would be possible to supplement a cogeneration plant
with PV as a path to net zero emissions. However, implementation of a cogeneration or tri-generation strategy will require more planning and ongoing
operations and maintenance effort by DHA than a PV strategy. Furthermore, while a PV system can be installed under a PPA, a cogeneration plant would require
the consent of the utility for such an arrangement. Because the utility has little incentive to agree to this type of arrangement, a PPA for a cogeneration plant is
very unlikely.
Neither solar hot water systems nor a district ground source heat pump system is recommended for this project. Both of these systems show poor economics
and minimal savings in GHG emissions. While some tri-generation systems show comparatively good economics and GHG reductions, these systems are not
recommended because the initial recommendation to reduce cooling loads and cooling energy use would make district cooling unnecessary. Also, the same
issues listed above for cogeneration systems apply equally to tri-generation systems.
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Appendix 1: Analysis Assumptions and Sources
Economic Parameters:
Parameter
Project Lifetime
Real Discount Rate
Electricity Escalation Rate
Natural Gas Escalation Rate
Blended Residential Electricity Rate (Energy)
Residential Electric Demand Rate
Commercial Electricity Rate
Commercial Summer Electric Demand Rate
Commercial Winter Electric Demand Rate
Natural Gas Rate
Value
25yrs
3%
0.50%
0.40%
0.104($/kWh)
0.00 ($/kW)
0.033 ($/kWh)
20.24 ($/kW)
17.24 ($/kW)
0.673 ($/therm)
Source
FEMP discount rate (valid from April 1, 2010 to
March 31, 2011)
Energy Escalation Rate Calculator
Energy Escalation Rate Calculator
Sampling of South Lincoln Utility Bills (2010)
Sampling of South Lincoln Utility Bills (2010)
Xcel Energy
Xcel Energy
Xcel Energy
Sampling of South Lincoln Utility Bills (2010)
Greenhouse Gas Emissions:
Energy Source
Electricity (Generated in
Colorado)
Natural Gas
Emission Compound
Carbon Dioxide
Methane
Nitrogen Oxide
Carbon Dioxide
Methane
Nitrogen Oxide
Equivalent CO2 Emissions
1,883 (Ibs/MWh)
0.0228 (Ibs/MWh)
0.02875 (Ibs/MWh)
53.06 (kg/MMbtu)
0.005 (kg/MMbtu)
0.0001 (kg/MMbtu)
Source
US Energy Information Administration (1)
US Energy Information Administration (1)
US Energy Information Administration (1)
Environmental Protection Agency (2)
Environmental Protection Agency (2)
Environmental Protection Agency (2)
Sources:
1. Electricity: US Energy Information Administration, 2008 Colorado Electricity Profile Statistics, http://www.eia.doe.gov/cneaf/electricity/st profiles/Colorado, htm I
2. Natural Gas: Natural Gas Emissions Data, Environmental Protection Agency, http://www.epa.gov/climateleaders/documents/resources/comm boiler proto.pdf
Base Case:
Parameter
Overall Boiler Efficiency
Boiler Costs
Overall A/C Efficiency
A/C Costs
Value
85%
20.7($/MBTUH)
3.1 (COP)
3291 ($/ton)
Source
Based on ASHRAE Standard 90.1
R.S. Means
Based on ASHRAE Standard 90.1
R.S. Means
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Distribution System (for all applicable district systems):
Parameter
Length of Piping Needed
Installed Piping Costs
Value
5000 (ft)
75 ($/ft) (based on 5" Pipe)
Source
Estimated based on site map
Based on a study at Oregon Institute of Technology (1)
Sources:
1. Selected Cost Considerations for Geothermal District Heating in Existing Single-Family Residential Areas, Kevin Rafferty, Jun-96 - http://geoheat.oit.edu/pdf/tp93.pdf
Cogeneration and Tri-generation Systems:
Parameter
Value
Source
Gas Turbine
Overall Efficiency
Electrical Efficiency
Thermal Efficiency
Altitude Derate
Installed Cost (Cogen)
Installed Cost (Trigen)
O&M Cost
Investment Tax Credit
75%
28.4%
46.6%
80% of rated capacity
2500 ($/kWe)
3550 ($/kWe)
0.008 ($/kWh)
10% of Initial Cost
Product Data, RETScreen Database
Product Data, RETScreen Database
Product Data, RETScreen Database
EPA estimates (1)
EPA estimates, manufacturer quotes (2)
EPA estimates, manufacturer quotes (2)
Manufacturer recommendation
DSIRE Database
1C Engine
Overall Efficiency
Electrical Efficiency
Thermal Efficiency
Altitude Derate
Installed Cost (Cogen)
Installed Cost (Trigen)
O&M Cost
Investment Tax Credit
70%
35%
35%
80% of rated capacity
1500 ($/kWe)
2020 ($/kWe)
0.009 ($/kWh)
10% of Initial Cost
Product Data, RETScreen Database
Product Data, RETScreen Database
Product Data, RETScreen Database
EPA estimates (1)
EPA estimates, manufacturer quotes (2)
EPA estimates, manufacturer quotes (2)
Manufacturer recommendation
DSIRE Database
Fuel Cell
Overall Efficiency
Electrical Efficiency
Thermal Efficiency
Altitude Derate
Installed Cost (Cogen)
Installed Cost (Trigen)
O&M Cost
Investment Tax Credit
65%
45%
20%
80%
5000 ($/kWe)
5320 ($/kWe)
0.02 ($/kWh)
30% of Initial Cost
Product Data, RETScreen Database
Product Data, RETScreen Database
Product Data, RETScreen Database
EPA estimates (1)
EPA estimates, manufacturer quotes (2)
EPA estimates, manufacturer quotes (2)
Manufacturer recommendation
DSIRE Database
Sources:
1. EPA Catalog ofCHP Technologies, US Environmental Protection Agency, http://www.epa.gov/chp/basic/catalog.html
2. Catalog ofCHP Technologies, Environmental Protection Agency Combined Heat and Power Partnership, December 2008, http://www.epa.gov/chp/
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 83
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Bio mass District Heating:
Parameter
Fuel Energy Content
Fuel Moisture Content
Fuel Density
Tractor Trailer Volume
Boiler Efficiency
Distribution Losses
Woodchip Fuel Cost
Installed Cost
O&M Cost
Cost of Auxiliary Natural Gas Boiler
Investment Tax Credit
Value
8500 Btu/dry Ib
20%
12.6 (Ib/ft3)
130 (cubic yards)
75%
5%
4.44 ($/MMbtu)
248 ($/Mbtu/hr)
1.19 ($/Mbtu/hr)
16 ($/MBTUH)
10% of Initial Cost
Source
NREL biomass plant operator (Chris Gaul)
NREL biomass plant operator (Chris Gaul)
NREL biomass plant operator (Chris Gaul)
NREL biomass plant operator (Chris Gaul)
NREL biomass plant operator (Chris Gaul)
NREL biomass plant operator (Chris Gaul)
Manufacturer quotes, construction estimates
(Randy Hunsberger, NREL)
Calculated labor and maintenance estimates
(Randy Hunsberger, NREL)
R.S. Means
DSIRE Database
District Ground Source Heat Pump:
Parameter
Installed Cost
Overall System Efficiencies
Investment Tax Credit
Value
568 ($/Mbtu/hr)
Source
Final installed cost for 1099 Osage GSHP
Calculated based on 1099 Osage Model
30% of Initial Cost
DSIRE Database
Photovoltaics:
Parameter
Installed Cost (15% efficient)
Installed Cost (19% efficient)
Installed Cost (Carport Installation)
O&M Cost
Xcel Energy Production Incentive (lOkW to SOOkW systems)
Xcel Energy Rebate
Investment Tax Credit
Panel Efficiencies
Value
5 (S/W)
5.25 ($/W)
6.50 ($/W)
12.50 ($/kW)
0.025 ($/kWh)
2 ($/W) ($200,000 cap)
30% of Initial Cost
15% and 19%
Source
Approximated based on real installation data
Approximated based on real installation data
Approximated based on real installation data
Xcel Energy Solar Rewards Program (1)
Xcel Energy Solar Rewards Program (1)
DSIRE Database (2)
Approximated based on product data
Sources:
1. Xcel Energy Solar Rewards Program, http://www.xcelenergy.com/Colorado/Residential/RenewableEnergy/Solar Rewards/Pages/home.aspx
2. Federal Investment Tax Credit, http://www.dsireusa.org/incentives/incentive.cfm7lncentive Code=US02F&re=l&ee=l
84 Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO
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Solar Hot Water:
Parameter
Installed Cost
O&M Cost
Investment Tax Credit
Value
90 ($/ft2)
1% of Installed Cost ($/yr)
30% of Initial Cost
Source
Approximated based on real installation data
DSIRE Database
Partnership for Sustainable Communities EPA Brownfield Pilot - Denver, CO 85
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