PB88-239090
ALTERNATIVE ENERGY SOURCES FOR
WASTEWATER TREATMENT PLANTS
Roy F. Western, Incorporated
West Chester, PA
Aug 88
U.S. DEPARTMENT OF COMMERCE
National Technical Information Service
••
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PB8B-2390yO
EPA/600/2-88/043
August 1988
ALTERNATIVE ENERGY SOURCES
FOR
WASTEWATER TREATMENT PLANTS
by
Roy F. Weston, Inc.
Desi riners-Consul tants
West Chester, Pennsylvania 1?OQ0
Contract No.
Project Officer
Francis L. Evans
K'astewater Research Division
Water Engineering Research Laboratory
Cincinnati, OMo
WATER ENGINEERING RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
. REPORT NO.
EPA/600/2-88/043
4. TITLE AND SUBTITLE
Alternative Energy Sources for Wastewater Treatment
Plants
4T'S ACCESSION NO.
- J J l ENDED TERMS
c. COSATI Field/Croup
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThuReport)
Unclassified
21. NO. OF PAGES
2O. SECURITY CLASS fThtt page)
Unclassified
22. PRICE
A&7
EPA Form 2220-1 (9-73)
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DISCLAIMER
This material has been funded wholly or in part hv the United States
Environmental Protection Agency under contract number fiB-n^-3n«;«; to Roy. F.
'•leston, Inc. It has been subject to the Agency's review, and it has been
approved for publication as an EPA document. Mention of trade names or
commercial products does not constitrute endorsement or recommendation for use.
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FOREWORD
The U.S. Environmental Protection Agency is charged by Congress with
protecting the Nation's land, air, and water systems. Under a mandate of
national environmental laws, the Agency strives to formulate and implement
actions leading to a compatible balance between human activities and the
ability of natural systems to support and nurture life. The Clean Water Act,
the Safe Drinking Water Act, and the Toxics Substances Control Act are three
of the major congressional laws that provide the framework for restoring and
maintaining the integrity of our Nation's water, for preserving and enhancing
the water we drink, and for protecting the environment from toxic substances.
These laws direct the EPA to perform research to define our environmental
problems, measure the impacts, and search for solutions.
The Water Engineering Laboratory is that component of EPA's research and
development program concerned with preventing, treating, and managing munici-
pal and industrial wastewater discharges; with establishing practices to
control and remove contaminants from drinking water and to prevent its deteri-
oration during storage and distribution; and with assessing the nature and
controllability of releases of toxic substances to the air, water, and land
from manufacturing processes and subsequent product use. This publication is
one of the products of that research and provides a vital communication link
between the researcher and the user community.
This document discusses the applicability and economic feasibility of
various technologies that can make use of alternative energy sources to reduce
reliance on conventional energy sources for municipal wastewater treatment
facilities.
Francis T. Mayo, Director
Water Engineering Research Laboratory
m
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ABSTRACT
This technology assessment provides an introduction to the use of several
alternative energy sources at wastewater treatment plants. This document
assumes that the reader has little or no knowledge of the technologies
presented. The report contains fact sheets (technical descriptions) and data
sheets (cost and design information) for the technologies. Cost figures and
schematic diagrams of the technologies are included. Case histories of seven
treatment plants that have used one or more of the alternative technologies
are presented.
Based on this assessment the following alternative energy technologies
appear to be potentially cost effective:
1. Heat pumps which use influent or effuent wastewater, as an
alternative to distilled oil, residual oil, and natural gas for
supplying process or building heat.
2. Geothermal direct-use systems for satisfying large energy loads
(greater than 10^ kJ/d) when the geothermal temperature gradient is
45°C/km or greater, and sufficient geothermal well flows exist.
3. 'Jind power systems for satisfying electrical loads greater than 1,000
kWh/d, when the annual wind flux is approximately 4,000 KWh/m^-yr
or greater.
4. Passive solar systems where they can be cost-effectively integrated
into the overall architectural design of a facility.
•5. Low-head hydro systems may be appropriate for smaller plants which
have an available head greater than three meters.
This report was submitted in fulfillment of Contract No. 68-03-3055 by Roy
F. Weston, Inc., under the sponsorship of the U.S. Environmental Protection
Agency. This report covers the period of October 1981 to August 1983, and the
work was completed as of August 19*??.
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CONTENTS
Foreword i i i
Abstract iv
Fi gures vi
Tab! es vi i i
Fact Sheets x
Data Sheets xi
Acknowl edgment xii
1. Introduction 1
2. Conclusions ">
3. Conventional Energy Requirements in POTW's 5
4. Technical Descriptions 13
5. Case Histories 7p
General 7fi
Wilton, Maine--Active solar for process heat, passive
sol ar, heat pumps 77
Lake Tapos Sewerage Project (Bonney Lake, Washington^ --
Low-head hydro nS
Newport, Vermont--Active solar for process heat op
Hillshorough, New Hampshire—Passive solar inn
Livingston, Montana—Wind Power in?
Southtown Sewage Treatment Center (Woodlawn, New York^--
WinH Power iin
Waynesburg-Magnolia, Ohio—Photovoltaic IT*
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FIGURES
Number Page
1. Heat pump coefficient of performance ............ 17
2. Heat pump schematic diagram ................. 18
3. Water-to-water/water-to-air heat pump costs ......... ?0
4. Air-to-air heat pump costs ................. 21
5. Typical air flat-plate solar energy collection system .... 2*
6. Typical liquid flat-plate solar energy collection system . . ?4
7. Solar insolation — Total horizontal annual average day values 77
8. Simplified block diagram of the photovoltaic electrical system 3fl
9. Typical geothermal direct use system ............ 33
10. Geothermal gradient map of the conterminous United States . . 34
11. Applications versus source temperature range of geothermal
water and steam ..................... 37
12. Typical well and wellhead heat exchange installed capital
cost for geothermal well ................. ^8
13. Total installed capital cost for geothermal wellhead pump . . 3°
14. Small WECS with storage ................... A?
15. Distribution of favorable wind regimes over the contiguous
48 states and offshore areas ............... 44
16. Total installed capital cost of wind power systems as a
function of peak power output ............... 45
17. Low-head hydroelectric system ................ ^8
18. Total installed capital cost of low- head hydro power .... 50
19. Typical Tromhe wall design ................ 53
20. Typical solar roof pond system .............. 54
VI
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21. Heat pipe augmented water wall concpot ........... *>*>
??. Thermic diode solar panel .................. 56
?3. Typical thermosiphon air panel collector .......... ^7
24. Typical geothermal steam power generating system ...... fin
?.*>, Schematic diagram of a fuel cell .............. F3
2fi. Point-focus central receiver/Rankine (PFCR/R^ system flow
schematic drawing .................... fiP
?7. Two-axis tracking heliostat (PFCR)
2R. Low concentration nontracking (LCMT) system flow schematic
drawing .......................... R7
?9. Low concentration nontracking (LCNT> collector module ... 67
TO. Conceptual energy flow diagram for VJilton, Maine ...... 7°
31. Estimated/actual energy production for VJilton, Maine--
active solar ....................... 34
3?. Estimated/actual energy production for Wilton, Maine —
passive solar ....................... PS
33. Estimated/actual energy production for Wilton, Maine — heat pump 9?
34. Schematic diagram of Lake Taops Sewerage Project (Bonney
Lake, Washington) ..................... o"7
35. Control system flow diagram for Newport, Vermont
vii
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TABLES
NUMBER Page
1. Estimated total energy budget for municipal wastewater
treatment pi ants fi
?. Electrical energy consumption for municipal wastewater
treatment pi ants 7
3. Energy prices and escalation rates (United States average^ . 10
4. Information needed to size the various alternative enerqy
systems 14
5. Active solar specification data and design criteria for
Wilton, Maine 81
6. Net active solar contribution for Wilton, Maine P3
7. Energy and cost-effectiveness summary—Active solar for
process heat for Wilton, Maine Rfi
8. Net estimated passive solar contribution for Wilton, Maine . 87
9. Energy and cost-effectiveness summary—passive solar system
for Wilton, Maine 8°
10. Heat pump specification data for Wilton, Maine °0
11. Heat pump sumnary for Wilton, Maine °3
12. Energy and cost-effectiveness summary—Heat pumn for Wilton,
Maine 9A
13. Selected design criteria for active solar system for digester
heating at Newnort, Vermont ................ in?
14. Preliminary cost estimates for Newport, Vermont ....... T03
IB. Estimated annual electrical energy requirements for
Newport, Vermont ..................... m4
16. Estimated annual costs of electrical energy for Newport, Vermont
17. Estimated first year O^M costs for Newport, Vermont ..... 106
VI 1 1
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18. Total net energy for passive solar system—Hillsborough,
New Hampshire 107
19. Cost-effectiveness analysis for Southtown Sewage Treatment
Center Ill
20. Wastewater treatment plant costs for Wayneshurg-Magnolia,
Ohio—Innovative design US
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FACT SHEETS
Number Page
1. Heat Pumps 15
2. Active solar systems for heating and cooling 2?
3. Photovoltaic systems 2P
4. Geothermal direct use systems v?
5. Wind power systems 40
6. Within plant low-head hydro systems ifi
?. Passive solar systems 51
8. Geothermal power systems K8
9. Fuel Cells 61
10. Active solar systems for power generation 54
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DATA SHEETS
Number Page
1. Heat Pumps 19
2. Active solar systems for heating and cooling 25
3. Photovoltaic systems 3]
A. Geothermal direct use systems 3S
5. Wind power systems A3
fi. Within plant low-head hydro systems 4°
xi
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Region I
Region II
Region III
Region IV
Region V
Region VI
Region VII
ACKNOWLEDGMENT
REGIONAL AND STATE I/A COORDINATORS CONTACTED
Jim Lord, U.S. EPA
Charles King, Maine
Robert Cruess, New Hampshire
William Brierly, Vermont
Bruce Kiselica, U.S. EPA
Joseph Tuttle, New York
Lee Murphy, U.S. EPA
John Harkins, U.S. EPA
Charles Pycha, U.S. EPA
Gregory Binder, Ohio
Ancil Jones, U.S. EPA
Mario Nuncio, U.S. EPA
xii
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Region VIII
Joel Webster, U.S. EPA
James Boyter, Montana
Region IX
Tinito Caratini, U.S. EPA
Region X
Norm Sieverson, U.S. EPA
Gary Rothwell, Washington
xm
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SECTION 1
INTRODUCTION
This technology assessment provides an introduction to the use of several
alternative energy sources at wastewater treatment plants. The report assumes
that the reader has little or no knowledge of the technologies presented.
Section 2 of the report presents the conclusions reached by the technology
assessment. Section 3 contains brief general discussions of energy
requirements at wastewater treatment plants, and other energy use
considerations.
Section 4 contains fact sheets (technical descriptions) and data sheets
(cost and design information) for the technologies. Cost figures and
schematic drawings of the technologies are in this section. Data collection
for the report was done in 1985?, therefore, the costs presented should only be
used to gauge the relative costs of the various technologies. Current cost
information should be obtained from equipment vendors or other current sources
for actual cost estimating.
Section 5 presents the case histories of seven treatment plants that have
used one or more of the alternative technologies discussed.
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SECTION 2
CONCLUSIONS
HEAT PUMPS
Heat pumps are commercially available. The temperature of the alternative
energy source is the principal potential technical limitation on the
application of these systems in POTW's; however, the use of the wastewater
itself as the alternative energy source minimizes the impact of this
limitation. The use of influent or effluent wastewater heat pumps is
generally cost-effective in comparison to distilled oil, residual oil, and
natural gas for supplying process or building heat to the POTW.
ACTIVE SOLAR HEATING AND COOLING SYSTEMS
Active solar heating and cooling systems are commercially available. The
available solar insolation rate and system cost are the principal limitations
on the application of these systems in POTW's. Active solar heating and
cooling systems are not cost-effective alternatives to the use of conventional
energy supplies in POTW's due to the high capital investment.
PHOTOVOLTAIC SYSTEMS
Photovoltaic systems are cornmercially available. The available solar
insolation rate, system energy conversion efficiency, and system cost are the
principal limitations on the application of these systems in POTW's. Because
of the high initial capital investment photovoltaic systems are not
cost-effective alternatives to the use of conventional electrical energy
supplies in POTW's.
GEOTHERMAL — DIRECT USE SYSTEMS
Geothermal direct use systems are commercially available. Geographical
limitations, associated with the geothermal temperature gradient and available
well flow, as well as site investigation and well construction costs, are the
principal limitations on the application of these systems in POTW's.
Geothermal direct use systems appear to be cost-effective in comparison with
the use of conventional fuels for satisfying thermal energy loads greater than
108 kJ/d when the geothermal temperature gradient is approximately 45°C/km
or greater, and when well flows are of a sufficient magnitude. Locations with
geothermal gradients in excess of 45°C/km are predominantly limited to the
Rocky Mountain states.
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WIND POWER SYSTEMS
Wind power systems are commercially available. Geographical limitations,
associated with the available wind flux regimes, as well as overall system
costs, are the principal limitations on the application of these systems.
Wind power systems appear to be cost-effective in comparison with the use of
conventional fuels for satisfying energy loads greater than 1,000 kWh/d, when
the annual wind flux is approximately 4,000 kWh/yr-m^ or greater.
Locations with annual wind flux greater than 4,000 kWh/yr-m? are
predominantly limited to areas in the following states:
0 Maine ° Colorado
0 Vermont ° Wyoming
0 New Hampshire ° Montana
0 New York ° Idaho
o Virginia ° Utah
0 North Carolina ° Nevada
0 Kansas ° Washington
0 Oklahoma ° California
LOW-HEAD HYDRO SYSTEMS
Low-head hydro systems are commercially availahle. Geographical
limitations, associated with the available head for these systems, and the
fraction of the total POTW energy requirements satisfied, are the principal
limitations on the application of these systems in POTW's. From the
standpoint of satisfying a significant portion of a POTW's electrical
requirement, these systems appear to be more appropriate for smaller POTH's.
The use of these systems should be seriously considered in any application
that has an available head greater than 3 m.
PASSIVE SOLAR SYSTEMS
Passive solar systems are commercially available. These systems have been
used previously to reduce the consumption of conventional heating fuels in
POTW's, as well as many other architectural applications. The principal
technical limitations of passive solar systems are possible site-specific
limitations on available solar insolation, and the integration of the passive
system into the overall architectural plan. Potential economic limitations
are primarily associated with the incremental costs for construction of the
passive solar system, instead of a conventional architectural design. These
incremental costs must be considered, along with the amount of alternative
energy supplied, on a case-by-case basis to potentially justify the use of a
passive solar system in specific applications. In light of the rising costs
for Conventional fuels, these systems should be seriously considered in future
construction at POTW's throughout the United States.
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GEOTHERMAL — POWER SYSTEMS
Geothermal power systems are commercially available. However, current
technological limitations on minimum system size, as well as the limited
availability of acceptable sites exhibiting the necessary geothermal
characteristics, will likely prevent the use of these systems in POTW's.
FUEL CELLS
Fuel cells are not expected to be commercially available until
approximately the year 2000.
ACTIVE SOLAR SYSTEMS FOR POWER GENERATION
Active solar systems for power generation are not expected to be
commercially available until the mid 1990's. In addition, these systems can
only use direct sunlight, and, therefore, their applications would be
primarily limited to arid regions of the southwest.
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SECTION ?
CONVENTIONAL ENERGY REQUIREMENTS IN POTVJ's
In order to evaluate the usefulness of "alternative energy sources" in
meeting the demand for energy in publicly owned treatment wo^s (POTW's^, it
is necessary to understand the energy retirements for these v;astewater
treatment facilities. The purpose of this section is to characterize typical
energy requirements. The factors included in this analysis of energy
requirements in POTW's include:
1. The types and amounts of energy required by treatment facilities.
2. The extent of daily, seasonal, and yearly variations in these energy
requirements.
3. The geographic and local availaMlitv of the sources of conventional
energy.
TYPES AMD AMOUNTS OF ENERGY REQUIRED
The energy requirements of POTW's have been discussed in a variety of
places in the literature. For example, two comprehensive sources of
information are reports (1, 2^ published ^y EPA on the total energy
consumption for municipal wastewater treatment.
In addition, estimates of the primary energy requirements for over 1nO
different municipal wastewater treatment plant operations have been published.
(?) Likewise, summaries and detailed estimates of the numbers of these unit
operations in existence today and forecasted for the future fyear ?nw\ t are
available in the EPA Meeds Survey. (3)
Table 1 presents estimates of the total energy budget for three sizes of
municipal wastewater treatment plants. T^e energy requirements in this table
are expressed in terms of kWh/?,78F m^/d (kl-lh/mgd). For the treatment plant
as a whole, these estimates range from n.A^p HJh/m''-d f\^^ kWh/mgd^ to
0.390 kWh/m^-d (1*77 H-Jh/mgd>. The greatest demand for energy at a POTH is
for electrical energy. For the type of POTVJ's s^own, the demand for
electrical energy represents fiO to 7o percent of the total energy demand of
the facility. However, this percentage can change significantly Depending on
the types of unit operation and method of sludge disposal.
The information presented in Table ° breaks down the estimated electrical
energy consumption into the energy requirements for snecific unit onerations.
As shown in Table ?, the greatest consumption of electrical energv is
associated with the aeration equipment for secondary treatment of the
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wastev/ater. In order of descending magnitude, this Demand is follov/ed by that
for influent (and trickling filter recycle) pumoing, anaerobic Digestion
mixing, and then other less significant demands.
TABLE 1. ESTIMATED TOTAL ENERGY BUDGET FOR MUNICIPAL WASTEVIATER TREATMENT
PLANTS*
Item
IS0* rnVd
(1 mgdl
(1 n mqd^
( 100 mgd ^
Electrical energy 1,1™
Chemicals ISP MO?) 1*8
Digester heating !«P (10?) i^P Ml*) !«P
(supplementary fuel)
Building heat 1*8 (in*) K.P ra*,} ofi
Sludge hauling ?0 M*)
Sludge incineration °?0 MS?)
Total energy consumption !
* In terms of ^ilowatt-hours per ^,78* m-^ 'million gallons^ of wastewater
treated. Estimates are based on activated sludge plants with anaerobic
digestion. SI udqe disposal is by incineration in the JJ7^p.Rn mVd Mn
mgt4) and 378,^00 m-/d MOP mgd) sizes, and by haul inn dewatered si udqe
64 km (^n miles) one-way to land spreading at the 1,73^ m^/d M mgd)
size. Heat energv has been converted to electrical energy by assuming
that 1 kWh is equivalent to 11,in" kj.
Source: Reference 1, p.4.
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TABLE ?. ELECTRICAL ENERGY CONSUMPTION FOR MUNICIPAL MASTEWATER
TREATMENT PLANTS
Process Energy consumption, kl-lh/d
I1 mgd) fin mgd) '(inn
Preliminary treatment
Bar screens l.1^ 1.5? in.7
Comminutors 15.1 *1 ?nA
Grit removal I."7 '.A ?.A
Influent Dumping (°m, 30ft TDH) i^1 ^ ,A51 i?,(
Primary sedimentation
(I? m-Vm2- d, inn nad/dft9> 30.6 12? ;
Trickling filters
Recirculation pumping (Qr/Q = ^.0)133 1,740 15,'
Final sedimentation ^0.6 1??
Activated sludge process
Diffused air fAEF* = cr) W. 5
Mechanical aeration O.^P. kg Oo/ An/! /I
MJ CMS Oo/hp-hr)
Recirculation pumping (50*,, 5.1* m, AR
17.5 ft TDH^
'33 m?/m? • d, POO qal/d/ft?) 3n.P
Chi ori nation 1.70+
Sludge handling and disposal
Sludge pumping ?.P5
Gravity thickeners 10.? °n.A An.
Air flotation thickeners
Anaerobic digesters
Mixing 106 ??4 1,12?
Heating 17.fi ]??.* 7PR
Vacuum filtration 57 'Afi
Mul tipie-hearth incineration w °AS
Lights and miscellaneous power 57 '10 ?,Aon
AEF - Aeration efficiency in percent for diffused air and KqO-9/MJ Mh
0?/hp-hr) for mechanical aeration.
+ Energy requirements approximately the same for Ann- and
chlorination units.
Note: KWh/d x 3.6 = MJ/D*
Source: Reference A, p. IR.
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DAILY, SEASONAL, AND YEARLY VARIATIONS IN ENERGY REQUIREMENTS
Among the demands for electrical energy, the greatest demands are
associated with influent/recycle pumping, and secondary aeration equipment.
For this reason, the factors which influence periodic variations in energy
requirements, i.e., hourly, daily, seasonal, or yearly, are those factors
which influence either the organic or hydraulic loading on the facility.
Variation of the Organic Loading
Among the factors which influence the organic loading on a facility are:
1. Variations in the magnitude of the industrial contribution of organic
wastes to the POTW, for example:
a. Variations due to shift changes in industrial or commercial
operations, and clean-up activities — a daily effect.
b. Response to market demands, e.g., fruit canning operations after
the harvest season — a seasonal effect.
c. Industrial growth within the service area — a yearly trend.
2. Treatment of periodic, high strength sidestreams generated within the
POTW itself, e.g., from solids-handling equipment — an hourly,
daily, or weekly effect.
3. Septage disposal at the treatment plant — a daily or seasonal effect.
4. Temperature variations due to seasonal weather changes, resulting in
either poorer performance of the oxygen transfer equipment (a sunrner
effect), or increased recycle and mixing to compensate for reduced
kinetic performance (a winter effect).
The Water Pollution Control Federation Manual of Practice No. 8 (5)
provides a discussion of the variations in wastewater characteristics.
Variation of the Hydraulic Loading
Among the factors which influence the hydraulic loading on a POTW are:
1. The diurnal variation typically associated with the generation of
domestic wastewater.
2. Variations in the amount of industrial wastewater discharged to the
facility^or example:
a. Process and clean-up wastewaters generated on a batchwise or
semi-continuous basis — a daily effect.
b. Sources of noncontact cooling water — a seasonal or yearly
effect.
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3. SiHestreams, generated on an intermittent basis, within the POTVJ,
such as from solids dewatering or filter backwash — a daily or
weekly effect.
4. Excessive inflow or infiltration associated with the sewerage svstem
— daily, seasonal, or yearly effect.
Manual of Practice Mo. ° (fi) provides a discussion of the variations in
sanitary wastewater flow.
GEOGRAPHIC AMD LOCAL AVAILABILITY OF CONVENTIOMAL POWER SOURCES
The most convenient way to evaluate thp geographic and local availability
of conventional power sources is to analyze thp costs of providing that
power. A variety of periodical reference sources are available which provide
estimates of the current prices of conventional power on a regional basis
throughout the United States. Two of these sources are:
1. Federal Register publications and updates of in CFR Part
"Federal Energy Management and Planning Programs; Methodology and
Procedures for Life Cycle Cost Analyses" (average fuel costs^. f\
This publication is undated on an approximately annual basis.
?.. Energy User News, (R^ a weekly newspaper by Fairchild Publications of
Mew York City.
The variations in the orices for natural gas, electricity, and Mo. "> fuel
oil for eight metropolitan areas scattered throughout the U.S. have
estimated (R) as follows:
1. Natural gas — $?.^7 to /i.n«Vinfi kj
?. Electricity — $n.O??R to
3. No. ' fuel oil — $0.2*" to
These prices are based on May l°Rl Collars.
Estimates (7) of the average U.S. prices and escalation rates for various
fuels are presented in Table "*. These estimates are also expressed in
mid-ln31 dollars, and have hepn broken down for various sectors of the
economy. Also included in this table are Department of Energy 'DOE) forecasts
of the prices in mid-lnRS, mid-i°°n, and mid-1nn5. it should he noted that,
in addition to these countrywide average estimates, this publication (~M also
provides similar estimates for each of the 10 DOE regions.
REDUCING ENERGY COSTS
The reason for considering alternative energy sources is usually to reduce
energy costs. Two items which greatly affpct energy costs are electrical rate
structures and energy conservation. A detailed discussion of these topics is
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TABLE 3. ENERGY PRICES_AND ESCALATION RATES
(UNITED STATES AVERAGE)
Current: and
projected
energy
Mid-1981
prices (in
base-year
mid-1981 dollars)
198S 1990
Fuel type
(Dollars per
sales unit) *
(Dol-
lars
Per
106
Btu)
(dol-
lars
P«r
106
Btu)
(dol-
lars
Per
106
Btu)
Mid-
1995
(dol-
lars
P*r
10«
Btu)
Residential sector
Electricity
Distillate
L?G
Natural gas
0
1
0
0
.057
.334
.900
.004
(kWh)
(gal)
(gal)
(ft3)
16.74
9.62
9.42
4.42
20.56
10.62
10.41
6.21
20.81
12.05
11.69
6.62
20.
16.
15.
7.
62
25
65
45
Commercial sector
Electricity
Distillate
Residual
Natural gas
Steam coal
0
1
0
0
39
.038
.262
.949
.004
.375
(kWh)
(gal)
(gal)
(ft3j
(ton)
17.10
9.10
6.34
3.98
1.75
21.01
10. OS
8.94
5.59
2.22
21.10
11.47
10.19
6.01
2.42
20.
15.
12.
6.
2.
86
66
29
82
49
Industrial sector
Electricity
Distillate
Residual
Natural gas
Natural gas — MFBI
Steam coal
0
1
Q
Q
0
39
.042
.266
.949
.004
.005
.800
(kWh)
(gal)
(gal)
(ft?)
(ft3)
(ton)
12.32
9.13
6.34
3.52
4.52
1.68
15.13
10.08
8.96
4.94
6.35
2.82
15.58
11.50
10.13
5.12
5.10
3.19
15.
15.
10.
5.
5.
3.
48
69
92
89
83
35
Transportation
Gasoline
1
.622
(gal)
12.97
15.92
17.09
21.
92
Projected energy price
escalation rates
(percentage change
compounded
Mid-
1981-
mid-
1985
5.28
2.51
2.52
8.88
5.28
2.51
8.99
8.85
6.11
5.27
2.51
9.02
8.84
8.89
13.80
5.26
annually)
Mid-
1985-
aid-
1990
0.24
2.55
2.35
1.28
0.09
2.69
2.64
1.46
1.77
0.58
2.66
2.50
0.72
-4.32
2.51
1.42
Mld-
1990-
mid-
1995
and
be-
yond
-0.19
6.16
6.00
2.38
-0.23
6.42
3.82
2.58
0.59
-0.12
6.42
1.52
2.83
2.72
0.96
5.11
•Note that these prices are equivalent to those in the adjacent column (both Cor mid-1981), but
they are stated in different units of energy. Price per sales unit of energy is derived from
price per million Btu by dividing the price by a million and multiplying by the Btu content of a
sales unit of energy, assuming the following Btu content per sales unit of energy: 3,412 Btu/kWh
of electricity; 138,690 Btu/gal of distillate; 95.500 Btu/gal of LPG: 1.016 Btu/ft3 of natural
gas; 149,690 Btu/gal of residual; 22.500,000 Btu/ton of steam coal; and 125.071 Btu/gal of gaso-
line. For example, in DoE Region 1, for electricity. S0.086/kHh - 324.82/1,000,000 Btu x 3,412
Btu/kHh.
Source: Reference 7. p. 56733.
10
-------
beyond the scone of this report but they will be discussed briefly. Many
other sources discuss these items and should be consulted for more information
(l, 2, 3, 9, 10, 11).
Rate Structures
The effect of the electrical rate structure is very significant. Electric
company bills usually include charges for both how much energy is used and
when the energy is used. There are typically different rates for on-peak and
off-peak usage, maximum demand charges which reflect all-time peak energy
usage, ratchet clauses which can escalate minimum demand charges based on
yearly 15 minute peaks, and penalties for low power factors on motors.
Understanding the billing structure of the electric company and the energy
usage profile of the POTW is an essential first step in reducing energy
costs. Energy savings can often be achieved by just changing the schedule of
electrical energy usage rather than reducing the amount of electrical energy
used.
Energy Conservation
Although altering energy scheduling can reduce electrical energy usage,
energy conservation is also an important step in reducing energy costs. f*any
conservation measures have low capital costs and short pay-back periods. Some
conservation techniques require no capital expenditures at all, such as,
improving pump and motor performance through improved maintenance procedures,
running efficient pumps more frequently than inefficient pumps, and oroperly
matching pumping equipment to demand loads. Energy conservation steps should
be considered in any cost-effective analysis that compares conventional and
alternative energy sources.
-------
REFERENCES
1. U.S. Environmental Protection Agency. Total Energy Consumption for
Municipal Hastewater Treatment. EPA-600/2-78/1A9. Municipal
EnvironmentalResearch Laboratory, Cincinnati, Ohio, August 1978.
2. U.S. Environmental Protection Agency. Energy Conservation in Municipal
Wastewater Treatment. EPA-430/P-77-011. Office of Water Program
Operations, Washington, D.C., March 1978.
3. U.S. Environmental Protection Agency. The 1QRO Needs Survey. Tables 40
and 41. EPA-430/9-81-P08. Washington, D.C., 1981.
4. Energy Conservation in the Design and Operation of Wastewater Treatment
Facil itiesTWater Pollution Control Federation Manual of Practice Mo.
FD-2. 1982.
5. Sewage Treatment Plant Design. Water Pollution Control Federal Manual of
Practice No. 8. Lancaster Press Inc., Lancaster, Pennsylvania, 1977.
6. Design and Construction of Sanitary and Storm Sewers. Water Pollution
Control Federation Manual of Practice No. 9.1974.
7. U.S. Department of Energy, Office of Conservation and Renewable Energy.
10 CFR 436, Federal Register, Volume 46, Mo. ??.?., 18 November 1981. pp.
56716-56733.
8. Energy User News. Volume ^6, Mo. 44, Fairchild Publications, A Division
of Capital Cities Media, Inc., New York, New York, ?. November 1?81. p.6.
9. Coad, W.J. "A Primer on Electric Rates." Heating/Piping/Air
Conditioning, March 1980. pp. 95-°6.
10. Manna!, H.C. "Understanding the Controllable Factors that Affect Your
Electric Bill." Plant Engineering, 17 August 1978. pp. 127-130.
11. Ayres, Lewis, Morris & May, Inc. "Energy Conservation in Municipal Water
and Wastewater Treatment Systems." Workbook from training workshop
sponsored by the Ohio Department of Development, Office of Energy
Conservation, 1984.
19
-------
SECTION a
TECHNICAL DESCRIPTIONS
This section contains overall technical descriptions for the followinq
alternative energy systems:
1. Heat pumps.
?. Active solar systems for heating and cooling.
">.. Photovoltaic systems.
4. Geothermal--direct use systems.
5. Wind power systems.
6. Low-head hydro systems.
7. Passive solar systems.
8. Geothermal--power generation systems.
°. Fuel cells.
10. Active solar systems for power generation.
These descriptions provide a summary of the overall technical status of
each alternative enerqy technology with respect to its design, construction,
costs, and constraints on its application. These descriptions are presented
in a fact/data sheet format, with supplementary figures 'including process
diagrams) and costs, where appropriate. This overall format was chosen in
order to permit hoth an overall assessment of the technologies, and where
possible, an estimate of system size and costs. T'le information is presented
to allow for a preliminary assessment for comparing these technologies with
conventional energy supplies. Appropriate references are includpd for
additional information regarding these technologies.
The information presented in this section has resulted from a review of
the literature and vendor/manufacturer contacts to confirm Design bases and
costs.
Table d summarizes the type of information needed to use the data sheets
to size the various alternative energy svstems, and to develop preliminary
estimates of the capital and operation/maintenance costs for the systems.
Data sheets were not prepared for geothermal power generation systems,
fuel cells, and active solar systems for power generation because, ^ased on
the technology review, extremely limited notential currently exists for their
application in POTW's. These limitations are summarized in the fact sheets.
Also, a data sheet was not prepared for passive solar systems. While
potential applications for this technology exist in POTW's, a generalized data
sheet was not prepared due to the significant variations in possible solar
-------
apnlications, which result from the variations in building architecture and
corresponding passive solar systems and costs. In the case of passive solar
systems, the fact sheet identifies specific literature references for nuisance
on system design.
TABLE 4. INFORMATION NEEDED TO SIZE THE VARIOUS ALTERNATIVE ENERGY SYSTEMS
System
PARAMETER
Heat pumps
Annual ambient temperature profile of heat source
Active sol ar for
heating and cooling
Photovoltaic
Geothermal — direct
use
Wind power
Low-head hydro
Passive solar
Solar insolation rate — i'J/d-m
or
Solar insolation rate— WJh/d-m7
Earth thermal gradient~°C/km
Well yield (flow- rate )--m7/hr
Wi nd fl ux — kUh/m^-yr
Available head — m
Available flow — m?/rf
Solar insolation rate —
14
-------
FACT SHEET FS-1—HEAT PUMPS
Description - A heat pump is a thermoHynamic refrigeration cycle machine which
moves heat from a low-temperature source to a higher temperature s^ by the
addition of work. When high-temperature Beating applications are Desired, the
heat pump supplies this energy by drawing it from a low-temperature source.
The useful heat output is a function of that extracted from the cold reqion,
plus the energy added to the heat pump. Therefore, the total heat output,
usually expressed as the coefficient of performance (COP\ is always greater
than unity. Typically the COP ranges from 3 to 4, where the COP is defined as
total heat output divided by the energy added (See Fig. 1). Common types of
heat pumps include water-to-water, water-to-air, and air-to-air (See Figure
2 >
£• • , •
Technical Status - Heat pumps were widely used for residential and light
commercial building applications as early as the l°^0's. Recent improvements
in design and components have resulted in a dramatic growth in heat pump
applications including some applications in wastewater treatment plants.
Recent interest has focused on the recovery of heat from wastewater effluent.
Applications - Heat pumps can supply heat for domestic hot water, space
heating, and process heat (e.g., anaerobic diqester, sludge drying).
Technical Data - Primary source of energy - Electricity.
Alternative source of energy - Directly driven by internal
combustion engine utilizing
anaerobic digester qas or
fossil fuels.
Mature of output - Varies with the temperature
of heat source
Comments - A standby or auxiliary
heating system is required
when the source temperature
falls below 4°c.
Design Considerations - Total and maximum heat load requirements, coefficient
of performance (COP) of heat pump, and temperature data of heat source.
Performance - The performance of the heat pump, as measured by COP, varies
with source temperature (see Figure 1). In general, the heat pumo becomes
inefficient if the source temperature drops below 40C. Maximum heat load
may occur at minimum COP, e.g., heating an anaerobic diqester in cold weather.
jfc
Reliability - Heat pumps have been used widely in the HVAC field with no
history of operational or desiqn problems other than the installation of these
units in unsuitable geographic (climatic) locations. Heat pumps are generally
considered low O&M equipment. Potential concerns for use at a POTW include
corrosion for installations using a chlorinated effluent, and scaling and
biological fouling which adversely affect the efficiency of the heat exchanger.
IS
-------
Limitations -
0 Geographical - Operation of air-to-air heat pumps in nothern climates
(35° north latitude and above) requires consideration of a heat
energy wheel, air-to-air preheat exchanger, or Z duct to increase the
COP. There are no geographical limitations for water-to-water and
water-to-air heat pumps using wastewater effluent because the
wastewater is relatively warm (10°C) throughout the year.
0 Production/distribution - None.
0 Environmental effects - None other than the possible release of
fluorocarbons to the atmosphere due to leakage.
0 Legal, social, or institutional barriers - None.
References - 1 through 6.
16
-------
3.5
Q.
O
"3.0
we
t«r- to- -water J^
30 40 50
Source Temperature, °F
Figure 1 Heat pump coefficient of performance.
(Adapted from Ref. 3)
17
-------
Wastewater Effluent
Return Line
Heat Exchanger
Compressor
Blower
- Filn
I Heat
~ Exchanger
Figure 2. Heat pump schematic diagram.
18
-------
DATA SHEET DS-1--HEAT PUMPS
Step 1.
Heat Load Requirement - The maximum heat load for specific process
operations can be estimated from information provided in references
1, 9, and 3.
Heat Load
kJ/hr
Step ?.
Step 3.
Selection of Heat Pump - Select type of heat pump (water-to-water,
water-to-air, air-to-air^ and use Fig. 1 to determine the COP. COP
should he based on minimum source wastewater or air temperature. COP
for air-to-air can be increased if source air is preheated.
Type of heat Pumn COP
Estimated Costs
Installed capital costs --
Use the heat load from Step 1 and Figures 3 and A to estimate the
total installed capital costs
Annual ORM Costs --
a) Electricity:
Total
service x
hours
x
(hr/yr)
Total
load x
(Step 1)
x
Conversion Electrical I/COP
factor x unit x (Step ?)
cost
0.000?7« x x
b) Other O&M costs: ='b)$
(usually n.04-0.08 of total installed capital
costs)
Total Annual OM1 costs 'a & h>
-------
ra 100.000
0
^J-
n
o
O . 10.000
1000
>
X
I
x
X
^f
/
.,•""
I
J
-------
1.000
M
o
•o
100
•a
c
a
M
3
10
M
1
'
/
X
k
2
!j
2
* 1 1
|
1
ll
2
i
—
x
^
^
-
L*
/
H"T"i
3
-^
%
T7 —
•f!
— 1
1
1
I'll
10 100 1,000 10.000
Heat Pump Capacity, thousand kJ/hr
ENR cost index = 3729
Installed capital cost
- - - Construction cost
Figure 4. Air-to-air heat pump costs.
(Adapted from Ref. 3)
21
-------
FACT SHEET FS-?
ACTIVE SOLAR SYSTEMS FOR HEATING AMD COOLING
Description - Solar energy is collected as heat for heating or cooling. A
solar collector converts incident solar radiation (insolation) to usable
thermal energy by adsorption on a suitable surface. A heat storage reservoir
is used so that energy can be supplied during evening hours and cloudy days.
A distribution system distributes energy from the collector or storage to the
point of consumption. Solar cooling is typically accomplished by using solar
heat to operate a thermal refrigeration cycle. There are three basic
heat-activated refrigeration cycles: absorption cycle, organic RanHne cycle,
and desiccant cycle. (See Figures 5 and 5.)
Technical Status - The basic concepts are well established and many designs
are available commercially. Active solar systems have been installed in
wastewater treatment plants.
Application - Active solar systems can supply heat for domestic hot water,
space heating, sludge drying, and space cooling. Active solar systems do not
appear to be cost-effective for anaerobic digester heating.
Technical Data - Primary source of energy - Sunlight.
Alternative energy source- None
Nature of output - Outnut varies with seasonal and
daily sunlight cycle and with
cloud cover variation; sufficient
heat storage can adequately buffer
nost heat fluctuations.
Comments - Connection to auxiliary heating or
cooling systems is required.
- Heat storage for niqht time and
cloudy periods is required.
Design Considerations - Heating requirements (domestic hot water and space
heating), cooling requirements, storage requirements, system efficiencies,
local insolation data, and weather/climate conditions.
Performance - The performance of an active solar system is primarily dependent
on geographical location and local weather conditions. Studies indicate that
local weather conditions limit the optimum performance (output^ of the active
solar system. A solar heating system typically has an efficiency of '0-?n
percent, while a solar cooling system has an efficiency of only P-12 percent.
-------
Reliability - The reliahility of the solar heating and cooling system over the
life expectancy of the unit is questionable (?1^. A recent national study of
12 active solar units showed only one provided the expected solar energy. A
number of problems were reported as causing poor system performance: air
leakage, water leakage, freezing problems, control problems, storage hpat loss
problems, severe weather, lower energy requirement than design load, and
supplemental heat problems.
Limitations -
0 Geographical - The application of active solar heating anH cooling is
feasible throughout the United States.
0 Production/distribution - There is no evidence currently available to
show any reduction in costs for active solar heating and cooling in
the near future.
0 Environmental effects - Active solar heating and cooling systems have
relatively minor environmental impacts. The major concerns are the
potential hazards associated with a toxic working fluid and storage
media (contamination of water and direct human impacts from
inhalation or contact^, collector overheating, and degradation of
living space air quality (e.g., stagnant air, accumulation of
airborne contaminants, buildup of molds, fungus, and bacteria^ in
storage system.
0 Legal, social, and institutional barriers - Large-scale glare,
sunrights, local codes, installation expertise, land availability and
acquisition, and public acceptance of the removal of tree canopy.
References - 7 through 21, 25, 101.
-------
Blower
3-Way Damper
Auxiliary
Furnace
Figure 5. Typical air flat-plate solar energy
collection system. (2)
I
Pump-
Solar
Thermal
Storage
Unit
Auxiliary
Furnace
(Boiler)
Automatic
Valve
Pump
Load
Figure 6. Typical liquid flat-plate solar energy
collection system. (2)
24
-------
Step 1.
Step 2.
DATA SHEET DS-?
SOLAR HEATING AND COOLING SYSTEMS
•J V Uf\l\ I I t r\ I A H\J r*l «LS \*\J\J L_ 1 II U
-------
Where:
Area
Specific load
Insolation
Efficiency
Collector area in m°
Heatinq or cooling load for application
in kJ/yr (Step 1^.
Step 9, in '-J/yr-m9 for sppcific anplication.
Total system efficiency (Step 3).
Step *. Economic Considerations -
Installed capital costs* (includinq storage) -
Item
Unit costs
Array area
Installed capital
costs
Hot water
(domestic^
Space heating
Space cooling 1,
Process heat
Net credit*
450 ($/m?) x fm^ =
540 ($/m?^ x (m7} =
inO-l,700f $/m^^ x fm^) =
540 ($/m^ x (m''} =
140 ($/m^ x (m?) =
Total
Annual oneration and maintenance costs* (usually n.ni-n.rn of
total capital costs^ -
* Costs supplied
"* T f Kn+ h c na f«o h
by equipment vendors (10R? costs)
oa + nnn anH r~nn1inn av«o i nf 1 nrlart in tho cnlar
$
$
$
$
$( )
$
$ yr
• rlacnnn a no t-
credit ($) is given for the redundancy in the collection system. This
credit equals the smaller of the space coolinq and snace heating area x
collector costs (
-------
Notes:
1. Units are KVVh/m2-d.
2. Data represent the average
lor the years 1945 Ihrourjh 1975.
3. Conversion Factors
1 KWh/MJDay = 3599 M Joules/M! Day
= 31695 BTU/Ft? Day
= 8598 Langleys/Day
o
200
400
600
I
Scale - Miles
Figure 7. Solar insolation - total horizontal annual
average day values.(101)
-------
FACT SHEET FS-1--PHOTOVOLTAIC SYSTEM
Description - Photovoltaic power systems convert sunlight directly to
electricity. The system consists of a solar array using flat plate or
concentrating-tyoe collectors, a power conditioninq system (dc or ac
conversion and voltage regulation), an energy storage system, and/or a utility
tie-in or standby generator. (See Figure 8.)
Technology Status - Single-crystal photovoltaic cell systems are the
state-of-the-art technology. The technology is well advanced for silicon and
gallium arsenide cells. Several photovoltaic demonstration projects are in
operation using single-crystal silicon cells. Low-cost photovoltaic
manufacturing technology for polycrystall ine and thin-film materials is still
in the development stages. Typical efficiencies of commerci ally-avail able
cells range from 10-14 percent.
Application - Photovoltaic power systems can supply electricity to the POTU.
Technical Data -
Primary source of energy - Sunlight
Alternate energy source - None.
Nature of output - Seasonal and daily sunlight cycle and cloud
cover variation.
Comments - Connection to auxiliary electrical system
required, i.e., batteries, central utility,
or standby generator.
Energy storage for night time and cloudy
periods is required.
Design Considerations - Power requirements, siting requirements, local
insolation data, storage requirements, array and system efficiency, and local
weather/climate conditions.
Performance - The performance of a photovoltaic system is primarily dependent
on geographical location and weather conditions. Studies have shown that the
local weather pattern is the most critical component limiting performance
(output) of the photovoltaic system. Overall system efficiencies range from
8-10 percent.
Reliabil ity - The photovoltaic system is generally considered very reliable.
The system has no moving parts and requires only periodic maintenance.
However, reliability data over the life of the photovoltaic system are
currently not available. The photovoltaic system will have to he subjected to
long-term testing under actual field conditions before sufficient data are
obtained to determine the actual reliability of the system.
-------
Limitations
0 Geographical - All areas of the United States to latitude fiO° north
have sufficient annual insolation to he potentially suitable for
photovoltaic power, with the southwestern region "of the United States
having the optimal insolation rates.
0 Production/distribution - Current production and system costs do not
reflect the large-scale manufacturing of these units. Increasing
demand for photovoltaic systems and optimization of production
processes will ultimately reduce the capital costs of these units.
0 Environmental effects - The environmental impacts regarding
installation and use of photovoltaic systems are minimal. Areas of
concern are predominantly safety-related: off-gasing of the array,
power conditioner, and batteries.
0 Legal, social, and institutional barriers - Utility interconnection,
insolation rights, large-scale glare, and installation area
availability and acquisition.
References - 1, 6, 7, 13, 22 through 31, 101.
29
-------
Utility Line
Solar
Array
CO
o
Energy
Storage
System
Power
Conditioning
System
AC Load
Figure 8. Simplified block diagram of the
photovoltaic electrical system. (26)
-------
DATA SHEET DS-3— PHOTOVOLTAIC SYSTEMS
Step 1. Load or Fraction of Load Requirements - The load requirements
for specific process operations can he estimated from
references ?. and **. _ kK'h/yr
Step ?. Insolation Data - Insolation data can be obtained from reference
1 or Fiatire 7. (See step "> of Data Sheet DS-?.)
Average annual insolation at proposed location
Step 3. Array Area Requirements -
_ Load requirements _
Array area (m?) = Cell efficiency x averaoe insolation = _ m?
I/here: Load requirements = Step 1 in klJh/yr.
Averaqe insolation = Step ? in kllh/m'-
Cell efficiency = n.in to n.lA
Step A. Peak Power Output 'kl-0 -
P peak (kW) = Array area x system efficiency x
peak insolation
Where: P peak = Peak power output in kM.
System efficiency = Usually n.OR _ p. in.
Array area = Step 1.
Peak insolation = Typically 0.75.0.015 H;I/m°.
Step 5. Economic Considerations -
*
Total installed capital costs -
Typical 1°8? unit costs - Hased on peak power outnut
(kW) from Step 4:
Photovoltaic array = $10,OOn/kW X P neak (Step 4) = $
Support structure = $ l ,nno-$«j1onn/kW X P peak (Step A) = $
Power conditioner = $ 5nO-$l,000/kW X P peak (Step ^ = $
Batteries (if req.) = $ (500-$?,non/n,' X P peak (Step A) = $
Total $
Annual operation and maintenance costs (tynically O.o?_
O.n?) of installed capital costs. " $ /yr
Costs supplied Hy equipment vendors '!°R? costs
-------
FACT SHEET FS-A—GEOTHERMAL - DIRECT USE SYSTEMS
Description - Direct use systems pump hot geothermal fluid through a heat
exchanger transferring the geothermal energy to a secondary thermodynamic
fluid. This fluid then transmits the heat energy from the geothermal fluid to
the thermal load. (See Figure 9.)
Technology Status - Direct use systems have been employed in the United States
for approximately the last 20 to ^0 years. Geothermal systems have been
considered for POTU's but have not been used.
Applications - Direct use systems can be applied to space heating, anaerobic
digestion, and sludge drying.
Technical Data -
Primary source of energy - Geothermal energy
Nature of output - Thermal energy
Design Considerations - Heating and/or power requirements, local geothermal
temperature gradient (see Figure 10), available local geothermal data
(including depth to source), geothermal fluid quality (including temperature^
and quantity data, and geothermal test well data.
Performance - Geothermal sources have been known to produce constant and
continuous output from 20 to 50 years. System efficiency for direct use is
90-95 percent.
Reliabil ity - The reliability of direct use systems has been proven both in
the United States and Europe. Direct use systems must be periodically shut
down for heat exchanger maintenance. This maintenance consists of scale
prevention and gasket replacement. This will be especially true for POTW
applications if wastewater is the secondary fluid in the heat exchanger
(greater potential for scaling and biological fouling).
Limitations -
0 Geographical - For successful application, the site must be located
near a suitable geothermal resource. This resource must be verified
by both available data and actual well testing.
0 Production/distribution - Direct use systems are commercially
available.
0 Environmental impacts - The impacts from waste heat are minimal for
direct use systems. A major concern is the proper disposal of spent
geothermal fluids to avoid upsetting the local aquatic environment.
Spent geothermal fluids are typically disposed of by reinjection.
0 Legal, social, and institutional barriers - None.
References - 32 through 47, 77, 102.
32
-------
Load Heat
Exchanger
Circulating
Pump
Secondary
Closed
Loop
Existing
or
Backup
Boiler
Well Head
Head Exchanger
A A A A
1
Geothermal
Well. Pump.
and Water
Treatment
r
L
Figure 9. Typical geothermal direct use system. (43)
33
-------
Key
Geothermal gradient in °C/km
0 15 30 45 60 +75°C/km
Figure 10. Geothermal gradient map of the conterminous United States. (41)
-------
DATA SHEET DS-A— GEOTHERMAL - DIRECT USE SYSTEMS
Step 1. Heat Load (HI) Requirements - Head loads for specific unit
operations can he estimated from the data provided in re-
ferences 1, ?, and 3. _ KJ/hr
Step ?. Geothermal Temperature Gradient at Site (Fig. in) (A) _ °C/km
Step 3. Highest Required Source Temperature for a given application
(Figure 11)7 (B)
Step 4. Total Required Well Depth
- 12.8
Well Depth = f ^TAl~ + n-015) 1-5 " (C)
Step 5. Wellhead Pump Size and Flow Rate3
The well flow rate is calculated as follows:
HL (kJ/hH
Required well flow rate (W) = T f°C) 4134 s
nr/hr
Where: HL - Heat load requirements in kJ/hr (Step
1.)
T = Overall geothermal temperature drop in
°C; generally 11°C for space heating
and domestic hot water, and ?0°C for
an anaerobic digestion and sludge drying
application.
V! x H
Pump Hlowatts (kW) = 350 e l
Where: W = Well flow rate in m-Vhr.
H = Pumping head in meters (m) which can he
assumed to be 30" m (l.nnn ft) for a
preliminary estimate.
e = Pump efficiency, tyoically n.fin_n.ps.
Step fi. Transmission Distance -
Estimated transmission distance from wellhead to thermal
load in meters. (D> m
35
-------
Steo 7. Economic Considerations -
Installed capital costs+ --
Well and well heart heat exchanger costs from Figure I9
'l°fl? dollars)
(E}$
Wellhead pump costs (SAW) from Figure 1^ '7°S? dollars^
x kW (in Step «5) =
Transmission piping costs (In8? dollars^ (D^ x $niVm =
Total engineering and related capital costs
Engineering Design: (H) x n.l^ = fp$
Site investigation and overhead: (FO x n.n? = (J)$
Resource exploration and test wells
ftvnically $]nn,nno^ fK)$
Total capital direct heating installed costs
(H) + (I) + (J) + 'K) = Total 'L)$
Annual operating and maintenance costs ^usually O.np.n.OA
of total capital costs (L)). $ /yr
Due to very limited information of this type, it is recommenced that the
evaluator contact the following office for site-specific test well flow
data:
U.S. Department of Energy
Division of Geothermal Energy, Resource Applications
Federal Building - MS?W
12th and Pennsylvania Avenue, N.U.
Washington, DC ZQAfil
Does not include reinjection well costs
-------
re
55
1
ra
o>
oo
°c
200r
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
to
J
Evaporation of Highly Concentrated Solutions Refrigeration by
Ammonia Absorption Digestion in Paper Pulp, Kraft
Heavy Water Via Hydrogen Sulfide Process
Drying of Diatomaceous Earth
Drying of Fish Meal
Drying of Timber
Alumina Via Bayer Process
oz
UJO
Drying Farm Products .at. High Rates
Canning of Food
Evaporation in Sugar Refining
Extraction of Salts by Evaporation and Crystallization
ANAEROBIC DIGESTER HEATING
uj
OO
00.
- Drying and Curing of Light Aggregate Cement Slabs
• SLUDGE DRYING APPLICATIONS
• Drying of Stock Fish
Intensive Deicing Operations
> SPACE
HEATING
APPLICATIONS
- Mushroom Growing
Therapeutic Baths
- Soil Warming
- Swimming Pools, Biodegradatiorx Fermentations
Warm Water for Year-found Mining in Cold Climates Deicing
L Hatching of Fish; Fish Farming
Figure 11. Applications versus source temperature range
of geothermal water and steam.(38)
37
-------
2
_ro
"o
0
vo
8
O
2 0.1
a.
as
O
L.Mean cost "
\ i 11111H i i
i I I I II! I i I ITT
Minimum cost
0.01
l
ii
— 100 1000 10.000
Well Depth (m)
ENR cost index = 3729
100.000
Figure 12. Typical well and wellhead heat exchange
installed capital costs for geothermal well. (44)
(Reinjection well costs not included.)
38
-------
2,000
* 1,000
r 900
i
800
= 700
5 600
in
w 500
O
O
Q.
E
Q.
400
"3
300
200
20
30
40 50
100 200
Required Pump Kilowatts (kW)
300 400 500
ENR cost index = 3729
Figure 13. Total installed capital cost for geothermal
wellhead pump. (43)
39
-------
FACT SHEET FS-S—WIND POWER SYSTEMS
Description - Wind energy conversion systems (WECS) harness the power of the
wind converting it to electricity. The system converts wind power to
mechanical energy through a rotor. The mechanical power is transferred to a
generator or alternator via a drive shaft. A power conditioning system
(inverter) is also employed to convert the power to ac or dc and to ensure a
steady output. (See Figure 14).
Technical Status - Units of 10 to over 100,000 kW are available commercially.
However, the larger units are special orders that are constructed on a
contractual turnkey basis with the manufacturer. Several wind energy
conversion system demonstration projects are in operation, hut the very large
units (over 100 kW) are not considered to be proven technology.
Applications - WECS can supply electricity to the POTW.
Technical Data -
Primany source of energy - Wind.
Nature of output - Zero to maximum rated capacity depending on
wind speed and duration
Comments - Connection to auxiliary system required,
i.e., batteries, central utility, standby
generator.
Design Considerations - Power requirements (loarO, siting requirements, local
wind data, energy storage requirements, and wind turbine/system efficiencies.
Performance - The performance (output) of a wind power system is significantly
affected by wind speed and direction. The electrical output of the WECS is
zero until the wind speed reaches the minimum cut-in velocity. Above the
cut-in velocity the power output increases with the cube of the increasing
wind velocity until the maximum design velocity is achieved. At velocities
greater than the maximum design velocity the power output remains constant.
The WECS efficiencies range between 38 and 56 percent when interconnected to a
public utility without storage. If storage is provided, the efficiencies
would range from ?8 to 40 percent because of the inefficiency (input/output)
of the storage system.
Reliability - The lower power (under 100 kW) units with a long history of
operation have proven very reliable. However, the earlier, large experimental
WECS (multimegawatt units) developed design failures including structural
failures and vibrational problems. Corrections of these design failures have
been incorporated into later models.
-------
Limitations -
0 Geographical - High wind areas (in general, wind speed over 2 m/s)
are the optimum locations for wind power systems with New England,
Pacific mountain areas, and central plains states the most suitable
regions for wind power applications. However, each site must be
considered on a case-by-case basis.
0 Productions/distribution - Current production and system costs do not
reflect the large-scale manufacturing of these units. Most of the
capital cost data currently available are for the experimental
units. An increase in the demand for wind power systems and
subsequent mass production would ultimately reduce the capital costs
of these units.
0 Environmental effects - Physical dimensions, such as blade diameter
and tower height, may result in a significant negative (aesthetic)
visual impact. Additionally, the placement of a large-scale WECS may
interfere with television reception due to the motion of the rotor
blade.
0 Legal, social, and institutional barriers - Availability and
acquisition of land and wind rights may limit the use of wind energy.
References - 6, ^8 through 62.
41
-------
Wind
Wind Turbine
Generator
Slip Ring Assembly
Tower
AC Output
Power Conditioning
System (Inverter)
Battery Pack
Controls
Useful Power Output
Figure 14. Small WECS with storage. (48)
42
-------
DATA SHEET DS-5—WIND POWER SYSTEMS
Step 1. Load or Fraction of Load Requirements - Electrical loads can he
estimated for the information presented in references ? and "*.
Yearly load requirements H!h/yr
Step ?. Hind Data (Wind Flux) -
Figure 15 can he used to estimate regional wind power
availahil ity. A detailed wind power survey is imperative
in cases where wind power appears to he cost effective.
Local wind power avail ahil ity may significantly differ from
regional data. Site features such as terrain, structures,
etc., may significantly affect the amount of availahle wind
nower. Suitahle site characteristics may he summarized
as follows:
0 Minimum annual average wind speed greater than ? m/sec.
0 No ohstructions fhuildinqs or trees) upwind or downwind
for a distance depending on the diameter of the rotor
(i .e., 5 diameters).
Step 3. Rotor Size and Area -
Load
Rotor area (m?) = Efficiency x Hind flux m9
Where: Load = Step 1, in kWh/jr.
Wind flux = Step ?, in Kwh/m^-yr.
Efficiency = Usually 0.38-0.5fi, assuming no storage.
Step 4. Peak Power Output of Wind System (klJ) -
P peak (kW) = Density air x rotor area x (rated velocity)3 x
K kW
Where; P peak = Peak power output in 1'W.
Density air = 1.?. kg/m?.
Rotor area = Step 3, in m?
Rate velocity = Typically 15 m/sec.
K = Constant, 0.000153.
Step 5. Economic Considerations -
Total installed capital costs (Figure 16) $
Total installed capital costs are given as a function of
peak power output in Figure Ifi. Step 4 provides the cal-
culation for the peak power output of the wind power system.
Annual operating and maintenance costs
(usually 0.02-0.04 percent of installed capital costs) /yr
-------
USWB Weather Plotting Chart
Wind Regimes
Low (2,000-3,000 kWh/m'/yr)
Moderate (4.000-7.000 kWh/mz/yr)
High ( > 7.000 kWh/m'/yr)
Figure 15. Distribution of favorable wind regimes over
the contiguous 48 states and offshore areas. (48)
-------
(A
•^
If)
o «
5 |i
Q. "O
10 _
O o
T3 U)
0) *O
= c
a CD
(/) 3
f ^
CO ~
.000
100
to
f
/
/
\
'
I
I
i
I
I
i
I
I
1 —
1
: ,
'x'
i
:
, —
X
f
1
J
J
1
II
1 ll
II;
i i1
ill!
Ml,
II
1 |
Mil
i •
1 ' X 1
:X ' •
/fill
i i ' !
i '
LLaJ
I i i i :
i | , . i
1 1 I i 1
1
;
:
l|
[I
E
•
n
Q
10 100 1,000 10.000
Peak Power Output (kw)
Figure 16. Total installed capital cost of wind power systems
as a function of peak power output.
45
-------
FACT SHEET FS-6
WITHIN PLANT LOW-HEAD HYDRO SYSTEMS
Description - Hydroelectric power is generated by converting kinetic energy
and potential energy to electrical energy via a mechanical impeller coupled
with an electrical generator. This system consists of an intake nenstock
which directs a water stream at a turbine runner that is directly coupled with
a synchronous electric generator. (See Figure 17)
Technology Status - Low-head hydroelectric systems have been in use in the
United States and Europe for over a hundred years. The technology is fully
proven and demonstrated. Engineered and prepackaged systems are available
through several commercial distributors. Significant technology improvements
that would improve the efficiency or applicability of the technology are not
expected in the foreseeable future. Low-head hydroelectric systems have been
installed in POTU's.
Applications - Feasible points of application in a POTW are the influent or
the outfall of a treatment plant. The point of application is dependent on
the available head.
Technical Data -
Primary energy source
Nature of outout
Comments
Available head and flow rate of treatment plant
wastewater.
Seasonal and daily variation dependent on
wastewater flow variations.
Interface with conventional electrical power
is required.
Design Considerations - Power requirements, siting requirements, available
head, available flow, variability of watewater flow.
Performance - Low-head hydropower systems require relatively low maintenance
and are easy to operate. The conversion efficiency between hydraulic energy
and electrical energy is between 85 and °0 percent.
Reliability - Low-head hydro systems are considered extremely reliable. These
systems generally require infrequent maintenance and essentially no operator
attention. System output varies in direct proportion to wastewater forward
flow. If influent flow powers the system, nrecantions should be taken to
minimize clogging of the intake penstock and in-line turbine mechanisms. If
effluent flow powers the system, the materials of construction must be of
sufficient quality to prevent corrosion Hue to the chlorine residual in the
effluent.
Limitations -
0 Geographical - Available head should be approximately 3 m or greater
to make the application feasible.
-------
0 Product!on/distrihution — None.
0 Environmental impacts - None.
0 "Legal, social, and institutional harriers - None.
References - 63 through 7?.
47
-------
—
- — . -
- —
-1
1
1
_J
Generator
Gear Box
Electrical Panel
Thrust Block
Valve
Penstock
Plan
Turbine
- Powerhouse
Equipment Access Hatch
Powerhouse
Turbine
Tailrace
Structure
Section
Figure 17. Low-head hydroelectric system.
48
-------
DATA SHEETS DS-fi
LOW-HEAD HYDROPOWER DESIGN DATA SHEET
Step 1. Load or Fraction of Load Requirements - An estimate of the
electrical load can he obtained from references ? and ?.
Step ?.. POTV1 Flow Data -
Design or projected average daily flow (Q^
Step 3. Available Head -
By accurate methods determine the available head (water ele-
vation difference at site, usually plant effluent). Typical-
ly, this is accomplished through a qualified surveyor.
Avail ahle head (m) = (H> _ m
Step 4. Installed Capacity of System -
System capacity (kW) = Q x H x 9. 65 x If)-* _ kW
Where: System capacity = Power output in kW.
Q = Daily flow in m^/d (Step 2).
H = Available head in m (Step 3).
_ System capacity _
Percent of load satisfied = Load requirements fStep
l)x 100 __ *
Step 5. Economic Considerations -
Total installed capital costs
$/kW (from Figure 18) x kW (Step 4) $ _
Operating and maintenance costs (typically
0.0?-0.04 percent of total installed capital cost) $ /yr
-------
100.000 f
100
10 100 1000
System Capacity (KW)
10.000
Figure 18. Total installed capital cost of low-head hydro power.
50
-------
FACT SHEET FS-7 — PASSIVE SOLAR SYSTEMS
Description - In a passive solar system, elements of the building are used to
collect, store, and distribute energy. In general, passive systems are
integral parts of a building's overall architectural design and construction.
The solar system is classified as passive if all significant energy exchanges
linking the system involve purely natural flow (conduction, convection,
radiation, evaporation) rather than forced flow (fans, pumps, compressors).
There are three general passive collection concepts:
0 Incidental heat traps, e.g., windows, skylights, and glass structures
o Thermosiphoning (convective loop).
0 Thermal storage pond and roof concept.
(See Figures 1°, ?n, ?l, ??, and 21.>
Technical Status - Architects commonly use passive heating and cooling in
contemporary building designs. The design procedures are well documented in
the literature. Current research regarding passive solar hardware involve
attempts to increase system performance (e.g. transparent insulation, an
"optical shutter," thermocrete, phase change insulation, and a thermic
diode). Passive systems have been incorporated into recent POTH building
designs.
Applications - Passive heating and cooling systems can be used to complement
conventional heating and cooling systems. In general, as much as 70 percent
of building heating can be met using passive solar systems. Additionally,
natural (solar) lighting can complement the building's interior illumination
systems.
Technical Data -
Primary source of energy - Sunlight.
Alternate fuel - None.
Nature of output - Seasonal and daily sunlight cycle, and cloud
cover variation.
Comments - Auxiliary heating and cooling systems
re qu i red
•
Design Considerations - Heating and cooling requirements, building layout,
design and orientation, and material of construction.
•SI
-------
Note: Due to the significant variations in possible passive solar
applications, resulting from the variations in-building
architecture, no generalized data sheet has been prepared. For
guidance "on system design, see references 74 and 75.
Performance - For a properly insulated structure the efficiency of a passive
solar system is generally independent of the geographical location. The
primary factor affecting performance is the local weather conditions, e.q.,
cloud variations.
Reliahil ity - A passive solar system is considered very rellabile. The system
has no moving parts and is typically constructed of low maintenance materials.
Limitations -
0 Geographical - None. Passive solar systems are applicable throughout
the United States.
0 Production/distribution - Traditional passive solar equipment is
readily available; however, the new/innovative passive hardware is
difficult to fabricate and is generally expensive.
0 Environmental impacts - There are few environmental problems
associated with passive systems other than limited concern for
potential degradation of interior air quality (as measured by
temperature, humidity, and air circulation^ and increased hazard from
glass breakage associated with large expanses of glass.
0 Legal, social, and institutional harriers - The inability of the
process to be easily adapted to existing structures; i.e.,
retrofitting is a major limitation. Sunrights and large-scale glare
must also be considered.
References - T, 7, in, 1?, 16, 17, 73 through 7«5.
-------
Radiation
From Storage
1. Exterior Glazing System
2. Concrete Wall
3. Air Vents
4. Foundation Insulation
Figure 19. Typical Trombe wall design.(16)
53
-------
Solar
Radiation
Radiation
From
Storage
1. Skylight Glazing System
2. Movable Insulation Plumbing
3. Movable Insulation Storage Tank
4. Reflector Wall
5. Water Bags
6. Steel Deck
Figure 20. Typical solar roof pond system. (74)
54
-------
Absorber
Plate
Heat Pipe
Room
Water
Insulation-
Figure 21. Heat pipe augmented water wall concept. (74)
55
-------
Oil Valve
Crossover
Tube
Air Out
Air Warms
& Rises
in Plenum
Chamber
Water Reservoir/
Heat Storage
Honeycomb
Insulation Layer
Water Channel
Heat Collector
Air In
Figure 22. Thermic diode solar panel. (74)
56
-------
1. Insulating Glass
2. Wall Framing
3. Metal Absorber Plate
4. Insulating Core
5. Interior Finish
6. Continuous Air Vents
Natural
Convection
(behind collector plate)
Figure 23. Typical thermosiphon air panel collector. (2)
57
-------
FACT SHEET FS-8 -- GEOTHERMAL - POWER SYSTEMS
Description - Geothermal systems can provide heat for the generation of
electricity. In geothermal power systems, very high temperature geotherinal
fluids are passed through a heat exchanger. A secondary working fluid is then
heated in the heat exchanger and expanded through a Rankine cycle power
turbine. This turbine then turns a synchronous generator thus creating
electrical power. (See Figure ?4).
Technical Status - Geothermal power systems have been used in Geysers,
California since !QfiO.
Applications - Geothermal power systems produce electrical power and therefore
could supply the entire energy requirements of a treatment plant.
Technical Data -
Primary source of energy
Alternate fuel
Nature of outout
Geothermal energy.
None.
Electrical energy.
Energy storage not
supply of source.
required due to continuous
Design Considerations - Power requirements, local geothermal temperature
gradient, available local geothermal data, geothermal fluid quality and
quantity data, and geothermal test well data.
Note; - Due to the limited applicability of these systems (see
geographical limitations, below) no generalized data sheet has been
prepared.
Performance - Geothermal sources have been known to produce constant and
continuous output from 20 to 50 years.
Reliabil ity - Geothermal power systems must be periodically shut down for heat
exchanger maintenance. This maintenance consists of scale prevention and
gasket replacement. Geothermal power systems are subject to the same
maintenance schedules as conventional power systems.
Limitations -
0 Geographical - For successful application, the site must be located
very near a suitable geothermal resource. This resource must be
verified by both available data and actual well testing. The
existence of suitable geothermal resources, i.e., thermal gradients
greater than 60°C/km (see Figure 10), severely restricts the
potential application of geothermal power systems in POTW's.
-------
0 Production/distribution - The smallest on-line geothermal electric
plant in the United States is 10 MW, which suggests that geothermal
power generation is applicable to treatment plants in excess of
378,500 mVd (100 mgd).
0 Environmental impacts - A major concern is the proper disposal of
spent geothermal fluids to avoid upsetting the local aquatic
environment. Spent geothermal fluids are typically disposed of by
reinjection.
0 Legal, social, and institutional barriers - None.
References - 32-34, 36, 42, 44, 47, 76, and 77.
-------
Steam
Steam
Turbine
Wellhead
Heat
Exchanger
Generator
( ) Condenser
Remjection
Well
Pump
Geothermal Well.
Pump, and Water
Treatment
Figure 24. Typical geothermal steam power
generating system. (45)
60
-------
FACT SHEET FS-9 — FUEL CELLS
Description - A fuel cell is an electrochemical device that converts the
chemical energy of a fuel directly into dc electricity. The dc electricity is
converted into ac electricity by means of a power conditioner. In addition to
the fuel cell and power conditioner, a fuel processing or converting system
(generation of hydrogen gas) is required. A waste heat recovery system is
also used sometimes. Types of fuel cells currently in development include a
phosphoric acid electrolyte, molten-carbonate electrolyte, and solid-oxide
electrolyte. (See Figure 25).
Technical Status - Several small fuel cell power plants (12-40 kW) were
demonstrated by 1975. Approximately 45 demonstration units of 4Q kW are
expected to be installed at various locations in the United States by 1982.
In New York state a much larger unit, approximately 4500 kW, is expected to
provide electricity by the mid-to-late 1980's. Although fuel cell technology
has been demonstrated, it has not reached commercial readiness.
Applications - Theoretically, fuel cells are applicable to any size wastewater
treatment plant. Due to their self-contained and modular nature, fuel cells
may be installed anywhere in the United States. Additionally, fuel cells may
be designed to supply the entire energy requirements of a treatment plant and
can supply electricity proportional to the instantaneous load requirements.
Technical Data -
Primary source of energy - Low sulfur oil or naphtha.
Alternate source of energy - Most clean hydrocarbon sources that can be
used to generate hydrogen, e.q., anaerobic
digester gas (methane), propane, methanol,
and hydrazine.
Nature of output - Extremely constant ac electricity. Energy
storage is not required due to the ability
of the fuel cells to closely follow load
power demands.
Design Considerations - Power requirements and available fuels.
Note - Due to the newly developing status of this technology, no
generalized data sheet has been prepared.
Performance - Although relatively few performance data are available, fuel
cells are expected to provide a continuous and constant energy output. The
efficiency of the fuel cell is in excess of °0 percent; however, when the
conversion of the primary fuel to hydrogen is included with the fuel cell
efficiency, the overall energy conversion to electricity is only 30-40
percent. (A conventional fossil fuel power plant conversion efficiency is
typically 33 percent.) It is anticipated that the overall system efficiency
of 47 percent can be obtained by the late IQRO's.
61
-------
Reliabil Ity - As with any newly developed technology, fuel cells may he
expected to be relatively unreliable, and require very specialized personnel
for O&M during the first few years of commercial availability. However, the
reliability of fuel cells is expected to increase thereafter once the
mechanical and system deficiencies are worked out.
Limitations -
0 Geographical - The application of fuel cells is technically feasible
throughout the United States.
0 Production/distribution - The fuel cells are not expected to be
commercially available until approximately the year 2000.
Additionally, the current life expectancy of the fuel cell is only
10,000 hours. The ongoing research and development programs are
anticipated to significantly improve the life expectancy of the cell.
0 Environmental effects - The primary fuel processor will have the same
air pollution and solid waste problems of a conventional fossil fuel
power plant.
0 Legal, social, and institutional barriers - Public acceptance of any
newly developing technology.
References - 5, 78 through 87.
-------
FUEL PROCESSOR
FUEL CELL
WASTE HEAT RECOVERY
AND POWER CONDITIONER
AIR
cr,
co
EXHAUST
AIR
BURNER
START AJ
FUEL ^
BY-PASS
CONTROL
/
M
ANODE EXHAUST
REFORMER
TURBO-
COMPRESSOR
(TWIN-FLOW)
START
BURNER
TURBINE
AIR EXHAUST
POWER
CONDITIONER
POWER SECTION
HEAT REMOVAL
COOLANT
WATER FROM
STORAGE
— AC
—• POWER
—• OUTPUT
COOLANT
Figure 25. Schematic diagram of a fuel cell system (82)
-------
FACT SHEET FS-10
ACTIVE SOLAR SYSTEMS FOR POWER GENERATION
Description - Heat from the solar collector is used to operate a heat engine
whose output can be utilized for electrical power generation. Systems can be
classified as to their levels of solar energy concentration/intensity (low,
medium, high) and configuration (centralized or decentralized). Storage is
provided as heat (molten salts, or heated oil, water, or rocks) or electricity
(batteries^. See Figures 26-?9)
Technical Status - These systems are not expected to be available commercially
until the mid-19Q0's. Only industrial process heat (steam) systems are
available commercially today. Several demonstration and prototype systems are
in operation, but none have been applied to POTW's.
Applications - Theoretically, solar thermal power systems can supply both
electricity and process heat to a POTW.
Technical Data - Primary source of energy - Sunlight
Alternate fuel - None.
Nature of output - Output varies with seasonal and
daily flucuations in solar
insolation and local weather
conditions.
Comments Sufficient storage would buffer
the system from short heat
interruptions and/or permit system
operation when solar energy is not
available. An auxiliary power
system is required, i.e., thermal
storage system, central utility,
or standby generator.
Additionally, most systems can
utilize only direct sunlight.
Design Considerations - Power requirements, siting requirements, storage
requirements, type of system (centralized or decentralized), level of solar
insolation, and system efficiency.
Note: Due to the newly developing status of this technology, no
generalized data sheet has been prepared.
Performance - The performance of a solar thermal system is primarily dependent
on geographical location, local weather conditions, and storage capacity.
System efficiencies are a function of solar energy concentrator intensity and
heat engine operating temperatures. Typical efficiencies are as follows:
64
-------
Low-level solar concentrator (flat plate/vacuum tubes) 5-7 percent
Medium-level solar concentrator (parabolic trough) 10-13 percent
High-level solar concentrator (point focus systems^ 17-22 percent
Reliability - Solar thermal power systems are still in the developmental stage
and may be somewhat unreliable and require very specialized personnel for 0 &
M during these early years of process development. However, the system
reliability is anticipated to increase once the mechanical and system
deficiencies are corrected.
Limitations -
0 Geographical - Solar thermal power systems are limited to areas with
suitable insolation characteristics, with the southwest region of the
United States the area most suitable for application of solar thermal
power units.
0 Production/distribution - Large-scale systems are not expected to be
commercially available and economically attractive until the
mid-1990's.
0 Environmental effects - Environmental impacts associated with the
thermal engine and storage system are primarily safety related
(working fluid leaks, noise, etc.). Environmental effects are also
attributable to heat rejection equipment (cooling tower plume).
Misdirected solar radiation is of great concern causing possible eye
injury, fires, and potential disruption of nearby air and ground
traffic (glare).
0 Legal, social, and institutional barriers - Aspects of concern
include insolation rights, land availability and acquisition, and
installation expertise.
References - 5, 88 through 100.
65
-------
Receiver
590°C (1090°F)
(1090°F)
590°C
540°C(1000°F)
9.7MPa(1400psi)
Condenser
31°C(88°F)
Feedwater Heaters
Figure 26. Point-focus central receiver/Rankine
(PFCR/R) system flow schematic drawing. (88)
Figure 27. Two-axis tracking heliostat (PFCR).(88)
66
-------
Receivers
295° C (560° F)
175°C (350° F)
285° C (540° F)
3.4 MPa (500 psi)
295° C
(560° F)
Dowtherm A
Thermal
Storage
Thermocline
175°C
'' (350° F)
f 240°C (460° F)
Boiler
175°C
Condenser
31°C(88°F)
(350°F) (330°F)
Feedwater Heaters
Figure 28. Low concentration nontracking (LCNT)system flow
schematic drawing. (88)
Figure 29. Low concentration nontracking (LCNT)
collector module. (88)
67
-------
REFERENCES
1. American Society of Heating, Refrigeration and Air-Conditioning, Inc.
ASHRAE Handbook 1981 Fundamentals. Atlanta, Georgia, 1981.
?.. U.S. Environmental Protection Agency. "Technology Assessment of Solar
Thermal Energy Applications in Wastewater Treatment." Municipal
Environmental Research Laboratory, EPA-500/2-82-Onfi, February 1982.
3. U.S. Environmental Protection Agency. "Energy Conservation in Municipal
Wastewater Treatment." Office of Water Programs Derations, EPA
430/9-77-011, March 1978.
4. Pallio, F.S. "Energy Conservation and Heat Recovery in Wastewatsr
Treatment Plants." Water and Sewage Uorks. February 1977. p. 62.
5. Sector, P.M. "Demonstration of Building Heating with a Heat Pump Using
Thermal Effluent." Special Report 77-11, Army Cold Regions Research and
Engineering Laboratory, Hanover, New Hampshire, May 1977.
6. U.S. Department of Energy. Distributed Energy Systems; A Review of
Related Technologies. DOE/PE 03871-01, Prepared by Arthur D. Little,
Inc., Cambridge, Massachusetts, November 1°79.
7. Williams, J.R. Solar Energy - Technology and Applications. Ann Arbor
Williams, J.K. boiar hnergy - Technology and Appnc
Science Publishers, Inc., Ann Arbor, Michigan, i<>77.
8. King, T.A. and J.B. Carlock, III. "Construction Costs in Commercial
Solar." Energy Engineering. 11-31 December 1979/January 1980.
9. U.S. Department of Commerce. NBS Handbook 135, Life-Cycle Costing Manual
for the Federal Energy Management Programs^Washington, DC, 1980.
10. Solar Energy Industries Association. Solar Industry Index. Washington,
DC, 1977.
11. U.S. Department of Energy. "Solar Collector Manufacturing Activity,
January through June 1980." DOE/EIA-0174 (80/1) Energy Information
Administration, Washington, DC, 1980.
12. Solar Vision Inc. "Solar Products Specification Guide." Solar Age
Magazine. Harrisville, Mew Hamoshire, 1Q79.
13. Montgomery, R.H. The Solar Decision Book. Dow Corning Corporation,
Midland, Michigan, 1978.
68
-------
14. U.S. Department of Energy. DOE Facilities Solar Design Handbook.
DOE/AD-0006/1, Director of Administration, Office of Construction and
Facility Management, Washington, DC, 1978
15. U.S. Environmental Protection Agency. "Use of Solar Energy to Heat
Anaerobic Digesters." EPA-600/2-73-114. Municipal Environmental Research
Laboratory, Cincinnati, Ohio, 1973.
16. U.S. Energy Research and Development Administration, Transportable Solar
Laboratory Workshop, Washington, DC, 1977.
17. U.S. Environmental Protection Agency. "Integrated Energy Systems
Monitoring Municipal Wastewater Treatment Plant." Wilton, Maine,
EPA-CI-77-0198, Municipal Environmental Research Laboratory, Cincinnati,
Ohio, 1980.
18. U.S. Environmental Protection Agency. "Energy Requirements for Municipal
Pollution Control Facilities." EPA-600/2-77-214, Municipal Environmental
Research Laboratory, Cincinnati, OH., 1977.
19. Hills, D.J., and J.R. Stephens. "Solar Energy Heating of Dairy Manure
Anaerobic Digesters." Agricultural Wastes. (2) 2, 103-118, 1°80.
20. Podder, A., and C. Bosnia. "Innovative and Alternatiave Technologies for
Energy Utilization in Wastewater Treatment Plants." Proceedings of the
Energy Optimization of Water and Wastewater Management for Municipal and
Industrial Applications Conference. ANL/EES-TM-%, Vol., I, Argonne
National Laboratory, 1980.
21. Spielvogel, L.6. "The Solar Bottom Line." ASHRAE Journal. 38-40,
November 1980.
22. Spectrolab, Inc. "Photovoltaic Systems Concept Study." Final Report,
Report Mo. ALO/2748-12, Vol. 1-5, April 1977.
23. Stang, L.6. "Environmental, Health, and Safety Aspects of Photovoltaics."
BNL-28436, Brookhaven National Laboratory, Upton, New York, Sept. 1980.
24. "World's Largest Solar Cell Electric Power Station Activated" Public
Utilities Fortnightly. P-65-68, 13 September 197°.
25. U.S. Department of Energy, Assistant Secretary of Conservation and Solar
Energy. Solar Energy Program Summary Document FY 1°81, DOE/C5-0050,
August 1980.
26. Solar Photovoltaic Applications Seminar; Design, Installation, and
Operation of Small, Stand-Alone Photovoltaic Power Systems.
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October 1981.
75
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SECTION 5
CASE HISTORIES
GENERAL
Section 5 presents case histories of alternative energy technologies at
POTW's across the United States. The case histories presented in this section
include examples of the following technologies:
1. Low-head hydroelectric generation (Bonney Lake, Washington).
?. Active solar system for process heating (Newport, Vermont and Wilton,
Maine).
3. Passive solar system (Hillsborough, New Hampshire and Wilton, Maine).
4. Wind power (Livingston, Montana and Southtown, New York.
5. Heat pumps (Wilton, Maine).
6. Photovoltaic system (Waynesburg-Magnolia, Ohio).
The preliminary information included in Section 5 was gathered from EPA's
Innovative/Alternative Technology Staff at WERL in Cincinnati, Ohio, and from
the literature. The status of each case history project was verified by the
regional and/or state innovative/alternative coordinator. Additional
technical information (e.g., design criteria, performance, etc.) was provided
by the consulting engineer, as required.
All of the case histories included here were at least in the design phase
at the time the report was written '198?). At the time of writing, only one
POTW (Wilton, Maine) had been on-line long enough for meaningful operating
data to have been collected. (Wilton has been operational since September
1978).
76
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WILTON, MAINE « ACTIVE SOLAR FOR PROCESS HEAT, PASSIVE SOLAR, HEAT PUMPS
Background
The Wilton, Maine wastewater treatment system was designed by
Wright-Pierce Architects and Engineers, Topsham, Maine. Although the Wilton
plant was constructed before the innovative/alternative program, EPA grant
funds were used for construction. A full report describing the Wilton
facility is available (1).
The 1,700 m^/d (0.45 mgd) wastewater treatment system at Wilton was one
of the first POTW's in the country to use alternative energy technology. The
energy sources are interdependent and include the following:
1. Active solar system for anaerobic digester heating.
2. Digester gas (methane) utilization in a gas boiler for heating and
electricity generation.
3. Effluent heat recovery by heat pumps.
4. Passive solar system for building heat.
5. Exhaust air and cooling jacket heat recovery by air-to-air heat
recovery (energy wheels).
Wastewater is lifted into the plant by screw pumps that automatically
provide variable flow, thus preventing overloading the treatment processes.
The wastewater flow is by gravity throughout the rest of the plant.
Pretreatment is provided by comminution and grit removal. Gross solids are
removed by rotary screens.
Secondary biological treatment is accomplished via the rotating biological
contactor (RBC) process, followed by secondary clarifiers. Solids from the
secondary clarifiers are combined with the primary screenings and pumped to
anaerobic digesters for stabilization before being dewatered and disposed.
Effluent is disinfected with sodium hypochlorite (which is generated onsite
electrochemically from salt and water) prior to discharge to the receiving
stream.
Due to Wilton's cold climate, the entire plant is enclosed in two
structures. To save energy, unit processes have been brought close together,
while still leaving room for future expansion. The building is well insulated
and zoned to enable different rooms to be heated to different temperatures.
It is constructed of concrete block and brick with insulation in-between to
provide a large mass that holds the heat at night. The roof is also designed
to hold snow to provide good natural insulation. The surrounding juniper
groundcover will also hold the snow for insulation. The building is built
into a hillside, with little exposure to the north, to minimize the exterior
surface. This results in lower demands for heating, lighting, and system
1oads.
77
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The treatment process and energy systems are coupled to produce more
alternative sources of energy. The maximum amount of excess heat energy,
including excess heat from exhausted air, generator coolant,- and effluent
water, is recovered within the building for reuse. The recovery of 60 percent
of the heat from exhaust air in the ventilation system is used to preheat cold
air drawn into the plant. The effluent from the olant normally is discharged
at 7.2°C to 10°C (45°F to 50°F), even in winter, which represents a
potential usable source of heat. By using an electric heat pump, the Wilton
plant recovers much of this wasted heat, producing three units of heat energy
for every equivalent unit of electrical energy used. Not only does this help
heat the building, but the resultant lowering of the effluent temperature
prevents thermal shock on the stream.
The conceptual energy flow diagram (Figure 30) shows the interaction of
the various energy sources and the heating requirements of the treatment
plant. It is this interdependency of energy sources and the sophisticated
control of them which make the energy system unique. The design is an
integrated energy source and utilization system. The sources of energy can
work individually, or in combination, in conjunction with the three basic heat
utilization systems. The general philosophy is that the plant will use solar
energy as the primary source, gas produced in the digesters as the secondary
source, and the heat recovered from the process effluent by the heat pump as
the back-up and final supplementary energy source. The generator will heat
the plant as a primary source only in the event of a power failure, but it
will provide power for general building use when excess methane is available.
The digester/methane subsystem is not especially unique in its function
and design; however, the integration with the total system and its role in the
energy-conserving nature of the facility is unusual. The gas released becomes
an important part of the total operation since it is used for the boiler in
normal operation, and for the emergency electrical generator when excess gas
is available.
Treatment Plant Design Criteria
The design criteria for the wastewater treatment plant, including the
energy system, are as follows:
Quantity of sewage 1,700 m3/d
Influent BODs 200 mg/L
Influent suspended solids 200 mg/L
Effluent BOD5 20 mg/L — 90 percent removal
Effluent suspended solids 20 mg/L — 90 percent removal
Sludge quantity to digesters 9.46 m3/d at 3.5 percent solids
Methane yield 110 to 125 m3/d
Methane heat value 2.235 x 104 kJ/m3 or
2.4 x 106 to 2.7 x 106 kJ/d
78
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Propane
1 (Standby) ,
1 J_
'
Heat
Exchanger
JL
Plant
Effluent
Electric ^J
Power
Electric Power .
(Supplementary)
Domestic
Hot
Water
Hydronic
Solar
Collectors
Heat
Distribution
System
Exhaust Air
Heat Recovery
— 1
1
1-
[ ^
Water
Heater
Methane
Storage
Source Wright-Pierce Architects and Engineers.
engineers lor the Wilton. Maine project
Figure 30. Conceptual energy flow diagram for Wilton,Maine
-------
Active Solar System for Process Heating
The most significant innovation that reduces the requirements for offsite
energy is the application of solar energy, which has been user1 for the first
time in a sophisticated manner as an integral part of the wastewater treatment
process. The enclosing structures are oriente^ southward to achieve t^e
maximum value from the sun's direct energy throng11 both passive and hydronic
solar energy collection devices. Passive solar collection is achieved through
the use of fiberglass pannels that let solar heat into the process rooms of
the plant to heat t^e air directly without letting the heat out. Blacl' metal
solar collector panels, set at a 6°° slope, form the south roof of t^e
treatment plant. An anti-freeze solution is pumned through these panels and
heated to between W.°°C and 600C (l?nop to idOOp^ by the sun.
Although this solar energy is used to heat the building and the hot water
supply, its primary purpose is to provide heat for the anaerobic digesters.
Using solar energy to heat the digesters frees the digester gas for beating
the building, running the electric generator, and long-term storage. This
overcomes one of the main problems of solar energy, t^at of storage. Digester
gas is a much more economical material to store than heated water, and it is
also much more flexibile to use.
Svstem Description —
The active solar energy system is a hydronic type with flat-plate
collectors, an ethylene gi ycol/water collection loon, a heat exchanger, and
storage systems. The active solar collectors provide ?V to °"7/l x \^ '"J
(22n to 260 MBtu)/yr, while the passive collectors will add another 10* to I"*"7
x IP*5 kJ (100 to 130 MBtu)/yr. Ethylene glycol is circulated through
collector plates which are heated from the sun's rays, and this energy is t^en
exchanged to the plant's circulating water system.
The active solar array consists of R4 double-glazed panels with an
effective collection area of 119.5 m7(l,?nf> ft?^ facing ?° west of south
at an angle of 60° from the horizontal. The plant site is located at /i^°
north latitude. The specifications and installation details are describe^ in
Table 5.
-------
TABLE «? ACTIVE SOLAR SPECIFICATION DATA AND DESIGN
CRITERIA FOR WILTON, MAINE
Item Specification
Number of collector panels 54
Gross area 13° m^
Aperature 119 m^
Glazing thickness 0.47R cm
(double glazed)
Transmissivity °0.5 percent/sheet
Insulation Fiberglass R-22
Water/glycol solution 50/50
Solution temperature 48.9°C to 60°C
Source: Wright-Pierce Architects and Engineers, engineers for
the Wilton, Maine project.
The monthly
January
February
March
April
May
June
average ambient
°C
-7.4
-3.9
1.7
7.2
13.3
18.3
temperatures are as
July
August
September
Octoher
November
December
follows:
QC
2T.7
71.1
IP. 7
12.2
5.0
-2.2
The average wind speed is 2.2 m/s.
81
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The heating energy supplier! by the active solar system was estimated hy
the manufacturer. Since the heating provided by the active solar system is
useful only when such heating is required, the net estimated active solar
contribution is shown in Table 6.
Energy System Performance Data —
The designers of the Wilton plant monitored the energy system at Hilton
from June 1979 to March 1?PO. The actual operating results were then compared
with the estimated or "design" conditions. The energy production (estimated
and actual) is shown on Figure 31. The only months during which the actual
total collected energy equalled or exceeded the estimated total were September
and December.
Estimated/Actual Energy Production --
The overall active solar system efficiency (i.e., the net energy collected
divided by the total incident available) was ?3 percent. An overall
efficiency of 23 percent was signifgicantly lower than anticipated. A great
deal of effort was spent in investigating the reasons, which were presumed to
be one or more of the following:
1. Data/instrumentation error
2. Collector heat loss factor
a. Inadequate thermal insulation.
b. Possible convective losses between the absorber plate and the
rigid insulation.
3. Collector heat transfer losses
a. Air within the fluid loop.
b. Effect of the glycol solution.
4. Control sequencing and response.
5. Collector efficiency losses due to dirt accumulated during
construction.
While all of these factors (excluding the first) contributed to the solar
system's performance, the cause appeared to be the combination of all of them,
coupled with actual weather conditions and the lack of an accurate calculation
procedure to simulate this interaction.
There is obviously a significant difference between instantaneous
collector efficiency and day-long, or more importantly, year-lonq collector
efficiency. Instantaneous efficiencies are useful in comparing various types
of collectors under similar steady-state conditions, but tend to create a
misleading picture of the efficiency of water-heating systems operating over
long periods.
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TABLE 6 NET ACTIVE SOLAR CONTRIBUTION FOR WILTON, MAINE
Total heating
requirement
remaining after
Month passive solar
contribution
fcj x 106
Available active
solar energy
kJ x 106
Net active
solar contribution
•
-------
CD
5
>•
O)
5
55
jo
o
25
20
15
10
J F M A M J J
S O N D
Legend
U Estimated energy
I Actual energy
Note: Summer building heating
losses due to circulation
losses.
Source: Wright-Pierce Architects and Engineers,
engineers for the Wilton. Maine project
Figure 31. Estimated /actual energy production for
Wilton, Maine — active solar.
84
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The energy and cost-effectiveness of the active solar system are
summarized in Table 7, which shows that the active solar subsystem was a net
energy producer and net cost saver. However, due to the long payback period,
the system is not cost-effective.
Passive Solar System
System Description and Design Criteria —
Passive solar energy is used to heat the clarifier room at the Wilton
plant. The passive solar array consists of 83.2 m2(896 ft2) of panels
with an effective collection area of 75.4 m2(812 ft2) facing 2° west of
south at an angle of 60° from the horizontal. The transmissivity is listed
as 66 percent in the manufacturer's literature.
The heating energy supplied by the passive solar system is estimated by
using the following factors:
1. Estimated incident solar insolation.
2. Cloud cover factor.
3. A transmissivity of 66 percent.
4. An overhead shading factor.
The net estimated contribution of the passive system is shown in Table 8.
Energy System Performance Data —
Energy production (estimated and actual) is shown on Figure 32. The only
month during which the actual total collected energy equalled or exceeded the
estimated total was October. The passive solar system produced 55.6 x 106
kj(52.7 MBtu) during the study period. The average annual transmissivity was
32 percent. The overhang is responsible for a decrease in transmissivity
during the summer up to a daily average of 14 percent.
The energy and cost-effectiveness of the passive solar system are
summarized in Table 9.
Heat Pumps
Component Description and Design Criteria —
The water-to-water heat pump is used as a source of hot water heating when
digester gas is not available and solar production is inadequate. The heat
pump recovers heat from the plant effluent prior to discharge from the
facility. The temperature sensors located at various points in the process
lines indicate that the temperature of the wastewater increases as it proceeds
through the plant. By recovering the energy from the effluent, the effluent
temperature is lowered. The heat pump has been the major source of heating
during the winter, since gas has been unavailable and solar energy has been
inadequate. The heat pump provided 60 percent of the total heating
requirement from June 1979 to March 1980. The specifications for the heat
pump are listed in Table 10.
85
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TABLE 7 ENERGY AND COST-EFFECTIVENESS SUMMARY —
ACTIVE SOLAR FOR PROCESS HEAT FOR WILTON, MAINE
Item
Value
Output, kJ x 106 — $
Input, kJ x 106 — 3
Net gain, kJ x 106 — 3
Initial investment -- 3
153.7 — 3921
13.4 — 3168
140.3 — 3753
341,025
Energy output/input ratio3
Value output/input ratiob
Simple payback (yrs)c
153.7
13.4
$921
$168
$41,025
$753
= 11.5
= 5.5
= 54
aEnergy ratio -- Total energy produced divided by energy input
required.
bValue ratio — Dollar value of the energy produced divided by
the input energy cost.
GSimple payback — Installed cost divided by the net savings.
No inflation factor for replaced fuels was applied.
Source: Wright-Pierce Architects and Engineers, engineers for
the Wilton, Maine project.
86
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Table 8 NET ESTIMATED PASSIVE SOLAR CONTRIBUTION FOR
WILTON, MAINE
Design heat loss
monthly
kJ x 10*
Month
Passive solar
collected
kJ x 106
Net passive
solar contribution
kJ x 106
January
February
March
April
May
June
July
August
September
October
November
December
19.7
18.0
13.9
7.0
0
0
0
0
0
2.2
8.4
13.3
12.4
15.6
18.6
16.5
15.5
15.2
16.2
18.0
18.5
18.1
11.7
10.0
12.4
15.6
13.9
7.0
0
0
0
0
0
2.2
8.4
10.0
Source: Wright-Pierce Architects and Engineers, engineers for
the Wilton, Maine project.
87
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~ 20
10
I
H
5 5
1
S. n
z z
Jl
FMAMJJ AS ON
Legend
LJ
Estimated energy
Actual energy
Note: Summer building heating
losses due to circulation
losses.
Source: Wright-Pierce Architects and Engineers.
engineers for the Wilton, Maine protect.
Figure 32. Estimated/actual energy production
Wilton, Maine — passive solar.
88
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TABLE 9 ENERGY AND COST-EFFECTIVENESS SUMMARY — PASSIVE
SOLAR SYSTEM FOR WILTON, MAINE
Item Value
Output, kJ x 106 -- 3 40.7 3243
Input, kJ x 106 -- 3 _0 S 0
Net gain, kJ x 10^ — 3 40.7 3243
Initial investment 37,200
Energy output/input ratio3 N/A
Value output/input ratiob N/A
Simple payback (yrs)c 3243 = 30
aEnergy ratio -- Total energy produced divided by energy input
required.
bValue ratio -- Dollar value of the energy produced divided by
the input energy cost.
GSimple payback — Installed cost divided by the net savings.
No inflation factor for replaced fuels was applied.
Source: Wright-Pierce Architects and Engineers, engineers for
the Wilton, Maine project.
89
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TABLE 10 HEAT PUMP SPECIFICATION DATA
FOR WILTON, MAINE
I. Total heat output — 337,600 kJ/hr.
2. Condenser side —
a. 151 Ipn heating system water.
b. Leaving water temperature — S4.4°C.
c. Entering water temperature -- 45.6°C.
d. Water pressure drop -- 0.39 a on.
e. Refrigerant staturated discharge temperature --
60°C.
f. Electricity input at full load -- 28.4 kW.
g. Coefficient of performance(COP) • heat output • 3.3.
3. Evaporator side --
a. Fluid -- Sewage effluent with 10 ppm chlorine resid-
ual and minimal suspended solids.
b. Fluid flow — 227 1pm.
c. Entering water temperature -- 10°C.
d. Leaving water temperature — As required.
e. Maximum water pressure drop -- 0.34 atm.
4. Refrigerant — R-22.
5. Saturated suction temperature — 2.2°C.
6. Acceptable variation in performance from specified
conditions —
a. Total heat output -- 337,600 kJ/hr minimum.
b. Condenser water flow — Hone.
c. Leaving condenser water temperature -- None.
d. Coefficient of performance -- 3.1 minimum.
e. Evaporator water flow -- 303 1pm maximum.
f. Leaving evaporator water temperature -- S.6°C
minimum.
g. Refrigerant -- Others will be acceptable pro-
viding they meet performance requirements.
Source: Wright-Pierce Architects and Engineers, engineers to
the Wilton, Maine project.
90
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Energy System Performance Data --
The energy production (estimated and actual) for the heat pumps is shown
on Figure 33.
Table 11 summarizes the monthly heat pump energy production and
coefficient of performance. The coefficient of performance (COP) of the heat
pump varies with the temperature of the effluent, rising with a rise in
effluent temperature and dropping as the effluent temperature falls.
The heat pump operating time was greater than anticipated from June 1979
to March 1980. The coefficient of performance was quite acceptable during the
heating season. The generation of heating energy had a net cost savings, and
the payback period, 18.7 years, as shown in Table 12, was reasonable. Had the
heat pump operating time equaled the projected operating time, the payback
period would have been closer to 25 years.
O&M Requirements —
To date, the O&M problems encountered have been relatively small. A
significant amount of time, however, has been spent in cleaning the effluent
strainers. Records should be kept for several years to determine realistic
O&M costs for the system.
91
-------
m
5
>.
O)
S3
o>
Q.
£
3
a
CD
80
60
40
20
0
2 Z
J F M A M J
S O N D
Legend
U Estimated energy
I Actual energy
Note: Summer building heating
losses due to circulation
losses.
Source: Wright-Pierce Architects and Engineers.
engineers (or the Wilton, Maine proiect
Figure 33. Estimated/actual energy production for
Wilton, Maine — heat pump.
92
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TABLE 11 HEAT PUMP SUMMARY FOR WILTON, MAINE
Effluent Energy input
temperature (kWh)
Month
January
February
March
April*
May*
June
July
August
September
October
November
December
Annual
°c
7.8
6.8
6.1
15.7
18.3
20.0
19.3
16.7
13.7
10. 2
total
Compressor
6,807
6,717
6,388
2,112
2,327
40.5
0
241.9
224.9
2,327
2,112
4,363
33,660
Pump
204
202
192
63
70
1
0
7
7
70
63
131
1,010
Energy
output
kJ x 106
68.80
64.15
62.64
25.3
28.4
0.515
0
3.540
2.750
28.39
25.32
51.07
362.14
COP
2.73
2.58
2.64
3.43
3.95
3.29
3.29
3. 23
3.16
2.90
* Estimated.
Source: Wright-Pierce Architects and Engineers, engineers for
the Wilton, Maine project.
93
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TABLE 12 ENERGY AND COST-EFFECTIVENESS SUMMARY — HEAT PUMP
MflTMF
Item Value
Output, kJ x 106 — 3 362.14 -- $2,170
Input, kJ x 106 -- $ 124.84 — 31,560
Net gain, kJ x 10$ -- 3 237.30 — 3 610
Initial investment — 3 $11,025
Energy output/input ratio* 12 4*. 8 4 = 1]"5
Value output/input ratiob Sl'seo = 1.4
Simple payback (yrs)C =18.7
aEnergy ratio -- Total energy produced divided by energy input
required.
bValue ratio -- Dollar value of the energy produced divided by
the input energy cost.
cSimple payback — Installed cost divided by the savings. No
inflation factor for replaced fuels was applied. Maintenance
costs have not been included.
Source: Wright-Pierce Architects and Engineers, engineers for
the Wilton, Maine project.
94
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LAKE TAPPS SEWERAGE PROJECT 'BONNEY LAKE, WASHINGTON* — LOW-HEAD HYDRO (°, ',
d)
Background
Under the EPA innovative/alternative technology program, a hydraulic
turbine will he used for the first time in the United States to produce
electrical energy from an elevation drop in a sewage interceptor. Power
produced hy the turbine will he placed on the grin of the local electric
utility, and will more than offset all power used hy 11 lift stations in the
Lake Tapps Sewerage Project (located in northern Pierce County near Tacoma,
Washington). This project has Keen declared innovative hy EPA. Philip M.
Botch and Associates, Inc., of Bellevue, Washington designed the °,^n m?/d
(?..?. mgd) system.
System Description
Wastewater is collected from residences and businesses around Lal'e Tapps
near the City of Bonney Lal'e, Washington. Lake Tanps is a storage reservoir
for the White River Hydroelectric Plant. After wastewater is collected from
the area, it is to be lifted over a ridge and then dropped approximately 1°? m
(AOO ft) vertical distance over approximately I,fi07 m (3,*no ft* horizontal
distance to the Puyallup River flood plain after which it will flow *y gravity
to an existing sewage treatment plant at Sumner, Washington.
Initially, the Lake Tapps sewerage facility plan proposed a gravity sewer
interceptor to a treatment plant site on the floor of the Puyallup Valley at
Alderton. Although this was the most cost-effective alternative for the
participants, it was not environmentally-acceptable to the residents of the
region, who preferred routing the sewage to the City of Sumner Wastewater
Treatment Plant. The Sumner option is much more energy-intensive and requires
a large lift station to pump sewage over a hill and into the valley. The
energy necessary for pumping provided a strong incentive to seek a way of
recovering energy costs. In fact, the consumption of power to operate lift
stations was the primary environmental effect noted in the statement of
nonsignificant environmental impact.
The sewage collection area lies near a glacially-formed escarpment rising
from the Puyallup River flood nlain. The interceptor traverses the escarnment
en route to the Sumner Regional Treatment Plant. Various methods were
considered for dissipating energy across the escarpment. Deep-Hrop manholes
presented difficult construction and maintenance problems. A pressure sewer
with energy destruction presented erosion, cavitation, an^ foaming problems.
Reclaiming energy with a turbine generator offered a more cost-effective
solution with energy revenues offsetting tbe lift station energy costs. This
system will provide a shelter agajnst ever-increasing lift station energy
costs. " *
Component Description and Design Criteria
The proposed alternative technology includes the use of 1,0°5 m '3,^°? ft)
-------
of 4F.7-cm (18-in.) ductile iron 'DI) penstoc1" (hydrostatically-pressurized
force main) and a hydroel ectric generating station that will tie directly into
the utility power grid. The generating station will include a two-jet impulse
turbine and induction generator. The nozzles will he fixed open without
needles. A schematic of the system is shown on Figure "M. Characteristics
and performance information follows:
Penstock diameter
Penstock length
Vertical drop
Turbine/generator rating
Average flow ~ 1 0
$P,71?
Value of power in POP? with a ° 1/3 percent
annual compounded escalation rate M.e.,
617, <5m kWh at $n.?3R/kHh>
Turbine type
Number of nozzles
Governor
Generator type 1
Method of operation
Type of plant
Pel ton-imnul se
One
None
Induction
Automatic, unattended
"Run of river"
A preliminary treatment station, consisting of a comminutor, qrit
collector, and screen, will be located in the interceptor ahead of the
penstock. The turbine will have an automatic jet deflector to prevent
overspeed. A surge-relief valve will protect against inadvertent surges. In
the event the surge renef valve malfunctions, a blowout-rupture disc is
provided. If the turbine is down for repair, V-ball bv-pass throttling valves
will maintain the water level automatically in the forebay.
-------
Float Switches
High-level
Valve #2
Valve #1
Low-level
From
Lift
Station
vo
Valve #1
OPERATION
Level in Forebay trips Valve 81 float switch
1) Valve ill opens, flow to nozzle 81
2) Turbine starts
3) Generator comes on line
when speed is synchronous
Level in Forebay trips Valve 82 float switch
1) Valve 82 opens, flow to nozzle 82
Level in Forebay trips Low-level float switch
1) Valves close
2) Generator taken off line automatically
Level in Forebay trips high-level float switch
1) By-pass valve opens
2) Alarm sounds at City Hall
By -pass Valve
Nozzle #1
To Treatment Plant
>
Generating Station
Figure 34. Schematic diagram of Lake Tapps sewerage project (Bonney Lake, WA).
(Source: P.M. Botch and Assoc.,lnc., engineers for the Lake Tapps project.)
-------
A snecial variable opening nozzle employing a modifier! V-port valve will
be used to substitute for the nozzle in a common Pel ton turbine. THe nozzle
commonly used in a Pelton turbine uses a controlled needle opening. The
smaller annular space around the needle at low loads, along with the vane
straighteners supporting the needle steady bearing, appeared to present an
additional risk factor for clogging. The special nozzle will be tested in a
hydraulic laboratory before incorporating it in the turbine.
Energy System Performance Data
The energy analysis indicates that the five lift stations will require
137,984 kWh/yr at startup (?,575 m3/d or 0.68 mgd) and 461,Q25 kWh/yr in the
year 2000 (8,325 m^/d or 2.19 mgd). Similarly, the generating station will
produce 217,800 kWh/yr and 6°7,600 kWh/yr. Therefore, the net energy
production of the proposed innovative alternative is 79,816 kWh/vr at 2,575
m3/d (0.68 mgd) and 235,675 kWh/yr at 8,325 m-?/d (2.19 mgd).
NEWPORT, VERMONT — ACTIVE SOLAR FOR PROCESS HEAT (5^
Background
The wastewater treatment facility designed for the City of Newport,
Vermont incorporates innovative technology in its energy conservation
methods. The treatment processes include the following:
1. Bar screening.
2. Grit separation.
3. Primary clarification.
4. Aeration with fine-bubble diffusers.
5. Secondary clarification.
6. Chiorination.
7. Sludge thickening.
8. Two-stage high-rate anaerobic digestion.
The methane generated from anaerobic digestion is used to generate some of
the process heat for the digester. The innovative technology for energy
conservation includes an active solar system which is the primary heat source
for the digester.
The Newport wastewater treatment system was constructed under a grant from
EPA. Webster-Martin, Inc., of South Burlington, Vermont, designed the 4,540
m^/d (1.2 mgd) plant. Most of the information contained in this subsection
was obtained from the consultant.
System Description
The solar system has been designed for ?3? m2(?,5DO ft2) of
solar-collection field area, based on optimizing the auxiliary fuel purchase
against the cost of the system. With the solar energy being the prime heat
source for the digester, the methane gas produced in the digester could he
Q8
-------
considered as a fuel for an engine-powered generator that cou"M continuously
produce 15 kW of electric power. Through further consideration of this
operation, it was determined that the system could efficiently recover both
the heat from the engine jacket water and the exhaust stack. A reservoir for
short-term storage of heated water for the solar collection system could he
easily provided in the lower level of the control building.
The Newport system utilizes a two-stage high-rate anaerobic digestion
process. The first stage is mixed by compressed gas (methane) generated by
the process and injected near the bottom of the tank. The contents are
maintained at 3SOC (95°F) by a methane-fired boiler system and a
fuel-oil-fired boiler system. The second stage (not mixed) is heated to a
maximum temperature of 60°C (140°F). This second stage provides
additional passive stabilization, gravity concentration through supernatant
withdrawal, and residual gas accumulation and storage.
An additional innovative design incorporated in the Newport treatment
facility is the capability to utilize the contents of the secondary digester
for long-term storage of solar-collected heat energy. This feature will allow
recovery of not only the excess solar energy collected during warm weather,
but also recovery of the heat energy resulting from the ^50C (Q5°F) sludge
being transferred daily from the primary digester to the secondary diqester.
The treatment facility will also conserve heat enerqy by the following
means:
1. Use of activated carbon filtration to reduce the level of outdoor
ventilation air required by certain areas of the treatment facility
that need frequent complete air changes, such as pump galleries.
2. Use of rejected heat from the large horsepower aeration blowers to
heat the polymer feed room and janitorial area.
T. Use of radiant heat rejected by the engine-generator to heat the
plant control room, workshop, and toilet room.
In summary, the heatinq system designed for the Newport treatment facility
consists of several interconnected subsystems, as follows:
1. Solar collection system.
?.. Heat recovery system from the methane-powered electric generator.
3. Short-term hot-water storage.
4. Long-term heat storage in the secondary digest^.
The operation of these subsystems as one large heating system appears
possible in theory. While there is historical operational data from other
installations on subsystems 1, ?, and 3 there are no operational data on
subsystem 4, nor on the overall heating system. Control of the overall
heating system will take regular monitoring and fine tuning. The complete
aq
-------
heating system will reduce energy costs, and, if operated properly, should
result in increased reliability.
Component Description and Design Criteria
The control system flow diagram for the total heating system at the
Newport facility is shown on Figure ^. Table 13 summarizes the design
criteria for the active solar system at Newport.
Estimated Costs
Table 14 shows the estimated capital and installation costs for the
facility. The estimated annual electrical energy requirements (in kWVyr) are
shown in Table 1^. The estimated annual costs for electrical energy are
listed in Table 16. Table 17 shows estimated first-year OfcM costs, including
chemicals, electrical energy, fuel, sludge disposal, salaries, and maintenance.
HILLSBOROUGH, NEW HAMPSHIRE — PASSIVE SOLAR (?, 5)
Background
The Town of Hillsborough, New Hampshire, has chosen to inclement an
alternate energy systems approach in the design of their 1,800-m^/d fO.47^
mgd) wastev/ater treatment plant. The features included in this system are as
fo11ows:
1. Active and passive solar comfort heatinq.
2. Active domestic hot water heating.
3. Active solar heating of anaerobic digesters.
4. Passive solar enclosure for heating of rotating biological contactors
(RBC's)
5. Recycling of methane gas to power gas-driven electric generators.
6. Generator coolant heat recovery.
7. Ventilation system heat recovery via air-to-air heat exchangers.
8. Effluent heat recovery via heat pumps.
This project was approved as innovative technology by both EPA and the
State of New Hampshire. Anderson-Nichols (Boston) designed the Hillsborough
plant.
Special architectural design features that were incorporated include the
following:
1. Underground construction was utilized wherever possible.
?. Northern exposure of the facility was^inimized.
3. Concrete block and brick were used in conjunction with heavy
insulation to retain heat at night.
4. Facility roof was designed to retain a heavy snow load for natural
insulation.
100
-------
Sludge ioi 95'
60-
/• Sludge P'jmo
Switcnmg Valves
Secondary
Digester/ Heat
Storage Tank
Max 140"
725 000 Gal
Primary Heal/Water Storage Tanks
Control System Flow Diagram
ECS — Engine Cooling System
EHS — Engine Heat Storage
POH — Primary Digester Heating
SOS — Secondary Oigesier Storage
SHS — Solar Heating System
SHG — Solar Heating Glycol
HE — Heat Exchanger
V — Control Valve
T — Thermostat-Controller
P — Pump
PS — Pressure Sensor
Source Weeiur Mirtm me. irgin«era
lor m« N.woon. vT oroiect
Figure 35. Control system flow diagram for
Newport, VT
101
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TABLE 13 SELECTED DESIGN CRITERIA FOR ACTIVE SOLAR SYSTEM
FOR DIGESTER HEATING AT NEWPORT, VERMONT
Parameter
Value
Collector
Collector area
Collector area flow rate x
specific heat/area
Collector slope
Ground reflectance
Latitude (Burlington, VT)
Storage unit
Tank capacity/collector area
Storage unit height: diameter
ratio
Heat loss coefficient
Delivery device
Minimum temperature for
heat exchanger operation
Load
Daily operation time
Load return temperature
Auxiliary device
Auxiliary fuel type
Auxiliary device efficiency
232 m2
195.5 kJ/(hr x m2 x °C)
55°
0.5
44. 3°N
7,929 kJ/(°C x m2)
0.78
2.03 kJ/(hr x m2 x °C)
12. 8<>C
24 hr/day
Gas
0.8
Source: Webster-Martin, Inc., engineers for the Newport, Ver-
mont, project.
102
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TABLE 14 PRELIMINARY COST ESTIMATES FOR NEWPORT, VERMONT
Item Cost
($)
Existing building - preliminary treatment, pumping,
laboratory, etc. 345,300
Primary clarification, including flow split
Aeration tanks with diffusers 37?, 000
Secondary clarification with flow split 503,500
Gravity thickener and sludge blend 10R,000
Chlorine contact chamber 81,600
Basic building with basic equipment without heat 1,169,600
Primary digester 184,?00
Refurbish existing digester 134,500
Heating system Peo.SOO
Methane- fueled generator 30,000
Site work 470,000
Sludge storage (liquid) PP. OOP
Total $3, "60, 800
Source: Webster-Martin, Inc., engineers for the Newport, Vermont, project.
103
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TABLE 15. ESTIMATED ANNUAL ELECTRICAL ENERGY REQUIREMENTS FOR NEWPORT,
VERMONT.
Electrical
Unit Enerqy
(kWh/yr)
Continuous Operation
Influent pump 360,900
Comminutor and grit separator 12,300
Primary clarifier 8,800
Aeration ~ blowers 431,000
Secondary clarifiers 8,800
RAS pumps 149,000
Gas mixing 57,800
Sludge blend and gravity thickening 124,400
Plant water system 50,800
Chlorine rapid mix 15.700
Total continuous kWh 1,219,500
Intermittent Operation
Primary clarifier sludge pumps 6,200
Activated sludge wasting pumps 6,500
Grit-air scour and removal pump 16,000
Sludge pumping — heating and transfer 11,800
Miscellaneous and lighting 37.000
Total intermittent kWh 77.500
Total annual kWh 1,297,000
Source: Webster-Martin, Inc., engineers for the Newport, Vermont, project.
104
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TABLE 16 ESTIMATED ANNUAL COSTS OF ELECTRICAL ENERGY FOR NEWPORT, VERMONT.
Design/cost Total
Annual use 1,?97,000 kWh
Monthly average 108,100 kUh
Energy cost
First 25,000 kUh at $0.025/kWh $ 62^
83,100 kWh at $0.01913/kWh $ 1,594
135 kW demand at $1.55/kH $ ?09
$ 2,4?8 per month
$ 29,136 per year
Generated electrical energy 15 kW
Credit
15 kW demand x $1.55 x 12 $ ?80
IS x 24 x 365 x $0.01918 $ 2.5?0
- $ 2.800
Total annual,electrical energy cost $26,336
Source: Webster-Martin, Inc., engineers for the Newport, Vermont project
105
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TABLE 17 ESTIMATED FIRST YEAR OftM COSTS FOR NEWPORT, VERMONT
Item Cost
Chemical purchases $ 12,000
Electrical energy 26,150
Fuel — heat 1,000*
Sludge disposal IF,600
Salaries and administration 56,500
General equioment maintenance and replacement 11,000
$173,450
Present worth - 20 years at 7-2/8? $ 1,270,550
-Construction cost (estimated) 3,9*0.800.
$ 5,231,350
Annual heat energy cost as per computer run based on design year
conditions was $86^.57. The first year projected cost of purchased fuel
for heat was estimated at $1,000.
Source: Webster-Martin, Inc., engineers for the Newport, Vermont project.
10P
-------
Covered rotating biological contactors were selected to treat the
wastewater because the large surface area of the contactor is alternately
exposed to warmer air (which is passively heated by the sun), and to the
cooler wastewater. This procedure maintains the wastewater temperature,
thereby improving both RBC performance and effluent heat recovery via the heat
pumps.
System Description and Design Criteria
The wastewater treatment system consists of coarse screening and grit
removal prior to influent pumping to the primary clarifiers, covered RBC's,
secondary clarification, chlorination, and discharge. Primary and waste
secondary sludge is transferred to a solar-heated anaerobic digester. A
second unheated digester is provided to store and thicken the digested
sludge. Heat can be recovered from this unit.
Energy System Performance (Design) Data
Based on a unit-by-unit breakdown of power usage of individual pieces of
equipment, the basic energy requirement of the treatment system has been
estimated at 1,536 MkJ/yr (1,456 MBtu/yr). However, when energy credits are
applied for solar space heating, solar digester heating, and methane
utilization with heat recovery (by means of heat pumps), the total net energy
is as shown in Table 18.
TABLE 18. TOTAL NET ENERGY FOR PASSIVE SOLAR SYSTEM -- HILLSBOROUGH, MEW
HAMPSHIRE
Energy parameters
Net energy requirements
MkJ/yr
Basic requirements
Space heating credit from solar space heating
Digester heating credit from solar digester heating
Credit from methane utilization
Credit from heat recovery
Total net energy
1,536
(407)
(?76)
(36P)
Source: Anderson-Nichols X Co., Inc., engineers for the Hillsborough,
New Hampshire project.
107
-------
By implementing alternative energy sources, an estimated 80 nercent of the
energy requirements of the wastewater treatment system can he met
independently of outside sources.
Estimated Costs
The present worth of the estimated treatment plant construction, plus
project costs, is $2,428,000. The annual operation and maintenance cost
estimates for the wastewater treatment system are as follows:
Labor $ 31,000
Electrical power 9,715
Chemicals 3,155
Heating 1,0?S
Administrative and equipment allowance 7,500
Subtotal $ «\>,395
Credit for methane and heat recovery
Total $
The labor estimate is based on three full-time workers. The electrical
power cost estimate was developed from a breakdown of the various electrical
equipment requirements and estimates of approximate average running horsepower
requirements. Chemical costs were based on chlorine requirements, and on
expected chemical usage for sludge dewaterinq and miscellaneous laboratory
analyses. Heating requirements were based on the control building soace
requirements. A portion of the heat requirement for the digesters was
included to account for periods during which the solar-heating equipment might
not be adequate to meet that requirement (approximately 25 percent of the
time).
108
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LIVINGSTON, MONTANA — WIND POWER (?, 7, 8^
Background
The City of Livingston, Montana, has upgraded its wastewater treatment
plant to increase the treatment level from primary to secondary. The plant
utilizes rotating biological contactors to achieve secondary treatment. Basic
design criteria for the plant are as follows:
Design population 10,500 persons
Average daily flow 7,ci'70 m^/d
Peak flow 18,9?5 m3/d
BOD5 1,064 kg/d
TSS - 1,07? kg/d
Livingston is located in southwestern Montana P5.3 km (*?. mi ^, north of
Yellowstone Park along the Yellowstone River, and is an area of high wind
potential. Accordingly, the City of Livingston, in conjunction with the
Montana Energy and Research and Development Institute (MERDI), has received
funding from the State of Montana to construct a wind energy conversion system
(WECS) to generate electricity to power the wastewater treatment plant.
Because of the limited availability of funding, the WECS is to he constructed
in phases. The original design specified a wind farm consisting of eight
windmills. However, under available funding, only four windmills have been
installed thus far. The remaining four will be added as funds become
available. The wind farm as originally designed (i.e., with eight windmills^
is expected to supply a significant portion of the electricity for the
wastewater treatment plant.
The wastewater treatment plant expansion was funded by EPA. The windmills
were added later and have been funded by the State of Montana and through
private sources. The treatment plant was designed by Christian, Spring,
Seilbach and Associates (CSSA) of Billings, Montana. CSSA worked with Montana
Power Company, MERDI, and City of Livingston officials to determine the best
approach for incorporating WECS into the design.
System Description
The WECS is tied into the utility comnany grid system prior to reaching
the treatment plant. The necessary transformers, relays, and switches have
been designed into the system. The WECS output is metered prior to hoo|'up
with the utility grid. At the point of hookup, a relayed oil circuit breaker
is used to combine the WECS output with the utility grid so that sufficient
power may be supplied to the treatment plant.
The oil circuit breaker senses the energy being delivered by the WECS and
supplies the difference in load from the utility grid. The total energy being
ino
-------
delivered to the treatment plant is then metered downstream from the circuit
breaker. In this design, the treatment plant is assured of sufficient power
to operate when the wind is not Mowing. However, if the utility grid or the
line supplying the treatment plant qoes down, a switch automatically shuts
down the WECS, and simultaneously, a transfer switch activates the standby
generator. The standhy generator will supply energy to the primary loop until
the utility line comes hack into service and the WECS is turned hack on.
Component Description and Design Criteria
The total connected electrical energy load for the treatment plant is 177
kW (2?7 hp), and the probable onerating horsepower is 11^ HJ (IF? hp). The
wind farm has been designed to supply energy to meet these requirements.
Component Capital, Installation, and OEM Costs
The total installed capital cost for the eight-windmill wind farm is
estimated to be S^.onr) (1°PO dollars). The annual ORM costs are expected to
be $?,non.
SOUTHTOWN SEWAGE TREATMENT CENTER (WOODLAWM, NEW YORlO — WIND POWER (?, °, lf^
Background
The new wastewater treatment facilities at the Southtown Sewage Treatment
Center in Woodlawn, New York, will he powered hy wind turbine generators
(UTG). The Southtown facility is located on the shore of Lake Erie, near
Buffalo, New York, which is an area of strong and persistent winds. Initial
construction of the treatment facility began at Southtown in the fall of 1°77,
and all construction, including the wind turbine generator system, is expected
to be finished in February 1983. Design flow for the Southtown Sewage
Treatment Center is 60.5FO m^/d (16 mgd). Major unit operations include
pure oxygen activated sludge, chemical addition for phosphorus removal, sand
filtration, and chlorination. Sludge will he disposed of by incineration;
•however, this portion of the project has not yet been built. The effluent
will be discharged to Lake Erie.
WTG Energy Systems, Inc., Buffalo, New Yor1', designed the wind power
system for the treatment plant.
When the treatment plant reaches full operation, it is estimated that the
peak demand at the facility will be 1,7^0 kW. Using an estimated load factor
of W. percent, the annual kWh demand is projected to he l,7?n,0.00 kWh. A
system of three 200-kH wind turbine generators will provide over 11 percent of
the annual demand, displacing the equivalent of /I77 m^O.Onn bhl) of oil per
year. Based on a cost-effectiveness analysis, it is estimated that the net
annual savings from the wind turbine generator system will he in excess of
$21,nnn, as shown in Table 19.
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TABLE 19 COST-EFFECTIVE ANALYSIS FOR SOUTHTOWN SEWAGE
TREATMENT CENTER3'b
Period of analysis — 20 years
Life of equipment — 30 years
Discount rate — 7-1/8 percent
New York State Power Pool fuel oil rate -- ($/kWh)
Average statewide: summer (June-Sept.) — 30.0704/kWh
Average statewide: winter (Oct.-May) — S0.0618/kWh
Average statewide: annual rate
4/12 (0.0704) + 8/12 (0.0618) = 30.0689/kWh
First cost (installed unit) $1,010,688
Salvage value (1980 3) 336,896
Present worth of wind generators $ 673,792
Annual principal and interest payments
$673,792 x 0.093119 capital recovery factor 362,743
Annual operating costs
Lubricants and spare parts 3 4,500
Labor (234 hrs @ $10/hr) 3 2,340
Total operating costs $ 6,840
Total annual costs 369,583
Annual savings
1,320,000 kWh at 30.0689/kWh 390,948
Net annual savings 321,365
aJuly 1980.
DMultiple-unit (3) installation.
Source: "Proposal for the Installation of a Wind Turbine Gener-
ator (Model MP-200) at the Southtown Sewage Treatment
Center," by WTG Energy Systems, Inc.
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System Description
Three 200-kW wind turbine generators (model MP-?on, supplied by WTG Energy
Systems, Inc.) will provide the power. A typical wind turbine system has been
previously presented in Section 2.
The model MP-200 consists of a ?4.4 m (80 ft) diameter, three-blade upwind
rotor driving a 200 kW, 480-V, 60-cycle AC generator through a 1 to An ratio
speed-increaser fully-enclosed gear-drive assembly. The rotor, gear drive
assembly, generator, and hydraulic system are mounted on a rotating base and
are enclosed within the machine cabin. This assembly is mounted atop a ?4.4 m
(80 ft) pinned truss steel tower, and is yawed by a hydraulically-controlled
bull-gear unit that provides 360° positioning to ensure maximum upwind
efficiency of the rotor.
The rotor blades are a fixed pitch GA(w)-l airfoil desiqn incorporating
blade-tip drag flaps that are automatically activated to stop the rotor under
conditions of excessive wind speed, vibration, or any system malfunction.
This "fail-safe" system permits unattended operation of the wind turbine, and
prevents any aggravated system failures.
Electrical generation begins in wind speeds of ?.riR m/s (8 mph). The
rated generator output of POO kW is achieved at 13.4 m/s (30 mph), and the
maximum generator output of 313 kW is reached at a 15.fi m/s (35 mph) wind
velocity. Shutdown occurs at ?6.8 m/s (RO mph). The survival wind speed is
R7.1 m/s (150 mph). Throughout its operating range, the rotor of the MP-700
system will maintain a constant 30 rpm for the production of constant
frequency 60-Hz power.
The control unit of the MP-POO system is a solid-state microprocessor
located in the control house at the base of the tower. This preprogrammed
computer continually monitors and controls all generating and operational
functions of the wind turbine. The microprocessor ensures that, within the
range of productive wind speed, the maximum power output is introduced into
the utility grid system at precision-controlled voltage and frequency. Even
if the MP-200 system is the only generator on the transmission line system,
precise voltage and frequency will still be maintained.
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Component Capital and Installation Costs
The estimated capital and installation costs for the wind turbine
generator system, consisting of three 200-kW units, are as follows:
Three 200-kW wind turgine generators $ 787,300
Foundation $ 79,ROD
Erection $ 73,500
480-V distribution (305 m) $ fiO.ono
Testing $ 10.100
Total installed cost $ 1,010,700
Manpower Requirements
The estimated manpower requirements are based on operating experience from
other UTG, Inc., installations with MP-200 systems. The system is Designed
for unattended operation; however, the system will require an annual
allocation of approximately 78 man-hours for scheduled maintenance on each of
three wind turbine generators.
The estimated annual maintenance requirement for the MP-700 system has
been calculated based on data obtained from a wind analysis program conducted
at the Southtown facility, as follows:
Annual machine availability 90 percent (minimum)
Annual estimated machine operating time 5,804 hr (66 percent per year)
OftM Requirements and Costs
The estimated O&M requirements and costs are as follows:
Lubricants and spare parts (3 wind turbine generators
at $1,500) $4,500
Labor (3 wind turbine generators at 78 hr,
$10/hr) $?.34Q
Total annual operating costs $6,840
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WAYNESBURG-MAGNOLIA, OHIO -- PHOTOVOLTAIC '5
Background
The desiqn of the Waynesburg-Magnolia, Ohio, wastewater treatment system
incorporates both innovative treatment processes and energy-supply methods.
The treatment sequence includes the following unit processes:
1. In-line flow equalization.
2. Fabric belt primary filtration units.
3. Random-cage biological oxidation units.
4. Final clarification.
5. Disinfection (ultraviolet or sodium hypochlorite).
6. Sludge treatment by composting.
It is proposed that the entire plant be powered by solar (photovoltaic^
energy generated at the treatment plant. It is anticipated that ourchased
electricity will not exceed 25 percent of the total demand on a year-round
basis. The Waynesb'jrg-Magnolia project was gra-nted design and construction
funding from EPA in the summer of 1°81. Hammontree and Associates, Ltd.
(North Canton, Ohio) designed the 1,500 m^/d (0.4 mgd) plant.
System Description
All of the process units will be powered by the output from a photovoltaic
cell array located on the site. The primary heat source within the structure
will be latent heat from sewage in the treatment processes, augmented hy a
thermosolar heating system. Thermosolar panels will be located on the roof of
the structure.
As a backup source of a electrical power for the 20 to 25 percent of the
year when photovoltaic electrical generation may fall short of immediate
needs, a standby diesel-powered generator will be included in the equipment
design to ensure continuity of electrical supply. The photovoltaic and
standby systems could make the plant completely independent, and not require
any outside commercial power. By this arrangement, plant operation could be
100 percent self-sufficient for electrical energy.
Component Description and Desiqn Criteria
Construction of the Waynesburg-Magnolia Plant was expected to begin in
late 1982. The photovoltaic (PV) system has been provided hy Solarex
Corporation (Rockville, Maryland). Since their photovoltaic process has been
improved substantially, the size of the solar collector system has been
reduced to one-third the size originally estimated in the facilities plan.
The energy demand of the wastewater treatment system is estimated to be ?5
kW (33.5 hp). Solarex has estimated that to provide only the photovoltaic
grid system would cost $354,000, while installing both the photovoltaic grid
system and a battery storage system to provide a 20-day backup would cost
approximately $3,000,000. This would eliminate the necessity of providing a
hookup with the local utility. However, the decision has been made to not
provide the battery storage system at this time.
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The electrical system for the wastewater treatment plant will have
controls to determine the percentage of power provided ty the photovoltaic
system vs. the percentage required from the local utility. This photovoltaic
project was the first to receive innovative/alternative (I/A) fundinq in
Region V. It will serve as a pilot system, and data will be gathered on
collector efficiency, operation, OfcM problems, etc.
Component Capital and Installation Costs
Component capital, installation, and annual operating cost estimates for
the innovative design are shown in TaMe ?0.
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TABLE 20 WASTEWATER TREATMENT PLANT COSTS* FOR WAYNES-
BURG -MAGNOLIA, OHIO* -- INNOVATIVE DESIGN
Item Cost
(S)
Bar screen and conununitoc pad 3,000
In-Line Clow equalization 74,000
Paper filtration 70,000
Bio-drum secondary treatment 84,000
Final clarifiers 99,000
Upgrade laboratory and building 35,000
Disinfection 40,000
Cascade aeration 23,000
Composting equipment 38,000
Rehabilitate spiralgester 20,000
Building and concrete floor 170,000
Fencing 25,000
Solar power system (photovoltaic grid system) 354,000
Total plant construction costs SI,035,000
Engineering
- Solar energy system 55,000
- Plant design 140,000
Interest during construction 65,000
Resident engineer and construction supervision 92,000
Fiscal, administrative, and land acquisition 26,000
Contingency costs (5 percent)
Total plant capital costs
Annual 0&M costs
Manpower costs 18,000
Power costs 1,400
Supplies, including fabric cost 12,000
Maintenance of equipment 9.000
Total annual O&M costs $ 40,400
Present worth of 20-year O&M
20 years at 7 percent (10.594) x 40,400 - $428,000
Total plant construction costs present net worth including 20-
year O&M - $1,893,000
*March 1980.
#Plant capacity - 1.514 ra3/d
Source: Hammontree and Associates, Ltd., engineers for the
Waynesburg-Magnolia, Ohio project.
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REFERENCES
1. D.R. Fuller. "Integrated Energy Systems Monitoring, Municipal Wastewater
Treatment Plant, Wilton, Maine." Intermediate Report, U.S. EPA Contract
No. 6^-03
?. U.S. Environmental Protection Aaency. "Innovative Technology: Meeting
the Challenge of the Ws." !°«U).
T. Philip M. Botch and Associates, Inc. Consultant for Lake Tapps Sewerage
Project, l°ao.
A. U.S. Environmental Protection Agency. Internal memorandum from G.R.
Lubin, MERL TSG, to S.P. Duhois, Regional Administrator (Region X), 1^
August 1980. Subject: Review of Bonney Lake, Washington proposed
innovative energy recovery project.
5. B. Chenette. Personal communication. Consultant for Newport, Vermont
project, Webster-Martin, Inc., S. Burlington, Vermont, lnR?.
*. Rushbroo1', E.L. and D.A. Mi Ike. "Energy Conservation and Alternative
Energy Sources in Wastewater Treatment." Journal of the Matpr Pollution
Control Federation, In8n. p. ?&77 .
7. U.S. Environmental Protection Agency. Internal memorandum from R.L.
Williams, Regional Administrator 'Region VIII), to H.G. Pippen, Jr.,
Director of Grants Administration Division, ?* August 1°RO. Subject:
Wind energy system for the City of Livingston, Montana.
8. J. Boyter. Personal communication. U.S. Environmental Protection Agency
Innovati ve/ Alternative Coordinator for Montana.
n. U.S. Environmental Protection Agency. Internal memorandum from J.J.
McCarthy, MERL TSG, to C.S. Warren, Regional Administrator (Region IP, 1
January 1°R1. Subject: Innovative technology review for the Southtown,
New York sewage treatment center.
10. WTG Energy Systems, Inc. General information and system descriotion of
Model MP-?nn"wind turbine generator, loon.
11. U.^7 Environmental Protection Agency. Internal memorandum from C.J.
Pycha, Region V I/A coordinator to J.M. Smith, MERL, ?~> April ]°81.
Subject: Review of Wayneshuro-Magnolia, Ohio, innovative project.
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