United States
Environmental Protection
Agency
Research and Development
Water Engineering -~^1»"
Research Laboratory 't jrj v
Cincinnati OH 45268
EPA/600/S2-88/043 Nov. 1988
&EPA Project Summary
Alternative Energy Sources for
Wastewater Treatment Plants
This technology assessment pro-
vides 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 de-
scriptions) and data sheets (cost and
design information) for the tech-
nologies. 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 technol-
ogies are presented.
Based on this assessment the fol-
lowing alternative energy technol-
ogies appear to be potentially cost
effective:
1. Heat pumps which use influent or
effluent wastewater as their heat
source, for supplying process or
building heat
2. Geothermal direct-use systems
for large energy loads when geo-
thermal source is adequate.
3. Wind power systems for large
electrical loads when annual wind
flux is adequate.
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 Project Summary was devel-
oped by EPA's Water Engineering
Research Laboratory, Cincinnati, OH
to announce key findings of the
research project that Is fully docu-
mented in a separate report of the
same title (see Project Report
ordering Information at back).
Introduction
This technology assessment provides
an introduction to the use of several
alternative energy sources at wastewater
treatment plants. This document as-
sumes that the reader has little or no
knowledge of the following technologies:
1. Heat pumps,
2. Active solar systems for heating and
cooling,
3. 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,
9. Fuel cells, and
10. Active solar systems for power
generation.
For each of these technologies, the
report presents a "fact sheet" that
contains a description of the technology
(including schematic diagrams), the
current status of development and
applications, design considerations,
performance and reliability information,
and a reference list. For the first six
technologies listed above, simplified
design and cost-estimating information
is presented in "data sheets". Data
collection for the report was done in
1982, therefore, the costs presented
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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.
1. Wilton, ME (active solar for process
heating, passive solar, and heat
pumps),
2. Lake Tapps (Bonney Lake, WA)
sewerage project (Low-head hydro),
3. Newport, VT (active solar for process
heating),
4. Hillsborough, NH (passive solar),
5. Livingston, MT (wind power),
6. Woodlawn, NY (Southtown plant)
(wind power), and
7. Waynesburg-Magnolia, OH (photo-
voltaic).
Of the seven case histories, only
Wilton, ME had been on-line long
enough at the time the report was written
to have meaningful operating data.
Conclusions
Heat Pumps
Heat pumps are commercially avail-
able. 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 invest-
ment.
Photovoltaic Systems
Photovoltaic systems are commercially
available. The available solar insolation
rate, system energy conversion effi-
ciency, 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 alterna-
tives to the use of conventional electrical
energy supplies in POTW's.
Geotherma/ - Direct Use
Systems
Geothermal direct use systems are
commercially available. Geographical
limitations associated with the geo-
thermal 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.
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-m2 or greater.
Locations with annual wind flux greater
than 4,000 kWh/yr-m2 are predomin-
antly limited to areas in the following
states:
• Maine
• Vermont
• New Hampshire
• New York
• Virginia
• North Carolina
• Kansas
• Oklahoma
• Colorado
• Wyoming
• Montana
• Idaho
• Utah
• Nevada
• Washington
• California
Low-Head Hydro Systems
Low-head hydro systems are com-
mercially available. Geographical limita-
tions 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
satisfying a significant portion of
POTW's electrical requirement, the
systems appear to be more approprie
for smaller POTW's. The use of the
systems should be seriously consider
in any application that has an availat
head greater than 3 m.
Passive Solar Systems
Passive solar systems are cor
mercially available. These systems ha
been used previously to reduce tl
consumption of conventional heatir
fuels in POTW's, as well as many oth
architectural applications. The princip
technical limitations of passive sol
systems are possible site-specif
limitations on available solar insolatk
and the integration of the passive syste
into the overall architectural pla
Potential economic limitations a
primarily associated with the increment
costs for construction of the passive sol
system instead of a convention
architectural design. These increment
costs must he considered, along with tl
amount of alternative energy supplied, (
a case-by-case basis to potential
justify the use of a passive solar syste
in specific applications. In light of tt
rising costs for conventional fuels, the;
systems should be seriously consider*
in future construction at POTW
throughout the United States.
Geothermal - Power System
Geothermal power systems ai
commercially available, however, curre
technological limitations on minimu
system size, as well as the limite
availability of acceptable sites exhibitir
the necessary geothermal characteristic
will likely prevent the use of thes
systems in POTW's.
Fuel Cells
Fuel cells are not expected to b
commercially available until approx
mately the year 2000.
Active Solar Systems for Powt
Generation
Active solar systems for powe
generation are not expected to b
commercially available until the mi
1990's. In addition, these systems ce
only use direct sunlight, and, therefor
their applications would be primari
limited to arid regions of the southwest.
The full report was submitted i
fulfillment of Contract No. 68-03-305
by Roy F. Weston, Inc., under th
sponsorship of the U.S. Environment
Protection Agency.
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This Project Summary was prepared by staff of Roy F. Weston, Inc., West Chester,
PA 19380.
Francis L Evans was the EPA Project Officer (see below for present contact).
The complete report, entitled "Alternative Energy Sources for Wastewater Treat-
ment Plants," (Order No. PB 88-239 090/AS; Cost: $21.95, subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
For further information, Donald S. Brown can be contacted at:
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
A
Official Business
Penalty for Private Use $300
EPA/600/S2-88/043
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