The Small Community Solar Thermal Power Experiment will test a point-focusing, distributed receiver system in a small community, electric utility application. Site planning is becoming increasingly important for solar experiments as well as all kinds of development due to increased competition for desirable sites and increased complexity of regulatory requirements. Siting issues can be categorized as: (1) resources and physical environmental at this site; (2) acquisition, permits and regulations; and (3) development requirements and costs. These issues are addressed with respect to the unique requirements of solar thermal power experiments

Holbeck, H. J.

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N84 24'783
SITING SOLAR THERMAL POWER EXPERIMENTS
H.J. Holbeck
Jet Propulsion Laboratory
Pasadena, California
ABSTRACT
Solar thermal power experiments will provide experimental operation data bases
leading to later full.-scale demonstrations. The Small. Community Solar Thermal
Power Experiment will test a point-focusing, distributed receiver system in
a small community, electric utility application. Site participation and system
development for this experiment are being pursued in separate, coordinated
efforts.
Site planning is becoming increasingly important for solar experiments as well
as all kinds of development due to increased competition for desirable sites
and increased complexity of regulatory requirements. Siting issues can be
categorized as:
1) Resources and physical environment at this site
2) Acquisition, permits and regulations
3) Development requirements and costs.
In this paper these issues are addressed with respect to the unique requirements
of solar thermal power experiments.
INTRODUCTION
Solar Thermal Power Applications Experiments
Purpose of Applications Experiments
Point-focusing distributed receiver system technologies and applications are
being developed as part of a program to provide solar thermal power alternatives
for future energy needs. Key elements in this development are system experiments
which test technologies in representative user environments. These experiments
provide realistic data bases for design modifications, user interfaces and
extrapolations of experimental operation which will lead to full--scale demon-
strations and then to commercial applications.
Application Experiment Plans
Applications for point-focusing distributed receiver systems include electric
utilities, isolated loads and industrial thermal and electric power. Two
applications experiments have been defined. The Small Community Solar Thermal
Power Experiment will be on-line in 1983. Preliminary system design is underway,
and site participation proposals are being evaluated by DOE. The Military
Module Power Experiment is a cooperative project with the Navy and will also
be on-line in 1983. The system development procurement is in process for a
100 KWe experiment at the Yuma Marine Air Station. Additional experiments
are planned.
169
https://ntrs.nasa.gov/search.jsp?R=19800016290 2020-03-21T18:58:31+00:00Z
DIRECT AND TOTAL INSOLATION
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	 TRACKING HELIOI
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TOTAL HORIZONTAL INSOLATION
/	 (PYRANOMETER)
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(b) 3 DEC 1974
UNCLEAR
TOTAL HORIZONTAL INSOLATIOI(PYRANOMETER) I
DIRECT NORMAL INSOLATIO1(TRACKING HELIOMETER)
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6	 8	 10	 12	 14	 16
TIME (PST), hours
170
Small Community Solar Thermal Power Experiment
The first experiment in the electric utility application area will use near-
term point-focusing distributed receiver technologies. The experiment will
be located in a distinct urban or rural community, preferably, with a peak
electric power requirement of less than 20 MWe served by an electric distribu-
tion system owned and operated by its own utility. The construction of the
experimental solar thermal power plant will be accomplished by a system
contractor in a parallel but separate action to site participation. The
site participant as a cooperative partncx will provide support including:
1. A suitable 10 acre site with appropriate zoning and permits for experi-
mental plant activities.
2. Access roads and utility service to the site.
3. An electrical interface to the participant's distributional network.
4. Various data, maintenance and operational support services.
Site Development Trends
Increased competition for the most desirable sites is resulting in higher costs
and the use of marginal sites. Regulatory requirements are also increasing,
and the involvement of more agencies is leading to increased permit acquisi-
tion time. At the same time construction costs are rsing more rapidl y than
general inflation. Further, local authorities are imposing additional
development requirements including peripheral and off-site development.
These trends increase the importance of site planning.
SITING FACTORS
xactoro for any kind of site development can be considered within three cate-
gories. Resource availability includes not only the resources important to
the development, but also those environmental factors which mitigate the
effectiveness of the resources. Site availability includes the actual
acquisition of the site together with the regulatory environment which affects
the timely availability of the site for the intended development. The
remainder of this paper addresses these siting categories as they affect an
experimental solar thermal power plant.
Site Resources
Solar Thermal System Requirements
The most important resource required by a solar thermal power plant is direct
normal insulation. Whl.le this is primarily a regional resource it also varies
with local atmospheric shading conditions. Environmental, factors such as
wind impact the effective utilization of the solar resource while dust and
pollutants can degrade the ability of the system to utilize the solar resource.
Direct .Normal Insolation
The solar resource includes direct and diffuse components. Flat plate, low
temperature technologies utilize both components, and most solar data is
171
measured as total insolation on a horizontal surface, Point-focusing solar
thermal systems track the sun and concentrate the solar energy to produce
high temperatures. Since the diffuse insolation component cannot be effec-
tively concentrated, these systems utilize only the direct normal, insolation
component.
Figure 1 illustrates the difference between direct and total insolation for
two winter days in the California desert. On a clear day the direct normal
insolation exceeds the total horizontal insolation because of the cosine
of the sun's inclination angle. On the unclear day the situation reverses.
The total horizontal insolation remains at about half of the clear day levels,
consisting primarily of the diffuse component. However, there is litC; w
effective direct normal insolation. This difference between direct an.
total insolation results in different regional, distributions. There is a
dominant latitudinal variation in total horizontal insolation while there
is a dominant longitudinal variation in direct normal insolation, primarily
due to cloud cover.
Local. Obscuration and Shading
Local available direct insolation may differ significantly from the indicated
regional values. Fog or clouds can reduce the fndieatled regional insolation
while regional insolation may be understated if there are local cloud
conditions at the nearby measuring station. The local insolation resource
can also be reduced by shading from nearby topographic features or buildings
which interrupt the solar view i,n southerly directions above a 10 degree
angle from the horizontal.. North facing slopes on the site require greater
spacing between concentrators to preclude shading from adjacent concentrators.
Future land uses adjacent to the site must be considered, and this may involve
easements for solar access.
Environmental Factors
The effective availability of the insolation resource may be mitigated by
various environmental factors. Concentrator structures are designed to
withstand 100 mph winds when stowed, but they will not operate at full
efficiency in winds exceeding 30 mph. Dust and air pollution require more
frequent concentrator cleaning and may lower the efficiency of concentrator
surfaces.
Site Availability
Site and Permit Acquisition
Competition for land has led to the increased use of sites with some kind of
development problem. Indeed, some land may not be available for development
at any reasonable cost or effort. Additionally, the acquisition of title
is no guarantee that the land will be available for the ,intended development.
Zoning and land use plans are becoming increasingly important factors, and
proposed developments proceed more smoothly if they are compatible with these
plans rather than in opposition. This can mean the difference between a
minimum permitting effort and costly, time-consuming public hearings.
172
Environmental Impact
One of the advantages of solar thermal power is the renewable, clean nature
of the solar energy resourceo hence, solar thermal power will have leas
environmental impact than fossil or nuclear power plants. In addition solar
power is perceived by the public to be environmentally desirable. However,
potential environmental impacts cannot be ignored. Any development project
disrupts the env ironment on and around its site. Washing of collectors
and potential spills of heat transfer fluids could affect nearby aquifers.
The visual impact of collectors may be offensive to some. These potentialimpacts
and alternative land uses need to be considered not only with respect to
the permitting of the experimental plant, but also with respect to public
perception of eventual large-scale solar thermal. development.
Site Development
Solar Thermal Land Requirements
The dispersed nature of the solar resource leads to rather large land area
requirements for solar thermal power plants. Land requirements for near term
technologies are approximately lO acres for a plant with a peak power output
of 1 MWe. As system efficiency increases it is expected that this will he
reduced to about 3 acres per MWe, still a large area compared to direct fossil
plant requirements.
Site Preparation Costs
Because of the large area requirements, site preparation is an important
part of the total. cost of a solar thermal power plant, Site preparation
includes clearing, grading, drainage, access and perimeter improvement.
These activities are part of a mature construction technology with little
opportunity for cost reduction through technology improvement.
Site preparation costs are also signiV cantly affected by size. The land
requirements for a plant are non-linear because of the unused area around
the plant perimeter. Unit costs for clearing and grading are fairly constant
with size but perimeter costs vary with the square root of area because
of the geometric relationship. Perimeter development requirements for
architectural walls, landscaping, et cetera cannot be overlooked, particularly
when the plant is located in or near town close to the end user.
Potential Reduction of Site Preparation Costs
As solar thermal system costs are reduced, site preparation and construction
becomes proportionally a more important cost factor. Several approaches to
cost reduction have been considered. Higher system efficiency with the
resulting lower area requirement has an obvious effect as does the selection
of sites with minimum development requirements. Beyond this, cola no.tor
foundation construction similar to that for transmission towers is being
considered to reduce the grading at each collector location and to minimize
access requirements to constru r .tion equipment. Field layouts can be considered
,Yhich utilize a site primarily in situ. This may increase collector spacing
Wt could still considerably reduce site preparation efforts.
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Siting solar thermal power experiments

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