Topic Area: Solar Energy
Geographic Area: Wyoming, United States
Focal Question: Is solar energy a cost-effective alternative
energy source for pumping water in rural areas?
Sources:
(1) Chowdhury, Badrul H., Sadrul Ula, and Kirk Stokes.
"Photovoltaic-Powered Water Pumping - Design, and Implementation:
Case Studies in Wyoming." IEEE Transactions on Energy
Conversion volume 8, number 4, December 1993: 646-652.
(2) Hoagland, William. "Solar Energy." Scientific American.
volume 273, number 3, September 1995: 170-173.
Reviewer: Jill M. Maccaferri, Colby College '96
Review:
This study, conducted by five rural electric cooperatives in the
state of Wyoming with the help of Sandia National Labs and the
University of Wyoming, examined photovoltaic-powered water pumping
systems installed in seven rural areas in Wyoming. A major objective
of the project was to introduce and test alternative energy sources
in rural areas located far from the established electricity grid. The
study found that indeed photovoltaic-powered systems were
cost-effective for these sites and were denoted as satisfactory
sources of energy by the system owners.
Photovoltaic pumps use solar panels to collect and convert solar
energy into electricity which is then used to power the electric
water pumps. Systems may include batteries or sun trackers although
these are not necessary. The systems have few moving parts and are
relatively easy to maintain. Owner feedback from the study asserted
that an example of the maintenance required was simply to clean the
modules periodically due to the accumulation of dust and bird
droppings. On days with insufficient sunlight to run the system, a
battery or generator may be used as a back-up power supply.
Before the systems were set up in the rural areas, extensive site
testing was needed in order to determine the type of system necessary
for the specific area as changes in pump requirements change the cost
of the systems. Technical factors that needed to be examined were the
site terrain, storage system details, the amount of water that was to
be pumped, the season during which the water would be pumped, and the
uses for the water. It was important to optimize the technical
factors in order to provide the user with the correct type of pump.
For each of the seven locations chosen the end use for the water was
for livestock, although the seasonal use of the water varied from
location to location. Six of the seven sites used a panel-direct
system without a battery. The panel-direct system is used for low
volume pumping, requires a large number of photovoltaic modules to
generate enough energy to run the motor, and generally will not
operate on days with inadequate sunlight. As such the storage systems
are very important so that water will be available even on those
cloudy days when the system does not operate to capacity. The
remaining system used a battery to run the motor and was studied to
determine the ability of batteries to withstand freezing
temperatures.
The study found that the photovoltaic-powered pumping systems were
cost-effective alternatives to extending the existing power lines to
the rural areas. Although the photovoltaic systems do have high
initial capital costs, the same is true for extending power lines to
remote areas (See table). Once the costs of excavation, wiring costs,
and the costs of transformers are considered, it is evident that
extending the power lines can be quite costly. The cost of the
photovoltaic system is related to the amount of water pumped and the
distance from which the water needs to be pumped. As either of these
requirements increases, the amount of energy required also increases.
In order to generate a sufficient amount of power, more solar panels
would need to be added. This can significantly increase the cost of
the photovoltaic system. For instance, the cost of a photovoltaic
system to pump 570 gallons of water per day up 50 feet would amount
to $1400 and would use 40 watts of electricity. To pump 6480 gallons
of water per day up the same 50 feet would require a system that cost
$6500 and used 250 watts.
The sites were monitored and owner feedback was recorded. Of the
seven systems in operation, five reported system problems. However it
must be noted that the majority of problems were not directly due to
the failures of the systems themselves but instead to
non-system-related problems. One problem was damage caused by wind.
The high winds that can often occur in Wyoming damaged the shock
absorber at one site but on both occasions the shock absorber was
repaired. At two locations the pump clogged due to sand from the
well. Another site reported a well collapse and the final site
reported the electric float switch froze due to freezing
temperatures. The switch was replaced by a ball float and continued
to operate as planned. Despite these setbacks, on the whole owners
reported they were satisfied with their systems. The results of the
study sparked interest for other rural sites in Wyoming. Currently
over 20,000 photovoltaic-powered water pumps are in operation around
the world.
Utilizing photovoltaic-powered water pumps promotes sustainability by
decreasing the demand for non-renewable energy sources such as fossil
fuels. This can result in many environmental benefits such as
decreasing the levels of atmospheric carbon dioxide, air pollution,
and acid rain. The photovoltaic pumps in Wyoming benefited both
parties involved as neither the owners of the sites nor the local
utility had to pay for extending the power grid to remote areas,
while at the same time improving the environment by reducing the
demand for fossil fuels. In conclusion, this study has demonstrated
that photovoltaic-powered water pumps are a cost-effective solution
to conventional energy sources for rural sites and photovoltaics are
certain to become more prevalent in other aspects of daily life.
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Design flow rate (gal/day) |
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End Use |
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Seasonal Use |
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Total rated power (Watts) |
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Installed Cost ($) |
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Utility Line Extension |
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Distance (miles) |
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Cost ($) |
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