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Renewable and Sustainable Energy Reviews
12 (2008) 472–487
Solar photovoltaic water pumping
for remote locations
Kala Meah
, Steven Fletcher, Sadrul Ula
Wyoming Motor Testing and Training Center, Electrical and Computer Engineering Department,
1000 E. University Avenue, University of Wyoming, Laramie, WY 82071, USA
Received 8 August 2006; accepted 13 October 2006
Abstract
Many parts of the world as well as the western US are rural in nature and consequently do not
have electrical distribution lines in many parts of villages, farms, and ranches. Distribution line
extension costs can run from USD 10,000 to USD 16,000/km, thereby making availability of
electricity to small water pumping projects economically unattractive. But, ground water and
sunlight are available, which make solar photovoltaic (SPV) powered water pumping more cost
effective in these areas’ small scale applications. Many western states including Wyoming are passing
through the sixth year of drought with the consequent shortages of water for many applications. The
Wyoming State Climatologist is predicting a possible 5–10 years of drought. Drought impacts the
surface water right away, while it takes much longer to impact the underground aquifers. To mitigate
the effect on the livestock and wildlife, Wyoming Governor Dave Freudenthal initiated a solar water
pumping initiative in cooperation with the University of Wyoming, County Conservation Districts,
Rural Electric Cooperatives, and ranching organizations. Solar water pumping has several
advantages over traditional systems; for example, diesel or propane engines require not only
expensive fuels, they also create noise and air pollution in many remote pristine areas. Solar systems
are environment friendly, low maintenance, and have no fuel cost. In this paper the design,
installation, site selection, and performance monitoring of the solar system for small-scale remote
water pumping will be presented. This paper also presents technical, environmental, and economic
benefits of the SPV water pumping system compared to stand alone generator and electric utility.
r2006 Elsevier Ltd. All rights reserved.
Keywords: Solar photovoltaic; Water pumping; Remote locations; Environment
ARTICLE IN PRESS
www.elsevier.com/locate/rser
1364-0321/$ - see front matter r2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.rser.2006.10.008
Corresponding author. Tel.: +1 307 766 2702; fax: +1 307 766 2248.
E-mail address: kmsujon@uwyo.edu (K. Meah).
Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473
2. Solar photovoltaic water pumping systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474
2.1. The PV array . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475
2.2. The pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475
2.3. The pump–motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476
2.4. The controller. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476
3. Technical factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476
4. Economic aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478
5. Environmental aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480
6. Site selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481
7. Design and installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482
8. Performance monitoring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483
8.1. Fifteen-year assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484
8.2. Five-year assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485
8.3. One-year assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485
9. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487
1. Introduction
Solar photovoltaic (SPV) water pumping (SPVWP) has been implemented around
the globe as an alternative electric energy source for remote locations since SPV
was invented [1–9]. The SPV system are cost effective in many remote applications
such as water pumping for households, livestock and wildlife, space heating, lighting
remote vacation homes, and emergency traffic applications [10–12]. The photovoltaic
(PV) is a mature technology to convert sunlight into electricity. The efficiency of
the PV cell has increased significantly in the last 25 years. About 1460 MW of
solar PV systems were installed in worldwide in 2005 that represents a growth
of 34% over 2004 installations. Annual PV domestic shipments in the USA in 2005
were 104 MW, which is 33% more than 2004 [13]. But, still the PV system cannot
compete with the traditional energy resources such as coal, oil, natural gas and
conventional hydro for the large-scale commercial, industrial and residential applications.
A PV system is suitable for a small scale remote application where 24 h electrical
service is not necessary and maintenance is an issue. Wyoming is the least populated
state in the USA and most of the ranching areas are in remote locations. The grid
electricity supply is not available to all ranches throughout the state that makes the
situation worse during summer to pump underground water. The state of Wyoming
stepped into the sixth year of drought and most surface water is drying up in early
June. Fig. 1 shows drought condition in the USA and Wyoming is one the most affected
states [14].
Long-term drought has severe impact on the surface water, which is the only source
of water for the wildlife and in many cases for the livestock. To help the drought
affected remote livestock and wildlife, Governor Freudenthal started a solar water
pumping initiative in cooperation with the University of Wyoming Motor Testing and
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K. Meah et al. / Renewable and Sustainable Energy Reviews 12 (2008) 472–487 473
Training Center (UWMTTC). This initiative allows the UWMTTC to install four solar
pumping systems in each county of the state during 2005–2006. The UWMTTC also
supervised the installation of 15 SPVWP systems during 1991–2002. The project objectives
were to:
supply solar water pumping system to drought affected remote livestock and wildlife,
educate people about clean and alternative energy,
monitor system performance and give free maintenance service for 2 years,
monitor customer satisfaction,
evaluate performance of old PV systems.
This paper describes technical, economical, and environmental aspects, along with
performance evaluations and other details that include site selection, system design, and
installation.
2. Solar photovoltaic water pumping systems
PV system is based on semiconductor technology that converts sunlight into electricity.
This is a proven technology but costs more than other electricity generation methods such
as power plant based on coal, oil, natural gas and conventional hydro. Fig. 2 shows
a schematic diagram of a solar water pumping system. This section provides a brief
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Fig. 1. Drought situation in the USA, July 2006.
K. Meah et al. / Renewable and Sustainable Energy Reviews 12 (2008) 472 –487474
discussion about the main component of an SPV water pumping system for livestock and
wildlife in remote locations.
2.1. The PV array
The source of electrical energy of the SPVWP systems is the PV arrays. Every PV
array has its own (I–V) characteristics. The maximum power point (MPP) depends on
several factors including on site solar radiation, temperature, and the connected load—if
the load is directly connected. For the same amount of power, array size depends on the
efficiency of the cell. Solar cells could be divided into three categories according to
the type of crystal: monocrystalline, polycrystalline and amorphous. The level of
efficiencies in production is about 7%, 15%, and 17% for amorphous, polycrystalline,
and monocrystalline silicon, respectively.
2.2. The pump
Solar water pumps may be subdivided into three types according to their applications:
submersible, surface, and floating water pumps. A submersible pump draws water from
deep wells, a surface pump draws water from shallow wells, springs, ponds, rivers or tanks,
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Fig. 2. Schematic diagram of a solar water pumping system.
K. Meah et al. / Renewable and Sustainable Energy Reviews 12 (2008) 472–487 475
and a floating water pump draws water from reservoirs with adjusting height ability. There
are several types of pumps according to their pumping principle:
Centrifugal pumps, where liquid is sucked by the centrifugal force created by the
impeller and the casing directs the liquid to the outlet as the impeller rotates. The liquid
leaves with a higher velocity and pressure than it had when it entered.
Screw pumps, where a screw traps the liquid in the suction side of the pump casing and
forces it to the outlet.
Piston pumps, where motion of the piston draws water into a chamber using the inlet
valve, and expels it to the outlet using the outlet valve.
The selection of pump in a solar water pumping is solely application dependent, such as
water requirement, water height, and water quality.
2.3. The pump– motor
Several types of motors are currently available in the market, such as AC, DC, permanent
magnet, brushed, brushless, synchronous and asynchronous, variable reluctance, and
many more. The PV array could be directly connected to the motor, if the application needs
a DC motor. If the application needs an AC motor, an inverter (usually called controller)
needs to be placed in between the PV array and the motor. The motor and pump are built in
together for the submersible and floating systems, in this case, the consumer does not
have an option to choose the pump and motor separately. In the surface system, it is possible
to choose the pump and motor separately and examine the performance along with the
controller and panel.
2.4. The controller
The controller is mandatory if the AC motor is in use. The controller effectively isolates
the PV array from the pump–motor system for greater safety and provides the
pump–motor with the optimum voltage/current for the site conditions. The controller
also protects the pump–motor from running dry and conserves water by turning off the
system when the tank is full. However, one of the most vulnerable components in the SPV
water pumping system is the controller because it contains sophisticated electronics and
has to operate in various environmental conditions.
3. Technical factors
The SPVWP is proven technically and economically in Wyoming [8]. Technical
discussion is limited to a small scale (less than 1500 W) water pumping system and in a
remote location, which is 1 km or more away from the power distribution line. One
kilometer of distribution line extension costs between USD 10,000 and USD 16,000: but a
complete small-scale solar water pumping system costs between USD 3000 and USD
10,000. On the other hand, power companies are not eager to build a single transmission
line just for a remote water pumping because of the low seasonal revenue. A solar water
pumping system usually does not include any battery back up. This makes it maintenance
free and stand alone PV system, and lowers both the complexity and the capital costs.
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K. Meah et al. / Renewable and Sustainable Energy Reviews 12 (2008) 472 –487476
Typically, ranches have more than one pasture and usually different pastures are used for
grazing in different time of the year for the efficient use of land. The solar water pumping
system on a trailer could be a good choice in this case. Fig. 3 shows an SPV system
mounted on a trailer for use in multiple water wells.
One of the main challenges of this project is to make the SPVWP system more user
friendly, and adopt locally available materials for convenience of handling future
maintenance problems. The UWMTTC took some initiatives to facilitate the local level
operation and maintenance (O&M):
(a) modify the system based on local materials,
(b) use materials from local suppliers,
(c) educate people through the workshop, training, and demonstration.
Local level O&M is very important for any small scale system, because the system
provider will not be there for a long time. Also, it is not cost effective to call the system
provider to maintain small systems, such as SPVWP systems. Fig. 4 shows the rack
mounted and pole mounted solar panels, where rack mounted solar panels are a modified
version of pole mounted solar panels. In this case, local materials are used to reduce the
system cost as well as to add mobility to the system. The UWMTTC used materials from
local suppliers in order to make future maintenance problems easier. If any component
fails in future, the owner can get the component from local suppliers. The UWMTTC
arranged a series of workshops, demonstrations, and training sessions throughout the state
to educate the people about the SPVWP system. The goal of this initiative is to employ
local skills, resources, and materials for O&M.
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Fig. 3. Solar pumping system mounted on a trailer.
K. Meah et al. / Renewable and Sustainable Energy Reviews 12 (2008) 472–487 477
Small generators and windmills can be alternatives for remote water pumping but they
have some significant downsides. A generator could be turned on and off using a remote
switch but regular maintenance and refueling requires physical presence at the site. Windmill
has mechanical moving parts that make noises and need regular high maintenance, costly
repair, difficult to find parts, special tools for installation, and intensive labor. Windmills do
not have any remote control or automatic shut off in case of overflow. Windmills cannot be
used for multiple water wells in different pastures. On the other hand, PV water pumping
systems are equipped with automatic turn off mechanism when the tank is full. They also
sense the water level of the well, when the water level is low, the system is turned off and
waits a few minutes for the well to be recharged. A PV system is a maintenance free auto
operative stand alone water pumping system that is cost effective and technically suitable for
remote livestock and wildlife. Table 1 shows a comprehensive comparison of alternative
energy options for small scale remote water pumping.
4. Economic aspects
The capital cost of the PV system includes solar panels, pump, controller/inverter, power
cables, draw down pipe and accessories. The capital cost of electric utility includes
transmission line instead of solar panels and other system components are the same.
The capital cost of a diesel generator includes an electric generator instead of solar panels
and other system components remain the same. The PV system does not have any
operating cost, but electric utility costs 5–13 b/kWh and diesel costs $0.6/kWh with high
maintenance cost. The efficiency of a diesel generator goes down with time, where as the
PV system produces same power throughout its life span. A project can be justified using
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Table 1
Comparison of energy options for remote water pumping
Energy source Estimated capital cost Operation cost Maintenance Life span (year)
PV system $6.8/Wp None Low 10–15
Electric utility $22/W 5–13 b/kWh Low N/A
Gasoline Generator $2.5/W $0.6/kWh High 5–10
Fig. 4. Rack mounted and pole mounted solar panels.
K. Meah et al. / Renewable and Sustainable Energy Reviews 12 (2008) 472 –487478
net present value (NPV), when NPV is positive over a seasonable time period, the project
could be profitable. The NPV can be expressed as
NPV ¼X
n
t¼1
Rt
ð1þrÞtC, (1)
where nis the total time period, R
t
the cash flow, rthe discount rate, and Cthe capital cost.
The cash flow R
t
, could be calculated by comparing diesel generator and solar system,
because there is no direct cash flow associated in the investment. The R
t
may be written as
Rt¼ðO&M cost of diesel generatorÞðO&M cost of solar systemÞ, (2)
where O&M costs include fuel, transportation, replacement, and maintenance costs. The
discount rate, ris taken as 7%. For a 25-year project life, NPV is really high for a 1000 W
SPV water pumping system. Eq. (1) can be used to predict the pay back period by
calculating the n, which makes NPV zero. For a 1000 W system the pay back period is
8 years.
Fig. 5 compares the three water pumping methods—solar PV, diesel generator, and AC
with a new distribution line. Each system pumps the same amount of water. The cost for
the diesel generator includes capital cost, fuel for the generator, and fuel for the vehicle
used on a 16 km round trip every day. The AC with distribution line includes capital cost
for the pump and/or controller, capital cost for the line ($13,000/km), fuel to visit the
system on site twice a week and the electricity cost. The SPVWP system cost includes the
capital cost of the system and fuel cost to check on the system once a week. The sharp
rise in the plot indicates the replacement of generator, pump and/or controller. Fig. 5 is
calculated under the following assumptions:
System capacity 1000 W.
Capital costs: SPVWP USD 6850, diesel generator water pumping USD 2450, and
electric utility with 1.61 km (1 mile) new line extension USD 22,000.
Transportation costs: SPVWP USD 78/season, diesel generator USD 500/season, and
utility USD 150/season with 10% increase in fuel price every year.
Fuel cost for diesel generator USD 500 per season.
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0
5000
10000
15000
20000
25000
30000
0 5 10 15 20 25
Year
Cost in USD
Diesel Generator Solar Electric Utility
Fig. 5. Cost comparison among the new utility line, solar pumping system, and diesel generator.
K. Meah et al. / Renewable and Sustainable Energy Reviews 12 (2008) 472–487 479
Maintenance cost: SPV, USD 50/season, diesel generator, USD 200/season, and
electricity cost for utility is USD 110/season.
It is evident from Fig. 5 that the SPVWP system is the most cost effective for remote
water pumping, even though it has higher capital cost than the diesel generator. Electric
utility has the highest capital cost, also it has higher O&M cost than the SPVWP. The
replacement is scheduled after 10 years—for the SPVWP the replacement is the pump
and/or controller, for the diesel generator, the only option is to buy new generator and the
pump, and for the utility connection it is the pump and/or controller, if one is used. Fig. 6
shows the total life cycle cost comparison over a 25-year period among SPVWP, diesel
generator, and utility under the same assumptions above. It can be seen from Fig. 6 that
the SPVWP system has the lowest life cycle cost, which makes it more suitable for remote
applications.
5. Environmental aspects
In the United States, energy related carbon dioxide emissions by fossil fuel were 5973
million metric tons in 2004, which is 1.7% higher than 2003—in which 40% is contributed
by electric power plants. Coal accounts for over 50% of electricity generation and is the
largest source of carbon dioxide emissions ranging from 83% to 86% since 1990 in
electricity production. Carbon dioxide emissions and total energy usages are highly
correlated and it is a strong indicator of economical growth of a country. Fossil fuels are
the biggest source of energy in the United States and during 2004, 82.4% of total US
greenhouse gas emissions consisted of carbon dioxide from the combustion of fossil fuels
such as coal, petroleum, and natural gas [15].
Increasing the power generation from renewable resources means decreasing the power
generation from the fossil fuels, mostly from coal. Each kilowatt hour generation from fossil
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0
5000
10000
15000
20000
25000
30000
Ca
p
ital Cost Fuel Trans
p
ortation Re
p
lacement O & M Present Value
Cost in USD
Diesel Generator Solar Electric Utility
Fig. 6. Difference in 25-year cost compared to solar PV.
K. Meah et al. / Renewable and Sustainable Energy Reviews 12 (2008) 472 –487480
fuels emits carbon dioxide into the air. Carbon dioxide emissions from coal, diesel, and
natural gas are 976, 733, and 531 g/kWh, respectively [16].Fig. 7 shows the carbon dioxide
emissions from different fossil fuels for a 1000W power generation over 25 years, which is a
nominal life cycle for the SPV water pumping system, with few replacements. The
calculations in Fig. 7 are conducted assuming a 25% capacity factor, because of the low
capacity factor of the SPV system. The UWMTTC installed over 45,000W SPVWP system
from 1991 to present. This SPVWP installations saved carbon dioxide emissions—24,045
metric tons with respect to coal fired power generation or 1308 metric tons with respect to
natural gas fired power or 1806 metric tons with respect to on site diesel generators.
Among the three alternatives, generators, windmills, and solar systems for remote water
pumping, only solar systems do not have any adverse effect on the environment. Generators,
which produce CO
2
emission and harsh noise, are responsible for the air pollution and sound
pollution, respectively. Windmills do not produce any emissions but they have visual impact
and cause sound pollution. Alternatively, PV systems do not create any emissions and use of
SPVWP systems for remote water pumping could reduce both air and sound pollution.
6. Site selection
Site selection is the most critical and sensitive issue because this initiative planned to install
a minimum of three and a maximum of four solar water pumping systems in each county,
while the interest level from ranchers is very high. The UWMTTC is not directly involved
with ranchers or other people throughout the state who are willing to receive a system. To
achieve a fair and equitable selection, the UWMTTC coordinated the site selection process
through the Conservation Districts in each county. The same guide lines were used for every
county and Conservation District ranked the applications before sending them to the
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0
10
20
30
40
50
60
Coal Diesel Natural gas SPV
Fuel/Source
Carbon Dioxide Emission (Metric Tons)
Fig. 7. Carbon dioxide emissions from fossil fuels over 25 years for 1000 W power generation.
K. Meah et al. / Renewable and Sustainable Energy Reviews 12 (2008) 472–487 481
UWMTTC. The interested ranchers were asked to answer the following questions:
1. Does the proposed project improve livestock distribution? Explain: (15 pts. Possible).
2. Does the project provide off stream water for livestock to reduce grazing on riparian
areas? Explain: (15 pts. Possible).
3. Is water development part of a planned grazing system? Explain: (15 pts. Possible).
4. Does the project provide water for the wildlife? Explain: (15 pts. Possible).
5. Will the project provide necessary water for all species during severe drought? Explain:
(20 pts. Possible).
6. Will matching dollars from local, state, or federal cost share programs be used to help
fund the project? Explain: (20 pts. Possible).
7. What is the distance to the nearest distribution line and other benefits? Explain: (15 pts.
Possible).
7. Design and installation
The goal of the final output of the design and installation is to provide enough water for
the livestock and wildlife. The design process needs accurate information about water
requirement, water source, solar radiation, and duration of system use in a year. System
design starts from the information about the water requirement for a particular
application, well characteristics and/or other source of water, and the water storage
facilities. One objective of this initiative is not only to provide sufficient water to the
livestock and wildlife, but also conservation of water for future use. Unnecessary overflow
can be controlled using a proper water storage tank and an automatic turn off float switch.
The design includes solar panels sizing, pump sizing, and controller selection. Solar water
pumping systems should supply sufficient water year around. To ensure satisfying this
requirement the worst scenario, for example fall or winter operation is considered for the
design. Table 2 shows the water use information.
Pump sizing needs three basic pieces of information: water requirement m
3
/day, total
water head, and continuous water flow or recharge rate of the well. During the
pump sizing, cloudy days should be considered by allowing for 5% over design of the
pump. In this process, one complete cloudy day can be covered in every 20 days, but
the tank must be large enough to store extra water. A pump can be selected using total
head and water requirement but the water requirement in gallons per minute should be less
than the well recharge rate. Otherwise, a well dry sensor should be used with a proper
delay. The total power requirement can be found from the pump selection and traditional
design practice adds 20% more power to secure sufficient water flow. Next, a controller is
selected using the information about the solar array power, open circuit voltage,
nominal voltage, and power. A controller which incorporates an inverter is needed if an
AC pump is used.
The installation involves paying attention to some crucial issues to make the solar
system more efficient and safe. The first consideration is how to mount the solar array? It
could be a fixed angle or a tracking system. The tracking could capture more solar
radiation during the early morning and the late afternoon hours, but in many windy areas
like Wyoming, wind gust may force the panel in the wrong direction. On the other hand,
the fixed angle system gets less sunlight but ends up to be more reliable and need less
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K. Meah et al. / Renewable and Sustainable Energy Reviews 12 (2008) 472 –487482
maintenance. The same solar system could be used in more than one location for pumping
water. The solar system could be installed on a trailer to move around as shown in Fig. 3.
Otherwise, the solar system is pole mounted or rack mounted to pump water at one fixed
location as shown in Fig. 4. As the sun changes its angular position over the year, the solar
array angle needs to be adjusted according to the sun’s angle. The wind loading could be
an issue for a solar system with large panel areas. Providing appropriate gaps between the
solar panels reduces wind loading.
8. Performance monitoring
One of the key benefits of using solar PV in remote pumping applications is the
durability and low maintenance nature of panel. With no moving parts, panels have little
wear and tear. The most problem prone component in a pumping system is the pump itself.
Before 2002, solar pumps were operated on a sealed diaphragm principle. Small moving
parts and diaphragms inside the submersible pump would routinely fail leading to higher
than expected maintenance costs. Secondarily, most solar pumps used a brushed DC
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Table 2
Water use information
Water use information
Daily pumping requirement
Summer _________ m
3
/day
Winter _________ m
3
/day
Spring/Fall _________ m
3
/day
Livestock
Cow Calf Pairs ______ feeder calves ______cattle ______ bulls _______ horses ______ Misc_______
Water storage information:(please circle one)
Above ground tank—size: ______________ m
3
Under ground tank—size: ______________ m
3
Pressure tank—pressure: ______________ N/m
2
Water source information
Number of water source locations: _____
Source of water (please circle one)
Drilled well: well casing diameter ______ centimeters
Result based on resent test? Yes___ No____
Surface water: pond _____ stream _____
Static water level
Distance from ground surface to water when not pumping ______ meters
Draw down level
Maximum water level drop when pumping __________________ meters
Discharge head:
Vertical distance from ground level to storage tank ____________ meters
Total head: (add all previous distances) _____________________ meters
Well recovery/recharge
Continuous water flow _________________________ m
3
/min
K. Meah et al. / Renewable and Sustainable Energy Reviews 12 (2008) 472–487 483
motor to drive the pump; this added the maintenance of changing the brushes every 2–3
years of operation.
With the introduction of the helical rotor (HR) solar pump many of these problems have
been eliminated or drastically reduced. The key benefit of the HR is that there is one
moving part, the rotor and no sealed diaphragms. The only wear and tear is seen
by the stainless steel rotor and rubber stator. In the case of the Lorentz HR pump, the
motor is a three phase motor with no sealed cavities. The Grundfos SQ Flex HR pump
consists of a similar rotor/stator set as the Lorentz design, however the pump has a seal
section containing the electronics and controls typically found in a controller located
on the surface. This design simplifies installation; however it adds complexity to the
pump unit.
One of the reasons to choose the SPVWP for remote locations is its ability to produce
water with very little attention. The performance and reliability of a system could be
judged by user feedback. Under this Governor’s funded project, 75 solar SPVWP systems
are already installed and 15 solar SPVWP systems were also installed earlier during
1991–2002 under UWMTTC’s supervision. This offers a good opportunity to compare the
system performance and reliability of the old systems to the new systems. A survey, which
is guided by demographic information, system specification and some questions about
system performance, was conducted to evaluate the system performance. All information
and questions are divided into six categories: (1) demographic information, (2) system
specifications, (3) previous system information, (4) consumer satisfaction, (5) failure
report, and (6) environmental impacts.
Each category includes detailed questions, for example, category 1 includes questions
about end use, geographic location, user’s familiarity, and system operation. System
specification in category 2 provides information about rated power, solar panel rating,
support structure, controller/inverter, pump, water storage, total head and designed and
actual flow rate (gallons/day). Category 3 asked questions about the previous system
(if any) that includes type, fuel cost, maintenance requirements, water pumping rate, and
years of service. For consumer satisfaction only two questions were asked: productivity
and reliability. The failure report in category 5 includes problem with pumps, controller/
inverter, well and other failures. Environmental impact is mainly looking for documenta-
tion of any types of pollution.
The UWMTTC is conducting a survey among the solar system recipients to document
field performance. A total of 90 SPV water pumping systems were installed under
UWMTTC’s supervision, so far 42 systems’ performance information are available and the
UWMTTC is in the process of collecting the rest of the information. Survey results are
divided into three categories depending on the system’s operation time: (I) 15-year
assessment, (II) 5-year assessment, and (III) 1-year assessment.
8.1. Fifteen-year assessment
The UWMTTC installed seven SPVWP systems in Wyoming in cooperation with five
rural electric cooperatives in the state of Wyoming and Sandia National Labs during
1991and 1992. These systems have been in operation for 15 years and a survey was
conducted to evaluate their performance. Five systems’ information is available and
presented here. All systems are in the operation, but multiple replacements were done.
Eleven failures were reported: 6 pump failures, 3 controller failures, one pipe failure, and
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one electric power cable failure. Two system owners had to replace the pump twice. The
respective owners replaced the failed parts and restored the system operation. Two
ranchers added more livestock because of increased water supplies and others wanted
to add more livestock, but they do not have enough land. Two ranchers ranked the
SPVWP system excellent on reliability, and two ranchers ranked the system good, one
rancher ranked the system adequate. On the basis of productivity, three ranchers ranked
the system as excellent, one ranked the system as good, and one ranked the system as
adequate.
8.2. Five-year assessment
During 2001–2002, the UWMTTC supervised the installation of eight SPVWP systems
in the state of Wyoming. A survey was conducted on seven systems. One system is out of
operation because the well dried out—the owner is planning to move it to the new location.
Five failures were reported: four pump failures and one controller failure. The common
problems for motor/pump are sand in the well and motor. One system owner had to
replace the pump three times due to the sand problem in the well. The respective owner
replaced the failed parts and restored system operation. Four ranchers added more
livestock because of increased water supplies. Five ranchers ranked the SPVWP system as
excellent on reliability, and two ranchers ranked the system as good. On the basis of
productivity, four ranchers ranked the system as excellent, and three ranked the system as
good. All ranchers agreed that they saved time, energy, and money by installing SPVWP
system in their ranches.
8.3. One-year assessment
Currently, the project has approximately 30 Lorentz based systems, 40 Grundfos based
systems and 5 surface pump systems installed. The Lorentz systems have all been in
place over since 2005, while the Grundfos and surface systems were installed in Spring/
Summer 2006. Problems with the Lorentz systems have been limited to failures in the low
end PS200 controller, a specific problem with the stator rubber, one failed check valve
and a stator failure due to acid exposure. Corrupted microprocessor memory led to a 20%
failure rate of the PS200 systems installed. This problem was solved by replacing the
defective units. The leaky check valve caused a lower than expected flow rate and was
corrected by replacing the defective pump unit. The rest of the failures were due to a flawed
rubber formulation in the pump stator. Stock water pumps are typically in use for
only a portion of the calendar year. In the case of five units, the pumps were shut down in
late fall and were to be put back in service in the early summer. During this 6–8-month
period water in the well caused the stator rubber to swell. This in turn increased the
amount of torque required to start the pump. This caused the controllers to overload the
pump not run. Removal and replacement with a new unit was the solution to this problem.
Finally, one pump stator was destroyed by well water with low pH. Abandoned oil field
wells are often used as stock water wells. Water in these areas can often be high in
sulfur content and this lead to formation of a mild sulfuric acid in the well. The rubber in
the pump stator began to dissolve in this solution and eventually led to failure of the
pump. Removal and placement of the repaired pump in a higher quality water source fixed
this issue.
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Currently, the surface systems have had no maintenance issues beyond the expected.
One failure of a Grundfos SQ Flex pump has occurred and it is attributed to a faulty check
valve in the pump. Replacement of the unit has corrected this problem.
In total, 50% ranchers added more livestock because of increased water supply and 90%
ranchers agreed that SPVWP save their time, energy, and money. In total, 17 ranchers out
of 30 ranked the SPVWP system as excellent on reliability, 10 ranchers ranked the system
as good, and 3 ranchers ranked it as adequate. On the basis of productivity, 21 ranchers
ranked the system as excellent, and eight ranked the system as good, and 1 rancher ranked
it as adequate.
The average water head for all systems surveyed is 36.88 m; the average water pumping
rate is 0.0401 m
3
/min; the average distance from the distribution line is 2.70 km, and 100%
of the end users are livestock and wildlife. The existing system information which was
replaced by the SPVWP systems is shown in Fig. 8. Windmills comprised 37% of the old
system and the main reason to replace them was lack of wind on some days during peak
summer months. The problems with AC generators are maintenance, refueling, and time.
Surface streams dry out during the early summer and new pastures do not have any
existing water system. All system recipients strongly agreed to recommend others to
consider installing solar PV water pumping systems because of their productivity,
reliability and environmental friendliness.
9. Conclusion
SPVWP is a cost effective and environmental friendly way to pump water in remote
locations. In this paper, Wyoming Governor Dave Freudenthals’ solar water pumping
initiative to alleviate drought impact is presented. A total of 88 solar water pumping
systems are being installed in all 23 countries of the state, of which 75 systems are in
operation at present. The solar PV water pumping system has excellent performance in
terms of productivity, reliability, and cost effectiveness. Drought affected areas like
Wyoming, Montana, Idaho, Washington, Oregon, and part of Texas could use solar PV
water pumping systems to improve the water supply to livestock in remote locations. The
successful demonstration of these systems is encouraging other ranchers to try this
relatively new technology as another viable water supply option. The SPVWP system could
reduce the CO
2
emission considerably over its 25-year life span.
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Windmill
37%
Surface Stream
9%
AC Generator
31%
New Well
23%
Fig. 8. Previous system information.
K. Meah et al. / Renewable and Sustainable Energy Reviews 12 (2008) 472 –487486
This paper also presented a survey report of 15-, 5-, and 1-year-old SPVWP systems. The
survey report showed that solar PV is reliable for remote locations despite the failure of
component. Among the all major components, the pump/motor is the most vulnerable
part of the SPVWP system. Ranchers added more livestock because of increased water
supply and water conservation.
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