28-08-2014, 11:43 AM
Pumping Water for Irrigation Using Solar Energy1
Pumping Water.pdf (Size: 270.78 KB / Downloads: 132)
SYSTEM DESCRIPTION
A photovoltaic array comprised of two units of three
modules each was used to power the water pumping
system used in this demonstration (Figure 3c). The
six photovoltaic modules had a photon responsive
surface area of 3.17 m2
. The three modules of each
unit were connected end-to-end and reflectors,
constructed from sheet metal and aluminum foil tape,
were attached to the two long sides of each unit. The
reflectors doubled the area of the array structure
normal to the sun and increased the short circuit
amperage of the units up to 33 percent overall
SUBSYSTEM EFFICIENCIES
The photovoltaic system used in this demonstration
was mathematically analyzed as three separate
subsystems: 1) the photovoltaic modules with the
reflectors, 2) the EARC, and 3) the motor and pump
subsystem. The individual efficiencies of these
subsystems were 11 percent, 96 percent, and 44
percent respectively. Figure 5 shows the flow of
energy converted from solar radiation to fluid power.
The overall efficiency of the entire system was 4.6
percent.
WATER VOLUMES PUMPED PER DAY
The volume of water which a photovoltaic-powered
pump is able to produce is related to the irradiance
level which it receives throughout the day. On
October 7, 1989, high levels of irradiance were
available throughout the entire day and the
photovoltaic system pumped 20,180 gallons of water
against a static head of 2.44m (8ft) (Figure 6). On
January 6, 1990, clouds blocked the sun’s rays over a
large part of the day, and the system pumped only
1,655 gallons of water (Figure 7).
WATER VOLUMES PUMPED PER DAY
The volume of water which a photovoltaic-powered
pump is able to produce is related to the irradiance
level which it receives throughout the day. On
October 7, 1989, high levels of irradiance were
available throughout the entire day and the
photovoltaic system pumped 20,180 gallons of water
against a static head of 2.44m (8ft) (Figure 6). On
January 6, 1990, clouds blocked the sun’s rays over a
large part of the day, and the system pumped only
1,655 gallons of water (Figure 7).
WATER VOLUMES PUMPED PER DAY
The volume of water which a photovoltaic-powered
pump is able to produce is related to the irradiance
level which it receives throughout the day. On
October 7, 1989, high levels of irradiance were
available throughout the entire day and the
photovoltaic system pumped 20,180 gallons of water
against a static head of 2.44m (8ft) (Figure 6). On
January 6, 1990, clouds blocked the sun’s rays over a
large part of the day, and the system pumped only
1,655 gallons of water (Figure 7).
ENDNOTES
2. Irradiance: Solar power per unit area.
3. Cell temperature and cell type also influence
power output.
4. Standard operating conditions (SOC): Irradiance
- 1000 watts/m2
, Cell temperature - 45 degrees C.
5. Peak watt (Wp): Maximum power output of
photovoltaic system at SOC.
6. 1000 watts/m2 is considered to be the practical
maximum amount of solar irradiance which can
reach the earth’s surface after passing through the
atmosphere.
7. Insolation: Solar energy received during a
specific time interval.
8. An 80 percent chance of success means that on
any given day the chance that the power supply
will be unable to replace the daily water loss
through evapotranspiration is 20 percent. Eighty
percent is considered to be an appropriate success
percentage for irrigation system design by the
Florida Water Management Districts.
9. Price of module divided by the actual wattage
output of the module under 1000 watts/m2 of
solar irradiance as tested in the field.