2011 International Conference on Alternative Energy in Developing Countries and Emerging Economies
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current which is rather high. This condition does not
match the PV array characteristics where the current
output produced by a PV array almost linearly with solar
radiation intensity. Consequently, the batteries are used to
assist in power buffering between the PV array and the
pump as well as the energy storage bank. In addition,
batteries stabilize the voltage system whatever the power
provided by the PV array. The maximum power tracking
system may add in the system for maximizing power
loads. Stand-alone and grid-connected systems were
tested. The stand alone was compared with the cost of
extending the national electric grid. Results showed that
both systems were cost-effective and the increase in the
turbine and pump flow leads to higher friction losses
since the hydraulic circuit is the same. In both cases, the
optimized system is not composed of solar modules due
to the high cost. Some experimental data have been used
in empirical modeling and model verification of
photovoltaic water pumping systems [7-8]. For instance,
the model expresses the water flow output directly as a
function of the electrical power input to the motor-pump,
for different total heads was presented [7]. The pump
subsystem was centrifugal and positive displacement
motor-pump. Furthermore, a complex time-dependent
solar water pumping system is analyzed based on PV cell,
the battery and the assembly electric motor-centrifugal
pump existing models. In addition, the simple water tank
model was developed. The mathematical model consists
of the set of ordinary differential equations, as a function
of the operating mode. The model was tested based on the
meteorological data measured by the Meteorological and
Hydrological Institutes [7]. The long-term performance of
a photovoltaic water pumping system without battery
storage was estimated using a simple algorithm. This
method used the standard utilizability correlation
equation to compute the flowrate. The monthly average
solar radiation was the model input. At first, the non-
linear relation between flowrate and solar radiation
intensity was obtained experimentally and then used for
performance estimation. The average output of the
system predicted was compared with experimental
investigation [9]. A photovoltaic system can install close
to the demands, therefore, the transmission and
distribution costs as well as energy loss and voltage drop
are reduce. Furthermore, not require any fuel for
operation. Therefore, an operation of a photovoltaic water
pumping system in high level solar radiation insolation
area is a cost effective means of producing power
available in rural remote areas. In the sites where the grid
extension in infeasible, it is possible to power the
pumping system with diesel generators or with
photovoltaic system. The literature review revealed that
the photovoltaic water pumping system is more cost-
effective than diesel engines [10-11]. However, the main
disadvantage of a photovoltaic water pumping system is
the high initial investment cost. In photovoltaic water
pumping system, water unit cost is affected by system
productivity, capital investment, interest rate and
operating cost ordered from highest effect to lowest [11].
Apart from photovoltaic water pumping system, there is
another renewable energy based water pumping system,
i.e. wind water pumping system based on electricity
produced by a wind turbine generator. Recently, this kind
of water pumping system has become increasingly
popular due to greater flexibility over mechanical system
and the advantage of being able to use spare electricity
for other purposes [12]. The performance of electric wind
pumping system was evaluated. The maximum efficiency
was 17% for water pumping [13]. Since the average wind
speed is a crucial factor for wind water pumping system,
it is now widely accepted that wind pumping is
economically feasible at sites where wind speed is over 3
m/s. Furthermore, in some cases the average wind speed
at 2.5 m/s is sufficient. The pump’s output at differ
ent
wind speeds and monthly water output against average
wind velocity were investigated. However, the hybrid
system combining wind/solar photovoltaic/diesel power
generator was suggested for applying to power a water
supply in remote locations [14]. A survey of wind turbine
water pumping system either by direct pumping through
mechanical means, or indirectly by generating electric
power to drive pumps has been done. In general,
mechanical wind pumping system consists of a multi-
blade rotor connected to a piston pump through the crank
and another vertical shaft, a rotor, a nacelle, a tower, a
water storage tank, and a piping system. On the other
hand, the electrical wind pumping system consists of a
rotor, which drives a generator to produces electrical
power proportional to the wind speed. This system
required a control facility in order to control the generator
and the output voltage [15]. Since roto-dynamic pumps
offer better match with wind rotors for low lift-high
discharge water pumping system. A mathematical model
for estimating the performance of wind-driven roto-
dynamic pumps at various operating conditions was
proposed. The model was validated using the field
performance data [16]. A simplified algorithm to estimate
the monthly performance of autonomous small-scale
wind energy system with battery storage was also
presented [17]. The fast evolution of photovoltaic and the
already highly developed wind power technologies could
be combined making of the possible sustainable energy
solutions for water pumping systems. A hybrid renewable
power system is a system composed of more than one
renewable energy source. The advantage of this system is
the overcome of oversize problem when the resource is
less available. Therefore, the hybrid system depends on
more than one resource which means that when one
source is insufficient or in unavailable, the other might
support the system more reliable. A typical water supply
system powered by a hybrid solar and wind energy of a
Portuguese village was studied [18]. Since the solar
energy and wind energy have limitation in use while the
water demand is continuously and randomly, therefore
the use of hybrid solar and wind water pumping system
with battery storage is another means to overcome the
problem. This system was modeled for estimating yearly
wind fraction [19]. The hybrid solar and wind energy
system is more and more considered in China as a
renewable energy resource compared to conventional
