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Monday, October 5, 2015

Design and Analysis of PV Water Pumping System

Design PV Water Pumping System : 
There are many aspects of designing a solar pumping system. This guide provides the information to  correctly select a pump, controller, sensors, solar array, wiring, and pipe. The process is broken down into the following steps:
STEP 1 - Determining your basic amount of water required per day.The size and cost of your system depends on the amount of water required per day. Solar pumping  systems depends on the amount of water required per day. Solar pumping systems are designed to provide a certain quantity of water per day. Where the daily water quantity required is sum of all requirements during 24 hours. For more reliable design worst case of water requirement should be considered. If the amount of water used everyday varies, then weekly average or monthly average can be taken for calculations

STEP 2 - Calculating the Total dynamic head (TDH).It is an important parameter as far as design is considered. The TDH is given in meters. It  signifies the effective pressure at which pump must operate. It primarily consists of two parameters  total vertical  lift and total frictional  losses.  The total vertical lift is sum of elevation , standing water level and drawdown. The elevation is the height difference between the ground and the height at which water is discharged. Standing water level is the height difference between the ground surface and the water level is the height difference between the ground surface and the water level in the wall,  when the well is in fully charged condition. And drawdown is the height by which standing water level drops due to pumping  
Frictional losses: Frictional loss is the pressure required to overcome friction in the pipes from the water pump to the point of water discharge. It is given in equivalent meters and added to the total  vertical lift for TDH calculation. The frictional loss depends on many factors like size of pipe, flow rate, type of fittings, Number of bends etc. Usually tables are used to calculate frictional loss. But if the water discharge point or tank is close to the well then an approximation is taken. If the tank is within 10 meter of the well. Then friction is taken as 5% of the total vertical lift.

STEP 3 - Determining the hydraulic energy required per day (watt-hour/day)
Hydraulic energy required to raise water level

= mass × g ×TDH

= density × volume × g × TDH

STEP 4 Determine the solar radiation available at given location. Typically this number is 3.82 hours to 6.23hours varying form section to section and location to location.
STEP 5 Determine the size of solar PV array and motor, consider System output factor and pump efficiency.
STEP 6 - Selecting the right size pump cable and pipe.

STEP 7 - Using water level sensors and pump controls.

In the way a solar water pumping system can be designed the above design has been done assuming  the use of a DC motor. A system can also be designed for an AC motor but one must consider inverter and its efficiency in the calculation .also the cost of the solar PV irrigation system can be estimated by considering the individual component cost e.g. cost of solar panel .cost of motor .and cost of pump and wiring cost.