Agriculture Reference
In-Depth Information
Stand-Alone Photovoltaic System
Stand-alone photovoltaic system produces power independently of other energy
sources. It may be in three configurations: (a) direct coupled, (b) DC loads with
battery, (c) DC loads with battery and charge controller.
Batteries require strong energy for use at night time or on cloudy days. These
(with battery) stand-alone systems comprise the majority of photovoltaic installa-
tion in remote region because they are often the best, most cost-effective choice for
applications far from the utility grid, which requires reliable power supply and low
maintenance. Sun tracker may be used to increase the output of the photovoltaic
array.
Stand-Alone Hybrid System
In stand-alone hybrid system, the photovoltaic array is coupled with one or more
additional power sources. Hybrid systemmay be the cost-effective choice to provide
power for large-scale irrigation, especially when another power source is already
available or greater system is desired.
Grid System
In a grid connected system, the photovoltaic system acts as a miniature power plant,
feeding excess power direct to utility grid during the day, and drawing power from
the grid at night, in periods of low sunshine or load shedding time.
13.4.4.2 Photovoltaic System Design for Irrigation Water Pumping
In designing photovoltaic pumping system, possible supply and demand of energy
have to be matched. Energy demand can be calculated from the peak power
(water) demand during minimum irrigation interval required, and pumping plant
and irrigation efficiencies.
Steps/Procedures for the Designing of PV Pumping System
The steps in designing PV systems are:
- estimate the peak water demand of the irrigation scheme (considering minimum
irrigation interval)
- calculate power demand for the peak water demand
- calculate the requirement of PV cells for power generation (considering minimum
expected solar irradiance during the peak period).
Mathematical Formulation
The peak water demand per day ( Q p ) is estimated by taking into account the
irrigation efficiency, i.e.,
Q p =
Q c /
E ir
(13.1)
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