Major Components Solar Pumping System
Major components of the system are :
(a) Solar panels / Arrays.
(b) Charging and control circuit
(c) Pumps
(d) Water storage system.
Tanks may be overhead or underground based on the requirement. A schematic layout of a typical solar pumping system is shown in Figure.
1. Solar Panels :
The basic element of the panel is the solar cell. It is made of a semiconductor material and is provided with sufficient structural rigidity for mounting on panels and for the electric connections. A single cell would be able to give about 1.5 V of electricity with few milliamperes of current.
Hence a number of cells are connected in a series-parallel combination so that sufficient power is available. A combination so formed is called a solar panel. When a number of such panels are combined we get a solar array. Solar array is the basic power source of a solar pumping system. The exact voltage and power to be developed by the array will depend on the size of the pump to be operated.
2. Mounting of the Solar Arrays :
The solar arrays are generally mounted facing the south at a place which is clear of all vegetation and other shading objects. The array could be placed at an inclination towards south by an angle equal to the latitude of the location.
So a solar tracking system may be used to lift the array constantly as the sun moves across the horizon during the day . However, this will add to the cost of the system. Hence for saving cost, the tracking system may be dispensed with in simple systems.
Charging and control Circuits :
Solar cells when exposed to sun, start generating electricity. If the electricity is to be used directly, then it can be connected to the load directly. But this will lead to fluctuation in the power produce by the cells due to the fluctuations in the sun light.
Hence, instead of connecting the pump directly to the solar array, the electricity generated by the solar cells is stored in a storage battery. The pump is connected to the battery and draws the power from the battery and run it.
To enable this function a special charge control circuit is used. Its function is to ensure that when the electricity produced by the solar array is sufficiently high it charges the battery But when the straight becomes weak and the charge current from the battery is less, then the current from the battery will try to back flow through the cell. This is prevented or blocked the charging circuit, thereby avoiding severe damage to the cells.
3. Solar Pumps :
The types of motor used for the running of solar pumps may be any one of the following:
(a) DC motor
(b) Variable frequency AC single or three phase.
In continuation pumps used in conjunction with solar panels are especially designed to cater for the following additional requirements :
- The efficiency must be high so as to reduce the quantity of solar panels required.
- They must be able to run under low electric power situations.
4. Types of Pumps :
The most commonly used water pumps are centrifugal pumps. The pump may be single stage or multistage.
Positive displacement pumps such as reciprocating pumps or screw pumps may also be used, if the required pumping height is more.
The pump may be a surface pump i.e. the pump is placed on a ground outside the water source and the suction line is connected from the pump to the water source. Another type is the submersible pump. In this, the pump is immersed under water. These pumps are more efficient than surface pumps but are more costly.
Solar pumps are available in various sizes and power capacities. The minimum power of a solar pump is of 150 W.
5. Water Storage Systems :
The solar pumps once installed, are meant to function as a stand alone system. That means, the pump would be running and pumping water to a storage tank. The storage tank capacity is worked out based on the water requirement.
The tanks are fitted with float switches. Float switches control the water level in the tank. This is done by switching off the pumps when a preset level has been reached in the tank. Thus over flowing and wastage of water is avoided.