Glossary of Solar Water Pumping Systems:
1. What are solar water pumps?
A solar water pump or a solar photovoltaic water pumping system is a system powered by solar energy. It is just like the traditional electric pump with the only exception that it uses solar energy instead of fossil fuel or electricity. It consists of one or more solar panels, also known as solar photovoltaic modules, a motor pump set, electronic controls or a controller device to operate the pump, the required hardware and in some cases, other items like inverters, batteries, etc.
2. What is the use of solar water pumps?
A solar water pump is used for extracting water from ponds, rivers, borewells or other sources of water which are then used to meet the water requirements for irrigation, community water supply, livestock and other purposes.
3. How does a solar water pump work?
It works like any other pump set with the only difference being the solar energy used instead of nonrenewable energy for its operation. When sunlight falls on the solar panels it produces direct current (DC) which then feeds the motor to pump out the water. However, in the case where the motor requires an alternating current (AC), the DC produced by solar panels is converted to AC using an inverter.
4. How are solar water pumps more useful than conventional electric pumps?
The advantages of solar water pumps over conventional electric pumps are given below:
o Solar water pumps do not require any fuel or electricity to operate. Once installed, solar water pumps do not incur the recurring costs of electricity or fuel.
o Does not get affected by power cuts, low voltage, single phase problems or the motor burning.
o Can be installed in remote areas where electricity is unavailable or diesel is difficult to procure.
o Incurs low maintenance costs as solar water pumps have fewer moving parts as compared to a diesel- powered pump and thus,fewer chances of wear and tear.
o No lubricants are required for operation and hence no chances of water/soil contamination due to the lubricants.
o Easy to operate
5. What are the different types of solar water pumps?
There are several different types of solar-powered pumps depending on how they have been classified. But primarily
there are four types of solar water pumps--submersible pumps and surface pumps, direct current (DC) pumps and
alternate current (AC) pumps.
Submersible pumps:. As the name suggests, a submersible pump is located deep below the ground level and remains submerged under water. The suction head of the submersible pump is beyond a depth of 10 metres. The installation of these pumps is done by digging a borewell, which leads to an increase in its installation and maintenance cost.
Surface pumps:.The surface pumps remains out of water and in the open. They are installed where the water table is within a depth of 10 metres. As they need to be on the surface, these pumps are easier to install and maintain. They are, however, not apt for deep water table.
DC pump:.This pump runs on a motor which operates on direct current, therefore no battery or inverter is needed in this type of pump.
AC pump:.The motor of this pump operates on alternating current, which means the direct current produced by the solar panels gets converted to AC using the inverter. The conversion from DC to AC leads to loss of power from generation and consumption.
6. How does one know if they should use a submersible or a surface pump?
The selection is based on the groundwater level and the water source. In the case of a borewell with a water table
deeper than 10-15 metres, a submersible pump is used. If it is an open well, pond, etc, then using a surface pump is
better. Also, the surface pump is installed when the water level is less than 10 metres.
Based on the classification, the following types of motor pump sets are available:
o Surface mounted motor pump set
o Submersible motor pump set
o Floating motor pump set
o Any other type of motor pump set after approval from test centres of the Ministry of New and Renewable Energy.
7. Which is better--a DC or an AC pump?
Although DC pumps have an advantage over AC pumps in terms of higher efficiency and no requirement of an inverter for operation, the cost of DC pumps is higher. Also, the repair and maintenance of DC pumps are difficult in rural and remote areas due to lack of service centres in these areas.
8. Are there any criteria for selecting where to install the solar water pump sets?
Yes, there are certain criteria for selecting the location for both the solar panels and the pump. In the case of the
solar panels, they should be installed in an area which is shade free and has no dust or dirt, has a low incidence of
bird droppings and which can provide space for unrestricted tracking movement (keeping the orientation of the solar
panels in the direction of maximum solar irradiation). Also, the surface where the panels are mounted should be
even. Panels should be easily accessible for cleaning and should be as close as possible to the pump and water
The pumps should be located close to the solar panels but within the area to be irrigated. The suction lift for the pump should be low. If there are multiple water sources, the source with the highest water table should be chosen for placing the pump.
9. How much area can a system irrigate?
Generally, it is said that a 2 HP pump can cater to about two acres of land and a 7.5 HP is said to cater to 10 acres of land, but this data vary depending on the groundwater levels and the type of irrigation required for a particular crop.
10. What are the capacities at which solar water pumps are available and what is the average discharge?
The motor pump set for irrigation and domestic drinking water should have a capacity in the range of 0.1 HP to 5
HP. Although, municipal and rural community applications could choose a higher capacity solar pump.
For a DC motor pump set, the discharge varies from 14 - 100 litres of water per watt peak of PV array while for AC
motor pump, the discharge varies from 13 - 19 litre of water per watt peak of PV. The average discharge, however,
depends on solar intensity, location, season and other factors.
The details of the technical specification can be found here.
11. Once installed, is it possible to relocate the solar pump system?
Relocation of the solar pump system is not advisable. However, the system can be relocated using a mobile mounting platform but the process is expensive and may also cause damage to the system.
12. Does a solar water pump work during cloudy and foggy days?
No. Lack of sunlight affects the working of solar water pumps. On such days, however, a hybrid power supply can be given to the pump. The pump can be connected to the state electricity grid or a diesel generator set after making proper adjustments in the controller. But such an arrangement should be made only after consulting the manufacturer of the solar water pump.
13. Can hail storm and/or lighting lead to the damage of the panels? What precautions should be taken during cyclones/storms to save the panels?
The modern day solar panels have adequate safety features and are very unlikely to be damaged by a hail storm. However, in rare cases, a direct lightning strike might cause considerable damage to the solar panels. But the risk of a lightning strike can be mitigated by the integration of an external lightning protection system with the solar array. During a storm or a cyclone, the panel gets damaged only if the surface on which it is mounted collapses. In areas prone to cyclones and storms, special consideration should be given to building strong foundations for the installation of a fixed panel. Also, as a precaution during storms or cyclones, the array should be kept horizontally at 180 degrees so that minimum resistance is offered to the wind.
14. What maintenance is required for a solar powered pump? Does the performance of the solar water pumps get affected over the years of use?
The system needs very minimal maintenance which includes cleaning of the panels on a regular basis. Cleaning maintains the efficiency of the panel without which the panel’s surface gets reduced exposure to irradiation from the dust and dirt on it. In comparison to diesel pumps, solar water pumps have a significantly longer life expectancy and continue to produce electricity for even longer than 25 years.