Borehole first, then pump. Know your Pump

Agricultural development is one of the most powerful tools to end extreme poverty, boost shared prosperity and feed a projected 9.7 billion people by 2050.

Solar pumps present a clean, simple and energy-efficient alternative to traditional electric and fuel-driven pump sets. They are part of an environmentally friendly approach in agriculture and can be used to exploit every region, whether its developed or poor.

Solar Pumps from wisdomjobs

How does 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.


How are solar water pumps more useful than conventional electric pumps?

The advantages of solar water pumps over conventional electric pumps are given below:


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.

Does not get affected by power cuts, low voltage, single phase problems or the motor burning.

Can be installed in remote areas where electricity is unavailable or diesel is difficult to procure.

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.

No lubricants are required for operation and hence no chances of water/soil contamination due to the lubricants.

Easy to operate.


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 borehole, which leads to an increase in its installation and maintenance cost.

Surface pumps: The surface pumps remain 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.


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 borehole 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.


Which is better? 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.


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 source.

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.


Does 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.


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.


Understanding pump head and total head for pump performance

Put simply, head is the height at which a pump can raise fluid up and is measured in metres or feet. We use it when specifying centrifugal pumps because their pumping characteristics tend to be independent of the fluid’s specific gravity, often referred to as relative density.

Suction Levels
Suction conditions are also relevant to the pump head. If the suction level is lower, the head measured will be less, and vice versa. The pump’s motor converts electrical energy into mechanical energy, which the pump then imparts into the fluid as pressure. Raising or lowering the suction level therefore adjusts the potential pressure of the liquid. The more pressure the pump delivers, the higher the head will be.

Total head
Because pump manufacturers cannot know the suction level parameters, they calculate the pump’s total head (figure 1). To do this, they subtract the total suction head, which is measured as height above sea-level, from the total discharge head.

The next important consideration is how much friction needs to be taken into account. Friction loss depends on the length and size of the pipework, bends, and gate valves, through which the fluid flows. The sum of the head and friction loss will give total head.