Solar Pumps: An insight of its simplicity!

21st May 18  

Farming in India dates back to Indus valley civilization (3300 - 1300 BCE) where it was one of our primary occupation and source of income. Today India ranks second in the globe in cumulative farm output. It is also believed that around country’s 50% of workforce is indulged in farming which still makes it one of our important occupation. There are two basic yet important components of agriculture i.e. water and electricity. The electricity drives the pump which drives the water either from bore-well, and/or water bodies to the farm at desired throughput.This pump may alternatively run either on conventional fuel sources for generation of electricity. This makes the farmer dependent on electricity/continuous availability of fuel to ensure smooth operation of the pump. With almost scarcity in supply of electricity and availability of fuel at relatively higher rates, an alternate solution in this filed was needed. With advancement of utilizing solar irradiation to generate electricity, solar pumps have started emerging to be one of better solutions to this industry. Additionally the power output from the solar PV panel is in conjunction with the requirement of an agricultural pump which has paved way for utilization of solar pump. A solar pump as the name suggest (Figure 1)is the one which relies on solar photovoltaic (PV) panel for electricity. While the output of the panel may directly be fed into the pump, (almost all the time) a converter/inverter is provided to ensure that the required input power for the pump is achieved and maintained constantly. With its advantages in mind, this blog aims to educate its reader on basic introduction on solar pumps and its technical requirements.


Figure 1: A solar pumpinstalled by Waaree Energies in operation

A typical solar pump is as shown in Figure 2whose typical components are discussed below:


Figure 2: A typical solar pump (Source: Waaree Energies)

  1. Solar Panel: A solar panel is a typical mono/multi crystalline silicon panel which is capable of converting the sunlight falling on it to DC power. It has efficiency typically from 17 ~ 21% with a power output in range of 100Wp - 350Wp.
  2. Module Mounting Structure (MMS): In any kind of solar pumps (to control the cost of the system), batteries are generally not utilized. This makes it important for the solar panels to efficiently utilize the available solar irradiance. This is where the Module Mounting Structure (MMS) of the plant comes into play. In normal residential and utility scale power plants (generally) the MMS is fixed in nature. However the sun keeps moving with respect to earth’s horizon every day and seasonally. The sun traverses from east to south to west every day and its position changes from summer to autumn to winter. Thus in order to efficiently track the sun, the MMS used is dual axis tracker which rotates horizontally & vertically to track the sun daily & seasonally(as shown in Figure 3).

  3. Figure 3: A typical double axis solar tracker (Source: Google images)

  4. Pump: A pump is a mechanical device which runs on electricity to deliver water at required rate. A pump can use either DC power or AC power to run. Both these pumps have set of advantages and disadvantages. DC pump have higher discharge (around 10-15%) and have a simple design (as they do not require inverter). However servicing a DC pump is tedious process with availability of skilled manpower being an issue at the places where DC pumps are used. The AC pumps are easy to install and maintain. They however have lower efficiency and water discharge.
  5. Electronic pump enhancer (for DC pump): Fixed at an interconnection between a DC pump and solar panel, its main function is to regulate the available DC power from module to DC power as required by the motor for smooth operations. It may also be fitted with Maximum Power Point Tracking (MPPT) which may extract maximum power available from the solar module.
  6. Inverter (for AC pump): An inverter is an electronic device which is primarily converts DC power to AC power as required by the solar DC motor. It usually has MPPT fitted along with the device to extract the maximum power output from solar module.

The above parts are among the standard solar system. However considering the solar pumps (other than AC & DC)they can be classified based on their placement which is as under:

  1. Surface pumps: A surface pump is the one which is installed at the ground level for a water source like canals, open well and/or lakes. They are the ones whose pump and motor can be distinctly identified. They could also be a feasible option for source whose water table is between 8-12 meters. A typical surface pump comes at a low upfront cost when compared to other types and is easy to install & maintain. The surface pumps however may be damaged if they are running dry i.e. the pump are still "ON” even when there is no water. Additionally, surface pumps require to be primed every time they start (especially when the difference between). Priming of a pump is a process when at starting, the pump needs to be filled (automatically or manually) fully with water in order to initiate the pumping process. A typical solar powered surface pump is as shown in Figure 4.

  2. Figure 4: A typical surface pump (Source: Google images)

  3. Submersible pumps: A submersible pump is the one which is installed deep inside the ground level i.e. typically more than 10 meter. In such casesa bore is drilled (which is a costly affair) and then the submersible pump is inserted in the well. Sometimes these pumps are also installed in water bodies such as river, canals where sufficient water is available almost all the times in a year. Such pumps does not need priming because they are located deep inside the water. However one typical disadvantage is that these pumps get damaged due to presence of mud around the pump and this is almost undetectable from ground level. A typical solar powered submersible pump is shown as in Figure 5.


Figure 5: A typical submersible pump (Source: Google images)

While the technology is in place, it still needs support from the government. This is primarily due to the fact that the farmers cannot afford such high upfront costs for solar pumps. There are various schemes available from banks like National Bank for Agriculture and Rural Development (NABARD), commercial banks, state cooperative agricultural rural development banks (SCARDBs) which provide finance for solar powered pumps. MNRE in the past had also provided upfront capital subsidy via NABARDhowever it was stopped on 15th March, 2017. Now in order to bolster the off-grid power production and support solar pumps in agriculture, the Govt. of India in the Union budget of 2018-19 have declared new scheme for solar pumps namely KisanUrjaSurakshaevamUtthaanMahabhiyan (KUSUM). It is envisaged that the farmer would have to pay only 10% of the capital cost for the solar pump with the balance amount being supported from both state and central government. Additionally, such scheme shall also boost the power generation capacity of the country while also allowing the DISCOM to fulfill their Solar RPO. This scheme shall initially focus only on converting diesel pumps to solar pumps however we could expect something for new solar pumps as well.

In order to ensure that the right quality of system is delivered to end consumers MNRE has provided with the technical requirements of the system.The solar panel used in this system should be in accordance and certified as per IEC 61215, 61730 and their equivalent certificates. It is also expected that the solar modules should be of 13% efficiency with a minimum fill factor of 70%. The MMS should be a dual axis tracking system to efficiency track the sun and should be capable of withstanding load of module and wind velocity of up to 150 kmph. The technical specifications of pumps can be found here. However, we expect that with the release of KUSUM scheme the specifications (few of them) shall be changed/updated because of technical advancements.

Waaree has been providing solar water pumping solutions, thanks to its efficient and highly reliable solar modules. These solar pumping system have been tested and proven cost effective and reliable. Additionally with development of our AC modules and highly efficient PERC modules the solar pumping system would see considerable change in its operational efficiency.

Let us all pledge to make solar energy the primary source of energy in the near future.

RAHE ROSHAN HAMARA NATION