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Solar water pumps, along with appropriate agricultural technologies, can provide irrigation to remote areas. The government and many Non-Governmental Organisations (NGOs) have been trying to pilot such initiatives in different parts of India and have achieved some success.

Working of solar irrigation systems

The automatic irrigation system entails an irrigation pump that is operated with solar energy. It becomes tedious to manually operate the system and continuously monitor the water level. Hence, the system uses solar power by using photo-voltaic cells instead of commercial electricity. The project requires an op-amp IC that acts as comparator and senses the soil moisture level. To measure the soil moisture content, two copper wires are inserted into the soil at a certain distance. The sensors send the data to a micro-controller which is interfaced to relay to the driver IC that initiates the relay to operate the pump motor to switch on or off and the status of the pump is displayed on a LCD screen.

Present scenario in India

The Bihar Renewable Energy Development Agency has been trying to promote the use of solar pumps through various schemes and subsidies. But there are only a few pumps available now and they are mainly for demonstrations. The National Bank for Agriculture and Rural Development (NABARD) also has a capital subsidy scheme for promoting the solar photovoltaic water pumping system and provides a subsidy of around 40%.

A switch from the conventional diesel and electric powered irrigation pumps to solar powered ones can help the country achieve 38% of its envisaged 175 GW renewable energy target by 2022. The shift to solar-powered irrigation pumps can also save enormous sums of money and generate additional income for farmers, says a report from the US-based Institute for Energy Economics & Financial Analysis (IEEFA). The IEEFA report, titled ‘India: Vast Potential in Solar-Powered Irrigation’, notes that the idea of replacing some 30 million grid-attached diesel pumps with solar pumps is gaining traction but the pace of deployment is slow.

The Government of India’s Kisan Urja Suraksha Evam Utthan Mahaabhiyan (KUSUM) scheme and the Gujarat government’s Suryashakti Kisan Yojana (SKY) are steps in the right direction. The KUSUM scheme mandates deployment of 2.75 million solar pumps in the first phase of its implementation. “The government, to its credit, is encouraging farmers to instal stand-alone, solar powered, off-grid pumps to not only meet their irrigation needs but also to provide an extra income source from selling surplus power to distribution companies (discoms),” wrote Vibhuti Garg, an IEEFA energy economist.

“Considering the declining trend in prices of solar modules combined with economics of scale, IEEFA sees the all-in cost of solar-powered irrigation as a strong argument for reducing reliance on the current expensive government-subsidised model. The strategy also stands to give a strong push to the government’s ‘Make in India’ programme by stimulating domestic solar-pump manufacturing,” Garg added.

Only 48% of the country’s net sown area is irrigated and the rest is dependent on the vagaries of nature. Demand for sustainable irrigation far exceeds the current available pumping capacity and despite the government’s efforts to promote solar pumps, the uptake has been slow. A robust national solar irrigation programme could successfully contribute to the country reaching its goal of 100 GW of installed solar power capacity by 2022.

Advantages

The use of solar-powered pumps can decrease the input cost to 25% due to its cost effectiveness and low maintenance. In addition, solar water pumps operate with zero carbon footprints.  According to a study, the use of diesel-based irrigation systems across India results in the emission of an estimated 3.29 million metric tons of carbon. This represents approximately one percent of India's total carbon emissions. Bihar, with 48% of India's diesel-based pumps, is the primary contributor.

With over 900 thousand tube wells being used in every Indian state, energy of around ~ 18 million is used for pumping water for irrigation. Even though the initial investment in solar pumps is high, it can be earned back in two-and-a-half years. If the cost of power is ~ 1.5 million per kilo watt hour, ~ 18 million is used for pumping water alone in a year. By using the solar water pump, we can save up to 4.8 million KWh of energy annually. This system optimises the use of water by reducing wastage and human intervention for farmers. The excess energy produced can also be given to the grid with minor modifications.