Right-sizing solar irrigation pumps: in India, and beyond

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Solar irrigation pumps can bring significant benefits for food security, livelihoods, and the environment. They run on clean, renewable energy, with no reliance on costly and polluting fossil fuels, and once installed, they have no running costs – providing 1,400–2,200 hours of free, dependable energy per year, contributing to food security and boosting farmers’ incomes for decades. Farmers are understandably enthusiastic about the adoption of these pumps. However, the lack of running costs means there is no incentive to limit pumping, which can lead to the depletion of groundwater resources.

This is a particular concern in some parts of India. The country is the world leader in solar power for agriculture, with 93 percent of the global off-grid capacity deployed for agricultural use, according to the International Renewable Energy Agency. Roughly 350,000 solar irrigation pumps are already installed. Yet these comprise just a tiny fraction of the 21 million irrigation pumps that exist across India and the government is working to massively expand the number of solar pumps. In 2019, it launched the ambitious PM-KUSUM initiative in an effort to ensure energy security for farmers. This involves a pledge to install more than 3.5 million standalone and grid-connected solar irrigation pumps.

An ideal context for the nexus approach

Shilp Verma, a senior researcher at the International Water Management Institute (IWMI) in India, has been working on the nexus between water, energy, and food policies since 2001. The PM-KUSUM solar irrigation initiative, he explains, is “an ideal context to apply the nexus approach, not only looking at solar irrigation from the energy point of view, but also looking at its potential impact on water, agriculture and rural livelihoods, and using this to inform solar policies.”

Through the IWMI-Tata Water Policy Program, IWMI has been working on solar irrigation in India since 2012 and the CGIAR Research Initiative on NEXUS Gains is now benefiting from this decade of experience and experimentation. One critical issue identified by the researchers is sizing: a pump that is too large will use up precious public resources and will likely result in the over-pumping of groundwater. On the other hand, an undersized pump will not meet the farmer’s needs, meaning that the solar pump will only be used to supplement a diesel pump, rather than replace it. Therefore, right-sizing is important to ensure optimal utilization of public resources.

A simple yet flexible tool

In 2019, with support from GIZ, IWMI collaborated with the Indian Council for Agricultural Research (ICAR) and the Borlaug Institute for South Asia (BISA) to develop a simple Microsoft Excel-based tool for sizing solar irrigation pumps. This was done specifically to meet the requirements of PM-KUSUM and on the request of the Ministry of New and Renewable Energy (MNRE), Government of India.

The IWMI-ICAR-BISA tool processes technical, biophysical, and social factors using complex algorithms. Excel was selected as it is widely available and can function offline, making it accessible for regions with poor internet connectivity. The tool has been pre-loaded with substantial secondary datasets on climate, soil, and crop types, enabling sizing calculations at a regional scale. Users can also add their own data, producing a more accurate sizing calculation for a specific farm or field. This means the tool is adapted for use in data-poor and data-rich environments.

A further feature is future proofing. Given that the lifespan of solar irrigation pumps is typically 20–25 years, the tool considers current and future irrigation requirements. It can simulate scenarios such as a reduction in the groundwater table, a change of crop, or an adjustment to the crop water requirement due to rising temperatures. This enables users to choose a pump that will be able to fully service present and future irrigation needs.

The beta version of the tool has been adopted for use in India’s PM-KUSUM campaign. It is now available online along with a detailed user manual, and GIZ and MNRE are working to develop web-based and mobile versions of the tool.

Scaling the innovation in South Asia

The solar pump sizing tool has been identified by NEXUS Gains as an innovation that is ready for scaling in other countries and regions. While the architecture itself can be adapted to new contexts, one challenge is the availability of datasets. IWMI, through Solar Energy for Rural Livelihoods (SE4RL) and NEXUS Gains, is working with GIZ to develop a version of the tool for use in Nepal.

To explore scaling opportunities here, a stakeholder consultation workshop was conducted in Kathmandu, Nepal in June 2023. IWMI applied the new CGIAR Innovation Package and Scaling Readiness approach during the workshop. This approach supported a co-creation process to identify challenges and find solutions for scaling the solar irrigation pump sizing tool in the local context.

Solar irrigation pumps have vast potential to address some of the region’s most pressing challenges: reducing reliance on fossil fuels, providing more sustainable livelihoods, strengthening food security, and contributing to climate-resilient farming. A key issue that NEXUS Gains is also investigating is how women farmers can be empowered to access solar pumps.

The nexus approach considers the trade-offs as well as benefits, and the solar irrigation pump sizing tool enables governments and farmers to make decisions backed by science and take advantage of solar technologies.

For more information, contact Shilp Verma, Senior Researcher at IWMI India: shilp.verma@cgiar.org


This work was carried out under the CGIAR Initiative on NEXUS Gains, which is grateful for the support of CGIAR Trust Fund contributors: www.cgiar.org/funders

Header image: Aerial view of solar pumps in Samastipur district, Bihar, India. Photo by: Metro Media/IWMI

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