MIT researchers release evaluation of solar pumps for irrigation in India


In 2014, the government of India made an ambitious goal to replace 26 million groundwater pumps run on expensive diesel, for more efficient and environmentally friendly options such as solar pumps. The government had then allocated INR 4 billion ($61.5 million) for 100,000 solar pump installation. For 2017-18, the government has planned to install 67,000 more systems under the solar pump program.

Groundwater pumps are a critical technology in India, especially for small-scale farmers who depend on them for irrigating crops during dry seasons. With the lack of a reliable electrical grid connection, and the high price and variable supply of diesel fuel, solar-powered pumps have great potential to meet farmers’ needs while reducing costs and better preserving natural resources.

MIT researchers have just released a new report, “Solar Water Pumps: Technical, Systems, and Business Model Approaches to Evaluation,” evaluating a range of solar pump technologies and business models available in India for irrigation and salt mining to better understand which technologies can best fit farmers’ needs.

The report includes all the latest experimental evaluation implemented by the Comprehensive Initiative on Technology Evaluation (CITE), a program supported by the U.S. Agency for International Development (USAID) and led by a multidisciplinary team of faculty, staff, and students at MIT.

Designing the study to fill information gaps in the market

“There’s a lot of potential for these technologies to make a difference, but there is a large variance in the cost and performance of these pumps, and a lot of confusion in finding the right-sized pump for your application,” says Jennifer Green, CITE sustainability research lead and research scientist at MIT.

MIT mentioned that despite the potential, there is little information available to consumers about what works best for their needs. “In many areas, the only people to turn to for information are the people selling the pumps, so an independent evaluation of the pumps working with our partners provides a third-party, non-biased information alternative,” Green added.

To conduct the evaluation, MIT researchers worked closely with the Technology Exchange Lab in Cambridge, Massachusetts, as well as the Gujarat, India-based Self Employed Women’s Association (SEWA), a trade union that organizes women in India’s informal economy toward full employment and is currently piloting use of solar pumps in their programs.

Researchers tested the technical performance of small solar pump systems in the workshop at MIT D-Lab and tested larger solar pump systems in communities in India where they were in active use. This allowed for more rigorous, controlled lab testing as well as a more real-life, grounded look at how systems operated in the environment in which they would be deployed. Researchers also used a sophisticated systems modeling technique to examine how the pumps impacted the social, economic, and environmental conditions around them, and how different government policies might affect these conditions at a macro level.

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“That was very important because although these are ‘clean pumps’ from the perspective of using solar, there is a concern that there is not a cost incentive to pump less and use less water,” Green says. “When people are using diesel, they pay by the liter, so they use as little as possible. With solar, once people make the capital investment to purchase the equipment, they’re incentivized to pump as much as possible to get a good return on investment and have potential to do serious harm to the groundwater supply.”

Identifying the most appropriate, accessible technologies

In the lab, MIT researchers procured and tested five pumps (including cheap and expensive) and evaluated them concerning flow rate, priming ease, and overall efficiency, where more affordable pumps perform better than expensive ones. MIT researchers also studied pump usage, installing remote sensors in panels and pumps being used in Gujarat, India to ensure that the pumps were being used consistently over the course of a day, and operating correctly.

CITE also conducted a business case analysis, for example, evaluating government policies such as subsidizing the cost of solar equipment and paying for excess electricity production as a combination to understand what financing mechanisms might make solar pump technology more affordable for farmers.

“The cost of solar pumps is still prohibitively high for individual farmers to buy them straight out,” Green says. “It will be critical to ensure financing mechanisms are accessible to these users. Coupling solar pump systems with well-thought-out government policies and other technologies for minimizing water use is the best approach to optimizing the food-water-energy nexus.”

In addition to the evaluation, CITE created a pump sizing tool that can be used to help farmers understand what size pump they need given their particular field sizes, water requirements, and other factors.

Green said the tool would give the farmer the power to face the water pump manufacturers with confidence. “If they know what they need, they’re less likely to be talked into buying something too big for their needs. We don’t want them to overpay,” she added.

“CITE’s evaluation work has been a great value-add for us because we can better understand which pumps are most efficient,” says Reema Nanavaty, director of the SEWA. “We’re not a technical organization, and we did not want to set the livelihoods of these poor salt pan workers by bringing in the wrong kind of pump or an inefficient pump.”

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