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Solar technology and community engagement team up to help low-income farmers in India

Involving people who will directly benefit from technology research is critical to sustainable development, as researchers have experienced by working with chili farmers in India for more than four years.

A team led by Stanford University developed a solar-powered technology to improve the quality and quantity of dried agricultural produce and potentially increase incomes of smallholder farmers in India, which average around $5 per day. Due to better quality, chilies dried by the equipment were sold at 14 percent to 22 percent higher prices than chilies dried traditionally in the open air, according to a recent study in Energy for Sustainable Development. Depending on the farmer’s underlying costs such a revenue boost could double profits, but the cost of buying the equipment, learning how to use it and uncertainty of financial outcomes are barriers to adoption.

Credit: Frederick Tan and Michael Machala

To address these issues, the study also examines alternative financing available to the farmers and potential additional benefits, like avoiding the common waste of at least 10 percent of a crop from rains in open-air sun drying and using the equipment to grow seedlings when not drying. While still in development, the technology could improve the livelihood for many millions of farmers globally who grow and dry produce, such as grapes, spices, and beans.

“Technological energy innovation is only a part of the answer to reducing poverty in agriculture. Systems-level understanding and approaches are required to ensure that we adequately and ethically meet the needs of farmers while also designing for scalability,” said Sally Benson, senior author of the study and a professor in Stanford’s Department of Energy Resources Engineering.

Following a presentation at Stanford by the Deshpande Foundation and Deshpande Startups in 2017, lead author and postdoctoral scholar Michael Machala, PhD ’17, and co-author Andrey Poletayev, PhD ’20, went to Karnataka, India to meet with Innus Khan, the foundation’s senior director of agricultural initiatives and co-author of the study. The organization, based in the United States and India, develops sustainable and scalable enterprises that have significant social and economic impacts. Chili farmers told the researchers in field visits that traditional open-air drying can take weeks to complete and cause degradation or total spoilage from sun bleaching, pests, rain and fungus. The Deshpande Foundation was working with more than 2,000 chili farmers at the time, Khan said. The team found that damages from open-air sun drying of chili on Indian farms slashed revenue by one-third on average.

Researchers pose for a photo next to an area with many red chiles air drying
From left, researcher Innus Khan with a chili farmer, (who requested anonymity), and researchers Michael Machala and Andrey Poletayev after discussing the challenges of open-air drying of chilies in 2017. (Image courtesy of Michael Machala)

The team thought sustainable social entrepreneurship might unlock scalable solutions for India’s 125 million smallholder family farms, one-quarter of the world’s total. India is a world leader in dried chili production at 1.7 million tons per year, and many of the country’s other products are also open-air dried.

Systems-scale solution

Switching from open-air sun drying to drying in greenhouses is not a new idea, but previous research rarely looked at adoption. “People focused on technical questions, but they missed the user-facing questions that really determine whether a solution gets implemented or not,” said Poletayev.

The team found that using the equipment only for drying produce was a huge barrier to adoption of improved drying technology. The farmers, who have little disposable income, would take three to seven years to pay off the equipment purchase from their increased profits, according to the new study.

“Because solar dryers sit unused much of the year, we adapted the design of our system to meet another farming need of growing seedlings, which are more robust and productive when starting out in a greenhouse,” said Machala. “Farmers report that seedlings grown initially in our greenhouse and then transplanted to a field produce up to twice as many chilis as those sown in the field.”

two rows of dried red chiles, the first of which were dried in the open sun and are inconsistent in color. The second row is solar-dryer and are very consistent in bright red color
Comparison of chilies dried by the sun in the open air, above, and by a solar dryer. (Image credit: Mahammadmustap Halageri)


The operational and technical design are not trivial. For example, the pilot greenhouse has demanding technical requirements, like reaching temperatures up to 140 degrees Fahrenheit for drying and staying below 89 degrees for growing seedlings. In addition, the study explores how third-party organizations or companies could buy the equipment and provide the seedling growth and drying for a fee to farmers, who would avoid upfront equipment costs while seeing the financial benefits of equipment usage.

The research suggests that credit-worthy entities, such as farmer collective groups, traders or exporters, should be the investors in the greenhouse. With government subsidies and private loans for the equipment purchase, the owning entity could collect fees for two services from multiple farms over seven months of the year. In this scenario, the study finds that the cost of equipment would be recuperated in just one year, instead of the 6.5 years for a single farm using the equipment for drying only.


“Most of the projects [at Deshpande Foundation] are based on the demand and need from the community,” explained Khan. “Because we know this issue well, we got started with Michael and Andrey, co-creating this technology to address the dried chilies problem.”

Back at Stanford, the Suryodaya project – named after the Hindi word for "sunrise" – navigated technical challenges with help from undergraduate seniors majoring in mechanical engineering in the capstone course Mechanical Engineering Design: Integrating Context with Engineering. Every year since 2018, students in the course have helped solve key design challenges.

Researchers learning about the chili market in Karnataka, India
Mechanical engineering seniors Molly Dicke and Frederick Tan learn how chili quality affects price while visiting a market trader in Karnataka, India. (Image credit: Michael Machala)

“Over seventy students across six departments and three schools have contributed to this project. It’s truly been a transdisciplinary effort,” Benson shared.

One such student, Frederick Tan, B.S. ’18, visited India to learn more about his student team’s design challenge and eventually joined the research team full-time. “This project bridges academia to real-world problems. We got to tap into the resources that we're so lucky to have at Stanford to help other people around the world,” said Tan, now a master’s degree student in the Department of Civil & Environmental Engineering.

To date, the international research team has begun piloting the published concept in close collaboration with Deshpande Startups and Pequrel Technologies, working with smallholder farmers to dry 24,000 kilograms of red chili and grow 160,000 seedlings of chili, tomato, and eggplant. They hope to run a trial study on the fully implemented and financed system. And the team has begun growing and testing other dried products like turmeric, onion, mung beans, grapes and figs. Complementary produce seasons could raise the equipment utilization from seven months of the year to 12.

“We have a lot of promising results, but more R&D is needed to prepare for confirmation and adoption toward impact at scale,” said Machala.

This work was funded by Stanford’s Precourt Institute for Energy, Woods Institute for the Environment, TomKat Center for Sustainable Energy and Haas Center for Public Service, and by the Deshpande Foundation and Deshpande Startups. For more information on the Suryodaya project, contact Michael Machala: mmachala at stanford dot edu.

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