Contact Us  |  Search  
The National Academies of Sciences, Engineering and Medicine
Partnerships for Enhanced Engagement in Research
Development, Security, and Cooperation
Policy and Global Affairs
Home About Us For Applicants For Grant Recipients Funded Projects Email Updates
Cycle 7 (2018 Deadline)

Off-grid, clean energy cooling for affordable storage of perishables for bottom-of-the-pyramid farmers

PI: Sangeeta Chopra (, Indian Council of Agricultural Research-Indian Agricultural Research Institute (ICAR-IARI)
U.S. Partner: Norbert Mueller, Michigan State University
Dates:  January 2019 - December 2020 

Project Overview

A stand-alone, batteryless, off-grid, solar-refrigerated evaporatively-cooled (SREC) structure for storage of perishables has not previously been field evaluated by smallholder base-of-the-pyramid (BOP) farmers. The SREC chamber can easily achieve daytime temperatures as low as ~5-10 °C when the daily maximum temperature outside is approximately 45 °C. This technology promises a meaningful contribution to the capacity and stability of the BOP farmer. The innovations incorporated into the SREC structure are many: a design that can be largely self-built and permits staged construction and investment; the use of passive evaporation of water from the chamber walls for partial cooling both day and night, thereby reducing refrigeration load and cost; the use of a split evaporator coil system to shunt cooling to a thermal reservoir; the deployment of a new inverter technology with a secure power supply and integrated controls to maximize solar collector efficiency; the use of a cold water reservoir to provide low-cost thermal storage instead of using batteries for overnight cooling (reducing environmental impact, operational risks, initial capital, and maintenance costs); the deployment of an extremely large surface in the chamber to maximize cooling with a minimal temperature differential, thereby increasing humidity and minimizing perishable desiccation; the use of a dedicated relay circuit to ensure automatic start-up following overnight shutdown; and no dependence on electrical grid for cooling. Despite the novelty of the structure, it can be self-built by farmers with inexpensive locally available materials, minimizing extra labor costs and initial investment requirements. The specialized components required, like solar panels, inverters, and refrigeration systems, are readily available in India. This project is aimed at replicating initial technical successes by transitioning to field trials by farmers. The researchers will evaluate the amount of energy collected and converted to refrigeration, measure impact on the quality of perishables stored, determine the value to farmer households, and assess the impact on local and regional markets.

Deploying innovative off-grid batteryless SREC structures/chambers at farmers’ fields in villages in three hot and dry states of India will have several important impacts. This innovation will help India's transition to a low emission economy by adding decentralized solar PV capacity. Having access to on-farm cold storage will increase incomes for BOP farmers by avoiding distress sales, reducing spoilage, and enabling pre-processing of perishables. Adopters of SREC technology will keep produce cool without grid electricity, which frequently fails. Market panic following grid failures is avoided and market confidence and control improved. Higher profits will improve quality of life, increase purchasing power, support higher education for women and children and improve household affluence. Education is another important part of this work. Farmers and local tradesmen will be trained to build SREC chambers themselves, thereby improving community capabilities and opening up new opportunities for financial growth. The farmers will be educated on opportunities for light processing of perishables (e.g., pod stripping, pea or bean shelling, packaging) and will be able to run small processing machinery directly from solar panels. Additionally, extension professionals will be trained on the fundamentals of construction and use of this technology and will be encouraged to act as agents of change.

Summary of Recent Activities

7-360 SREC
A test SREC being finalized in a local town (Photo courtesy of Dr. Chopra).
By the end of the first year of her project in December 2019, Dr. Chopra and her colleagues had made a great deal of progress on their project. In recent months they continued working to optimize the performance of the solar-refrigerated, evaporatively-cooled (SREC) storage structures using the prototypes built on the IARI campus by evaluating electronic components and sourcing suitable materials for construction. Their electronics improvements included identifying and testing suitable inverters, the electronic components that convert solar energy to usable alternating current electricity. They tested several different commercially available brands that are capable of operating off-grid and without batteries, plus one on-grid model. As a result of the tests they selected one model as most suitable for deployment in villages based on its performance, reliability, and ease of use. In addition to the changes with electronic components, finding in-country sources of some of the more specialized materials used in construction of the SRECs has been challenging. The team did an extensive search for companies that make fabrics useful for the evaporative surface of the SREC room, requested test samples, and evaluated those materials. The lack of an online presence of manufacturers of these types of materials in India made this task more challenging than anticipated, but the researchers eventually found a supplier in New Delhi who could make the kind of aramid needle felt needed for the SREC chamber and then fabricate it into a product suitable for installation. The team also located a source of higher-quality polystyrene foam board for insulating the structure and arranged for its delivery to the first construction site, which is located in the village of Picholiya, Ajmer District, Rajasthan.

A foreman and two laborers worked to clear the land, lay the foundation, procure construction materials, and commence construction. The team carried out the work in Picholya from September 24 to October 13 and again from October 18 to November 17, 2019. Using engineering drawings with precise measurements for the workers to follow, these three persons, with the assistance of one local laborer and the landowner, took construction to the point of readiness for the installation of the fabric walls, solar panels, and refrigeration system. PEER project consultant Dr. Randolph Beaudry and Dr. Chopra visited the village and assisted in construction October 22-27, timing their visit so they could assist with critical constructional issues like fabricating and testing the thermal reservoir (i.e., water battery) and securing the water battery to the ceiling of the SREC chamber. This latter step was especially important in ensuring safe use of the structure, as the water battery will weigh about 1,500 pounds when full. Following the departure of Dr. Beaudry and Dr. Chopra, several construction items were completed, including the truss for support of the solar panels, a water storage reservoir, and a ramp to the structure door. Additionally, a security fence was installed by the Rajasthani partner in this project, Krishak Vikas Sansthan (KVS). Even though it was not yet complete, the structure attracted a lot of interest and curiosity among fellow farmers and the business community in nearby villages and markets, including Pisanganj, Ajmer, Rajasthan. A few farmers have approached the PI and her team enquiring about the costs involved, in case they want to build an SREC chamber at their farms themselves.

At the time the initial construction phase was completed in mid-November 2019, the SREC structure was shuttered and secured, awaiting further work. The solar panels and refrigeration system have been ordered and should be delivered in January 2020 so the SREC chamber can be completed and made operational in February. Dr. Chopra and Dr. Beaudry will install datalogging equipment at that time, train the KVS representative and farmers on use of the structure, and start up the system. They expect the farmers to start using the chamber for storage of fruits and vegetables soon thereafter, after which real-time data collection will also commence. The PI and her team are considering developing an educational workshop for farmers and local craftsmen to provide educational materials in English and Hindi. The materials will contain the package of practices of working with SREC storage structures and will include tours of the SREC facility. Meanwhile, in the coming months they also plan to start construction of an SREC chamber in the village of Chamrara, Israna Tehsil, Panipat District, Haryana, another village that has been selected after a survey of some villages in Haryana. Dr. Chopra has also submitted an abstract to the International Horticulture Conference, which will be held in February 2020 in Pakistan.

Back to PEER Cycle 7 Grant Recipients