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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 2021

Project Website:

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

The SREC structure (a.k.a Pusa Farm SunFridge, FSF) built on the grounds of IARI in Delhi with other (non-USAID) funding is performing very well, and continues to draw attention from many farmers, entrepreneurs, and policy makers. Several companies have obtained or are seeking a license from IARI for building Farm SunFridges. Two proposals have been submitted to State Governments for building these structures in villages of Uttarakhand and Assam. The proposals are under consideration by the respective state government authorities.

The administrative procedure for building the fourth Farm Sunfridge in the village of Kulakpur, block Palla, Delhi, has begun. After completion of the tender process, the construction work is expected to begin in August. In the meantime, the solar panels, refrigeration system, and MPP units have been received. The site at village Kulakpur has been finalised after a meeting of scientists from Michigan State University and IARI and a civil engineer from Chhatisgarh with a group of villagers and farmer producer organiztions (FPO) remotely. Pranav Pillai, a civil engineer with Mayur Construction Company, is engaged with the PEER team in making the drawings of the Farm SunFridge and will help them build the assemble-enabled-fabricated unit. The intention finally is to make a prefabricated Farm SunFridge that could be transported to remote locations and assembled easily.

7-360 Chopra SREC Picholiya
The fully constructed and operational SREC chamber in the village of Picholiya (Photo Cred: Dr. Chopra).

Dr. Chopra and her colleagues have licensed their technology to a company interested in building the Farm SunFridge at smallholder farmers’ fields, markets, or other spots, and they are in the process of giving the license to a few more companies as of July 2021. The wide publicity received by the FSF resulted in many companies, farmers, and FPOs approaching the team to get details about this technology. The team has made a bilingual policy brief on the Farm SunFridge technology to be used with policymakers, so that they may include this technology for a subsidy in the operational guidelines of the Mission for Integrated Development of Horticulture (MIDH). Currently, the guidelines of MIDH have specified subsidies for cold storage, evaporatively cooled (EC) storage, and solar panels separately. The attempt being undertaken is get the name “Farm SunFridge” directly in the MIDH guidelines to make it easy to get a subsidy on this structure.

Plans for the rest of 2021 include completing the FSF in Kulakpur. U.S. partner Dr. Randolph Beaudry and Dr. Chopra are planning to deliver talks at the American Society for Horticultural Science conference at Denver in August and the V Asia Symposium on Quality Management in Postharvest Systems in Bangkok in December. They are also in the process of writing technical papers and are doing data analysis for EC and SREC (FSF) structures. They have been asked to give both a technical and a keynote address at a conference on international development in the coming year in New Zealand. Meanwhile, they are attempting to engage young and talented individuals as the project continues to grow. Besides engineer Pranav Pillai, who is mentioned above, Dr. Chopra’s son Sameer Dhingra is helping on a volunteer basis to manage software development and digital technology interfaces.


Mahangade, P.S., I. Mani, R. Beaudry, N. Müller, and S. Chopra. 2020. Using Amaranth as a Model Plant for Evaluating Imperfect Storages: Assessment of Solar-refrigerated and Evaporatively-cooled Structures in India. HortScience 55,

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