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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

Despite the many challenges presented by the COVID pandemic and associated shutdowns and travel restrictions, Dr. Chopra and her team continued to make strong progress on their project during the third quarter of 2020. The first Farm SunFridge (FSF), the solar refrigerated evaporatively cooled (SREC) structure, continues to be operational in Picholiya village, Ajmer, Rajasthan. Local farmers are using it to store perishables, including gooseberry juice and green chilis. When the outside temperature is around 23-40 °C, the inside temperature during the day is around 15 °C and the nighttime temperature rises to 17-18 °C. A technician at Picholiya collects data hourly and transmits it to the research team once per day. They are also collecting data via the remote monitoring system at 30-minute intervals. The data are stored in the cloud at via the HOBOTM remote monitoring station installed in the FSF. Meanwhile, the second FSF is being built at Chamrara village in Haryana. The construction work was delayed due to the COVID pandemic but is proceeding in piecemeal fashion. The solar and inverter control panel has been installed, and because there is electricity on the farm, the structure will be a hybrid FSF, which will use solar power and/or the power grid during the day and a water battery for nighttime cooling. Due to the work being stalled at the site from March through July 2020, it became apparent that improved barriers were need to prevent small animals like mice, snakes, and lizards from getting into the structure and digging in the soil beneath it. Those corrective measures have been taken, and as of late October the FSF has become operational.

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

As a side benefit from their participation in the program, the PEER project team recently completed a two-month training series provided by USAID’s Center for Development Research (CDR) to build their capacity for stakeholder outreach and communications. Putting their training to use, the PI and her colleagues have reached out to several key groups and institutions, including the following:
  • Four farmers, to understand the necessity for cold stores
  • A manager at the National Bank for Agriculture and Rural Development (NABARD), to explore possibilities to fund FSF demonstration units for Farmer Producer Organization (FPOs) and/or on-farm FSF structures for use by farmers
  • Three policy makers at the Ministry of Agriculture and Farmers Welfare, India, to understand what policies govern the postharvest, especially for cold storage, and how to influence and motivate them to add the FSF to the guidelines followed by organizations like National Center for Cold Chain Development (NCCD) a key implementing agency under MIHD, for granting subsidy to farmers for cold stores. The team will provide a project report with a detailed cost analysis to support inclusion of the FSF in the MIHD guidelines for funding farmers to build these structures.
The FSF concept continues to attract strong interest even from individuals and institutions not targeted for outreach. The General Secretary of the NGO INDIA-AIDS, who works with farmers in Delhi and the surrounding region, has visited the FSF in Chamrara and asked how to take this technology to the many farmers who are interested in building this structure in Panipat, Jhajjar, and Sonepat. The FSF prototype at IARI is also receiving visits from many students, farmers, and officials from nearby villages, and the PEER team is receiving numerous enquiries and requests to make more of these structures at many more farms. In 2021 they will select a site in the Delhi region to build their third FSF according to their project workplan, incorporating new design features developed in the course of installing the previous two. The project team has recently submitted a patent application to the Indian Patent Office for the FSF technology.

In the remainder of 2020 and into 2021, three students (one PhD and two Master’s) will continue their research work on the FSF structure at IARI on various design and storage aspects. One additional student has completed his Master’s on making models for storage of tomatoes and spinach in FSF and other evaporatively cooled structures. Also in the coming months, the team will install remote monitoring sensors in the Chamrara FSF and make some modifications in the original structure at Picholiya. A no-cost extension has been issued through at least December 2021, as field trials also need to be completed after the FSFs are operational.


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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