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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 and co-partner Randall Beaudry, Michigan State University
Dates:  January 2019 - December 2022

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

On December 27, 2021, the fifth Farm SunFridge (FSF) went into operation in the village of Cullakpur, North Delhi, Delhi. This SunFridge is the third of three built with PEER funds. The first two were built in the villages of Picholiya, Ajmer, Rajasthan, and Chamrara, Panipat, Haryana. The other two non-PEER SunFridges were installed at IARI, one at the Division of Agricultural Engineering and the other at the exhibition (mela) ground. The locations of all SunFridges are shared on the project website Temperature and relative humidity data of the newest FSF can be retrieved from the cloud at Data from the FSF at IARI are available at

The Cullakpur SunFridge differs from the previous two PEER-funded FSF installations in that it is built using prefabricated iron frames and was almost completely assembled using nuts and bolts at the farm itself. This approach made the construction work faster, more efficient, and more precise. This construction methodology used detailed mechanical drawings for each structural element, leading to improved tightness of the insulation and overall better fit and finish. In addition to the new frame design, several design improvements were adopted from the modifications first employed at the Pusa Farm SunFridge at IARI. Major innovations include installing the solar panels on a truss framework on top of the metal sheeting roof to simplify electrical connections and improve maintainability; bolting the entire framework of the structure on metal plates fixed in the concrete foundation; adding a layer of polyurethane foam to the Styrofoam panels for improved insulation on walls; and giving a 10 ° slope to the metal roof to prevent water stagnation. A new innovation unique to the Cullakpur SunFridge was the design of the door, which was made heavier, with better hinges and rubber gaskets for tighter sealing. Another new modification was the addition of an automated solar adaptive controller that is programmed to change the demand of the refrigeration system in accordance with sunlight intensity. If the insolation (incoming solar energy) drops, the controller reduces the demand from the refrigeration compressor, enabling the refrigeration system to continue running even with low power output from solar panels. On the other hand, when the insolation increases, the refrigeration system shifts automatically to increase its demand and cool at full load. This technology enables improved efficiencies and obtaining lower temperatures inside the Farm SunFridge.

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

The farmer at the Cullakpur site (Abhishek Dhama, age 28) is part of a Farmer Producer Organization (FPO) and has a collection center next to the FSF in support of its operation. He is constructing a floor and a dock on the outside of the SunFridge. In addition to field-grown perishables, he plans to store fresh-cut fruits and vegetables in the FSF. He is selling his produce directly, using a B2B model, to Swiggy and Zomato, mobile app operators who supply fresh produce to urban areas. The FSF at Cullakpur will be monitored in the summer 2022 season, and those data along with feedback from Abhishek will enable the PEER team to make changes in the design of the FSF to improve its performance. Meanwhile, the FSF units built at the villages of Picholiya and Chamrara continue to operate since March and November 2020, respectively. They are being used by farmers from a cluster of nearby villages.

Due to the increased demand for FSFs, the technology has been included in the Revolving Fund Scheme (RFS) of the Division of Agricultural Engineering at IARI. The RFS tender has been floated for contractors and suppliers to bid for building FSFs at places where there is demand for them. The RFS scheme is handled by IARI to facilitate technology transfer, and IARI will help the contractors by providing technical design inputs and other logistical support to enable them to build the FSFs in farmers’ fields or near retail marketplaces.

In 2022, now that all the planned FSFs have been built, the PI and her team we will be monitoring the performance of all five units. They will also be modifying or adding more features to the FSF at Cullakpur, based on the experience and feedback of the farming community using it. The researchers will be trying some inexpensive alternate fabric material on the outside for enabling evaporative cooling. In addition, to the supplemental funding mentioned below, they have received $48,350 from the Department of Science and Technology of the Government of India for a project entitled “IOT-enabled Universal Monitoring and Control System for Environmental Parameters for Efficient Storage of Agricultural Produce (IOT-UMC system).”

Supplemental Funds

In October 2021, Dr. Chopra and her team received $9,999 in PEER supplemental funding to develop a ready-to-use building manual for the Farm SunFridge. The manual will include step-by-step instructions on how to build the unit, with detailed drawings, photos, part numbers, and specifications to enable easier and faster assembly. Along with the technical manual, the team will also create a detailed bankable project report with economic analysis to be used by farmers and entrepreneurs to obtain funds from an agricultural bank to build their own FSFs.


Chopra, S., N. Mueller, D. Dhingra, I. Mani, T. Kaushik, A. Kumar, and R. Beaudry. 2022. A mathematical description of evaporative cooling potential for perishables storage in India. Postharvest Biology and Technology 183:111727

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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