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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 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

Thanks to the hard work of the PI Dr. Sangeeta Chopra, her U.S. partners, and the rest of the project team, the Farm SunFridge, also called the solar refrigerated evaporatively cooled (SREC) structure, was completed and went into operation in mid-March 2020 in Picholiya village, Ajmer, Rajasthan. The team installed a remote monitoring station at the SREC structure to track its operations remotely. Many farmers have started storing their perishables including eggs, tomatoes, tomato paste and puree, potatoes, cauliflower, and coriander in this storage, which has a capacity of 2000 kg. When the outside temperature is around 41 C, the inside during the day is around 8-10 C and the nighttime temperature rises to 17-18 C. The environment data of the Picholiya Farm SunFridge are visible on the dashboard at the following link

The PI and her colleagues designed and installed a solar-sensing and compressor-control system for the Farm SunFridge at Picholiya, and it has three levels of control: (1) automatic, light-based, (2) user control, and (3) factory settings. In the automatic system, a programmable Arduino control board takes input from a photometer and uses that signal to control the refrigeration equipment so refrigeration demand is reduced when available light (insolation) is below the required level for running the refrigeration system at full power. The user control system is a manually operated variable resistor that directly regulates refrigeration demand. This system was developed to enable determination of thresholds (light and energy consumption) that could then be incorporated into the programming for the automatic system. Additional refinement of the automatic system is still needed. All electronic components are installed in a weatherproof cabinet to protect them from rain and dust. A technician at the village site manages cooling of the Farm SunFridge with the user control system employing a multistage switch to permit user selection of specific resistance levels to regulate the refrigeration system manually with greater precision. The technician collects data hourly and transmits it to Dr. Chopra once or twice per day, and data are also collected via the remote monitoring system at 30-minute intervals and stored on the cloud. 

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

The second Farm SunFridge is being built at Chamrara in Haryana. The concrete skeleton of the structure is completed and in good condition, and the thermal reservoir and the flow control components have been fabricated for later installation. Dr. Chopra and her team visited the village, met with the farmers, and identified trees that would need to be removed or trimmed to ensure full sunlight reception for the photovoltaic panels. The work has been temporarily suspended due to the COVID-19 pandemic and associated restrictions on travel and supply delivery. Meanwhile, in cooperation with a web design and social media firm in Michigan, the researchers have finalized the content and graphics to be placed on their planned website about the Farm SunFridge. Around 50 pictures detailing the construction process of the structure have been captioned, and a narrative has been written to make a video of the construction process for the Farm SunFridge.

On the outreach side, during the first quarter of 2020, consultant Dr. Randolph Beaudry presented a keynote lecture entitled "Off-grid solar refrigeration: Technical innovations for the storage of perishables for smallholder farmers," co-authored by himself, the PI Dr. Chopra, and U.S. partner Dr. Norbert Mueller. The venue was the International Horticultural Conference organized by The Pakistan Society for Horticultural Sciences on February 26, 2020, at Lahore, Pakistan. Individuals from 25 countries attended. Dr. Beaudry also participated as a judge for the student poster competition on February 27 and gave his second talk entitled: “Using amaranth as a model plant for evaluating imperfect storages: Evaluating the functionality of solar refrigerated and evaporatively cooled (SREC) structures” (authors P. Sharad Mahangade, I. Mani, R. Beaudry, N. Mueller, and S. Chopra). Drs. Beaudry and Chopra also presented technical details of the Farm SunFridge at the inaugural function to around 100 farmers at Picholiya village, Ajmer, Rajasthan, on March 17, 2020.

New installation activities on the second structure are on hold indefinitely until the Indian Government ends the current coronavirus lockdown so that the PI’s institute can reopen and supply deliveries can resume. In the meantime, during the lockdown period the farmers in Picholiya are finding the Farm SunFridge very beneficial for storing produce that they are unable to transport and sell. Some farmers in the Delhi area have contacted the PI asking about how they could build their own. As soon as the pandemic ends and activities resume, the PI and her team will resume work to complete the new structure at Chamrara, Haryana, so local farmers in nearby villages can start using it.

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