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

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.