Redesigning evaporatively cooled rooms to incorporate solar powered refrigeration in India

摘要

Evaporative cooling is an ancient technique for removing heat in warm, dry climates. It has been employed in the construction of relatively large structures containing over 2 t of produce in India for at least two decades. However, at best, these evaporatively cooled (EC) structures can reduce temperatures only 10 to 12°C below ambient temperatures during the warmest part of the day and can have temperatures above ambient in the cooler evening hours. As part of a project supported by the USAID/Global Center for Food Security Innovation at Michigan State University and by the Indian Agricultural Research Institute (IARI), we have redesigned these traditional cool stores to support active refrigeration using a direct current-based refrigeration system powered by photovoltaic cells for grid-independent operation. Important features of the redesign include full functionality as an EC room, capacity for retrofitting with solar power to augment cooling, and potential for extracting power from the photovoltaic array for minimal processing and packaging of perishable produce. Modeled thermal properties of the room suggest that the evaporative cooling will reduce the size of the refrigeration system and associated solar array by 1/3 relative to a non-EC room. The implications on duty cycle and utility will be discussed. Solar-augmented and traditional EC structures are being constructed at IARI in Delhi India for direct comparisons of utility and cost.