Mathematical modelling and sizing of solar photovoltaic powered decentralised cold room with hybrid storage system

Cold-chain management plays a crucial role in the agriculture sector. However, traditional centralized cold storage facilities often fail to meet the needs of rural and remote areas due to high logistics costs, inadequate infrastructure, and power supply challenges. Hence, decentralized cold rooms are essential for enhancing food security, reducing postharvest losses, and supporting small-scale farmers and businesses. Standalone cold storage systems preserve harvest at farm-gates, especially in rural areas with disrupted electric supply. This study proposes to develop a mathematical model for cold storage, working on vapour compression refrigeration system, using solar power with battery and thermal (hybrid) energy storage, making it a grid-independent, stand-alone unit. The developed model is simulated over a given time horizon for a specified set of weather conditions, to obtain a set of feasible options for the system parameters. A design space, which is a collection of all such feasible options, is generated on the plot of solar photovoltaic rating vs battery capacity for varying compressor power for a minimum of 6 hours of thermal backup. System optimisation is undertaken by minimising the Cost of Energy (CoE) to arrive at the optimum solution from these feasible options. For illustration, a 3.4m3 cold room operation on a typical day in April was simulated. The optimum combination comprised of 0.9 kW compressor power, 13.3 kW of solar PV rating and 4.54 kWh of battery capacity, for which CoE was evaluated as 8.57 Rs/kWh. Experimental results highlighted a reduction of 38% in the energy consumption with PCM integration in a decentralised cold room.This methodology is generic and can be flexibly adopted for cold room of varying storage capacity, proving to be advantageous for future scalability.