• Developed generalized PCM-VCR cold storage design space and sizing methodology. • Combined time-series simulation, optimization, and experimental validation. • Enabled quick identification of efficient system configs minimizing energy cost. • Demonstrated intermittent vs continuous PCM discharge for thermal backup. • Supports sustainable cold chain with energy savings and cost-effectiveness. Decentralized micro-cold storages (less than 5 metric tonnes of storage capacity) operating on vapor compression refrigeration (VCR) represent a key element in food preservation supply chain. Integration of thermal storage in cold room benefits from reduced temperature fluctuations along with reduction in compressor running time leading to energy savings. However, the energy consumed in charging the thermal storage is closely connected to the size (mass) of the phase change material (PCM) which is often overlooked. In this study, we propose a mathematical framework for sizing and optimization of the thermal storage unit through a systematic timestep simulation of energy balance of the entire system over a specified time horizon of operation. Inputs to the model are the ambient temperature and thermal load on the cold room along with the equipment characteristics. The design space is a graphical representation of all feasible design solutions on an evaporator area vs compressor power rating diagram with PCM mass as a variable. The key contribution of this work lies in identifying the feasible combinations and limiting values of the system design variables that enables a quick selection of an optimum configuration based on desired objective. Minimization of levelized cost of storage (LCOS) was chosen as the optimization objective. The optimum configuration for a 6-hour uninterrupted thermal backup capable of storing 0. 5 ton of produce comprise of a compressor rated power of 800 W with 3. 8 m 2 evaporator area and 142 kg of PCM for leading to a LCOS of US 0. 47/ kWh.
Sreelekha et al. (Thu,) studied this question.