Renewable refrigeration systems for food preservation in tropical countries

Food spoilage represents an urgent issue in tropical developing countries because of the lack of correctly refrigerated post-harvest storage, transportation and distribution facilities. Thus, finding refrigeration systems for preserving food at the proper temperature using the available energy sources in an efficient and cost-effective way is crucial to avoid serious food illnesses. This paper aims at providing guidelines for the best choice of configuration and design parameters of refrigeration systems coupled with renewable conversion units in tropical areas using as case study the Republic of Cuba. To this end, flexible and detailed design and off-design models of compression and absorption refrigeration systems and renewable conversion units are built. The design of six refrigeration systems configurations are first optimized according to the maximization of the Coefficient Of Performance (COP), and considering three different food storage temperatures (8, 2 and -20°C). Fifty-four technically feasible integrations of the optimized refrigeration systems with the most widely available renewable energy sources (biomass, biogas, solar heat and photovoltaic) are then identified and simulated in a typical year of operation to evaluate energetic, exergetic and economic performance. A thermal storage or the connection with the electric grid is considered in the integrated solutions fueled by solar energy to guarantee a continuous operation. Results show that the PV-powered flash-intercooled compression system is the most efficient solution for each food storage temperature (annual average COP in the range 2.3-5.7) but it represents the most economically viable solution only for the highest food conservation temperature. At lower temperatures, the single-effect absorption cycle coupled with a bagasse-fired boiler shows lower costs because of the very low price of bagasse in tropical countries. On the other hand, all solutions including the half-effect absorption cycle result to be the less promising both in terms of COP and costs.