Prediction and analysis of the seasonal performance of tri-generation and CO2 refrigeration systems in supermarkets

A modern supermarket energy control system has a concurrent need for electricity, space heating or cooling, and food refrigeration. The power supply to the supermarket is primarily from the national grid, where losses in efficiency are due to the processes of energy conversion and transmission. Combined heat and power (CHP) offers the potential to locally produce electrical power and heating which could save energy and reduce CO2 emissions in the long run. During the summer months, as the space heating requirement in a supermarket is relatively small, the energy efficiency of a CHP installation can be improved by using excess thermal energy to drive a sorption refrigeration system to provide space cooling or refrigeration. This process is also known as tri-generation. In recent years, the use of CO2 as a refrigerant in supermarkets has received considerable attention due to its negligible contribution to direct greenhouse gas emissions and excellent thermophysical and heat transfer properties. Consequently, the application of a tri-generation system in a supermarket with CO2 refrigeration merits further investigation.In this paper, to evaluate the performance of a tri-generation system in the supermarket, a previously tested 80 kWe microturbine device was applied into an operational supermarket to generate power and provide space heating and cooling through exhaust heat. The performance evaluation and comparison for this tri-generation application is based on the prediction from an integrated model of supermarket energy control, cascade CO2 refrigeration and tri-generation systems. The results from this simulation demonstrate the feasibility of a tri-generation system in the supermarket and pave the way for further consideration towards designs in future.

► Integration model of a trigeneration with CO2 refrigeration systems in supermarket.
► Validation of the developed integration model with site and laboratory measurement.
► Application of the trigeneration system in power generation and space conditioning.
► Performance analysis and comparison of the integrated system in supermarket.