Using the TEWI Methodology to Evaluate Alternative Refrigeration Technologies

Offering the possibility of environmental friendly operation, several alternative refrigeration technologies are emerging aiming to substitute current refrigerant fluids and even current vapor compression technologies. Among such technologies are the Stirling machines, CO2 cycles, Magnetocaloric, Thermoacoustic and Thermoelectric systems besides a broad range of other options. In most cases when comparing the performance aspects of such technologies with the current technologies some basic concepts are not taken into account. Statements such as " .... presenting the same performance level of current compressors ....", for example, are easily found in the open literature. Considering performance is a broad concept including aspects related to e.g. efficiency level, environmental impact, reliability issues, etc it is clear that a fair performance comparison among different technologies is not an easy task. This paper does not intend to present a unique and complete methodology to compare alternative technologies however will provide some key information and boundary conditions to make this comparison more realistic. As far as environmental impact is a concern, a Total Equivalent Warming Impact (TEWI) analysis is proposed, looking at both the direct and indirect global warming potential, presenting real data for different regions (North America, Europe and Asia) and different applications into both household and commercial refrigeration. A sensitivity analysis is performed for each world region and for each kind of application. The aim is to identify the critical contribution for obtaining a better environmental operation. The study is grounded on information available on technical literature and experimental data.