ELECTROCHEMICAL COMPRESSION WITH ION EXCHANGE MEMBRANES FOR AIR CONDITIONING, REFRIGERATION AND OTHER RELATED APPLICATIONS

Abstract

The refrigeration industry in the US are facing two main challenges. First of all, the phase down of HFCs in the future would require industries to seek alternative refrigerants which do not contribute to global warming. Secondly, the mechanical compressor in the small scale cooling system with a large energy impact is reaching its limitation due to heat transfer and manufacturing tolerances. Therefore there is an urgent need to develop a highly efficient compression process that works with environmentally friendly refrigerants. And the electrochemical compressor is developed to meet these requirement based on the following reasons. First of all, the electrochemical compressor can achieve an isothermal compression efficiency of greater than 90%. It also operates without moving parts, lubrication and noise. Most importantly, the compressor works with environmentally friendly refrigerants.

In this thesis, three distinct electrochemical compression processes were studied. The first study is focused on modeling a metal hydride heat pump driven by electrochemical hydrogen compressor. The performance of the cooling-generating desorption reactor, the heating-generating absorption reactor, as well as the whole system were demonstrated. The results showed the superior performance of electrochemical hydrogen compressor over mechanical compressor in the system with optimized operating condition and COP. The second study demonstrated the feasibility of electrochemical ammonia compression with hydrogen as a carrier gas. The reaction mechanisms and the compression principle were verified and the compression efficiency was measured to be greater than 90%. The technology can be applied to ammonia vapor compression refrigeration cycle and ammonia storage. The third study is about developing and studying the electrochemical CO2 compression process with oxygen as a carrier gas. The reaction mechanism was verified and compared for both Pt and CaRuO3 electro-catalysts. And the latter was selected due to better CO2 and O2 absorption. The technology can potentially be applied in carbon dioxide transcritical refrigeration cycle and carbon capture.

In conclusion, the electrochemical compression is a promising technology with higher compression efficiency and would bring a revolutionary change to the compressor engineering industry and global refrigeration and air conditioning market. It can also be used in fuel storage and separation based on the selective properties of the ion exchange membrane.