Present status of developments in physical sorption cooling for space applications

A sorption cooler uses the Joule–Thomson effect for cooling a gas by expanding it through a flow restriction. The flow of gas is sustained by a compressor consisting of one or more sorption cells, which cyclically adsorb and desorb gas according to the fully reversible process of physical sorption. The technology has been shown to provide active cooling in the cryogenic temperature range without exporting vibrations or electromagnetic interference. Due to full reversibility of the process and the absence of moving parts (apart from check valves, which open and close with a very low frequency), such a cooler has the potential for a very long life and high reliability. This paper starts with a recapitulation of the principles of physical sorption cooling followed by an overview of the strengths and weaknesses of the technology in relation to other space cooling technologies, such as pulse-tube cooling and Stirling cooling. Next, the present status of physical sorption cooling technology is presented based on developments previously and currently being performed by the University of Twente, Dutch Space and Kryoz Technologies. A summary will be given of the various existing demonstrator- and lab-models which have been built, along with an overview of the tests which have so far been performed. The central result of this paper is an assessment of the current Technology Readiness Level (TRL) of various sorption cooler configurations, along with their application range in terms of temperatures, heat loads and mission profile. Finally, an outline is given on the way forward currently being pursued by the developers to achieve full maturity of the technology