Adsorption chillers are most often run using the working pair water/silica gel. The refrigerant vapor that is generated in the evaporator collects in the highly porous adsorbent. Two separate chambers with adsorbent are necessary and a heat exchanger must be threaded through the adsorbent in each chamber. Once the adsorbent is saturated, it is regenerated via heat. To absorb more refrigerant vapor, the system switches to the second bed of adsorbent. A temperature of at least 60°C is required to operate the system, which is slightly lower than the operating temperature for absorption chillers. This lower operating temperature translates, usually, into a lower EER value for the chillers (EER = ca. 0.4 – 0.7).  Adsorption chillers occupy a limited market share for a number of reasons, including that they require notably higher capital expenditures, they have a larger footprint and are heavier in comparison to absorption chillers.
: Henning Hans-Martin, Urbaneck Thorsten, Morgenstern Alexander, Nunez Thomas, Wiemken, Edo, Thümmler, Egbert, Uhlig, Ulf (2015) Kühlen und Klimatisieren mit Wärme. Bine-Fachbuch.