Water, ethanol, or methanol for adsorption chillers? Model-based performance prediction from Infrared-Large-Temperature-Jump experiments

Abstract

Adsorption chillers are a promising technology to ease the burden on renewable electricity demand by using waste heat as driving energy. Their performance depends on the adsorbent’s kinetics, the chosen refrigerant, the design of the adsorber, and the selected temperatures. Thus, quantifying an adsorption chillers’ performance usually requires expensive experiments at full scale. Here, we efficiently characterize a broad set of working pairs for a wide range of conditions using a two-step approach: First, we conducted Large-Temperature-Jump and equilibrium experiments to extract kinetic and equilibrium parameters of water, ethanol, and methanol with a set of currently discussed adsorbents. Second, we inserted the parameters into a dynamic model to evaluate the working pairs’ performance in full-scale two-bed adsorption chillers. For chilling above 0 °C, water remains the benchmark refrigerant with the highest volumetric power and efficiency with the silica gels SG123 and Siogel. Ethanol and methanol working pairs offer higher mass transfer coefficients, but could not offset the benefits of water. Coatings of the MOFs aluminum fumarate and CAU–10–H provided exceptionally high heat transfer coefficients, but were too thin to compete. For chilling below 0 °C, ethanol and methanol were on par. ZIF–8 was competitive with the activated carbon CarboTech A35. Overall, CarboTech A35/methanol showed broad applicability, performing comparably to SG123/water above 0 °C while still providing reasonable performance below 0 °C.