Advances in active regenerative elastocaloric cooling

Elastocaloric (thermoelastic) heat pumping is a strong contender for next-generation cooling technology. It promises to be more energy efficient than vapor compression while also eliminating high global warming potential gaseous refrigerants. Employing active regeneration in the system design ensures temperature gradients exceeding adiabatic temperature changes alone and, therefore, enables utilization of small actuation stresses and low strains while pumping heat across substantial temperature spans. Low stresses reduce the risk of failure both in tension and compression, and increase the likelihood of reaching roughly 10⁷ cycle regenerator lifespans required for cooling and refrigeration applications.

We present advanced regenerators and laboratory-scale devices using commercially available NiTi materials as refrigerants to demonstrate feasibility, efficiency, and scalability of regenerative elastocaloric heat pumping. Unique active elastocaloric regenerator configurations utilize composite structures that reduce forces needed for actuation and enable the use of compact, low-cost actuators, thus increasing the practicality of elastocaloric cooling. Experimental and model results of temperature spans and cooling powers produced by the newly-developed elastocaloric regenerators will be discussed with a particular focus on efficiency and durability. Also presented are recent advances in design of active regenerative elastocaloric cooling systems, proof-of-concept experimental devices, and future research directions.

This work was performed with joint funding from the Advanced Manufacturing Office and the Building Technologies Office of the Office of Energy Efficiency and Renewable Energy of the United States Department of Energy. Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University of Science and Technology under Contract No. DE-AC02-07CH11358.