Elastocaloric cooling utilizes stress-induced crystal­lo­graphic phase trans­for­ma­tion which releases or absorbs latent heat upon stress loading or removal. It is a promis­ing next-gener­a­tion solid-state cooling due to its high caloric effect. However, one of the disad­van­tages is the huge electric actua­tor required. This project aims to integrate actua­tors driven by low-grade heat to reach the goal of reduc­ing driver-to-refrig­er­ant mass ratio and zero electric­ity input.

Super­elas­tic NiTi-based shape memory alloy (SMA) has been widely studied in elastocaloric cooling because of its superior perfor­mance from the reversible marten­site phase trans­for­ma­tion. Meanwhile, NiTi also possesses the shape memory effect which enables the mater­ial to return to its pre-programmed shape when temper­a­ture reaches the threshold.

This project is dedicated to combin­ing the two effects of SMA to develop a zero-electric­ity cooling device that utilizes super­elas­tic SMA as an elastocaloric refrig­er­ant and shape memory SMA as a heat-driven actua­tor for provid­ing a stress field. By chang­ing the temper­a­ture of the SMA actua­tor, it can exert actuat­ing force and displace­ment to strain the super­elas­tic SMA film to utilize the elastocaloric effect from the stress field alter­na­tion as a way to achieve heating and cooling.

Through­out the research, proto­type devices will be devel­oped to analyze the perfor­mance and optimize the design. The goal of this project is to reduce the oversized driver-to-refrig­er­ant mass ratio in current elastocaloric cooling devices by replac­ing high power consump­tion actua­tors with compact heat-driven actua­tors. The innova­tion will move the research field a step toward net-zero thermal manage­ment by neglect­ing electric­ity input but only utiliz­ing low-grade heat and keeping the high perfor­mance concurrently.