In traditional refrigeration, pressure changes drive a cooling cycle mediated by a fluid refrigerant such as Freon, which is harmful to the environment. New methods for cooling could save energy, permit miniaturization, and allow for faster startup times. One such approach is based on electrocaloric techniques, where voltage plays the role of pressure and the fluid refrigerant is replaced by a solid material whose temperature can be changed via an electric field. However, it is unclear how efficient such heat pumps can be in light of the limitations of the active electrocaloric materials at their hearts. Using detailed experimental data on an archetypal electrocaloric material, we calculate that the potential performance of such a cooling device is encouragingly high.

Based on dense electrical polarization and heat-capacity data, we construct thermodynamic maps, which track measurements of thermodynamic properties against temperature and voltage. These maps allow us to visualize, in high resolution, the transition at which we drive electrocaloric effects, and they obviate the standard practice of assuming a constant heat capacity. To permit the construction of cooling cycles over a wide range of temperatures, we assume that our material is used to develop a temperature gradient along a lossless column of heat-transfer fluid by dumping heat at the hot end and absorbing heat towards the cold end. We find that cooling cycles with well-defined energy efficiency require close control of voltage.

In the future, our approach should permit researchers to optimize and compare the performance of all caloric materials, including those driven by magnetic fields or mechanical stresses.