GaN Power Converter Applied to Electrocaloric Heat Pump Prototype and Carnot Cycle

A 99% efficient power converter is applied to an electrocaloric heat pump prototype for the first time, enabling cyclic electrical field variation in electrocaloric capacitors and high heat pump performance. The electrocaloric effect is an almost fully reversible temperature change in special dielectrics caused by changed electrical field. The GaN power converter achieves high efficiency by zero-voltage switching hysteretic current control. Blocks of commercial multi-layer ceramic capacitors which exhibit an electrocaloric effect are efficiently charged and discharged, synchronized to contacting to a heat sink and source by actuators, which forms a heat pump prototype. Brayton cycles are caused by trapezoidal voltage. Then, arbitrary voltage (E-field) variation for Carnot-like cycles with quasi-isothermal heat transfer is demonstrated and verified by the measured almost constant heat flux during contact to the heat sink. The performance of electrocaloric heat pump prototypes in literature was limited by losses of LC resonant circuits, and is improved by an up to 15.5-fold decrease by this work. The work demonstrates electrocalorics as an emerging power electronics application and contributes to realize future efficient and emission-free, solid state, and electrocaloric heat pump systems.