Continuous Phase Change Materials for Power Generation from Daily Air Temperature Cycles

Power generators that convert daily air temperature cycles to electricity should have both high power output and wide operating temperature range. Here, a power generator combining a thermoelectric device and a mixture of various encapsulated alkanes that undergo continuous phase transitions induced by ambient temperature cycles is demonstrated. The operating temperature range of such a power generator can be extended by selecting appropriate alkane capsules to be incorporated into the device. A power generator with an operating temperature range of -0.2-37.2 degrees C is demonstrated; this operating temperature range is obtained when the temperature difference between the highest and lowest temperatures of the ambient temperature cycle is 14.2 degrees C, which is the equivalent environment in a Stevenson screen outdoors. The wide operating temperature range would permit power generation from daily temperature variations in many temperate and subtropical countries. The electric powers obtained by this power generator when placed in an indoor room and an outdoor Stevenson screen are 180 and 300 mu W, respectively. Our temperature cycle-based power generators pave the way for power sources that can generate electricity semi-permanently in a broad range of environment.