Recharging batteries using energy harvested from thermal gradients

With the recent advances in wireless technology and low power electronics the idea of capturing the ambient energy surrounding a system and using it to provide electrical power to devices that do not rely on external power supplies has received a significant amount of attention. Much of this attention has been aimed at the use of piezoelectric materials to capture ambient vibrations. However, the energy generated by such materials is far too small to directly power most of the electronic devices. Therefore, in the present study a Seebeck heat pump is used to convert the ambient thermal gradient generated by solar radiation and waste heat into usable electrical energy. To increase the amount of thermal radiation captured by the power harvesting device, the hot side of the thermoelectric generator is placed in a small greenhouse, while the cold side is secured against a thermal sink, such as a highway bridge. The power generated by the thermoelectric device is shown to be substantially greater than that produced by piezoelectric materials and the ability to recharge a discharged battery is demonstrated. This research focuses on the use of thermal electric generators in a passive configuration where only conduction is used to remove heat from the device. The majority of previous studies have implemented convective heat transfer to increase power output and have only reported gross energy production. The results show that thermal electric materials when used in a passive fashion can form effective power sources with the ability to quickly recharge discharged batteries. © 2007 SAGE Publications