Thermal energy harvesting for WSNs

Because of the recent developments in both wireless technologies and low power electronics, wireless devices consume less and less power and are promising the possibility to operate continuously by using energy harvesting technologies. The interest in Wireless Sensor Networks (WSNs), powered by environment energy harvesters, has been increasing over the last decade, especially those using thermal energy harvesting. In this paper, a low temperature thermal energy harvesting system, which can harvest heat energy from a temperature gradient and convert it into electrical energy, which can be used to power wireless electronics, is proposed. A prototype based on three subsystems is presented to extract heat energy from a radiator and use it to power ZigBee electronics. High efficiency and a long system lifetime are two of the main advantages of this design. The experimental results show that a maximum of 150 mW power can be harvested by the prototype and the system can continue to operate normally when the harvesting voltage is as low as 0.45 V. Theoretical calculations suggest that by placing the two AA batteries by proposed thermal energy harvesting system, a ZigBee Wireless Radiator Valve can operate for more than eight years.