Thermoelectric Energy Harvesting From Gradients in the Earth Surface

In this article, we introduce an energy harvesting system capable of converting bipolar thermal gradients to electrical energy. An active rectification circuit, electrical impedance matching, and commodity thermoelectric generators are used to efficiently extract energy from very small temperature gradients found at the natural ground-to-air boundary. The full harvesting system is modeled in detail from thermal radiation to the electrical load. This end-to-end model enables system dimensioning to meet specific application requirements. A multiyear deployment of the harvesting system supplying a wireless sensor network for environment monitoring demonstrates the applicability of this system in a real application. The case study confirms self-sustainable operation of an application with a 550
$\mu {\rm W}$
power footprint. With a maximum harvested power of up to 27.2 mW during the day and 6.3 mW during the night, a significant improvement in both average and maximum harvested power is demonstrated compared to the state-of-the-art.