TEGBed: A thermal energy harvesting testbed for batteryless internet of things

This paper presents TEGBed, a testbed designed for the evaluation and testing of batteryless devices powered using thermal energy. TEGBed offers the capability to mimic real-life temperature gradients, providing researchers with a controlled environment for testing and evaluating batteryless devices. Researchers can leverage TEGBed to accelerate their investigations, gain insights into the behaviour of batteryless devices, and drive advancements in the field of sustainable and efficient IoT technologies. The TEGBed consists of a temperature emulator for emulating temperature differences, Joule Counter, a novel hardware tool for energy and power measurement, and a framework for non-supervised operation. By using the temperature emulator, TEGBed can emulate real-life energy harvesting situations in the lab. The Joule Counter allows gauging the power output from energy harvesting units for a wide range of output power. This enables researchers to gain insights into the energy harvesting capacity and efficiency of harvesting and power management units under different scenarios. With the help of different real-world use cases, we demonstrate the capabilities and effectiveness of TEGBed in assessing thermal energy harvesters and batteryless designs. In addition, we demonstrate how TEGBed can be used for the feasibility study of harvesting energy from two different underutilized heat sources; the temperature difference between soil and air and the temperature difference between the interior and exterior of a greenhouse. Emulations with the TEGBed show that, we could harvest an average of 0.89 mW power from soil-air temperature differences and 0.60 mW power from greenhouse temperature differences.