Thermoelectric generation for a self-powered autonomous sensor in satellites

Abstract

There are several benefits of using autonomous sensors in spacecraft. Avoidance of wired connections reduces cost, mass, and increases the flexibility and reliability of the system. The impact of wire reduction can be significant, especially for small satellites with many sensors, like temperature and sun sensors. Previous research has already focused on wireless intra- spacecraft communications. This research tests the self-powering capabilities of a system based on a COTS thermoelectric generator connected to a Bluetooth Low energy communication system, with a built-in controller and temperature sensor, and a power management interface. The system will be considered as a candidate for an autonomous temperature sensor in a future PocketQube mission of the university.

Controlled temperature differences can be achieved in a test environment, allowing the measurement of the generator power capabilities. It is tested that the system requires, for operation, a minimum temperature difference of 2.31 degrees between the extremes of the thermoelectric generator. It generates a peak power of 234 μW for that difference. In addition, the voltage difference obtained of 35.5 mV exceeds the minimum voltage required by the power management subsystem to be used. The power management sub-system consists of an ultra-low power converter that provides an output voltage of 4.1 V and a measured power efficiency of 32 % Moreover, thanks to the management of the Bluetooth sleeping modes, with the built-in controller and several operational amplifier comparators, an average power consumption of 5 μW is required during operation. The case studied would allow measuring temperature and sending the data over a Bluetooth link to the on-board computer every 16.2 seconds

It is concluded that the technology, based on COTS components, can be implemented and considered as the first step for a fully autonomous sensor with thermoelectric power generation in small satellites. Its implementation may provide substantial advantages for remote or/and locations where wiring is difficult to integrate. The tested performance values provide the foundation to develop the technology further.