Development and performance analysis of an energy-autonomous VHF-beacon for animal-tracking

In this paper we present a prototype of a VHF-beacon for animals that is fully energy-autonomous and does not need any battery. To achieve this, thermal energy was harvested directly from the temperature difference between the animal and the environment. The system consists of a small thermoelectric generator (TEG), a special ultra-low voltage converter, a comparator with hysteresis for power management, and a single-stage transmitter. The performance of the device was determined in a field test, where it was attached to a sheep. An average temperature difference of (0.6 +-0.3) K directly measured at the TEG was found. This resulted in an active system, sending VHF-pulses of 20 ms, in over 74 % of the time.