Self-sustaining batteries are needed for activities that use sensors. These include long-term tracking of?wildlife. ?CSIRO software aims to help devices operate in an energy-neutral way, so that the battery can last indefinitely or until its recharge cycles are exhausted. An example is a device attached to animals using collars that collects GPS data to understand their movements. It also has a tiny battery and solar panel to recharge each day.
https://blog.csiro.au/make-batteries-last-almost-forever/