Is there a way I could harness heat energy in a drone, if so, how?
Welcome to PF
energy from where and to use it for what ?
@davenn Heat energy from the sun to power the said drone
In order for a heat engine to work, you need a temperature difference. In a drone, you can easily pick up heat, giving you a "warm reservoir". You could try to use the surrounding air as a "cold reservoir", but the thermal resistance between a "heat sink" and air is fairly high (that is why CPU's use a fan).
I am trying to build a drone which could be used in African villages and am looking to find a backup energy, in case the battery fails. Solar seems like the predominant choice, but I feel like heat could work really well too, so I need a way of harnessing it.
Couple of points. The maximum attainable temperature with Solar flux is 120C. If you consider your cold reservoir at 0C, Carnot's efficiency is 30 percent. Practically it would be much lower. Also heat engines are generally not that light weight. You could better consider Photovoltaic panel instead.
You would never get enough useful energy
Solar cells would be much better, but you will still have a problem of collecting enough energy to keep a drone flying
The best you could do would be to use solar power to recharge batteries whilst they are not in use and then swap
them with the discharged ones from the drone
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