Wood to electricity
Electrical energy from burning wood.
There are some wood stoves on the market that use the heat of the fire to generate electrical energy. As with the device in the picture, this is then stored in a "power pack" (battery). (Small) consumers such as smartphones, radios, cameras, etc. can then be charged at the USB plug.
But that's not the only function of this stove: You can also use it to cook and heat!