Geothermal Generator is a generator used for generating power on Venus.
Specifically, it provides a way to generate power for your Venus base during the long Venus night when - obviously - Solar Panels will not work.
Geothermal Generators can be placed above Vapor Spouts, which are found only on Venus. A Vapor Spout is found at the surface, and indicates the position of a a Sulfuric Acid pocket below the surface. You can sometimes spot the vapor being released from the Vapor Spout.
Place down the Geothermal Generator directly on top of the Vapor Spout (do not break the Vapor Spout!) After being placed, it will generate power at an oscillating rate.
The Geothermal Generator does not consume any fuel or resources, it will generate power "for free" so long as it is above a Vapor Spout.