A traditional power plant is exactly such an engine: it turns fuel into heat. This heat is then used to convert water into a furious jet of steam directed at the blades of a turbine which, with their spinning, turn a shaft. This shaft then pokes into a giant electromagnet, and as the shaft spins inside the magnet, it produces an electric current. The efficiency of any system that converts a fuel—any fuel, coal, uranium, oil, biomass, or trash—into heat is limited by the maximum temperature of the engine.
