The Steam Engine is added by Thermal Expansion, and is a early-game form of power generation. It burns solid fuel, such as coal or wood. It requires a supply of water which can be either piped in, or supplied by an adjacent Aqueous Accumulator It outputs up to 2MJ/tick. The engine will stop working and spew out smoke if there is nothing consuming the power it is producing, or if it runs out of water. To fix this, add a load on for the power and right-click it with the Crescent Hammer, or any buildcraft compatible wrench.