Steam power is, literally, the power derived from steam (generally pure water [H2O]) expanding and cooling from high temperature and pressure to lower temperature and pressure. To derive power (and useful work) from steam, certain components are usually required to create a complete steam power system (a steam engine). The "typical" steam engine components are:

The history of steam power is well documented and widely known, as are many of steam power's past contributions to modern society. Most people today view the steam locomotive as the most familiar steam powered machine. Steam locomotives still operate throughout the world today (and new ones are being built); large coal, oil, and natural gas fueled steam power plants and combined cycle power plants are the most common uses of steam power in the world today. According to the U.S. Energy Information Administration more than 87% of the electricity in the US in 2011 was generated completely by steam power or in steam power combined cycle systems. And, solar thermal steam power plants are now in commercial operation worldwide.

Steam powered automobiles (many of which remain operational today) were proven feasible, even with technology from the late 1800's. With the advent of low cost gasoline in the 1900's, the internal combustion engine thrived and steam powered automobile technology development ended ... until now.