The Rankine cycle (named after the Scottish scientist William Rankine, who is attributed with its invention) is the cycle of heat flows used to drive a turbine. Typically, water is heated to form steam. The gas pushes the turbine as it expands through the rotors. Then heat is dumped so the gas can be reheated. Thermodynamic law says that the greater the difference in temperature between the heated and the cooled steam, the greater the power generated.
Typically, the Rankine cycle uses water because it is an abundant, cost-effective liquid. It also has properties that make it beneficial for power generation. When cooled to a liquid phase, it is more easily compressed by the pumps. This saves energy that otherwise would be lost in trying to compress a gas. However, other fluids can be used, including organic, volatile fluids like hexane and toluene. These boil at a much lower temperature and are applicable for concentrated solar power and other low-heat sources, like some geothermal. When these fluids are used, the cycle is termed an organic Rankine cycle.
The working fluid is in a closed-loop and is constantly reheated and cooled as it gives its energy to the rotors that spin the turbine. The large conical towers at power stations are for cooling the liquid. The white clouds emerging are water droplets from the cooling steam that have dissipated the unused heat by volatilization. The working fluid, however, is never released. It is constantly circulated, reheated and cooled as it drives the turbine.
Steam turbines are used in nearly all electrical power generation facilities, only the source of the heat changes. Whether the working fluid is heated with coal, uranium rods, geothermal or solar, the electrical generation is performed by a steam turbine generator, or a turbine suited for lower heated fluids as used in the organic Rankine cycle. In a wind turbine, the energy in the wind spins the turbine directly; there is no need for heat. However the generation of electricity from the mechanical energy of the spinning turbine to the generator is identical.
Another type of turbine, a gas turbine, is used in jet propulsion. Here, a hot gas forces the blades to spin and the engine moves the vehicle by creating thrust.