Steam turbines work by removing thermal energy from a fuel source to transform water into steam.  The steam that is created is used to turn the turbines.  There are a variety of fuel sources that rely on steam to turn turbines to produce electricity.

Fossil fuels plants use sources like coal, oil, and natural gas to heat water, which creates steam that turns a turbine.  While these resources have seen a decline in usage over the last few years, they are still some of the most common electricity generation resources.

Nuclear plants also work this way, although using a significantly more complicated method.  These plants use a process called nuclear fission to split atoms of uranium to generate extreme pressure and heat. Because the uranium fuel is surrounded by water, when the atoms are split, they release neutrons and heat which creates the steam that powers the turbine and generator.

There are also renewable energy sources that use steam to power turbines such as solar thermal energy, geothermal power, and biomass.

Gas turbines work by igniting natural gas to produce pressure, which turns the turbine.  As stated above, natural gas can also be used to heat water and generate steam, which then turns the turbine to generate electricity.

These are important because the ISO may call upon them if they need more electricity than they expected as they can ramp up generation quicker than most other turbines.

There are also combined cycle turbines that use both gas combustion as well as steam turbines to generate electricity.  These turbines produce 50% more electricity from their fuel than a single-cycle power system like described above.

Combined cycle turbines generate power in two stages. 

First, a gas turbine burns natural gas and uses that heat to turn a turbine.  Then, the residual heat from the gas turbine is sent into a heat recovery steam generator where it boils water to produce steam.  This steam is then used to turn an additional steam turbine generator, producing more electricity.  The steam is then condensed back into water and is recycled through the system.

Watch this Tennessee Valley Authority video below to see how combined cycle turbine generators work in action.

A renewable energy source, wind turbines rely on wind to turn large blades to create mechanical energy. This rotation turns gears inside the device extremely fast, which spins a generator that produces electricity. 

The large versions of these, often seen grouped together in the ocean or in large fields, contribute to the domestic power supply.  Because too much power to fuel their region is often produced, these ones often sell unused power back to the utility through the grid. 

Another renewable resource, hydroelectric turbine generators use the movement of water to turn turbines.  This includes falling water like in dams as well as the rise and fall of ocean tides, or even ocean thermal currents.