Coal-fired plants produce electricity by burning coal in a boiler to produce steam. The steam produced, under tremendous pressure, flows into a turbine, which spins a generator to create electricity. The steam is then cooled, condensed back into water and returned to the boiler to start the process over.

Here’s a real-life example: The Kingston Fossil Plant near Knoxville, Tenn., burns coal to heat its boilers to about 1,000 degrees Fahrenheit to create high-pressure steam. The steam is piped to the turbines at pressures of more than 1,800 pounds per square inch.

The turbines are connected to the generators and spin them at 3,600 revolutions per minute to make alternating current (AC) electricity at 20,000 volts. River water is pumped through tubes in a condenser to cool and condense the steam coming out of the turbines.

The Kingston plant generates about 10 billion kilowatt-hours a year, or enough electricity to supply 700,000 homes. To meet this demand, Kingston burns about 14,000 tons of coal a day, an amount that would fill 140 railroad cars.