CPS Energy ships low-sulfur coal by train from Wyoming to the J.K. Spruce Plant in south Bexar County. Individual rail cars each carry a maximum of 120 tons of coal.  Once the train arrives at the plant, the coal is unloaded and stored.

Coal enters the plant by conveyer belts that drop the pea-sized pieces into five silos.  At the bottom of each silo, a pulverizer grinds up the coal in to a talcum-powder consistency.  The coal is grinded to make it easier to deliver and burn as a fuel.

Large fans blow the coal powder into a boiler that stands 20 stories high.  The coal fuels a massive fireball that can reach 3,000 degrees Fahrenheit.  Steam pipes in the boiler carry ultra pure water that has been pumped from a nearby cooling lake and treated.  The heat of the furnace converts the water into steam. At a temperature of 1,005 degrees and a pressure of 2,400 pounds per square inch (PSI), the steam is sent over a turbine through a series of pipes.  Low pressure, intermediate pressure and high pressure steam are used to spin the blades of three turbines at a rate of 3,600 revolutions per minute.

The turbines, connected to a generator by a shaft, power the generator.  The generator is made of a large magnet spinning inside copper windings.  Electrons flow from the copper along a conductor to create 24,000 volts of electricity.  In order to push the electricity from the plant further out into the city, a step-up transformer is needed to increase the power from 24,000 volts to 345,000 volts to carry electricity over transmission lines to customers. See Energy Delivery