In practice to effect these three stages of conversion, many systems and sub systems have to be in service. Also involved are different technologies, like combustion, aerodynamics, heat transfer, thermodynamics, pollution control, and logistics.
As an example consider these facts for typical coal fired power plant of capacity 500 MW.
Around 2 million tons of coal will be required each year to produce the continuous power.
Coal combustion in the boiler requires air. Around 1.6 million cubic meter of air in an hour is delivered by air fans into the furnace.
The ash produced from this combustion is around 200,000 tons per year.
Electrostatic precipitators capture almost all of this ash without dispersing this to the atmosphere. Pollutants from coal power plants like carbon dioxide, sulphur dioxide, and nitrogen oxide can also affect the environment. Thermal power plants are the biggest producers of Carbon Dioxide.
The boiler for typical 500 MW units produces around 1600 tons per hour of steam at a temperature of 540 to 600 degrees Centigrade. The steam pressures is in the range of 200 bar. The boiler materials are designed to withstand these conditions with special consideration for operational safety.
Heat transfer from the hot combustion gases to the water in the boiler takes place due to Radiation and convection.
The Electrical generators carry very large electric currents that produce heat and are be cooled by Hydrogen and water.
The steam leaving the turbine is condensed and the water is pumped back for reuse in the boiler. To condense all the steam it will require around 50,000 cubic meter per hour of cooling water to be circulated from lakes, rivers or the sea. The water is returned to the source with only an increase of 3 to 4 degrees centigrade to prevent any effect to the environment.
Apart from the cooling water the power plant also requires around 400 cubic meter per day of fresh water for making up the losses in the water steam cycle.