How Thermal and Nuclear Power Plants Generate Electricity

Thermal Non-Nuclear Power Plants

These plants need the mechanical energy necessary to drive turbines that are connected to the generator rotor. The energy comes from the thermal water vapor pressure (due to the movement of water molecules) after heating in a boiler. The fuel used to produce water vapor determines the type of power plant: oil, natural gas, or coal.

Combined Cycle Power Plants

In combined cycle power plants, electricity is obtained through two combined cycles: the conventional thermal power cycle and another cycle in which air and gas are used. For the air and gas cycle, a gas turbine that includes a compressor is used. This compressor compresses the incoming air, which mixes with the gas prior to its combustion, through which electricity is generated in the turbine. The combustion gases are carried to a recovery boiler, which transfers their energy to the water of the second cycle. With this setup, yields are higher than those of single-cycle plants.

Nuclear Thermal Power Plants

This is a thermal power plant where the boiler is replaced by a nuclear reactor. The water vapor pressure occurs thanks to the steam generated in the fission (splitting) of the nuclei of radioactive elements, mainly uranium. It uses uranium isotopes U-235 and U-238. The nuclear power plants installed in Spain include the 466 MW Santa María de Garoña plant, in towns, and the 1087 MW Vandellòs plant, in Tarragona. The main advantage of nuclear power is its high capacity in energy production, while its inconveniences are the management and disposal of radioactive waste, as well as the fears of the population regarding any nuclear accidents.

The Environmental Problem of Waste

Non-nuclear power stations produce three types of waste, each of which gives rise to a different environmental problem:

• Air Pollution: They generate airborne particles, diverse heavy metal molecules, and gases such as carbon monoxide.
• Greenhouse Effect: They emit large amounts of CO2, which increases the so-called greenhouse effect, with serious climatic consequences that are difficult to predict.
• Acid Rain: Finally, thermal power plants emit sulfur and nitrogen oxides, gases that cause acid rain, which can be devastating to forests, the water of rivers and lakes, and monuments.

In contrast, nuclear power stations do not emit CO2 and other polluting gases.