Power station

A power station is an industrial facility designed to generate electric power. These plants are usually connected to an electrical grid, which is a network that carries electricity to homes and businesses. Most power stations rely on generators to do this work. A generator is a rotating machine that converts mechanical power into three-phase electric power. This process happens because of the relative motion between a magnetic field and a conductor. This movement creates the electric current that flows through our wires.

Thermal power stations are a very common type of plant. These facilities use a heat engine to transform thermal energy into rotational energy. Most of these are known as steam power stations because they produce steam to do the work. The heat often comes from burning fossil fuels like coal, oil, or natural gas. In a coal-fired station, coal is burned in a large boiler to create steam. This steam then drives a steam turbine and a generator. It is important to note that the second law of thermodynamics means not all thermal energy can become mechanical power. Some heat is always lost to the environment.

Engineers use several methods to make these thermal plants more efficient. One method is called cogeneration, or combined heat-and-power (CHP). In a CHP plant, the heat that would normally be wasted is used for industrial processes or district heating. Another advanced method is the combined cycle plant. These plants use two different thermodynamic cycles together. A gas turbine burns natural gas to create power first. Then, the hot exhaust gases from that turbine are used to create steam for a second turbine. This "top" and "bottom" cycle approach creates much higher efficiency than a single cycle could alone.

Other types of power stations use different energy sources to create motion. Nuclear power plants use the fission process inside a reactor core to create intense heat. This heat produces steam to operate a turbine and generator. In the United States, nuclear power provides about 20 percent of all electric generation. Geothermal power plants use steam that comes from hot rocks deep underground. These rocks are heated by the decay of radioactive material in the Earth's core.

Solar thermal plants use sunlight to boil water and create steam.

There are also biomass plants that use waste from sugar cane or landfills as fuel.

We can also classify power stations by how they are used to meet demand. Base load power plants run nearly all the time to provide a steady supply of energy. These are often large coal-fired, nuclear, or hydroelectric plants. They are optimized for low fuel costs but cannot start or stop quickly. Peaking power plants are different. They only run during periods of high demand, which might last only one or two hours. Gas turbines and internal combustion engines are good for this because they can start up very rapidly.

The history of these facilities shows how much technology has changed. In 1871, Zénobe Gramme invented a generator for commercial industrial use. In 1878, William, Lord Armstrong built a hydroelectric station at Cragside, England. This station used water from local lakes to power lights and heating. In 1882, Thomas Edison and Edward Johnson built the first public coal-fired station in London. Later that year, Edison opened the Pearl Street Station in New York. That station used reciprocating steam engines to turn direct-current (DC) generators.

As time passed, the way we move electricity improved. George Westinghouse developed an alternating current (AC) system in 1886. This system used a transformer to step up voltage for long-distance transmission. It then stepped the voltage back down for indoor use. This was much more efficient than the DC systems, which were limited by voltage drop. The "war of the currents" eventually led to AC becoming the standard. The invention of the steam turbine around 1906 allowed plants to grow much larger. Generators were no longer limited by the slow speeds of old engines. This allowed for the massive generating capacity we see in the world today.