Coal, nuclear or solar, most power plants are really giant steam kettles
A coal furnace, a nuclear reactor and a field of sun-focusing mirrors look nothing alike, yet most such plants do the same job in the end: boil water, let the steam spin a turbine, turn a generator. About 90 percent of the world's electricity passes through steam turbines. The fuel is just the stove.
Inside a generator, a magnetic field moves relative to a conductor and pushes current along it. Something has to provide the spin. A coal plant burns fuel under a boiler; a nuclear plant uses heat from fission in its core; geothermal plants tap steam from rocks warmed deep underground; solar thermal plants concentrate sunlight to boil water. Gas turbines are the main exception among fuel-burning plants, driven directly by hot flowing gas. Because they start quickly, they tend to cover peaks in demand, at a higher price than plants running around the clock.
Physics sets a ceiling. The second law of thermodynamics means no heat engine converts all its heat into motion, and efficiency depends on how hot the steam gets rather than on what fuel made it; with identical steam conditions, coal, nuclear and gas plants share the same theoretical limit. Engineers claw back losses by piping leftover heat to factories or homes, by stacking a gas turbine and a steam turbine in one combined cycle, or, in parts of the Middle East, by using the waste heat to desalinate seawater.
The business began in the 1870s. Zénobe Gramme built a generator strong enough for industry in 1871, and in 1878 Lord Armstrong lit and heated his house at Cragside, England, with hydroelectric power from his estate lakes. Thomas Edison's team opened the first public coal-fired station in London in January 1882, threading cables through a viaduct's culverts to avoid digging roads controlled by gas companies. Edison's Pearl Street Station in Manhattan followed that September.
Edison's direct current could only travel about a mile, so George Westinghouse's alternating current, stepped up by transformers for long-distance transmission, won the war of the currents. Around 1906 steam turbines replaced piston engines, freeing generators to grow enormous, and high-voltage lines let distant waterfalls light faraway cities.
Source: Power station
