Editing Magnetohydrodynamic generator (section)

==Background==
In a conventional thermal power plant, like a [[coal-fired power station]] or [[nuclear power plant]], the energy created by the chemical or nuclear reactions is absorbed in a [[working fluid]], usually water. In a coal plant, for instance, the coal burns in an open chamber which is surrounded by tubes carrying water. The heat from the combustion is absorbed by the water which boils into steam. The steam is then sent into a [[steam turbine]] which extracts energy from the steam by turning it into rotational motion. The steam is slowed and cooled as it passes through the turbine. The rotational motion then turns an [[electrical generator]].<ref name=tva>{{cite web |url=https://www.tva.com/energy/our-power-system/coal/how-a-coal-plant-works |title=How a Coal Plant Works |publisher=Tennessee Valley Authority}}</ref>

The efficiency of this overall cycle, known as the [[Rankine cycle]], is a function of the temperature difference between the inlet to the boiler and the outlet to the turbine. The maximum temperature at the turbine is a function of the energy source; and the minimum temperature at the inlet is a function of the surrounding environment's ability to absorb waste heat. For many practical reasons, coal plants generally extract about 35% of the heat energy from the coal, the rest is ultimately dumped into the cooling system or escapes through other losses.<ref name=ucal>{{cite web |url=https://energyeducation.ca/encyclopedia/Rankine_cycle |title=Rankine cycle |website=University of Calgary}}</ref>

MHD generators can extract more energy from the fuel source than turbine-generator systems. They do this by skipping the step where the heat is transferred to another working fluid. Instead, they use the hot exhaust directly as the working fluid. In the case of a coal plant, the exhaust is directed through a nozzle that increases its velocity, essentially a [[rocket nozzle]], and then directs it through a magnetic system that directly generates electricity. In a conventional generator, rotating magnets move past a material filled with nearly-free electrons, typically copper wire (or vice versa depending on the design). In the MHD system the electrons in the exhaust gas move past a stationary magnet. Ultimately the effect is the same, the working fluid is slowed down and cools as its [[kinetic energy]] is transferred to electrons, and is thereby converted to electrical power.<ref name=mhd>{{cite book |url=https://thermopedia.com/ru/content/934/ |title=Magnetohydrodynamic Electrical Power Generators |first=S.A. |last=Medin |date=2 February 2011 |website=Thermopedia|doi=10.1615/AtoZ.m.magnetohydrodynamic_electrical_power_generators |isbn=978-0-8493-9356-3 }}</ref>

MHD can only be used with power sources that produce large amounts of fast moving [[plasma (physics)|plasma]], like the gas from burning coal. This means it is not suitable for systems that work at lower temperatures or do not produce an ionized gas, like a [[solar power tower]] or [[nuclear reactor]]. In the early days of development of [[nuclear power]], one alternative design was the [[gaseous fission reactor]], which did produce plasma, and this led to some interest in MHD for this role. This style of reactor was never built, however, and interest from the nuclear industry waned. The vast majority of work on MHD for electrical generation has been related to coal fired plants.{{cn|date=September 2024}}