ELECTRICITY GENERATION

Date: 2015-10-07; view: 751.

Electricity generation is the process of converting non-electrical energy to electricity. For electric utilities, it is the first process in the delivery of electricity to consumers. The other processes, electric power transmission and electricity distribution, are normally carried out by the electrical power industry.

Electricity has been generated at central stations since 1881. The first power plants were run on water power or coal, and today we rely mainly on coal, nuclear, natural gas, hydroelectric, and petroleum with a small amount from solar energy, fuel cells, tidal harnesses, wind generators, and geothermal sources. Most power plants burn fuel - coal, oil, natural gas, biomass - which creates steam to drive a turbine that generates electricity. Other technologies - such as solar photovoltaics or fuel cells - rely upon chemical reactions to generate electricity.

The demand for electricity is met in several ways. Large centralized generators have been the primary method thus far. Distributed generation uses a larger number of smaller generators throughout the electricity network. Some use waste heat from industrial processes; others use fuels that would otherwise be wasted, such as landfill gas. Wind and solar generation tend to be distributed because of the low density of the natural energy they collect.

Scientists and engineers are devoting an increasing amount of at­tention to what are commonly called "new" or "unconventional" power sources. The impetus for this development effort stems from many things. In a general way, the continually increasing demand for electric power, and the eventual inability of present energy sources to supply our needs are the dominant factors. However, there are others — the need for specialized power plants to serve in space or in remote land areas, to name one.

Four of the most promising of the "new" power sources are ther­moelectric, thermionic and magnetohydrodynamic generators, and fuel cells. None of these power generation methods are new in prin­ciple. The concept of thermoelectric devices dates back to 1822; the thermionic principle to 1878; magnetohydrodynamics to about 1835, and, the fuel cell to 1802. However, only recently have these prin­ciples come in for serious attention as the basis for large-scale power generators. The present interest stems largely from a better under­standing of the physics and chemistry involved, and our ability to de­velop new materials to meet the unusual requirements.