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Useful output energy is always lower than input energy. Efficiency of power plants, world total, 2008. Energy conversion efficiency (η) is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The input, as well as the useful output may be chemical, electric power, mechanical work, light (radiation ...
In mechanical engineering, mechanical efficiency is a dimensionless ratio that measures the efficiency of a mechanism or machine in transforming the power input to the device to power output. A machine is a mechanical linkage in which force is applied at one point, and the force does work moving a load at another point.
This thermal energy input of 1 kWh = 3.6 MJ = 3,412 Btu Therefore, the heat rate of a 100% efficient plant is simply 1, or 1 kWh/kWh, or 3.6 MJ/kWh, or 3,412 Btu/kWh To express the efficiency of a generator or power plant as a percentage, invert the value if dimensionless notation or same unit are used.
If energy output and input are expressed in the same units, efficiency is a dimensionless number. [1] Where it is not customary or convenient to represent input and output energy in the same units, efficiency-like quantities have units associated with them. For example, the heat rate of a fossil fuel power plant may be expressed in BTU per ...
For example, |2|ft|6|in may be used to specify 2 feet 6 inches as the input unit in a conversion. See the Input multiples section. Composites are defined in pairs, but any number of pairs can be used to specify an input. For example, given that ch is defined as a subdivision of mi, and that ft is a subdivision of ch, an input length could be ...
The length of the equator is close to 40 000 000 m (more precisely 40 075 014.2 m). [22] In fact, the dimensions of our planet were used by the French Academy in the original definition of the metre. [23] A dining tabletop is typically about 0.75 metres high. [24] A very tall human is about 2 metres tall. [25]
Output (mechanical) energy is always lower than input energy. In general, energy conversion efficiency is the ratio between the useful output of a device and the input, in energy terms. For thermal efficiency, the input, , to the device is heat, or the heat-content of a fuel that is consumed.
Conversions between units in the metric system are defined by their prefixes (for example, 1 kilogram = 1000 grams, 1 milligram = 0.001 grams) and are thus not listed in this article. Exceptions are made if the unit is commonly known by another name (for example, 1 micron = 10 −6 metre).