Energy Efficiency

In Physical and Mechanical engineering , the energy efficiency (or thermodynamic effectiveness ) is a number without Dimension, which is the relationship between what can be recovered machine usefully on what was spent to make it function.

This concept is very often confused with the output which is the relationship between the real effectiveness of the machine and the maximum effectiveness theoretical that one can await from it. The output always has a value ranging between 0 and 1 (or 0 and 100%), whereas according to the system, the effectiveness can take any positive value

The increase in the energy efficiency makes it possible to reduce consumption of energy, with service rendered equal, and that involves the reduction in the costs ecological, economic and social related on the production and the consumption of energy. To arrive at a Control of energy, one of the main objectives is the improvement of energy efficiency.

Physics

Energy efficiency for a system depends on the vocation of the system:
  • in the case of an engine it acts of:
\ mathrm {Efficacit \ acute {E}} = {W \ over \ mathrm {\ acute {E} nergie}}

where W is the useful quantity of work produced by the system (in Joule S), and energy is the quantity of energy (also in joules) used to make function the system.

Energy efficiency can also refer to the use of the techniques or the practices to reduce the use of energy.

An effectiveness of 1 (100%) is impossible for an engine: the Second principle of thermodynamics the interdict.

  • in the case of a Refrigerating or of a Heat pump it acts of:

\ mathrm {Efficacit \ acute {E}} = {Q \ over \ mathrm {\ acute {E} nergie}}

where Q is the useful Chaleur exchanged by the system (in Joule S), and energy is the quantity of energy (also in joules) used to make function the system. In the case of a refrigerator the useful heat is that which is used to cool food, in the case of a heat pump it is that which is used to heat the interior of the house.

Energy efficiency with the daily newspaper

An apparatus is known as effective in energy when it consumes less energy for the same rendered service.

Energy efficiency in the car

This concept led to that of Hypervoiture: vehicles which consume 3 to 5 times less than the cars of reference.

Energy efficiency in the building

To decrease the energy consumption of the buildings by 22% from here 2010 in Europe, a Directive " energy performance of the buildings " (EPBD) is in the course of transposition in 2007 in the national rights.

For the lighting, it is light which one wishes to produce. The share of the power consumption transforming itself into another form of energy as heat is thus lost. One generally produces the light starting from electricity, but according to the Lampe S used, the same illumination will require a quantity of electricity being able to go from 1 to 15 (see table).

Energy efficiency in industry

In industry energy efficiency is the relationship between minimal energy necessary to ensure the production divided by total energy entering the factory. On average the energy efficiency of a factory is of 41% it be-with saying that when all the processes and utilities of a factory consume 41 kWh, the entering energy bought by the industrialist represents 100 kWh. In industries, the increase in energy efficiency is a track of very important financial economy for the industrialists.

See too

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