Energy transformation
Energy converter exchange energy between a system and the environment in at least two forms of energy from: for example, chemical energy to kinetic energy as (motor). Large-scale energy conversion systems such as power plants consist of several energy converters that convert stepwise primary forms of energy in technically usable forms of energy like electrical energy or thermal energy (process and district heating).
Energy conversion are called according to a category of processes in which energy between a system and its surroundings is exchanged in at least two forms of energy. Especially for an energy conversion into electrical energy also the colloquial term energy production is common and refers to the provided after the trial form of energy ( electrical energy), see power generation.
Basics
Energy changes are subject to physical laws. Thus, the energy is conserved in closed systems, so it can be neither created nor destroyed. Key to the technical application is the efficiency of conversion, as in real systems 100% of a form of energy can not be transferred to another. It occurs there is always losses in other channels, usually in the form of unused heat, ie thermal energy.
Examples
Electric motor
Example 1: An electric motor lifts a weight piece, it is converted to electrical energy into mechanical energy. Both forms of energy contribute only in an ideal model of thinking no entropy, so that conversion losses, mostly heat, prevent a perpetual motion absolutely secure. The entropy associated with this heat generated in the process and ensures that required by the second law of thermodynamics in real processes increase the total entropy.
Steam turbine
Example 2: A steam turbine drives an electric generator, it is converted to thermal energy into electrical energy. The turbine at the temperature T1 heat supplied ΔQ1 carries the entropy ΔS1 = ΔQ1/T1 with it. The electric power generated? W bears no entropy. If all of the heat into electrical energy, so it would disappear ΔS1 the entropy, but contrary to the Second Law. Thus, the turbine has a heat ΔQ2 bother with the temperature T2, which carries at least the entropy ΔS1. It therefore applies to the energy: ΔQ1 =? W ΔQ2 and for the entropy: DELTA.S2 ≥ ΔS1 ⇔ ΔQ2/T2 ≥ ΔQ1/T1. From the second equation follows ΔQ2 ≥ ΔQ1 · T2/T1. This waste heat losses ΔQ2 are due to the second law required mandatory and could not be achieved at given temperatures T1 and T2 by any technical measures. This limit of efficiency for a heat engine is implemented in the theoretical cycle processes such as the Carnot cycle. In addition there are technical reasons conversion losses.
Solar energy
The efficiency of conversions increases with the temperature differences (or their equivalent), which can be used in the conversion system. For example, is finding increasing the photoelectric effect in photovoltaic use. The efficiencies achieved by the direct photoelectric conversion but are still below the conventional, double thermal- mechanical- electrical conversion. Contrast, much higher temperature differences occur in solar heat power plants, for example, where the concentrated by mirrors radiant energy are first, then conventionally converted by absorption into thermal to mechanical and finally electrical energy.