Distributed generation

With decentralized power generation, electrical energy is generated close to the consumer, eg within or near residential areas and industrial plants using small power plants. The efficiency of electricity generation plants is usually designed only to meet the energy needs of the connected immediately or in the nearby area electricity consumers. Also isolated networks, ie the interconnection of small, less power producers and consumers in remote locations that are not connected to the public power grid, one counts for decentralized power generation. Likewise, wind farms and solar parks are commonly counted towards decentralized power supply, but here is the transition to centralized power generation, especially for larger systems, flowing.

General

In contrast to centralized power generation, electrical energy is not fed in decentralized power supply into the power grid, but in the medium and low voltage network. An important advantage of distributed generation is therefore the most extensive avoidance of losses in the transformation to other voltage levels and transmission losses through high-voltage lines. Between 2000 and 2012, the transmission losses in Germany fell from 34.1 to 24.6 TWh, a decrease of about 28 %. This decrease is attributed to the significantly during this period greatly expanded distributed generation. Next can be, for example, stabilize by the combination of wind power and photovoltaic systems with variable biomass power plants, the variable power supply to the first two types of generation.

Often, the distributed generation is seen as one aspect of the energy transition and associated with the transition from fossil-nuclear energy to renewable energy in conjunction. Both are however not necessarily linked. Thus, for example CHP plants are operated with renewable biogas as well as fossil natural gas, at the same time there are also central approaches to the generation of energy from alternative sources. Examples of this can be offshore wind farms and the Desertec concept cite, in which the construction of large solar power plants is planned with performances by some gigawatts in North Africa.

Since early 2010, Mayor hit of more than 20 German cities to a dialogue on strategic issues of "sustainable city ". The mayor put on a special way for sustainable development in their cities. This is caused, inter alia, " With strong communities make the energy revolution a success story ," the paper to the municipal energy policy to decentralize energy supply.

According to the Institute for Ecological Economy Research two-thirds of the value came from renewable energy sources ( 2012: EUR 25 billion ) cities and towns to Good bar and contribute to the development of structurally weak areas. In addition, the jobs renewable energy spread wide across the entire country.

Cogeneration

The advantage of the very low transmission losses is offset by the disadvantage of tending smaller power generation efficiency at small power plants in relation to large power plants. However, this is not the case in the combined generation of electricity and heat in cogeneration, where the overall efficiency utilization of both energy forms is much higher. Biomass power plants and biogas plants will be built, and avoid high transport costs by limiting the catchment area, for example, at the location of the fuel source of biomass. In cogeneration plants, the waste heat can be used in the form of district heating.

Small plants, such as those used in decentralized arrangements, generally lead to higher specific investment sums. Thus, the value achieved by decentralized renewable energies in the German towns and cities annually, around 6.8 billion euros.

These plants have lower electrical efficiencies, but this by the use of waste heat is generally more than compensated for example, in a combined heat and power generation. The efficiency refers to the freely available part of the electric energy and the possibly freely available heat energy in relation to the primary energy. If the system is operated without combined heat and power (CHP ), is the other part of the primary energy used for the generated entropy irretrievably lost. With CHP, the overall efficiency of the plant is usually above the efficiency of large centralized power stations, where the waste heat is often not used at all. In cogeneration units so that the efficiency is due to the high degree of use in which the primary energy is converted to both electrical energy and useful heat, usually much greater than for large systems that do not have co-generation. So, for example, went VDE 2007 already assumes that the efficiency of power plants can be increased by 10% through the development of decentralized energy supply, with which primary energy is saved, the dependence on energy imported raw materials is reduced and the CO2 emissions can be reduced.

With the change of the energy system as a result of the energy revolution decentralized cogeneration comes to the function of the provision of control energy to make electricity especially available if only a little wind and / or solar power is available. To ensure heat supply nevertheless any time the plants are equipped with heat buffers and heating elements, so that the times when the supply of volatile energy sources is high and the cogeneration unit is not required for the generation of electricity, heat can be generated electrically. Thus equipped CHP would be able to produce as needed electrical energy or to consume, so they can play an important role in ensuring network stability.

Photovoltaic

(: Sunlight here ) generates electrical energy through photovoltaic is a direct route from electromagnetic radiation. Although it is used to power spacecraft since 1958, she has in electricity generation in Germany only by lowering the investment costs, triggered by the Renewable Energy Act (EEG ), have become important. Although there are quite large ground-mounted photovoltaic plants with a peak performance in the high double-digit megawatt range, a large part of the photovoltaic systems will be built locally. Classic examples include roof systems, which are mounted on the roof of residential, commercial and industrial buildings and their power is consumed in a relatively large proportion itself. Therefore, a decentralized feed- standard for photovoltaic systems. While typical rooftop installations of residential buildings usually afford only a few kW peak, the peak performance of solar systems ranges on industrial and commercial buildings up to the MW range. Even smaller ground mounted solar plants generate decentralized electrical energy. Only larger ground-mounted photovoltaic systems mark the transition to a central power supply.

In photovoltaic systems although can generally be safely predicted the generation of electricity, but they are currently (2012 ) only rarely coupled with storage possibilities, and not adjustable. They are therefore not suitable as the sole power generators, but work in conjunction with other power producers. Through photovoltaic power but is also exclusively during the day, the main demand time are generated. Therefore, the Nahverbrauch the current produced is assured. Even in the winter months, with significantly lower amounts of electricity generated, relieves the photovoltaic daytime other producers as well as the transmission networks and dampens the prices for peak load electricity.

The head of Tennet transmission network Martin Fuchs commented on this in February 2012: " Lunch feed the plants in our network area currently with a capacity of about 5,000 megawatts a That dampens the last strong increase of the electricity price on the stock exchange during the peak load in the. . However, early evening falls naturally out of the photovoltaic. Nevertheless, the performance of some storage power plants can be throttled at noon in favor of the early evening hours. " Similarly, other operators took to the influences of decentralized power generation through photovoltaics.

To reduce the strong regional variations in the PV power generation and to increase the proportion of direct self- consumption, solar inverters have been designed with built-in storage batteries. Through this hybrid inverter will also enforce the possibility of the uninterruptible power supply and thus increasing the security of supply of electricity customers. The power supply through decentralized PV power generation is smoothed and the decentralized self- consumption optimized. This small local stores for electrical energy is given a central role in the energy revolution along with other storage technologies and the expansion of renewable electricity producers and electricity networks.