Primary energy

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In the energy industry, primary energy is the energy that is available with the originally occurring forms of energy or energy sources , such as fuel (e.g. coal or natural gas ), but also energy sources such as sun, wind or nuclear fuel . Primary energy can be obtained by a process entailing losses conversion in secondary energy converted are. Primary or secondary energy becomes final energy that can be used by the consumer after transmission losses . The actually usable energy, i.e. the final energy minus the losses that arise when the consumer uses it, is then the useful energy .

The conversions and the associated losses are necessary in many cases, since primary energy sources often cannot be used directly by the consumer. An example of this would be uranium , which is used in nuclear power plants. Sometimes a conversion is also useful, e.g. B. to increase the energy content of the energy source, such as the drying or pyrolysis of wood.

Energy sources

Primary energy demand

Since the 2009 version of the Energy Saving Ordinance (EnEV), the primary energy requirement of residential and non-residential buildings has been calculated using DIN V 18599. From the building physics data of the building (heat transfer coefficient / U-values ​​of the components), the geometry and meteorological conditions, the useful energy requirement Q n for keeping the building at the desired temperature is first calculated. This is followed by the determination of the losses within the building for the generation, storage, distribution and delivery of heating, hot water and ventilation. The sum of this gives the final energy Q e , which can be measured on the gas meter, for example.

Final energy Q e = useful energy Q n + system losses

The final energy Q e is converted to the primary energy Q p using a primary energy factor f p .

Primary energy Q p = final energy Q e × f p

The factor f p includes the losses that occur during the provision of the energy carrier (e.g. extraction, transport, refining, drying or storage).

In a further step, the primary energy factor is divided into a renewable and a non-renewable part. CO 2 emissions are only associated with the non-renewable primary energy consumption. The exact numerical determination also takes place with a political or ecological objective. The ratio of the total primary energy factor to the non-renewable share is a measure of sustainability.

For example, wood has a total primary energy factor of f p = 1.2 (ie, for 100 kWh of final energy wood that is used in a combustion, for example, an additional 20 kWh must be applied until the wood is delivered at the door ). For the non-renewable part, however, the value is f p = 0.2. This means: for the 100 kWh of final energy consumed, only 20 kWh of non-renewable primary energy are consumed, and CO 2 emissions are only associated with this 20 kWh .

For natural gas, the total primary energy factor is equal to the primary energy factor for the non-renewable portion here f p = 1.1. This means that the additional expenditure for the provision of natural gas to the end consumer is set at 10%, and no or negligibly little renewable energies are used in the entire process chain.

In DIN V 18599, the other fossil fuels (heating oil, liquid gas, hard coal and lignite) are assigned the same primary energy factor as natural gas. Here, the political component is evident in these determinations, since both the energy consumption up to the point of provision and the CO 2 emissions of these various energy sources differ greatly.

For electricity, in an earlier version of DIN V 18599, the value f p = 3.0 was set for the entire primary energy factor (due to the high energy losses for producing the electricity) and the value f p = 2.7 for the non-renewable part . In the version of the Energy Saving Ordinance of October 1, 2009, the value for the non-renewable share is reduced to f p = 2.6 due to the increasing share of renewable electricity generation . In the current version of DIN 18599 in Part 100, the primary energy factor for electricity has now also been changed to 2.4. However, the current version of the EnEV 2014 in Appendix 1 number 2.1.1 sentence 6 states that a primary energy factor for electricity of 1.8 must be used from January 1, 2016, regardless of the calculations in DIN V 18599. However, this does not apply to the factor that is used for feeding into the power grid from a generator with combined heat and power. The factor for the displacement current mix of 2.8 still applies here. With an increasing share of renewable energies in power generation, the primary energy factor is expected to continue to decrease.

In the internationally dominant efficiency method, a conversion efficiency of 100% is assumed for hydropower , wind energy and photovoltaics , which have no calorific value, and thus the final energy is set equal to the primary energy. In the case of conventional energy sources , however, the efficiency with which the primary energy is converted into final energy is used. An exception is nuclear energy, for which an efficiency of 33% is applied across the board. This means that three times as much primary energy is used there as z. B. in wind power or photovoltaic systems. Due to this special feature of the calculation method, renewable energies tend to be underrepresented in primary energy statistics. For the same reason there is the strange phenomenon that nuclear energy has a higher share in the global primary energy statistics than hydropower, even though hydropower plants overall deliver significantly more electricity than nuclear power plants.

Conversely, this means that energy systems that are predominantly or completely based on renewable energies have a significantly lower primary energy consumption than conventional energy systems with the same final energy consumption. For Denmark z. For example, in three different energy transition scenarios, each with 100% renewable energies, roughly halving the primary energy requirement compared to a largely fossil reference scenario.

Primary energy generation

The primary energy consumption is offset by the primary energy generation. This is done in different ways. When comparing the proportions of primary energy generation, the different values ​​of the energy sources must be taken into account. Above all, energy density and efficiency play a role.

Fossil primary energy is obtained by burning fossil fuels. Primary electricity is generated, for example, in hydropower plants, solar or wind power plants. Thermal power plants can be operated with nuclear energy, solar energy or fossil fuels, in most cases part of the energy is converted into electricity. During this conversion, part of the primary energy is lost as waste heat and is no longer available as useful energy. With the cogeneration is an attempt to reduce these losses.

Primary energy consumption

The primary energy consumption is part of the national accounts . If a country's primary energy production is less than its primary energy consumption, the difference must be covered by imports. Both Germany and almost all countries of the European Union are net importers of primary energy, especially oil, gas and coal.

Primary energy in the life cycle assessment

In the life cycle assessment, the primary energy is divided into "primary energy renewable" and "primary energy non-renewable". These values ​​can in turn be divided into "materially bound" and "energetically used". The values ​​can also be differentiated according to their origin in “production” and “disposal”.

Primary energy in Switzerland

In Switzerland, “gray energy” corresponds to “primary energy not renewable”. Here there is a list of generic construction products, including the indication of the primary energy, divided into renewable and non-renewable as well as production and disposal. These indicators are calculated according to EN 15804, slightly different to the EPD calculation rules. For example, the lower calorific value is used for wood and biogenic carbon storage is not taken into account for GWP.

Web links

Wiktionary: primary energy  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. Lisa Thormann, Diana Pfeiffer, Karina Bloche-Daub, Daniela Thrän and Martin Kaltschmitt: Biomass in the energy system . In: Martin Kaltschmitt, Hans Hartmann & Hermann Hofbauer (eds.): Energy from biomass - fundamentals, techniques and processes . 3rd updated and expanded edition. Springer Vieweg, Berlin 2016, ISBN 978-3-662-47437-2 , 1.2, p. 9-64 .
  2. DIN V 18599-100: 2009-10
  3. Viktor Wesselak , Thomas Schabbach , Thomas Link, Joachim Fischer, Regenerative Energietechnik. Berlin / Heidelberg 2013, p. 6.
  4. ^ Nicola Armaroli , Vincenzo Balzani : Energy for a Sustainable World. From the Oil Age to a Sun-Powered Future. Weinheim 2011, p. 231.
  5. ^ Brian Vad Mathiesen et al .: Smart Energy Systems for coherent 100% renewable energy and transport solutions . In: Applied Energy 145, (2015), 139–154, 149f, doi : 10.1016 / j.apenergy.2015.01.075 .
  6. Eurostat: Statistical Aspects of the Energy Industry 2005 - Increasing Energy Dependency of the EU-25 ( Memento of July 3, 2007 in the Internet Archive ) ( PDF ; 153 kB)