Power-to-heat

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Under power-to-heat (short PtH or P2H , German as "electric energy to heat") refers to the generation of heat by the use of electric power. This can be done using both electric boilers and heat pumps . PtH is a possibility to use electrical surpluses from renewable energies for the heat supply (coupling of electricity and heat sector), whereby fossil fuels and emissions can be saved in the heat sector . In contrast to pure electric heaters such. B. Night storage heaters , which cover the entire heating requirement, are power-to-heat systems hybrid systems that always have a conventional heat generator operated with chemical fuel such as wood or natural gas. If there is a surplus of electricity, heat can be obtained from electrical energy, otherwise the conventional heating system is used. To increase flexibility, power-to-heat systems are often coupled with heat storage . The feed mostly takes place in local or district heating networks , but power-to-heat systems can also supply individual buildings or large industrial plants with heat.

business

Mission profile

Power-to-Heat is a Power-to-X technology that is intended to enable better integration of renewable energies in an intelligent power grid through sector coupling in the course of the ongoing transformation of energy supply structures in the context of energy market liberalization and the energy transition . If there is a strong feed-in of variable renewable energies (in particular wind energy and photovoltaics ) and high electricity production is only offset by low demand for electricity, heat should be generated from electricity using power-to-heat systems. This is intended to avoid or reduce curtailments by renewable producers. The heat generated in this way can, for example, for heating systems and water heating are used and replaced there by Virtual Energy Storage turn fossil fuels such as natural gas and petroleum. In this way, there is a saving in fuel from fossil fuels and thus also in greenhouse gas and pollutant emissions .

The heat can be generated directly using a resistance hot water boiler and / or in electrode hot water boilers. This application is used e.g. B. in district heating networks for the supply of heating systems and hot water or to feed district heating storage. It is also possible to use heat pumps instead of generating heat directly from electricity. Heat pumps are more energy efficient than heating rods and electrode boilers , so that less electricity is required for the same heating energy. The electrical energy saved in this way is available for other purposes. Both electrode boilers and heat pumps are mature technologies that are available on the market. However, the application profiles differ significantly: While electrode boilers can be operated particularly flexibly, heat pumps are more suitable as a base load technology because they have high investment costs but low operating costs.

PtH in the form of heating rods or electrode boilers is a technology with low investment costs (100 € / kW) and is therefore very well suited for absorbing high power peaks, which only rarely occur each year. The potential for PtH systems is huge: Theoretically, 200 GW in winter and 50 GW in summer can be achieved in Germany . In practice, on the other hand, classic PtH systems based on the resistance principle should only be used as a supplement to the significantly more efficient heat pump heating systems.

From an energy point of view, the use of power-to-heat systems only makes sense during times of very high feed-in from renewable sources, since electricity is a significantly higher quality form of energy than thermal energy and therefore usually has a much higher value. From a financial perspective, converting it into heat is therefore only worthwhile at very low market electricity prices . In addition, for ecological reasons, the production of heat from electricity is always counterproductive if fossil power plants also deliver larger amounts of electricity, since the conversion of electricity in a power plant (with subsequent heat generation from electrical energy) is much less efficient than direct heat generation using fossil fuels Energy source . If, on the other hand, heat is obtained from (almost emission-free) wind or solar power and, in return, the burning of fossil fuels is avoided, emissions are reduced.

In addition, the increased use of power-to-heat can provide low-cost negative control power and thus replace the need for fossil must-run capacities. These must-run capacities result from the function previously assumed by conventional power plants of providing necessary system services and negative control power and depend, among other things, on the control power to be provided in the power grid and the technically drivable minimum power of a conventional power plant. For example, if a power plant with a nominal output of 500 MW and 40% technically drivable minimum load is to provide 50 MW of negative control power, this results in a must-run capacity of at least 250 MW. If, on the other hand, PtH systems are available as an alternative, which can provide negative control power instead of the fossil power plant, there is no need for must-run capacity and the power plant can be completely shut down in times of high renewable generation. By quickly switching off PtH systems, PtH systems can also provide positive control power at short notice. It is also beneficial to couple it with systems operated in combined heat and power , such as combined heat and power plants , which can start up in the event of a low level of regenerative energy generation and feed their heat into a heat storage system that is shared with the PtH system.

Comparison with power-to-gas

Technically, power-to-heat functions as a so-called "virtual memory", which is why power-to-heat with memory technologies such as B. Power-to-Gas can be compared. Since the efficiency of converting electricity into heat with power-to-heat is almost 100%, there are clear advantages over storage using a power-to-gas approach. Through the use of power-to-heat in the heating sector, electricity replaces fossil fuels in a ratio of 1: 1, while the production of methane with the help of the power-to-gas process results in greater losses and thus only part of the originally available electrical energy is used can be. In the heating sector, power-to-heat saves significantly more natural gas than can be generated with power-to-gas. The natural gas thus saved can in turn be used entirely for other purposes; this means that the overall efficiency of power-to-heat is significantly higher than that of power-to-gas.

In addition to heating resistors, heat pumps can also be used for power-to-heat systems , but these require higher investment costs than resistance heating. Due to their great efficiency advantages compared to direct heat generation in resistance heating, the use of heat pumps is still preferable. The use of future green electricity surpluses to operate heat pumps has the greatest environmental benefit of all Power-to-X concepts in terms of greenhouse gas reduction and saving fossil fuels. While using power-to-gas systems of one kWh of electrical energy, only 0.24 to 0.84 kWh remain as usable thermal energy (depending on the respective further use of the gas and any existing waste heat recovery) heat pumps do the same Amount of energy between 3 and 4.5 kWh of heating energy available. This means that the energy efficiency of heat pumps is 4 to 19 times that of power-to-gas systems. Even if the heat obtained with heat pumps is stored seasonally and thus certain storage losses occur, this method is still far more efficient than the production of synthetic methane.

Since power-to-heat systems can replace fuels , but not generate them, they must be supplemented in the long term towards the end of the energy transition by power-to-gas systems that produce fuel (and, if necessary, convert it back into electricity ) allow. However, this reconversion of electricity is only necessary when the share of renewable energies in the electricity mix is ​​very high, in order to enable seasonal storage. Such seasonal long-term storage systems, which can practically only be based on power-to-gas technology, are necessary from a solar and wind power share of around 80%. There are also scenarios that manage completely without reconverting synthetically produced fuels such as hydrogen or methane into electricity. In these models, synthetically produced fuels are required exclusively for transport (especially long-distance shipping, aviation) and as raw materials for industrial applications.

Planned and implemented large-scale power-to-heat systems (selection)

Denmark

Denmark has the greatest experience with power-to-heat systems , where the energy transition there, with wind power shares of approx. 42.1% in 2015, is already much more advanced than e.g. B. in Germany. In Denmark, the construction of PtH plants began in the mid-2000s. Around 350 MW had been installed by the end of 2014, including heat pumps with a thermal output of around 30 MW. For the end of 2015 [obsolete] an increase to 44 plants with around 450 MW is targeted.

Germany

In operation

Many systems with electrode boilers and resistance boilers have now been implemented in Germany. Here are some well-known projects:

In planning or under construction

Austria

Czech Republic

  • Kladno power plant 1 × 14 MW, operated by Auxilien, as
  • Pribram Stadtwerke 1 × 12 MW, operated by Auxilien, as
  • Tusimice power plant 1 × 7 MW

Slovakia

  • Stadtwerke Kosice 1 × 8 MW, operated by Auxilien, as
  • Stadtwerke Zvolen 1 × 2.5 MW, operated by Auxilien, as

Web links

literature

Individual evidence

  1. ↑ Jyri Salpakari, Jani Mikkola, Peter D. Lund: Improved flexibility with large-scale variable renewable power in cities through optimal demand side management and power-to-heat conversion . In: Energy Conversion and Management . tape 126 , 2016, p. 649-661 , doi : 10.1016 / j.enconman.2016.08.041 .
  2. ↑ Andreas Bloess, Wolf-Peter Schill, Alexander Zerrahn: Power-to-heat for renewable energy integration: A review of technologies, modeling approaches, and flexibility potentials . In: Applied Energy . tape 212 , p. 1611-1626 , doi : 10.1016 / j.apenergy.2017.12.073 .
  3. ↑ Michael Sterner, Ingo Stadler: Energy storage - requirements, technologies, integration . Berlin - Heidelberg 2014, p. 124.
  4. ^ Gerald Schweiger et al .: The potential of power-to-heat in Swedish district heating systems . In: Energy . 2017, doi : 10.1016 / j.energy.2017.02.075 .
  5. ↑ a b Christoph Pieper et al .: The economic use of power-to-heat systems in the balancing energy market . In: Chemical Engineer Technology . tape 87 , no. 4 , 2015, p. 390-402 , doi : 10.1002 / cite.201400118 .
  6. ↑ Matthias Koch et al., Model-based evaluation of network expansion in the European network and flexibility options in the German electricity system in the period 2020–2050 . In: Zeitschrift für Energiewirtschaft 39, (2015), 1–17, p. 15, doi: 10.1007 / s12398-015-0147-2 .
  7. ↑ Jon Gustav Kirkerud, Erik Trømborg, Torjus Folsland Bolkesjø: Impacts of electricity grid tariffs on flexible use of electricity to heat generation . In: Energy . tape 115 , 2016, p. 1679–1687 , doi : 10.1016 / j.energy.2016.06.147 .
  8. ↑ a b Michael Sterner, Ingo Stadler: Energy storage - requirements, technologies, integration . Berlin - Heidelberg 2014, p. 134.
  9. ↑ Diana Böttger et al .: Control power provision with power-to-heat plants in systems with high shares of renewable energy sources e An illustrative analysis for Germany based on the use of electric boilers in district heating grids . In: Energy . tape 82 , 2015, p. 157–167 , doi : 10.1016 / j.energy.2015.01.022 .
  10. ↑ Helmuth-M. Groscurth, Sven Bode Discussion Paper No. 9 “Power-to-heat” or “Power-to-gas”? . Retrieved May 15, 2014.
  11. ↑ Wolfram Münch et al., Hybrid heat generators as a contribution to the system integration of renewable energies . In: Energiewirtschaftliche Tagesfragen 62, No. 5, (2012), pp. 44–48, online
  12. ^ André Sternberg, André Bardow, Power-to-What? - Environmental assessment of energy storage systems . In: Energy and Environmental Science 8, (2015), 389-400, pp. 398f, doi: 10.1039 / c4ee03051f .
  13. ↑ heat turnaround 2030. Schöüsseltechnologien 17 to achieve the medium and long-term climate change targets in the building sector, p . Agora Energiewende . Retrieved March 15, 2017.
  14. ↑ Stefan Weitemeyer, David Kleinhans, Thomas Vogt, Carsten Agert, Integration of Renewable Energy Sources in future power systems: The role of storage . In: Renewable Energy 75, (2015), 14-20, doi: 10.1016 / j.renene.2014.09.028 .
  15. ^ Mark Z. Jacobson et al .: 100% clean and renewable wind, water, and sunlight (WWS) all-sector energy roadmaps for the 50 United States . In: Energy and Environmental Science 8, (2015), 2093-2117, doi: 10.1039 / c5ee01283j .
  16. ↑ Wind energy in Denmark breaking world records . In: The Copenhagen Post , January 15, 2016. Retrieved January 17, 2016.
  17. ↑ Power-to-Heat for the integration of otherwise regulated electricity from renewable energies ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. . Study on behalf of Agora Energiewende. Retrieved August 21, 2015. @1@ 2Template: Webachiv / IABot / www.agora-energiewende.de
  18. ↑ website of Energstorage GmbH , July 30, 2015
  19. ^ First balance at Power to Heat , February 20, 2013.
  20. ↑ Schwerin municipal utilities. In: Power-to-Heat Forum Schwerin. 2014, accessed January 29, 2018 .
  21. ↑ Schwerin municipal utilities. In: Stadtwerke contribute to the energy transition. 2014, accessed January 29, 2018 .
  22. ↑ In Westphalia, too, heat from wind power ( memento of the original dated February 3, 2016 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. . In: newspaper for local economy , February 2, 2016. Accessed February 2, 2016. @1@ 2Template: Webachiv / IABot / www.zfk.de
  23. ↑ geothermal Grünwald - Glood GmbH. Retrieved August 24, 2017 .
  24. ↑ Power-to-Heat: Vattenfall puts 120 MW system into operation . In: Euwid Neue Energie , September 16, 2019. Retrieved September 16, 2019.
  25. ↑ Drewag begins building a power-to-heat system . In: Euwid Neue Energie , July 3, 2017. Accessed July 3, 2017.
  26. ↑ Together heat from green electricity. Accessed January 24, 2020 (German).
  27. ↑ Use green electricity instead of switching it off. Accessed January 24, 2020 (German).
  28. ↑ Yearbook 2016. (PDF) Wien Energie , accessed on January 29, 2018 .
  29. ↑ http://eventmaker.at/uploads/4261/downloads/SCHULLER_Power2Heat_-_Erste_Betriebs-_und_Einsatzerfahrungen.pdf
  30. ↑ Hall.AG: Hall AG - Tirol's first "Power-To-Heat system" is in Hall i. T. Reality. Retrieved January 29, 2018 (German).