Die Wärmewende ist ein unverzichtbarer Teil der Energiewende, da gut die Hälfte des gesamten Endenergieverbrauchs in Deutschland durch die Erzeugung von Wärme entsteht. Während die Erneuerbaren Energien im Stromsektor bereits an der 50-Prozent-Marke kratzen, verläuft die Substitution fossiler Energieträger im Wärmesektor bislang noch viel zu langsam. Hier liegt der Anteil Erneuerbarer Energie gerade einmal bei 15 Prozent. Entscheidende Fortschritte ließen sich jedoch erzielen, wenn Strom- und Wärmeerzeugung intelligent miteinander vernetzt werden. Die Denker & Wulf AG engagiert sich aktuell im Bereich Power-To-Heat – z.B. über unsere Partnerschaft mit der Glood GmbH und dem gemeinsamen Projekt „Hafenwärme Papenburg“. Im Folgenden geben wir Ihnen einen kurzen, englischsprachigen Überblick über die verschiedenen Ansätze für wirksamen Klimaschutz im Wärmebereich:

Renewable Energy in Heating Sector

The term “Renewable Energy” is often associated with producing electricity from replenishable sources like sun, wind and water. There has been a significant development to produce clean electricity through photovoltaics, wind turbines, biomass plants, hydropower plants etc. In fact, in Germany, the share of renewable energy sources in the electricity sector has risen considerably from about 5% in 1990 to 42% in 2019 and the trend continues to grow. The switch towards using renewables in the electricity sector has been quite successful so far, the development in other sectors has not been as dynamics until now. However, electricity is not the only sector, which needs renewable energy to become environment friendly, there is one more sector, which needs attention: the “heating sector”. In Germany, the share of renewable energy sources in the heating sector has grown steadily but slowly. From about 2% in 1990 to 15% in 2019, this shows the significant difference in use of renewable energy between the heating and the electricity sector. A ‘heating transition’ is now required as part of the energy transition (Energiewende) to reach carbon-neutrality in the heating sector. Apart from the unlikelihood of an instant and complete shift to renewable heat sources and power-to-heat, it is very much possible to gradually increase the amount of renewable sources and combine them with fossil fuels transitionally. Less burning of fossil fuels means less CO2 emissions. On the other hand, shifting these reduced operating hours of, e.g. CHP plants, to times when there is low supply of renewable energy in the electricity grid, can help provide security of supply in an efficient manner.
Several technologies are available to make the heating sector more dependable on renewable energy and reduce CO2 emissions.

Solar Thermal

Solar thermal devices collect the heat energy from the Sun using solar collectors and use this heat to produce hot water. Even on a cloudy day, enough sunlight falls on the solar collectors, e.g. the roof of a house, to cover hot water demand. Solar collectors can be installed to supplement central heating systems with hot water tanks in existing houses, where they typically cover up to 60% of hot water, but no space heating demand. As a result, the cost of a single unit of heat from solar thermal is high, compared with alternative renewable heating technologies. According to the Federal Ministry for Economic Affairs and Energy, by 2019, Germany installed a solar thermal capacity of 13,5 million kilowatt, out of which 8,5 TWh was consumed for heat purposes.

Heat Pumps

As sunlight travels through the atmosphere and falls on the Earth’s surface, it warms the air and ground, resulting in a large store of ambient heat energy. However, this heat energy is at low temperatures, usually below that comfortable for homes and workplaces. Heat pumps use electricity to ‘pump’ this heat to higher temperatures and transfer it into buildings. They operate on the same principle as domestic refrigerators, only in this case the outside air or ground is being (slightly) cooled. When run in reverse, heat pumps can provide air-conditioning to cool the inside of buildings in summer. There are three main types. Air source, ground source and water source heat pumps. By 2030, Germany requires five to six million heat pumps to reduce greenhouse gases by 55 percent in 2030 and by at least 80 percent by 2050. According to the Federal Ministry for Economic Affairs and Energy, by 2019, in Germany there were 1.155 thousand heat pump plants installed and the total installed thermal capacity reached up to 11,2 million kilowatts.

Biomass Fuels

Renewable biomass fuels include wood from forestry, trimmings from parks and hedgerows, cereal straw from farms and wood pellets made from compressed sawdust. In the longer term, dedicated energy crops such as willow, poplar or novel grasses might become available. Biomass fuels can also be produced from waste. Biomass fuels emit no net CO2 when they are burned, as the same amount of CO2 is captured as the biomass grows. The main energy source in the renewable heat sector is biomass (solid, liquid or gaseous), providing still approximately 87 percent of renewable heat in 2019.

Geothermal Energy

Geothermal Energy is the heat derived within the sub-surface of the earth. Water and/or steam carry the geothermal energy to the Earth’s surface. Depending on its characteristics, geothermal energy can be used for heating and cooling purposes or be harnessed to generate clean electricity. The main advantages of using geothermal energy is that it is not depending on weather conditions and has very high capacity factors. There are different geothermal technologies with distinct levels of maturity. Technologies for direct uses like district heating, geothermal heat pumps, greenhouses, and for other applications are widely used and can be considered mature. In Germany, as of 2019, there has been an installed thermal capacity of 11,2 million kilowatt.

Our Contribution to the Heat Transition We at Denker & Wulf AG are committed and recognize the potential of using renewable energy in the heating sector. Denker & Wulf’s project ‚Hafenwärme Papenburg‘ is one example for a large-scale integration of significant amounts of renewable heat in combination with CHP. In this specific case, industrial size air-to-water heat pumps provide the renewable heat. We at Denker & Wulf are always happy to develop and invest in renewable heating projects. Therefore, if this article has awakened your interest in the renewable heating sector then we are always ready to make project ideas into a reality.


Opportunities and risks for Germany’s heating industry in a competitive global environment (pwc.de)

Key-Information_Renewable-Energy-Sources-in-Germany (erneuerbare-energien.de)

Renewable energy sources in figures (bmwi.de)

Postnote353 – renewable heating (parliament.uk)

Renewable energies in figures | Umweltbundesamt

20200525_Waermeverbrauchsanalyse_Foliensatz_2020_daQSUCb.pdf (bdew.de)

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