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Coal phaseout at Stuttgart-Münster

Climate-neutral by 2035 – based on this promise, EnBW is committed to playing its part in mitigating climate change in line with the 2015 Paris Agreement. For EnBW, this partly means continuing to systematically expand renewable energy capacity, while also pursuing its aim of phasing out the use of coal in the medium term and the use of fossil fuels as an energy source in the long term. EnBW is one step closer to achieving this aim with the construction of a new gas turbine plant for generating electricity and heat based on more climate-friendly natural gas at its Stuttgart-Münster site. The fuel switch to more climate-friendly natural gas is just a bridging technology on the way to energy generation using green gases such as hydrogen produced from renewable sources.

Large-scale heat pump at Stuttgart-Münster waste-to-energy CHP plant

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On the site of our Stuttgart-Münster waste-to-energy CHP plant, a further step toward climate neutrality is set to be taken involving the supply of district heating in the Stuttgart region. A large-scale heat pump will use the waste heat from the cooling water drained from the site to generate up to 24 MW of district heating. The large-scale heat pump in Stuttgart-Münster will be one of the first plants in Germany on this scale, setting new standards in how waste heat is used to meet energy needs.

The large-scale heat pump will be powered by certified green electricity produced during the waste incineration process. The climate-neutral district heating generated in this manner can cut annual carbon emissions by around 15,000 metric tons. The figure for climate-neutral district heating in the Stuttgart region will thus increase by roughly 10% to around 25%. Accordingly, the heat pump will not only play a key role in decarbonizing EnBW’s district heating generation, but also significantly help the city of Stuttgart to achieve its climate change mitigation goals.

The large-scale heat pump will be installed in one of the power plant’s existing buildings. The new plant is expected to be commissioned in 2023.

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How the large-scale heat pump works

The heat pump technology is familiar from the field of building heating. The heat pump extracts heat from the outside air in order to supply the interior of a house with heating. In the case of the large-scale heat pump, district heating is produced instead and the ambient heat is extracted from the cooling water of the waste-to-heat CHP.

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Heat pump technology on a scale as big as this is considered a promising stepping stone toward achieving a climate-neutral district heating supply. Given the current underlying conditions in the energy industry, however, it is generally not economically viable. That is why the Federal Ministry for Economic Affairs and Climate Action is funding this project as part of the ideas competition “Reallabore der Energiewende” (or “Living Labs for the Energy Transition”). The project in Stuttgart-Münster is part of the joint research project “Large-scale heat pumps in district heating networks – installation, operation, monitoring and system integration.”

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The benefits and challenges

Building the large-scale heat pump will reduce the amount of heat discharged into Neckar and make it possible to use the energy contained in the cooling water to generate climate-neutral district heating. One particular challenge for the project is the task of integrating the new large-scale heat pump into the existing plants at the Stuttgart-Münster power plant site, which has existed for a very long time, because ongoing operations must be maintained here during the construction period. In addition, the new plants must be integrated into the existing infrastructure and buildings.

Technical data

Output
approx. 20–24 MW district heating (depending on the temperature of the heat source)
COP
approx. 3
Heating circuit
District heating water that comes back from the customers to the combined heat and power plant (the so-called return) is heated in two stages to the required temperature level of the flow (the water that is transported to the customers). The heat pump is used for the first heating stage (90°C).
Cooling water withdrawal
approx. 4,300 m³/h (equivalent to approx. 1,200 l/s)
Investment
approx. €17 million
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The approximate size of the planned large-scale heat pump at EnBW's waste-to-heat CHP in Stuttgart-Münster

Further information on the subject of district heating can be found here.

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