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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. With this aim in mind, EnBW will continue to systematically expand renewable energy capacity and phase out the use of coal as an energy source in the medium term. In doing so, the number-one priority is to ensure that the supply of electricity and heat is never under threat. EnBW is therefore embracing the fuel switch principle at its Heilbronn site and initially replacing coal with more climate-friendly natural gas by constructing a new combined cycle gas turbine (CCGT) plant. This switch to natural gas represents a bridge on the way to green gases, such as hydrogen produced from renewable sources, with which complete climate neutrality can then be achieved by 2035.

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Upgrading the Heilbronn site

The Heilbronn site with a 3D image of the new plants.

The Heilbronn plant located in an industrial and commercial park on the outskirts of the city by the Neckar is currently being operated as a combined heat and power plant. With an electrical output of 1,100 MW and a thermal output of 320 MW capable of being drawn off, it is one of EnBW’s large-scale hard coal power plants..

Securing the supply of electricity and district heating

In total, there are seven blocks on the site, three of which are still in operation. Block 7 is one of the largest hard coal blocks operated by EnBW. Extensively modernized once again in 2009, it now guarantees a reliable supply of electricity and district heating in the Heilbronn area. The two older blocks 5 and 6 are part of the grid reserve and are only used by the transmission system operator in the event of bottlenecks in the high-voltage grid. The Marbach and Walheim power plants are smaller sites linked to the Heilbronn site.

On the way to more climate-friendly energy generation

According to the Coal Phaseout Act of 2020, coal power plants in Germany are due to be shut down by no later than 2038. In the medium term, this will therefore affect the blocks in Heilbronn. This cannot happen without a replacement being found for Heilbronn, however, if a secure electricity and district heating supply is to be maintained for the city of Heilbronn and the wider region. A combined cycle gas turbine (CCGT) plant is therefore set to be built to replace Block 7. With a maximum electrical output of 750 megawatts (MW) and thermal output of around 200 MW, this new combined heat and power plant would be an almost equivalent replacement for coal block 7. To secure the supply of district heating, a heat storage facility with a capacity of 600 MWh and a hot water boiler system with a thermal output of approx. 160 MW will also be built. This step alone will more than halve greenhouse gas emissions compared to the current coal power plant. Step by step, Block 7 can be shut down simultaneously to the commercial commissioning of the new plant. The same also goes for the two reserve blocks 5 and 6 at the power plant. The cooling tower, water building and associated water intake and discharge structures belonging to Block 7 can also be used for the new CCGT plant. This will make optimal use of their service life in terms of sustainability. The new plant will thus secure the district heating supply in Heilbronn in the long term. Yet the district heating network itself is also set to be modernized in the course of the new building works, increasing and optimizing its efficiency by converting it to run on hot water instead of steam.

Seamless transition from natural gas to hydrogen

Another advantage of gas-fired plants is that they can also be powered by “green gases” such as hydrogen produced from renewable energy sources. As soon as this “green” hydrogen is available in sufficient quantities and the supply infrastructure has been converted to accommodate it, the Heilbronn power plant site can be converted – and will then produce completely carbon-neutral electricity and district heating. Like the CCGT plant and the hot water boiler system, the South German natural gas pipeline (SEL) currently under construction, which will be used to supply the new CCGT plant in Heilbronn with natural gas, is already technically suitable for hydrogen, enabling this conversion to be completed without any major hurdles.