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From coal to natural gas to hydrogen

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Coal phaseout at the site in Altbach/Deizisau

By constructing a new combined cycle gas turbine (CCGT) plant, EnBW wants to replace coal with more climate-friendly natural gas at its Altbach/Deizisau site by means of a so-called fuel switch. This switch to natural gas represents the bridge that will ultimately lead to green gases such as hydrogen produced from renewable sources. EnBW thus plans to keep its promise of achieving climate neutrality by 2035 – the company’s contribution to climate change mitigation to which it has committed itself in line with the 2015 Paris Agreement. With this aim in mind, EnBW will continue to systematically expand renewable energy capacity and completely 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.

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A recent photo EnBW’s Altbach/Deizisau site
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Illustration: The Altbach/Deizisau site with a 3D image of the planned power plant.
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The Altbach/Deizisau site

The Altbach/Deizisau combined heat and power plant is located near Esslingen am Neckar on the boundaries between the municipalities of Altbach and Deizisau. It has a long history of power plants: Back in 1899, Heinrich Mayer, an industrial pioneer from the Neckar region in the field of electrification, built the “Kraftcentrale” – the first coal power plant on the Altbach site. The forerunner of today’s power plant was then built at the end of the 1940s. Today, the hard coal power plant consists of two blocks, supplemented by three gas turbines and a combined gas and oil block. In total, the power plant has an installed electrical output of around 837 MW.

Securing the supply of electricity and district heating

With a total of four blocks at the site, the power plant not only plays a key role in supplying electricity, but also secures the supply of district heating in the region. The two hard coal blocks work according to the principle of combined heat and power. In other words, they use the waste heat from electricity production to produce district heating. This is how a secured district heating capacity of 280 megawatts can be drawn off from combined heat and power plant 2. The power plant feeds this district heating into the “Mittlere Neckar Line” district heating system, via which it is connected to the Stuttgart-Gaisburg combined heat and power plant in the east of Stuttgart and the Stuttgart-Münster waste-to-energy plant. A considerable number of the industrial companies in Esslingen and Stuttgart are supplied with district heating in this manner, along with many private households and public buildings in Esslingen, Altbach, Deizisau, Plochingen and Stuttgart.

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Mittlere Neckar region district heating network
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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 power plant blocks in Altbach. This cannot happen without a replacement being found for Altbach, however, if a secure electricity and district heating supply is to be maintained for the region. A combined cycle gas turbine (CCGT) plant is therefore set to be built to replace the two hard coal blocks. With a maximum electrical output of 750 megawatts (MW) and thermal output of around 180 MW, this new combined heat and power plant would be an almost equivalent replacement for the existing blocks. To secure district heating here, a hot water boiler plant consisting of three boilers with a thermal output of around 120 MW will also be built. This switch to natural gas alone will more than halve greenhouse gas emissions compared to current coal-fired power generation. Step by step, the existing blocks can be shut down simultaneously to the commercial commissioning of the new plant.

The new plant thus secures the region’s long-term district heating supply. As a controllable power plant, it permits the successful continuation of the energy transition while maintaining security of supply. It would also continue the long tradition of power plants on the site.

Seamless transition from natural gas to hydrogen

Another advantage of gas-fired plants is that they are flexible in terms of the fuel gas used and can therefore 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 Altbach/Deizisau power plant site can be converted – and will then produce completely carbon-neutral electricity and district heating. Like the CCGT plant itself, the natural gas pipeline used to supply the new CCGT plant in Altbach/Deizisau with natural gas is already technically suitable for hydrogen, enabling this conversion to be completed without any major hurdles.