Altbach/Deizisau combined heat and power plant

The groundbreaking ceremony for the construction project was held on 6 November 2023. Construction work began in September 2023 because a permit had been obtained to start early. The main construction activities are expected to be completed by 2026, followed by the start-up phase and commercial commissioning.

Unfortunately, it is difficult to fully avoid construction work being noticeable in the area. However, EnBW is making every effort to minimize the impact. Most of the work is carried out during the day, with heavy haulage moved to nighttime whenever possible.

All measures will be carried out as per the approval process and in close consultation with Stuttgart Regional Council and the municipalities in the surrounding area. EnBW also continues to engage in dialogue with residents to address their concerns and questions.

The existing power plants will remain in operation until all new power plant and district heating facilities have been fully commissioned, ensuring that the power supplied by the power plant and the district heating supply in Altbach, Deizisau and the surrounding region is reliably maintained at all times.

As an additional district heating backup plan for the 2024/2025 and 2025/2026 heating periods, EnBW has already installed a temporary rented boiler system during the construction phase.

Before the two old HKW 1 and HKW 2 blocks are finally shut down, a hot water boiler system will be built in addition to the existing combined cycle gas turbine (CCGT) plant in order to ensure a secure district heating supply even during times when the CCGT plant is not in operation. The “Mittlere Neckar Line” pipe network can also be used to supply heat from Stuttgart’s power plants to the district of Esslingen.

If you have any questions, suggestions or criticism, please contact altbach-deizisau@enbw.com at any time.

EnBW provides regular information on the progress of the project and current milestones. This is done via the project page, which can be found at www.enbw.com/altbach-deizisau, and by distributing leaflets. Media outlets also report on the progress on the construction site at regular intervals.

As part of the approval process, noise reports and similar reports are produced to assess the impact of the new building on the surrounding area.

Once the new combined cycle gas turbine (CCGT) plant has been commissioned, blocks HKW 1 and HKW 2 will be shut down. Only a few large components – such as the gas turbine plants, the HKW 1 cooling tower and the water treatment plant – will remain in operation. Since the decommissioned plants previously made a significant contribution to the noise emissions at the site, noise pollution will be greatly reduced.

The CCGT will be fitted with the latest generation of silencers and sound traps in order to comply with the legal limits laid down by noise control regulations (TA Lärm). In addition, there will no longer be any disposal of residues or delivery of additives associated with the coal blocks’ flue gas cleaning system, which will in turn reduce the volume of traffic.

As part of the approval process, reports such as an air pollutant forecast are produced to assess the impact of the new building on the surrounding area.

Switching from coal to natural gas will significantly reduce emissions of carbon dioxide and other substances that have an impact on the climate. For Altbach and Deizisau, this means that the new combined cycle gas turbine (CCGT) plant can cut carbon dioxide emissions by over two million metric tons annually, which equates to around 40% of the coal power plant’s current emissions.

Furthermore, it leads to a significant improvement in the air quality: Emissions of nitrogen oxides (NOx) will be cut by about 25% compared to the current figure, while those of sulfur oxides (SOx) will fall by more than 75%. Dust pollution will also be almost completely removed and heavy metal emissions will be eliminated altogether.

As part of the approval process, reports are produced, including a survey on the impact on water pollution control, in order to assess the impact of the new building on the surrounding area.

The commissioning of the combined cycle gas turbine (CCGT) plant and the subsequent decommissioning of the old plants will result in significantly less heat being released into the Neckar, which borders the power plant site. This will lead to an improvement in water pollution control compared to the current situation.

There are three parts to the approval process for the combined cycle gas turbine (CCGT) plant pursuant to the Federal Immission Control Act (BImSchG):

• The first part of the application was submitted in May 2023. EnBW was granted the partial permit for this in January 2024.
• The second part of the application was submitted in spring 2025. The plant is expected to be commissioned in 2026.
• The third and final part of the application is currently being prepared and will then go through the approval process.

Stuttgart Regional Council is the approval authority.

EnBW currently estimates that around 600 million euros will be invested in the construction project.

Two new main structures are being built on the existing power plant site:

• The combined cycle gas turbine (CCGT) plant and its auxiliary facilities are being built in the area situated to the south of the HKW 1 cooling tower.
• A hot water boiler system is also being built, which will be located in the existing HKW 1 district heating building.
• The HKW 1 hybrid cooling tower will also be used by the new CCGT plant. The water treatment facilities will also be upgraded and remain in operation.

Plans for the future use of the freed up areas are currently still open and will be decided at a later date.

The decision in favor of a combined cycle gas turbine (CCGT) plant is based on its high degree of efficiency:

• For environmental and climate change mitigation reasons, it is essential to use the fuel as efficiently as possible in order to generate as much energy as possible from a given amount in the form of electricity and heat.
• Through combined heat and power generation, a CCGT plant achieves the best fuel utilization rate and an efficiency level of over 60%, making it the optimal choice for sustainable and efficient energy generation.

The aim of climate neutrality cannot be achieved in a single step – not even for individual companies. In the field of heat generation in particular, renewable energies are currently not in a position to fully replace fossil fuel within a matter of years.Natural gas represents a sensible intermediate step in this regard, not least because it can cut greenhouse gas emissions by about half in the short term compared to coal. It is important to remember that natural gas is only intended to be used for a transitional period and will not obstruct the long-term path to climate neutrality.

The gas turbines are flexible and can later be converted to burn “green gases” such as hydrogen. Green hydrogen is produced by means of electrolysis using electricity from renewable energy sources.

As soon as the combined cycle gas turbine (CCGT) plant is commissioned, it will be possible to add up to 20% hydrogen to the natural gas, further reducing greenhouse gas emissions. The switch to natural gas thus represents a bridging option culminating in a fully climate-neutral energy supply, which EnBW is aiming to achieve by 2035 with regard to its own emissions.

The new combined cycle gas turbine (CCGT) plant guarantees reliable security of supply and complements the fluctuating energy production from renewable energy sources. The CCGT plant will initially provide lower-carbon electricity and district heating.

In the future, by using hydrogen as a fuel, it will even be able to supply carbon-free energy. Thanks to its modern technology, the plant boasts particularly low emission values and thus plays an active role in reducing air pollutants.

Not directly and not all the time. Converting an urban area to run on regional renewables is a complex challenge. This is mainly due to the fact that renewable energy sources such as wind power and photovoltaics require a lot of space because their energy density is comparatively low.

What’s more, these energy sources are not dispatchable – they generate electricity when the wind or sun is available, and not necessarily when energy demand is at its highest. In order to compensate for these fluctuations, flexibly dispatchable power plants are needed to meet demand.

A combined cycle gas turbine (CCGT) plant consists of a gas turbine, a steam turbine and heat exchangers for the production of hot water. It utilizes the energy generated during the combustion of natural gas in a particularly efficient manner by using the produced heat three times:

1. Electricity generated by the gas turbine: The hot combustion gases produced during the combustion of natural gas firstly drive a gas turbine. This is connected to a generator that converts the turbine’s mechanical energy into electrical energy.

2. Additional electricity generated by the steam turbine: The exhaust gases from the gas turbine are still very hot. This heat is used in a waste heat boiler to evaporate water. The steam drives a steam turbine, which also generates electricity.

3. Further use made of the residual heat: Part of the steam that has already been used to generate electricity is withdrawn from the steam turbine and used to generate district heating. This process is much more efficient compared to direct heat generation in boiler systems.

This combined heat and power generation enables the CCGT plant to achieve a fuel utilization rate of over 70%. Carbon emissions can be cut by around 50% compared to those produced by a coal power plant. No other technology can help to cut carbon emissions to this extent in such a short space of time.

The combined heat and power generated by the combined cycle gas turbine (CCGT) plant allows the particularly efficient use of natural gas as a fuel and offers the possibility of fully switching to hydrogen in the future.

In the initial phase, a blend of natural gas and up to 20% hydrogen will be used, provided that it is available in sufficient quantities. There are plans to operate the plant using 100% hydrogen from 2035 by making adjustments.

The combined cycle gas turbine (CCGT) plant has the following advantages over the hard coal blocks that have been used until now in Altbach/Deizisau

• The gas-fired plant is more flexibly dispatchable than a coal power plant. It can thus better compensate for the fluctuating electricity production from wind and solar energy.
• Combined heat and power generated by the CCGT plant allows the most efficient use of natural gas as a fuel. Eventually, natural gas can also be replaced by hydrogen.
• Natural gas is a more climate-friendly fuel than hard coal. From 2027, carbon emissions per kilowatt-hour of electricity generated will be reduced by more than 50%.
• Air pollutants will be reduced. Nitrogen oxide (NOx) emissions will be cut by about 25%, while sulfur oxide (SOx) emissions and dust pollution will be almost completely removed and heavy metal emissions eliminated altogether.
• Due to the decommissioning of the coal blocks, the existing coal storage facility is no longer needed, putting an end to the associated dust and noise emissions.
• There will be less traffic. Coal deliveries will no longer be needed, nor many of the journeys to deliver additives and dispose of residual materials from the flue gas cleaning process.
• There will be much less noise thanks to modern noise reduction technology. The coal boilers, coal-fired auxiliary steam generators and the flue gas cleaning system will also be shut down.
• The CCGT plant will also be capable of running entirely on hydrogen in the future. If a climate-neutral method is used to produce the hydrogen, it will later generate fully carbon-neutral electricity and district heating.