Heilbronn combined heat and power plant

The groundbreaking ceremony for the construction project was held on 23 February 2024. Construction work began in November 2023 because a permit had been obtained to start early. The main construction activities are expected to be completed by 2027, 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 city of Heilbronn. 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 the city of Heilbronn and the surrounding region is reliably maintained at all times.

If you have any questions, suggestions or criticism, please contact heilbronn@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/heilbronn, 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 are scheduled to shut down. Only a few large components – such as the gas turbine plants, the HKW 1 cooling tower and the water treatment plant –are expected to remain in operation. Since the decommissioned plants previously made a significant contribution to the noise emissions at the site, the overall noise situation may improve.

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 in turn could 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 combined cycle gas turbine (CCGT) plant on the surrounding area.

The planned switch from coal to natural gas has the potential to reduce emissions of CO₂ and other climate-impacting substances. For Heilbronn, current plans call for a reduction in CO₂ emissions of approximately 50% compared to the current coal-fired power plant. This amounts to over one million metric tons of CO₂ per year. Forecasts also indicate a reduction in other air pollutants: Emissions of nitrogen oxides (NOₓ) could drop by about 80% compared to current levels, and those of sulfur oxides (SOₓ) by more than 90%. In addition, dust pollution is expected to decrease by 44 percent, and heavy metal emissions – which occur during coal-fired power generation – will cease after the transition.

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.

According to current plans, 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, compared with today. This can contribute to an improvement in water pollution control compared to the current situation.

There are two 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 June 2023. EnBW was granted the partial permit for this in July 2024.
• The second part of the application was submitted in June 2025. The plant is expected to be commissioned in 2027.

Stuttgart Regional Council is the approval authority. The city of Heilbronn already made adjustments to the development plan for the site back in 2022.

EnBW currently estimates that a mid-three-digit million euro amount 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 east of the cooling tower.
• A district heating storage facility is also being built, which is also located in the area situated to the east of the cooling tower.

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 a reliable energy supply, it is essential to use the fuel as efficiently as possible in order to generate as much electricity and heat as possible from a given amount.
• By combining electricity and heat generation in the combined heat and power process, a CCGT plant can achieve a fuel utilization rate with an efficiency level of over 60% based on the current state of the art.

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 and in all applications.

Natural gas is therefore considered a temporary solution, not least because it has the potential to reduce greenhouse gas emissions compared to coal. It is important to remember that natural gas is only intended to be used for a transitional period.

The gas turbines are flexible and can later be converted to burn other gases such as green 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 according to current plans, which can further reduce greenhouse gas emissions. The switch to natural gas thus represents a transitional step culminating in a future energy supply with hydrogen.

The new combined cycle gas turbine (CCGT) plant supports the security of supply and can complement the fluctuating energy production from renewable energy sources. In the initial phase, the CCGT plant will provide electricity and district heating with lower CO₂ emissions than coal-fired power generation.

In the long term, the plant could contribute to a further reduction in CO₂ emissions if it operates using hydrogen as fuel. Based on current technology, a combined-cycle gas turbine plant produces lower emissions of certain air pollutants than older fossil-fuel-fired power plants.

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% based on current state-of-the-art technology. With this approach, CO₂ emissions can be reduced by about 50% compared to those produced by a coal power plant according to current plans. Switching from coal to natural gas is therefore viewed as a transitional step that can contribute to a reduction in greenhouse gas emissions.

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 would be used, provided that it is available in sufficient quantities. Starting around the late 2030s, adjustments would then make it possible to operate on 100% hydrogen.

The combined cycle gas turbine (CCGT) plant could offer the following advantages over the hard coal blocks that have been used until now in Heilbronn:

• The gas-fired plant can be controlled more flexibly than a coal-fired power plant and can therefore better compensate for fluctuations in wind and solar power.
• Combined heat and power (CHP) in the gas-and-steam (GuD) plant contributes to efficient fuel utilization. In the future, conversion for the use of hydrogen is possible, provided the technical and economic requirements are met.
• Natural gas produces lower direct CO₂ emissions compared to hard coal. According to current plans, emissions per kilowatt-hour of electricity generated could fall by more than 50% starting in 2027 – depending on the operating mode.
• According to forecasts, a reduction in air pollutants is expected: nitrogen oxide emissions (NOₓ) and sulfur oxide emissions (SOₓ) will decrease significantly, and particulate matter pollution will drop by about 44 percent; heavy metal emissions from coal combustion will be eliminated.
• With the decommissioning of the coal-fired units, the existing coal storage facility will be eliminated, thereby eliminating the dust and noise emissions previously associated with it.
• Traffic volume may decrease, as coal deliveries will no longer be necessary and additional transport for flue gas cleaning will largely be eliminated.
• The plant’s noise level is to be limited through modern noise reduction technology. In addition, coal-fired boilers, auxiliary steam generators, and flue gas cleaning systems will be taken out of service.