Stuttgart-Gaisburg combined heat and power plant generates reliable and cost-effective energy for Stuttgart’s district heating grid. In operation since 1950, the site was fundamentally modernized from 2017 to 2019. Today, three gas engines produce electricity and district heating in combined heat and power mode. Five natural gas-fired boilers are also available to generate district heating. With an additional heat storage facility boasting a capacity of 300 megawatt-hours, it plays an important role as a peak and reserve power plant for the Stuttgart / mid-Neckar district heating region. EnBW has set itself the goal of phasing out coal-fired power generation before the legally mandated phase-out, provided regulatory and economic conditions allow for it. That is why the site has been converted to use natural gas (known as a fuel switch): A much smaller gas-fired heating plant has replaced the primarily hard coal-fired combined heat and power plant, therefore enabling more efficient use of the fuel and lower emissions in the generation of electricity and district heating.
The year the plant was built
3 gas generators, 5 boilers, 1 heat accumulator (with 300 MWh capacity)
of gross electrical power
of power capable of being drawn off for district heating
Modernisation
The Gaisburg site has been generating electricity and heat for the Stuttgart region for over 70 years. Together with the combined heat and power plants Stuttgart-Münster and Altbach/Deizisau, it forms the Mittlerer Neckar district heating network and supplies over 25,000 homes, 1,300 companies, and 300 public facilities in Stuttgart and the region with heat.
Over the years, the generation structure of the Stuttgart-Gaisburg combined heat and power plant has been continuously changing. Today, the main function of the district heating network is to cover periods of high demand in winter and to serve as a reserve for the two larger locations of the district heating network. The most recent modernisation aims to ensure that the Gaisburg site can perform these tasks even efficiently and and with a lower environmental impact in the future. This ensures that citizens will continue to have a secure supply of district heating in the future.
In order to make the plant fit for the future in terms of the energy revolution the following components were used:
- gas-fired peak-load and reserve boilers for securing the Mittlerer Neckar district heating pipeline
- the integration of a heat accumulator in order to optimally supplement the use of the other generation plants along the Mittleren Neckar Line and the peak and reserve boilers
- a small gas-fired combined heat and power (CHP) plant
- the construction of new district heating stations
Technology
In a combined heat and power plant, useful heat energy is generated in addition to electrical energy in a coupling process. Because this is usually to be fed into a district heating network, combined heat and power plants are often located in urban conurbations with high heat requirements. The heat energy is routed directly to households and companies via district heating pipelines and supplies them with environmentally friendly and reliable district heating.
At the centre of the new combined heat and power plant plant is the boiler plant, which consists of several boilers. Water is heated to very high temperatures in a closed circuit by burning natural gas or, in exceptional cases, light fuel oil. The hot water is then passed through heat exchangers. They transfer the high temperature to the water circuit of the district heating network. Houses and apartments in Stuttgart and along the Neckar river are supplied with heat.
Through the newly built co-generation plant, the combined heat and power plant can also generate electricity in addition to heat: For this purpose, a combustion engine powered by natural gas drives a generator; the electricity generated can then be fed into the power grid. The heat of the engine and the exhaust gases is conducted through a heat exchanger and thus also used for the district heating network.
Approach
Project phases
This is where we inform you about important events and milestones relating to the modernisation of the Stuttgart-Gaisburg combined heat and power plant. You will find the latest information here on the timetable for the planning and approval process as well as the progress of the construction work.
Construction diary
April 2019: Completion
The entire plant was now complete.
March 2019: Building site facilities dismantled and outdoor spaces created
At the start of spring, the building site facilities were dismantled and work began on creating the outdoor spaces.
February 2019: District heating test operations underway
Test operations for district heating extraction and the district heating storage facility began.
January 2019: Fine-tuning for optimal efficiency
Once all the engines, boilers, pumps and heat exchangers had been commissioned, it was time to fine-tune everything – optimizing the combined heat and power plant so that it could operate with maximum efficiency.
December 2018: Test operations underway
Commissioning work on the CHP, the boilers and the electrical systems were completed and test operations began at the plant. The power plant was now being operated and tested by the future personnel.
November 2018: Calibration of the entire plant
As the heating season began, work was underway to commission the entire plant. Since, in contrast to summer, enough heat was now needed in the city to be able to operate the boilers and engines, all components were calibrated and tested together.
October 2018: Preparations for commissioning
The final stages of the process to commission the boilers and CHP engines were underway. On the construction site, all remaining tasks were being completed along with the clean-up work.
September 2018: Logos installed
As the final “major component,” the logos were installed, further increasing the visibility of the new site. There was also a touch of nostalgia involved because these logos originally adorned the facade of the former EnBW administration building on Kriegsbergstraße. They had been put into storage and could now be seen all lit up again.
August 2018: Engine and boiler tested
An important milestone was reached when the first engine and boiler were started up. In mid-August, the first engine was successfully started. Ignition tests were also successfully carried out on the first boiler. The combined heat and power plant was now generating electricity and heat for the first time – an important step that allowed further adjustments to be made to the district heating systems. The other engines and boilers were gradually commissioned in the weeks that followed.
July 2018: Pipelines completed
The pipelines were now in place and the power plant’s district heating pipe network was connected to the district heating grids. Commissioning work began in this area once the pipes and the heat storage facility had been filled. The pipes were firstly flushed and signal tests were carried out. This was followed by extensive adjustment work on the regulators and a series of test runs.
June 2018: Installation of gas engines completed
The gas engines were now installed and commissioning could begin. Just four months after being delivered, all installation work on the engines and auxiliary systems had been completed. Extensive signal tests, cleaning work and preliminary tests were now underway, leaving nothing standing in the way of starting the first engine in the summer.
May 2018: Completion of exterior facade work
Work on the buildings’ outer facade was completed, with the shape and look of the power plant now clearly visible. Only the district heating storage facility still had to be insulated before being clad in the same way as the buildings.
April 2018: Delivery of power transformer
The power transformer arrived on-site. The 110/10kV power transformer was the last major component to be delivered in mid-April and lifted onto its foundations. This meant that all large components were now on the construction site and could be connected. The transformer feeds the energy generated by the engines into Stuttgart’s 110kV grid.
March 2018: Heat storage facility growing
The heat storage facility was shooting up. The place where 11 million liters of district heating water are now stored was still an empty shell that was growing every day. This involved raising the storage facility slightly, rotating it and welding in a new shell segment. Now complete, the storage system is capable of storing 300,000 kWh of heat, the average annual heating demand of 40 residential buildings.
February 2018: Gas engines installed
In February, the time had come to install two of the three gas engines. The engines, each weighing 110 metric tons, were transported by flatbed truck from the port in Stuttgart to Gaisburg. Measuring roughly 10 meters in length, installing them in their precise position proved a complex task. A special rail structure was used for this purpose. Together, the three engines produce 30 MW of heat and 30 MW of electricity.
January 2018: Power plant taking shape
The power plant continued to take shape. While the buildings were slowly being enclosed by the steelwork and the installation of the roof and facade, work was underway to install the heat storage facility. The flue gas pipework was installed to enable the exhaust gases to be discharged from the engines and boilers via the chimneys later on, and the catalytic converters for purifying the exhaust gases were fitted in the gas engine building.
December 2017: Chimneys in place
In December, the most striking structures at the new power plant besides the heat storage facility were completed: the two 80-meter-tall chimneys. While in the smaller chimney (diameter: 3.40 m) the purified exhaust gases from the gas engines are discharged into three chimney pipes, the second chimney with a diameter of 3.90 m is used for the exhaust gases from the five boilers.
November 2017: Steelwork for the boiler house
Work on erecting the steelwork for the boiler house followed by the district heating transfer station was now underway. The gas engine building, meanwhile, was largely made of reinforced concrete. The facade of the entire power plant was then clad with box profile sheet metal.
October 2017: Boilers installed on the floor slab
The first machine technology arrived on the building site. Due to the size of the boilers, they were lifted onto the floor slab before the boiler house was even built. Final assembly and commissioning work was carried out once the buildings had been completed in 2018.
September 2017: Engine chambers built
Each of the three gas engines had to be located in its own engine chamber. The engine chambers are approx. 25 m long and approx. 10 m wide, providing enough space for the 20-cylinder gas engines and accompanying units.
August 2017: Floor slabs largely completed
The floor slabs for the main building were completed. While the walls of the building housing the gas engines were made of reinforced concrete, the other buildings were built using structural steelwork at a later date.
July 2017: Parallel construction phases
Different construction phases ran in parallel. While the drainage system, foundations and floor slabs were being built in some areas, the walls were already in place in other sections of the building.
June 2017: Reinforcement of foundations
The foundations were reinforced with steel prior to the concrete pouring process, as were the foundations for the heat storage facility, which will later be 39 meters tall.
May 2017: Shell construction work underway
For structural reasons, the power plant stands on around 600 driven piles, with work to produce them commencing in January 2017. Once they had been installed, shell construction work on the foundations, floor slabs and reinforced concrete walls could start in April and was progressing well.
12 April 2017: Official start of construction work for the new combined heat and power plant
In Stuttgart-Gaisburg, the starting signal was given for EnBW’s new combined heat and power plant. Baden-Württemberg’s Environment Minister Franz Untersteller, Stuttgart’s City Councilor for Construction Peter Pätzold, and EnBW’s Chief Technology Officer Dr. Hans-Josef Zimmer held the traditional groundbreaking ceremony. Almost two years after the first plans were presented in May 2015, the project was now underway. Upon completion at the end of 2018, it was set to take over from the mainly coal-fired combined heat and power plant.
1 December 2016: Investment decision made to build the new gas-fired combined heat and power plant in Stuttgart-Gaisburg
Almost one and a half years after the first plans were presented, the die was cast, with EnBW set to fundamentally modernize its power plant site in Stuttgart-Gaisburg at a cost of around 75.3 million euros. After the Board of Management had approved the necessary funding, the committee on EnBW’s Supervisory Board responsible for overseeing the project did the same.
The decision taken meant that the project remained on schedule, with EnBW expecting approval in line with immission control regulations from Stuttgart Regional Council in the weeks that followed. Construction work could then begin. Following a construction period expected to last two years, the new turbines were scheduled to be placed into operation at the end of 2018 or the beginning of 2019. They consist of four components: a gas heating plant for the district heating, a district heating storage facility, a gas-fired plant for electricity and heat generation (combined heat and power) and a district heating station. Compared to the interim plans revealed back in February 2016, only minor changes were made to the position of individual building sections in the detailed plans.
19 July 2016: Modernization of Gaisburg CHP discussed on the City of Stuttgart’s Committee for Environment and Technology
The public review of the approval documents at Stuttgart Regional Council and the City of Stuttgart’s Office for Environmental Protection gave the general public an opportunity to raise objections to the modernization project. The purpose of the meeting, which was also open to the public, was to discuss any objections raised. The four objectors present (Joseph Michl and Roland Kugler from the State Nature Conservation Association and the three private objectors Manfred Niess, Harry Block and Gudrun Vangermain) raised objections on conservation grounds (concerning wall lizards and bats, among others). They also voiced concerns about the higher nitrogen oxide emissions compared to the current power plant. In addition, there were demands for an overall district heating concept. The higher nitrogen oxide emissions – which are mainly attributable to the base-load operation of the gas engines and thus a higher capacity utilization rate compared to the current power plant – were discussed on account of their relevance to the approval process. As regards the maximum permissible limits, an application for reduced limits had already been submitted for the new plants in view of the initial pollution level in Stuttgart. The demands for an overall concept for the district heating supply in Stuttgart were not relevant in the context of discussions on the approval process under immission control regulations.
12 July 2016: Modernization of Gaisburg CHP discussed on the City of Stuttgart’s Committee for Environment and Technology
EnBW’s plans to modernize the combined heat and power plant in Stuttgart-Gaisburg were one of the items on the agenda of Stuttgart City Council’s Committee for Environment and Technology on 12 July 2016. The background was a request submitted by the Greens and the SPD, who were calling for an overall concept for the district heating supply in Stuttgart. As part of this, an explanation was also sought as to why a larger combined cycle gas turbine (CCGT) plant couldn’t be built instead of a combined heat and power plant that runs on gas engines. Besides presenting the latest modernization concept for Stuttgart-Gaisburg, EnBW representatives explained that such a plant would not be profitable due to the current economic conditions.
18 and 19 May 2015: Events as part of the early public consultation process
The project to modernize Stuttgart-Gaisburg combined heat and power plant met with a largely positive response at the events marking the start of the dialogue with the public. EnBW put a high value on initiating this early dialogue: Beyond the new legal requirements laid down in the Environmental Administration Act of the Federal State of Baden-Württemberg (UVwG), we wanted to provide comprehensive information early on, engage in discussions and listen to suggestions.
In mid-May, we held a special event to present the modernization concept to the committee responsible for such matters at Stuttgart City Council and to interested associations and institutions. More than 100 residents and interested citizens attended the public event at the combined heat and power plant to learn about the planned modernization project, but they equally took advantage of the opportunity to ask some critical questions. EnBW employees also explained the construction project plans during guided tours of the power plant site and around the existing facilities
Documentation on the early public consultation process (only in German)
Time-lapse of the construction
Frequently asked questions
The power plant complex in Gaisburg – consisting of one coal-fired and several gas-fired units for heat and electricity generation – was technically outdated. The modernization project was carried out to bring the facility up to current standards for a safe and efficient supply.
Our combined heat and power plants in the district heating network supply around 25,000 homes, 1,300 companies, and 300 public buildings via a 260 km district heating network along the Neckar valley from Plochingen via Altbach/Deizisau and Esslingen to Stuttgart.
District heating enables a centrally generated heat supply for many households at the same time. It provides a continuous and predictable supply and can be a cost-effective solution in the long term. In densely populated areas such as the Stuttgart Basin, a shared heating network also reduces the need for individual heating systems in buildings.
The modernisation of the combined heat and power plant at the Stuttgart-Gaisburg site could offer the following advantages:
- The new gas-fired plants can be operated more flexibly than the previous ones and are designed to reduce emissions such as CO₂ compared to the older plants. As a result, the modernization can contribute to a more efficient electricity and district heating supply.
- The Gaisburg site remains a central part of the district heating network known as the Mittlere Neckar Line, which connects combined heat and power plants and customers along the Neckar river to ensure a reliable district heating supply.
- With the modernization, the existing coal storage facility will be phased out due to the planned use of natural gas. The space freed up as a result opens up potential for urban development at the site in the medium term.