The joining of two major district heating networks after the fall of the Berlin Wall created what is said to be Europe’s largest decentralized energy system. Now, the city’s energy agency aims to stimulate the growth of more cogeneration capacity, including micro -CHP plants and plants fuelled with biogases 
– writes Rosalie Schaefer.

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Saving carbon dioxide with CHP technology – Senator for the environment, Katrin Lompscher, BEA managing director, Michael Geißler, and chairman of the board of BVG, Andreas Sturmowksi, at the commissioning of Berlin’s most powerful micro-gas turbine

Berlin is a vivid and vibrant metropolis full of energy. Some 3.4 million people live in more than 1.9 million households in Germany’s biggest city. Besides industry and construction engineering, it is primarily enterprises that shape the city’s economic structure. Therefore, Berlin needs lots of energy – households, transport, industry, trade and the service sector consume about 70,000 GWh per year.

Most of the energy is consumed by services and private households. Electric power consumption makes up approximately 15% of the total energy consumption of the average household, and some 5.9 tonnes of carbon dioxide per inhabitant, per year are released into the atmosphere by Berlin’s energy use.

Berlin is however, an outstanding example of the promotion of cogeneration by a city. The capital is already an important location for research, and the production of innovative cogeneration technologies. Berlin also takes a leading position in the appliance of combined heat and power (CHP).

The combined generation of heat and power has a long history in Berlin. When its western part was cut off from the rest of the Federal Republic from the late 1940s, it found itself fighting two forms of cold war simultaneously. With only limited primary energy available, the West Berlin authorities needed to make the most of what they had, and cogeneration was an obvious mechanism. The result was a huge system of district heating. Meanwhile, in the communist-run parts of the city, excess heat from factories was being used to heat surrounding apartment blocks. With the fall of the wall in 1989, the two systems were linked up, creating western Europe’s largest district heating system – some 1500 kilometres of pipes, connected to 10 CHP power plants, bringing heat to public and residential buildings.

A further development of the pipework is about to be realized, including the replacement of fossil fuels with biomass. Additionally, more than 300 cogeneration units are providing decentralized heating systems.


About 27% of all buildings in Berlin are connected to the district heating grid. The steel pipes of the grid are installed in the ground at a depth of approximately 90 centimetres and are heavily insulated. About 326,000 cubic metres of water circulate in Berlin’s district heating system. Buildings with existing collective heating systems (central heating) can easily be connected to the grid: A small district heating substation is installed in the basement which is not larger than a washing machine. Individual heating systems (self-contained central heating) in multi-family houses have to be converted to a collective heating system.

Various technologies are used in Berlin to produce heat through CHP. The energy supply company Vattenfall combines gas with steam turbines in its five combined cycle gas turbine (CCGT) power stations. The exhaust gases are routed through a waste heat boiler to generate steam which is used to drive a steam turbine that generates additional electricity. The residual energy contained in the steam when it exits the turbine is used to produce heat.

Operation of the power station is controlled by the heat demand, i.e. the station is ‘heat-led’. Thanks to CHP, this mode of operation enables a utilization of 90% of the energy contained in the fuel, as in the state-of-the-art CHP plant Berlin-Mitte, which is located on the banks of the river Spree near the city centre. Accordingly, just 10% of the energy is lost. The useful energy utilization in the other CHP plants is also good: 85% in the Moabit, 87% in the Klingenberg and 80% in the Reuter West CHP plant. If just electricity were generated, the loss would be about 62%.

In coming years, the Vattenfall group will invest more than €1000 million to build new power stations or modernize existing ones in Berlin. At the same time, these activities of Vattenfall support the government of Berlin in its effort to reduce carbon dioxide emissions in the city by more than 40% by 2020. Vattenfall intends to reduce its own absolute carbon dioxide emissions by more than half compared to 1990. This means an additional reduction of about one million tonnes of carbon dioxide annually by 2020.

In its plans to replace the Klingenberg and Lichterfelde CHP plants, the company relies on natural gas and biomass as fuel. Two biomass power plants (150 MWth) are to be erected at the location of the Klingenberg CHP plant. In addition, combined cycle gas turbine (CCGT) plants are planned (450 MWth). Vattenfall is currently examining the premises of the two old CHP plants Klingenberg and Lichtenberg at Rhinstraße as possible locations of the CCGT plants. The more than 40 year-old CHP plant Lichterfelde is to be replaced by a CCGT power station by 2014. And, finally, Vattenfall is planning to shut down the Reuter coal-fired CHP plant by 2020.

Apart from Vattenfall, BTB Blockheizkraftswerks-Träger and Betreibergesellschaft mbH Berlin, Fernheizwerk Märkisches Viertel GmbH and RWE are also operating CHP plants in Berlin.


In addition to large-scale, central CHP stations, decentralized CHP is becoming ever more important in Berlin.

Due to special support programmes by the federal government, 50 new cogeneration units have already been added since 2009. Decentralized combined heat and power is a versatile, flexible and environmentally friendly solution for intra-urban areas.

The field of application of decentralized CHP includes the supply of heat and power to single-family and multi-family houses, as well as entire residential quarters and streets. However, block heat and power plants are becoming ever more popular with industry and commerce, and the service sector such as hospitals. The energy sources used include natural gas, diesel fuel and biogas, which is converted into bio-natural gas and fed into the natural gas distribution system.

The advantage of decentralized solutions is obvious. Short and hence low-loss heat transport routes improve efficiency. Heat or cooling and power are produced where they are consumed and this enables the optimal use of fuels with minimal carbon dioxide emissions. The structure of the heating systems used in Berlin shows that there is substantial potential for increased use, primarily in the field of mini-CHP and micro-CHP. The regional gas supplier GASAG estimates that some 200,000 households might be provided with so-called ‘power-generating heating systems’ with an output of less than 5 KWe, in addition to other possible measures.

These smallest plants are not larger than a fridge and fit into any boiler room without a problem. In field trials, GASAG has tested an appliance it has developed in cooperation with a manufacturer from New Zealand. The ‘Whisper Gen’ has an especially low-noise Stirling engine that also requires little servicing. As the pilot phase has ended, the device is now to be launched on the market. GASAG will soon sell the first units and has designed a dedicated marketing scheme. Other manufacturers such as Remeha also have developed similar appliances which will be available soon.

Even today, larger plants are installed in many intra-urban areas where they reliably supply heat, cooling and power to flats, shops, offices and business enterprises. Forty-eight block heat and power (BHPP) plants of that size, some with trigeneration technology, are operated by Berliner Energieagentur (BEA), a modern energy service company located in Berlin and aiming to promote the efficient use of energy with innovative projects to reduce energy costs and carbon dioxide emissions. Moreover, BEA is involved in the development and practical application of advanced technologies in the field of micro-CHP.

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In 37 places in Berlin, 48 block heat and power plants operated by Berliner Energieagentur supply heat and power

The eco-power supplier Lichtblick also is planning to enter into the CHP technology and launches a so-called ‘home power station’ together with the car maker Volkwagen. In contrast to most of the other block heat and power plants it is ‘power-led’ and intended to be networked to create a large virtual power station with up to 100,000 other basement power stations. Lichtblick intends to start realising its vision in Hamburg and Hannover and, in particular, Berlin.

Meanwhile, a large number of BHPP manufacturers and units are available in Germany. The most common types are gas-powered plants, which in principle are nothing other than spark-ignition or compression-ignition engines which we all know from motor vehicles. In Berlin, BHPPs with fuel cells are also being tested. An example of this is the company ‘inhouse engineering’ in Berlin that focuses on the development of stationary fuel cell systems and on building automation and central building control systems. This includes complete solutions in the form of fuel cells in small BHPPs which are used to supply energy to buildings. The BHPPs use energy sources such as natural gas or hydrogen to produce energy efficiently.

In March this year, inhouse engineering joined as the fourteenth member of Berliner NetzwerkE. The network brings together partners from different fields: at Berliner NetzwerkE, energy producers and technology enterprises meet companies that apply energy. The network is aiming to strengthen companies in the energy efficiency and renewable energy industries in the city.


A number of laws help to profitably operate CHP plants, in particular the act on combined heat and power generation. As amended on 1 January 2009, the act provides that mini-CHP plants of up to 50 KWe will receive an extra fee of 5.11 cents/KWh for the entire electric energy generated in a BHPP for ten years after commissioning. This also goes for operators generating electricity for their own purposes, and not feeding it into general distribution grids. Moreover, BHPPs with an output of less than 2000 KW and an annual efficiency in excess of 70% are exempted from the tax on mineral oil and the electricity tax.

The amendment of the act has affected a considerable boost in the sales of small CHP plants. Additional incentives have been provided by an investment scheme set up by the federal government which, however, has been suspended due to the budgetary crisis this year. These schemes have caused more than 3000 new CHP plants to be connected to the grid all over the nation  – 50 of which are in Berlin.

All this adds up to a 30% share of cogeneration in the local heating and a 42% share of cogeneration in the local electricity market, while the nationwide target is only 25%.

‘Although Berlin already met that target, the city’s potential is not maxed out yet,’ says Michael Geißler, the director of Berliner Energieagentur. ‘It is possible to increase the CHP percentage of power consumption up to 60% within the next 10 years.’

By 2020, almost 10,000 small CHP plants might be installed and operated profitably, says a projection in the current Energiekonzept 2020 of the Senate of Berlin.


Berlin’s aim is to raise public awareness for this efficient way of generating heat and power, and to create pilot projects with innovative technologies.

Together with the cooperation partners Gasag, Vattenfall and the senate department for health, the environment and consumer protection of Berlin, the Berliner Energieagentur initiated the campaign ‘KWK Modellstadt Berlin’ (CHP Pilot City Berlin; The initiative defines CHP as a key technology for a climate-conscious future. The initiative aims to inform people living in Berlin about the technology and its advantages and make a substantial contribution to extending the share of CHP. Berlin is systematically positioned as a CHP pilot city for other regions as well, not only in Germany.

KWK Modellstadt Berlin won one of the COGEN Europe recognition awards in 2009 for its efforts to show how to promote cogeneration in an urban environment, and how to combine it with other innovative technologies. KWK Modellstadt was also one of the prize winners of the national contest ‘365 landmarks in the land of ideas’ in 2009. The campaign has recently focussed on launching four innovative CHP pilot projects, the first of which has been the installation and induction of a micro-gas turbine at Germany’s largest municipal public transport company (BVG) in May 2010.

The natural gas-fuelled micro gas turbine with an output of 50 KW electric and 110 KW thermal is Berlin’s first micro-gas turbine of that size. The small engine – gas turbines are usually operated in large power stations – and consist of a compressor, a heat exchanger, a combustor and a turbine with generator. All rotary parts are supported on a shaft with air bearing that revolves with a speed of up to 96 000 rpm. The micro-gas turbine was funded and erected by BEA, subsidised by Berliner Energiefonds. BEA also is responsible for efficient and trouble-free operation and all repair and maintenance work in the next ten years.

The plant is used in BVG’s 10,700 m² workshop, where underground vehicles are not only repaired and serviced but also cleaned in a washing plant. Due to their specific field of application, micro-gas turbines are an innovative solution in particular for buildings in which technological processes are associated with high water temperatures. There is a total of more than one thousand industrial firms in Berlin and hence a large potential for the technology.

The heat produced by the micro-gas turbine, in addition to an existing heating system, covers the annual base load of the main underground railway workshop. The CHP electricity generated in excess is fed into the public grid. The use of the micro-gas turbine reduces the company’s carbon dioxide emissions by 280 tonnes, a quantity corresponding to the annual carbon dioxide output of about 30 households in Berlin.

Until now, CHP fed with renewable energy sources has not been widespread and implemented. That is why the Berliner Energieagentur also initiated the ‘CHP goes green’ project. The project aims to increase the use of renewable energy sources as well as the share of renewable energy sources within CHP. In the project, a biogas BHPP with an output of 240 KWe is implemented in a Berlin fire station. Among the eight project partners are Cogen Europe, Rhonalpénergie (France), the Climate Protection Agency Hannover (Germany) and the Grazer Energieagentur (Austria).

Berlin’s energy supply already today relies on CHP to a remarkable extent. This provides a strong base for the State of Berlin to meet the nationwide requirements for the prevention of the emission of greenhouse gases in the long term.

Rosalie Schaefer is with Berliner Energieagentur GmbH, Berlin. Germany. Email:


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