Thermal power plants
Worldwide unique technology platform for micro gas turbines
CHP plants can generate decentralised energy not only with engines, but also with micro gas turbines. This has the great advantage of producing power and heat efficiently and flexibly where they are needed, thereby reducing losses during transport to a minimum. In order to test and further develop CHP plants based on micro gas turbines under real application conditions, the Institute of Combustion Technology at the German Aerospace Center (DLR) is using a new test plant: the "Decentralised Energies" technology platform. The engineers have already successfully commissioned a first gas turbine in the newly built laboratory.
At present, operators mainly use small cogeneration plants with gas engines to generate power and heat decentrally. This is due to the still slightly higher electrical efficiency and the advanced engine technology compared to micro gas turbines. However, these offer considerable advantages in terms of pollutant emissions, longer maintenance intervals and, in particular, fuel flexibility: Neither fluctuating fuel qualities nor biogases, syngases or hydrogen pose any major challenges for micro gas turbines with a suitable combustion chamber system. This means that they can in principle be used in private, commercial or public buildings as well as in small and medium-sized businesses.
Technology platform tests fuel- and load-flexible micro gas turbines
Within the research project TPDE, short for "Construction and commissioning of a development platform for technologies and systems for decentralised energy provision based on micro gas turbine-based cogeneration plants", scientists have developed and built a test platform and equipped it with new simulation tools and sensors. Here, they can test new supply concepts for their suitability for everyday use and develop concrete solutions immediately if challenges arise.
The test plant, the only one of its kind in the world, offers bays for several micro gas turbines of different manufacturers and outputs, such as turbines in the range of 4 kilowatts of electrical output for single- and multi-family homes, up to 300-kilowatt micro gas turbines for commercial facilities or hospitals.
The technology platform (TPDE) offers an extremely flexible test environment. On the one hand, researchers can investigate individual components, such as the combustion chamber system, in detail. The appropriate measurement technology, the necessary probes and a visually accessible combustion chamber are available for this purpose. It would also be possible to investigate ceramic turbines here. The Fraunhofer Institute IPK is currently working on this type of turbine with other industrial partners in the BonoKeram project.
On the other hand, the teams of scientists in Stuttgart are focussing on investigating CHP plants with micro gas turbines in real long-term operation. One of the aims here is to increase the flexibility and partial load capacity of the turbines. Furthermore, the entire power plant, including the necessary operating and control strategies, can be analysed and optimised during continuous operation.
Technology platform investigates combustion processes
In order to thermodynamically analyse and evaluate individual plant components of the micro gas turbine and the entire plant, pressure ratios, temperatures and flow conditions must be measured. This allows optimisation potentials to be identified. A homogeneous temperature profile at the outlet of the combustion chamber is essential for both maximum turbine efficiency and optimum component lifetime.
In addition, it is important to analyse the combustion processes within the combustion chamber. This makes it possible to assess the impact of alternative fuels. Comprehensive knowledge on this under real conditions has been unavailable up to now. In order to better understand the processes in detail and optimise the combustion chamber system, micro gas turbines can be equipped with a visually accessible combustion chamber in the TPDE laboratory. In addition, the engineers have constructed a so-called long-pulse laser. This measures the composition of the gas and the temperature. Water-cooled probes determine the material temperature at particularly critical points. Additional special probes analyse and evaluate the exhaust gas emissions at the combustion chamber outlet. A thermographic camera is also used to detect thermal loads on highly stressed components. This can increase material life and reduce maintenance costs.
Innovative simulation tool supports power plant systems
Currently, developers and manufacturers have various simulation programs at their disposal to dimension and calculate systems consisting of CHP plants, consumers, storage and other components. Often the level of detail of the available data is not sufficient and the informative value of the models is limited. For example, there are no modules to take into account the influence of the heating circuit and ambient temperatures and to map mutual dependencies between the heating temperatures and the CHP operation. Depending on the mode of operation, frequent start-up and shut-down manoeuvres may appear advantageous, which cannot be represented by simple models.
For this reason, the scientists have developed a new, thermodynamic and modular simulation tool based on an existing tool. This enables them to design entire power plant systems and create an overall thermodynamic model. In contrast to available tools, the simulation takes into account relevant dependencies, such as the influence of heating circuit and ambient air temperatures on the electrical and thermal efficiencies of the CHP plant. Interaction with external power and heat generators as well as heating/cooling networks is also possible in order to represent real site-dependent conditions. Dynamic effects such as start-up, heating and cooling processes are also included.
Mobile gas turbine in a practical test
The first plant to go into operation in the TPDE laboratory was a "mobile" gas turbine from the Institute of Combustion Technology. This is a micro gas turbine with an electrical output of 100 kilowatts. The turbine, which runs on natural gas and syngas, is equipped with an innovative combustion chamber system developed at the institute. After successful test runs at the TPDE, the mobile turbine is now on the premises of the KIT (Karlsruhe Institute of Technology). Scientists will commission it there in the context of Energy Labs 2.0 as part of a large plant network using a syngas as fuel.
Last updated: 20.07.2022