Research News
Micro gas turbines burn a variety of fuels efficiently, produce fewer harmful emissions and require relatively little servicing. Their advantages are particularly evident when large amounts of heat are required. Photo: DLR
Mini power stations for heat and electricity
Whether they are used in hospitals, industrial plants, vineyards, breweries, kindergartens or single-family homes – mini power stations that produce heat and electricity close to consumers are an efficient, low-emission supplement to large power plants. The Stuttgart-based German Aerospace Center (DLR) and the EnBW Energie Baden-Württemberg AG have now launched a joint research project to promote the development of such decentralised power stations. The aim is to produce heat and electric power using small natural gas-based power stations equipped with micro turbines. Axel Widenhorn heads the gas turbine working group at the DLR Institute of Combustion Technology.
Widenhorn and his team are conducting research into so-called micro gas turbines, which form the heart of these mini power stations. Although their capacity can range from just a few kilowatts to a maximum of 500 kilowatts, the basic technical principle behind them is the same. A hot compressed gas jet drives a turbine just a few centimetres in size that turns a generator on the same shaft to produce electricity. At the same time, the thermal energy in the hot exhaust gas is used by a water-heat exchanger or other system. The plants embody a principle called cogeneration. “But with a micro gas turbine you are not limited to producing warm water alone. You can also use the energy in the exhaust gas to produce cold,” Widenhorn explains.
The micro gas turbine features a simple design and requires little servicing. It can use a variety of fuels, including natural gas, biogas and heating oil. Since the fuel is continuously burnt, the mini power plant produces substantially fewer harmful emissions per kilowatt than a large power station. The hot gas jet that drives the micro gas turbine is formed in the combustion chamber. The DLR scientists have developed a glass combustion chamber in order to analyse the combustion processes by means of laser measurement technology and to further optimise the system. Currently, up to 90 percent of the burnt fuel can be converted into energy. If natural gas is used, the electrical efficiency of the micro gas turbines, at 30 percent, is still lower than that of conventional gas engines, which achieve levels of 40 percent. But if biogenic gases are burnt, the micro gas turbines achieve the same, or slightly better, efficiency.
The real potential of the robust micro gas turbines comes into play when the emphasis is on producing heat, says Widenhorn. Larger micro gas turbines, designed for industrial application, are already in operation in Germany. Smaller power stations the size of household boilers are being tested and could be marketed in just two years. Soon single-family homes equipped with their own cellar power station could be producing inexpensive, environmentally friendly heat and electricity.
