Renewable sources can provide stable power, German study shows

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Results from the German research project Kombikraftwerk 2 (Combined Power Plant 2) have shown that a nationwide power grid could be stably operated even if it were fed only with electricity from renewable sources, project partner Siemens has reported – indicating that one of the major technological challenges in transitioning to renewables, namely balancing the fluctuations that are caused by wind and solar power, may soon be solved.

Further, the project has also demonstrated that solar, wind, and biogas power plants can contribute to system stability if they are connected with one another to form an intelligently controlled power plant.

In addition to wind, solar, biogas, and geothermal facilities, hydroelectric plants, pumped storage electrical power stations and power-to-gas facilities also played a key role in the project scenario. Surplus electricity was used for the electrolytic generation of hydrogen, which was combined with CO2 that had been separated from the exhaust of fossil fuel power plants to form methane and then fed into the public gas network. Gas-fired power plants used this methane to generate electricity whenever bottlenecks arose. On the basis of weather data and electricity consumption data, the simulations calculated the power output and the demand for every hour of the year in great detail and determined how electricity had to be transmitted in the grid.

Grid frequency and voltage must be kept stable in order to prevent power outages. As a result, power plants must provide a certain amount of reactive and controlling power. To maintain such power reserves in the scenario, the settings of the wind power rotors were adjusted to reduce output and the inverters that feed electricity into the grid were used to limit the power generation of the photovoltaic facilities. The simulations and the field test showed that a combined power plant consisting of renewables, gas turbines, and storage systems can provide the required level of output within seconds.

Besides Siemens, the partners in the 3-year Kombikraftwerk 2 research project were the German Meteorological Service, Enercon, the Fraunhofer Institute for Wind Energy and Energy System Technology (IWES), Ökobit, Leibniz University in Hanover, SMA Solar Technology, SolarWorld, and the German Renewable Energies Agency.

Picture – Copyright: Fraunhofer-Institut für Windenergie und Energiesystemtechnik