By 2035, the German government plans to expand onshore and offshore wind farms, thereby more than doubling their capacity to 140 gigawatts. At the same time, conventional power plants are increasingly being shut down which presents a problem because power plants keep the grid stable. They do this by compensating for sudden increases or decreases in power consumption and feed-in so that there are no outages and our sockets always supply 230 volts. However, wind farms could provide a simpler, more environmentally friendly and cheaper solution for this task in the future.
Are wind farms the new power plants?
Wind farms could play a key role in a successful and secure energy transition by supplying renewable energy and, as alternative power plants, simultaneously keeping grids stable.
Are wind farms the new power plants?
Wind farms could play a key role in a successful and secure energy transition by supplying renewable energy and, as alternative power plants, simultaneously keeping grids stable.
Power plants can manage
A power plant works like cruise control in a car. If the vehicle reaches an incline, it needs more power to avoid slowing down, so the cruise control accelerates and keeps the speed constant. In the power plant, this is done by the power regulator. If more power is suddenly drawn than the power plant's turbine delivers, the difference is compensated from the flywheel mass of the generator-turbine set. The machine initially slows down but the regulator notices this and puts more steam on the turbine to maintain the voltage, and this is also true in the reverse case. The power regulator has about ten seconds to make this adjustment, during which the power does not drop thanks to the momentary reserve provided by the kinetic energy of the machines. The potential contribution of a power plant to grid stabilization generally depends on its proximity to the transmission grid.
Supply and demand for wind turbines
Wind turbines are not operated like conventional power plants since the amount of power they can feed into the grid depends on the available wind. When there are lulls, other generators have to take over and, in the future, if there is a supply surplus, the wind energy will be stored – either as heat (power-to-heat) or by means of electrolysis as hydrogen (power-to-gas). Fuel cells or gas-fired power plants can convert some of this gas back into electricity, thereby making the surplus usable. The expansion of wind energy will therefore be coupled with a considerable expansion of heat-storage systems and electrolysis plants. The planned construction of additional gas-fired power plants to stabilize the grids, on the other hand, is an unfortunate compromise that will make it more difficult to achieve gas independence and reduce CO2 emissions. Couldn't wind plants in the future compensate for load fluctuations with the help of their energy storage systems, together with fuel cells for reverse power generation? This concept is being researched by cooperative projects between industry and universities, in which Maschinenfabrik Reinhausen is participating.
„With wind turbines as power plants, we could keep the grids stable even as volatility increases.“
Achieving more with less effort
What is currently still a hurdle could be just the right lever for this challenge: Due to the decentralized location of wind turbines far from the core grid and their comparatively low output, they are not yet able to respond quickly enough to load fluctuations given the current state of technology. But this is precisely what will mean a large-scale supply of power reserves in the future, which will also enable faster reconstruction after a blackout. The required close connection to the grid core could be achieved with the help of DC grids and coupled wind turbines with a regulating head station which keeps the grid stable by using wind power and energy storage for instantaneous reserve and control power. In this way, wind turbines would be on a par with conventional power plants, and their conversion would even be cheaper and easier to implement than building new gas-fired power plants. This concept will soon be tested in field trials and may become a key technology in the energy transition.
Sponsored projects
In the Copernicus project ENSURE of the German Federal Ministry of Education and Research, new structures for the future power grid are being investigated. MR is participating in this project with studies on DC grids for connecting large-scale plants of renewable generators, as well as with the development of power electronic converters.
In the AC2DC project funded by the German Federal Ministry of Economics and Climate Protection, the suitability of 20 kV AC cables for DC grids of up to 60 kV is being investigated. Such grids could be a possible alternative to 110 kV distribution grids. MR is participating with investigations and developments on technical feasibility, including the specification of technical requirements for DC distribution grids and installations on DC distribution grids. Field testing is planned for a follow-up project.
