Change in the air
In its first phase, Siemens and its partners tried to figure out how renewable energy generators such as solar panels and windmills influence the stability of the distribution grid, and how e-mobility can be used in a rural community. Now, during the IREN2 project, the questions to be answered are even more serious. In Germany, the energy transition is in full swing. In 2015, already 30 percent of the country’s electricity was produced from renewables, and the trend is as clear as in most industrial countries: The share of centrally installed, large-scale fossil power plants will be phased out and replaced by renewable, mostly decentralized, installed generation sources. By 2050, 80 percent of the electricity generated in Germany is to come from renewable sources. That produces new challenges.
“In terms of the current state of technology, we still face a major challenge,” says Torsten Sowa of RWTH Aachen University, a partner in the Wildpoldsried research project. “That’s because power systems that use renewables are not capable today of providing so-called system services, such as making reactive power available to maintain the voltage in higher-level networks. In other words, we need a new solution if we want to achieve our target for 2050.” Smart grids are needed to ensure that distributed power systems can constantly supply sufficient electricity to consumers, even as electricity production fluctuates with the weather. Unlike today’s grids, such intelligent networks will be able to balance power generation and consumption while distributing electricity, and they will do so all the way to the end-consumer level.
So far, nuclear and coal- or gas-fired power plants still play an immensely important role. They are indispensable for ensuring stable frequency and voltage. In case of a blackout, the grid is powered up “from the top” with the help of a big power plant. But what will happen in ten or twenty years, when most of the big power plants will be offline? “We must make it possible to ‘unite’ 100 small power plants into a unit whose power the network operator can use,” says Markus Reischboeck. One of the main challenges will be to convert the distribution grids into systems that are able to transport power actively, especially in case of a blackout.
While keeping voltage and frequency in the desired range, the Wildpoldsried island grid must also provide services for grid stability to the main operating grid, serving as a so-called “topological power plant” that supplies ancillary services. This will allow the local grid to replace conventional power plants for a short period. To this end, the control systems have to provide reliable renewable generation forecasts and intelligent operations schedules, and reliable real-time operational data.