Ronde 8 van het programma ‘Take-off WO – fase 1: Haalbaarheidsstudies’ is open voor aanvragen. Dit programma is gericht op het stimuleren en ondersteunen van bedrijvigheid en ondernemerschap vanuit de wetenschap.
The transition to sustainable energy sources has the unpleasant side effect of making electricity grids more unstable. How to ensure that our power supply can take a hit? Those who live in Amsterdam may still remember the morning of 17 January 2017, when half the city was without electricity for hours. There were no trains, trams or metros, the MC Slotervaart had to postpone all operations, and the 112 emergency room was overloaded by all the calls. All this was caused by a single defective component of a high-voltage substation. Fortunately, such defects rarely occur. "The Dutch electricity grid is one of the most reliable in the world", says Dr Marjan Popov of the Delft University of Technology. Nevertheless, Popov and his team are researching through a AES-supported project how the network can be improved. Because it may be extremely reliable now, but without improvements that will no longer be the case in a few years. That has everything to do with our transition to sustainable energy. According to European guidelines, 20 percent of our energy must come from sustainable sources by 2020. By the end of 2016, the Netherlands had only achieved 5.9 percent. The Netherlands could make significant gains by replacing coal-fired plants with wind turbines and solar panels. That would be great for the environment, but a challenge when it comes to the reliability of the electricity grid.  Stable and verifiableThe best part of coal-fired power stations is that they provide a stable and verifiable amount of energy. In power plants, this energy is converted into electrical energy. If you want more electricity, you will need to burn more coal. This means that you can always adapt the supply to the demand. Due to the unpredictable Dutch weather, you never know exactly how much energy you will generate with wind and solar energy. This makes it much more difficult to maintain the balance between input and output in power stations. "If we don't do anything, the increasing uncertainty will result in a decreasing reliability of the system. We may then even reach the point that the security system no longer works properly," Popov said.  So this system must be improved. How to do that? First of all, it is crucial to constantly monitor the amount of energy everywhere, so one can intervene in time if something goes wrong. "If, for instance, the grid is overloaded somewhere, this may not take too long," Popov said. That is why he and his team work on devices that continuously measure the voltage, current and frequency at strategic locations. Such devices are called Phasor Measurement Units, or PMUs. Since PMUs use GPS, the exact time of each measurement is known, and the situation can accurately be analysed in different places at the same time. This ensures one always knows immediately whether a cable is overloaded somewhere. The next question is: how can such an overload be fixed? You can hardly demand that the wind stops blowing or that the sun stops shining. Fortunately, in such a situation, we can count on the support of our neighbouring countries. Cables to Germany, Belgium, Denmark and Great Britain can introduce feed energy in case of a shortage and remove in the event of a surplus. "Preventive measures have already been taken to ensure that we can distribute energy. That, for example, is the reason DC cables are used for the connections with Norway and Great Britain,” according to Popov. "We are now focusing on corrective measures: make sure that the energy is immediately distributed if something happens." In addition to the PMUs, computer algorithms also play an important role in the Delft research. If, for instance, the PMU data show that there is an overload somewhere, algorithms can immediately determine which part of the grid needs to be shut down to save the rest of the system. "The algorithms are now ready for some 75 percent," Popov explained. From second to secondOf course, you can't just change the Dutch electricity grid with PMUs and algorithms without first testing them. Therefore, Popov and his PhD students Matija Naglic and Ilya Tyuryukanov and postdoc Jose Chavez Muro are developing simulations with which they test the future network. A problem when simulating an electricity grid is that it requires a lot of computing power. "A normal computer will easily need twenty minutes to simulate one second," Popov explains.  That is why the researchers do not use an ordinary computer, but a supercomputer. The man-sized device combines the processing power of no fewer than 56 processors. The supercomputer is connected to a PMU and a regular computer with simulation software. The system is a so-called Real Time Digital Simulator (RTDS): a technology which allows the second-to-second analysis of a complete electricity grid. Only with such a real-time simulator one is able to see the direct consequences of a sudden change in the grid, such as the failure of a power station. You can immediately see which cables are overloaded, for example, and how to divert the current to rectify this overload. "This is the only supercomputer in the Netherlands with RTDS technology," Popov said.  Divided into isletsThe researchers from Delft work closely together with partners such as the national meteorological institute VSL and TenneT, the company that engages in the transport of electricity in the Netherlands. "It is up to us to eventually put the results into practice," says Jorrit Bos, network strategist at TenneT. "Ultimately, we want to be able to divide the network into a kind of islets that balance themselves. With the advent of new energy sources, everything becomes more dynamic and less well-organised, so it is very important that we can keep the grid afloat this way." It is not just the electricity grid that needs to be adapted to withstand the sustainable energy revolution. Together with other projects, Popov's project is part of the NWO research programme Uncertainty Reduction in Smart Energy Systems (URSES). This programme is dedicated to developing smart systems that prevent renewable sustainable sources from causing disruptions due to their unpredictability. This will ensure that we can take full advantage of wind and solar energy, without the need to eat by candlelight every week. ===== Research Programme URSESThe NWO research programme Uncertainty Reduction in Smart Energy Systems (URSES) ties in with the top sector Energy and the NWO theme Sustainable Energy. Together with Shell, NWO is investing 6.5 million euros, of which NWO contributes 4.5 million euros. URSES comprises eleven research projects that focus on reducing the uncertainties in the energy chain by developing the knowledge and tools needed for smart energy systems. In each project, researchers work together with partners from society, including grid operators, energy suppliers, local authorities and technology companies. The duration of the research projects is five years. The following universities are involved in the eleven projects: Delft University of Technology (5), University of Groningen (2), University of Twente, Eindhoven University of Technology, Erasmus University and Wageningen University & Research. ===== Text: Yannick FritschyPhotography: Ivar Pel