What is the load point in the power grid
Balancing act under high tension
Electricity cannot be stored. Power plants always deliver as much as we consumers need. The crowd fluctuates. Depending on the time of day or the season. The power plants have to deliver more or less electricity, i.e. to run up or down - or even to be switched off. Maintaining this balance, I was told, is still manual work. From engineers.
How they do it, and why wind energy is a particular challenge, I would have liked to see in Germany. But it didn't work. The large control rooms - the control centers - are "high security wings". Since nine-eleven. Nobody is allowed in who doesn't belong there. He might want to plunge Europe into darkness.
Instead, I found out how to do that from the Danes. They're more relaxed. In addition, Denmark already has 20 percent renewable electricity. With wind. Even 40 on stormy days. How do they balance that?
"Hello. Is it ok in English?"
So that was the control center right on the Baltic Sea near Fredericia. Smaller than I expected. Denmark is small. And on top of that it has two separate power grids. From here only the West Danish electricity network is controlled. Three computer workstations are sufficient for this - two of which are occupied. Then there is a wall with lines and displays on it, carpets, large windows - and a concentrated calm and serenity. Thomas Krogh is one of those people who keep the network stable here.
He has just a little time to explain the work of his colleagues.
"Lotte is (actually, is) over here, ... can get a lot of measurements, if you look at this screen here, it is - all the values here that is Voltage levels, 163 Kilovolts or 414 Kilovolts, so she can get some kind of overview on the status of the grid on the moment. "
Lotte Jensen watches over the cables. Dressed more casually in jeans and a sweater. In front of her large monitors - tables, numbers and even more numbers. Most of them show her the tension in the various cables. 163 or 414 kilovolts. The tension can affect them somewhat. Thomas wants to demonstrate that now. He leans towards the monitor on the far right - grabs a mouse and starts clicking on the screen.
"Yeah, perhaps we can - this is a substation calles Tjele - it is a - actually, this is the place,"
He dials a substation. The voltage can be changed there. With the help of transformers and coils. One is not yet switched on.
"So when I press this button, it will close the break, it is done now, and soon you get some kind of message back, that it is now closed, and you see the - if it is fast enough - that the voltage dropped . 4 kilovolts, this case ... "
The contact closes, the coil hangs in the network. The voltage drops by 4 kilovolts, 4000 volts. This is important - too much voltage, and the devices plugged into the socket at home will break.
"Nils has the most complicated job - he is the smart guy - Nils is responsible for the balance of the system. And also for schedules from all the market players. You see, we have a market, an acutally common nordic market, .. . pull softly, underneath "
Nils does something different: he pays attention to consumption and generation. So is the one who balances on a grand scale. He knows how much electricity the power plants want to deliver. How much electricity consumers want. And he keeps an eye on whether this equation works. In order for it to do so, the power plants inform him one day in advance of what they are planning. So for today, that's what they did yesterday. Nils writes a regular timetable out of it. It then says: Kraftwerk A supplies so much electricity from then until then. And maybe also: company y uses so much electricity from then until then that power plant a is supposed to supply it. Nils can use this to tell whether there is too much or too little electricity on the market - in other words, whether it will be in the grid. He can then instruct individual power plants: deliver more or less electricity.
That sounded like a lot of detailed work to me, but it was solvable. Until now, however, I hadn't heard anything about the wind - its electricity also has to be factored in. In the timetable. Only - wind is actually not a candidate for fixed travel times.
Here it is displayed - the power of the wind turbines. A number in a small box. On the monitor. Nils always keeps an eye on them.
So that he knows how much wind he can expect, he has received a wind energy forecast - together with the power plant reports. And incorporated them into the timetable.
"Today is a quite quiet day. Because you have - no wind power, lots of power plants online and no problems. But it can easily change. (...) it could be hundreds of Megawatts every five minutes. I think, the windpower can cover the entire load of the grid 1.5 times or something like that. Two times during night time or something. "
A quiet day - hardly any wind power. The work is mainly done by conventional power plants. But that can change quickly - if the wind picks up, the power mills generate hundreds of megawatts of additional electricity within five minutes. At peak times even more than this part of Denmark can need. A challenge for Nils. He has to keep an eye on the wind power - and react quickly: If the mills pick up speed, power plants have to be throttled. If the output drops, he has to ask power plants to produce more electricity.
"So it's quite a big challenge, I guess, you have to be quite on alert every time, if the wind goes up you might be in trouble before you know it."
A big job - you have to be constantly vigilant. Otherwise, when the wind comes up, you will be in trouble faster than you suspect.
So that's the crux with wind power. The engineers in Denmark seem to be coping well with this. The question arises: why?
I meet Antje Orths in another office. She works as a scientist for Energinet.dk, the Danish electricity grid operator.
"For Denmark, we are of course lucky that we are on the edge of the UCTE system ..."
UCTE is the Western European electricity network. It stretches from Spain to Germany and forms a large power grid.
"... we are on the edge of the system and are connected to water-based neighbors with direct current connections that can be regulated very quickly in both directions. That is extremely practical."
"... - we can import seventy percent of our consumption and we can export 40 percent of our production, so that is really a large order of magnitude."
What Antje Orths wants to say: If the wind turbines in Denmark turn too rapidly, the Jutlanders send the electricity to the neighbors as quickly as possible. If the wind turbines generate too little, Denmark has to import electricity on a large scale. It can send this amount of electricity back and forth because it has built power cables at home and abroad that can very quickly transport a lot of electricity back and forth.
So that was the answer to my question: The Danes built powerful power lines. So that the wind power can flow away quickly.
Well - I always thought we had something like that in Germany too. After all, the electricity in this country only fails for 20 minutes a year. This is a world record.
So I asked Klaus Kleinekorte about the German network. The power grids are a separate division of the energy suppliers - and before he became Technical Director of RWE Transportnetz Strom GmbH, Kleinekorte worked for many years in the headquarters from which the German power grid is controlled: in the Brauweiler control room. So if anyone knew it was Kleinekorte.
"... we as network operators also have to talk a lot about the fact that there are always bottlenecks in the energy supply. And from my point of view, as a transmission network operator (...) I would like to point out that these bottlenecks that we have today have that the consequence are the other use of our transport network. "
When Klaus Kleinekorte speaks of a bottleneck, something must be wrong in the German power grid. And not only he sees it that way. Wolfgang Glaunsinger is of the same opinion. He heads the Energietechnische Gesellschaft in the VDE, the association for electrical engineering, electronics and information technology. Both see the problem in the high-voltage lines that carry the electricity over long distances.
"... maybe comparable to our road network. There are also the Europe-wide long-distance motorways ..."
And has something changed since then?
"In the past, this interconnected network was set up to connect the large power plants with one another and to provide mutual reserves for these large generating units."
This is Wolfgang Glaunsinger.
"Today the transmission network has been given different or additional tasks, because we have had electricity trading since the liberalization, and with electricity trading, large power transits are transferred via the European transport network. This network is actually not built for this and that leads to the fact that today, too problems arise again. "
And then Glaunsinger gave an example:
"The original system, and in part it is still structured that way today, was close to the load"
Close to the load means: the power plants were located where the electricity was needed.
"One spoke of a distance of fifty or seventy kilometers between the point of generation and the point of load. (...)
Now we have a situation in which generation capacity may be fed into the Netherlands because a Dutch trader has agreed to do business with a consumer in the Czech Republic, and this electricity is then not distributed directly between the Netherlands and the Czech Republic, but loads many grids , so it is divided over the French network, over the network in Germany, goes via Switzerland, Austria, maybe even to Italy, until this electricity arrives in the Czech Republic. This requires capacities that were not planned when the network was originally designed. "
Because nobody can predict where the current will flow. Incidentally, such unpredictable power peaks do not occur in Denmark - thanks to its peripheral location: the country is located exactly between the Western European and Northern European electricity networks. In Germany, Holland and Belgium, however, engineers are concerned about these unexpected power peaks.
"The lines that we have have a certain ability to carry electricity. And if we then have too many sources in one place, we would overload the lines.
Line hum, slowly getting louder - or higher.
Inferior until shut down.
... - that's how it was on November 4th - you have a line that is under increasing strain ...
... - if the small needle here is in a vertical position, it means that it is 100 per cent loaded -
... and then you either have to relieve this line so that you can drive within this permissible bandwidth, or the protective device for this line switches the line off.
Recording of power failure in the Tagesschau
During the heavyweight boxing match, the audience suddenly sat in the dark. The lights went out and the electricity was gone.
Because - ... what happens if you don't switch off the line. If it is loaded beyond its thermal limit value. Then the sagging of this line becomes bigger and bigger, that means, the line gets closer and closer to the ground and becomes a safety risk.
If these developments - more and more electricity trading and more and more wind energy feed-in - continue in the future and we do not take any measures in the grids, this will lead to a deterioration in the quality of supply. "
And that probably means: more power outages. Because electricity trading and wind power overload the cables. Says Wolfgang Glaunsinger and Klaus Kleinekorte. And what do you propose?
"Let's start with the integration of the wind turbines. DENA, the German Energy Agency, carried out a study on how to integrate the wind turbines in the future ...
... whereby we assumed that we would achieve 20 percent, i.e. the target that the federal government has set itself. "
This is Stefan Kohler, the managing director of DENA.
"... 20 percent renewable energy sources then means, in this specific case, for example 10,000 megawatts offshore energy parks, and the result of this study is that 850 kilometers of new 380 kv power lines have to be built to integrate this amount of electricity.
That's a word.
... in particular the routes, from the coast into the Ruhr area, but also of course via the route for example Hamburg Hanover Rhine to the south, i.e. in the direction of Bavaria, and the network lines in eastern Germany, for example a network line from Thuringia to Bavaria around the Bringing electricity from the north to the load centers.
... you can say the other way around, if we don't get these strong transmission networks, the high shares of renewable energies won't work either. "
The expansion of today's high-voltage network is therefore part of the solution. In addition, engineers have other ideas. One of them comes from Kassel and there I visited Jürgen Schmid, the head of the independent institute for solar energy systems ISET.
On the North Sea, says Schmid, or on the Harz, the wind strength may fluctuate, but not when you look at all of Europe:
"The wind energy distributed throughout Europe has a very, very even range of services, which is much more even than the fluctuations in the consumer structure."
And if the wind is blowing evenly across Europe, then the systems have to be better linked across Europe, says Schmid.
"We need much more powerful power grids than we have today,
The expansion of the 380 KV lines can contribute to this, but I expect that we will be able to work better over long distances with new technologies, so-called high-voltage direct current transmission lines, because the losses will be smaller and the transmission capacities will be greater. "
Individual DC lines have been drawn for a number of years, explains Jürgen Schmid, for example between Norway and Denmark, Holland or Germany. But he wants to go further and lay the lines from the Mediterranean through the Bay of Biscay, the English Channel and the North Sea to Norway. A super grid that carries wind power to wherever it is needed.
The effort could be worth it ...
"... especially because in this scenario we have to include the enormous storage hydropower plants in Scandinavia, especially in Norway,"
I had heard of these memories. These are reservoirs that are filled with the help of electric pumps. If there is too much electricity in the grid, water is pumped up into the lake with the help of the electricity. If there is too little in the network, the energy providers drain the water again - and generate electricity using water wheels.
"So if we had the high-performance transmission network in the form in which it is needed, in my estimation we would not need any additional storage devices,
these services there are so great that they could supply the whole of Europe with electricity for about four weeks, and that alone shows how many opportunities for compensation are available through this facility. "
And what part of the electricity cake could wind deliver thanks to such a super-grid?
"You will be able to go into the ranges of 20, 30 percent, forty percent in extreme cases,"
Jürgen Schmid is sure of his cause. So safe that he recommends building no coal, gas or nuclear power plants as security for this 30 percent. Without them, nothing works so far - not even in Denmark.
Nils and Lotte's work would be a lot easier. You would no longer have to keep an eye on the wind energy display, but would always receive the same amount of wind power from the super cable.
A beautiful vision. Also finds Antje Orths from Energinet.dk
The idea is certainly very exciting, and we are also following it with interest,
But, as I said, that is at the very first level of research, right up to implementation, and until we receive the order, now we are building a mast there or laying a cable, there will certainly be a lot of time, but we are on that Discussion involved and continue to pursue it. "
Others also like the idea. In Germany, for example, EnBW. In Ireland Airtricity. A wind farm operator. They want to connect an offshore wind farm off the Thames estuary to England, the Netherlands and Germany using direct current as early as next year. That could become the core of such a European network. When is the cable ready? Nobody could say anything about that yet. Just this much: it should cost 20 billion euros. Raising the money will be difficult without the EU - and the Irish have to get excited about the project first.
Meanwhile, the Danes are thinking about improving their conventional power grid even further.
"A few years ago we had the case that there was a fault in the high-voltage network in the south of Denmark, as a result of which some block-type thermal power stations in the north of Denmark failed, which we could not explain to ourselves at first, and from this story it emerged that you too must take care of subordinate voltage levels, "
And then she told me how the company wants to avoid such incidents in the future: With the help of smart grids - clever, small power grids that keep the balance between consumption and generation even without the power highway. I went to Denmark to see what they should look like - at the Risoe energy research center near Copenhagen.
"Yeah, this used to be the turbine-hall, so when Risoe started it's activties in Windenergy in the seventies"
Oliver Gehrke. PhD student at the Energy Research Center in Risoe. Together with Hendrik Bindner he leads me to the headquarters of Syslab.
"Yeah - should we get inside? Because it's a little bit windy ... Open the door, go quietly."
A hall - hexagonal, full of computers, cables, tools and junk.
"Yes, here we are at one of the location of Syslab. Here at this switchboard we can connect two windturbines, a diesel"
Hendrik Bindner heads the project. He points to large cupboards with switches and displays. The Syslab components can be switched on and off from here: two wind turbines, a motor and a large, adjustable resistor.
"The idea is - or the vision is, that ideally there should be no central control at all in the end ..."
The idea is that all components manage themselves decentrally, says Oliver Gehrke. Exchange with each other how much they generate, consume and then control the network together.
"What can I see here? ...
You can see the two wind turbines, connected to the grid "...
At the moment the wind turbines are supplying the electricity to the nationwide grid. This is shown by the instruments on the control cabinets.
Syslab is not really working yet. Soon, however, it will be serving a small office barrack - a special one, of course
"Maybe we should have a look. - Yeah"
A hybrid car.
"This also serves a certain purpose because we would like to experiment with the possibilities"
The hybrid car is also part of the experiment: the large battery is to be connected to the grid. And then the driver can basically tell the power grid: I don't need the car from midnight to six. You can use the battery to compensate for power fluctuations. The battery only needs to be charged in the morning.
"... so just in the morning it would charge it full, so that you can commute again;"
The office shack. It is being built.
"Since it's the only building in Risoe that is not on district heating, so it's the only one which has electric heating."
This old barracks is the only house in Risoe that is not connected to a district heating pipe. Instead, it has electric heating. That makes it ideal for the researchers: They paved all the rooms with sensors and provided all electrical consumers with remote controls.
"Each room will have a screen on the wall, where you can enter a policy for the room, so the user can set a certain policy like: I allow you to increase the temperature by one degree celcius, because I don't care"
A small control screen is to be installed in each of the eight office rooms. With its help, office users can define a flexible profile. For the heating, for example: If the temperature should last 20 degrees, the user could give it a range of 19 to 21 degrees. If more wind blows than electricity is used, the intelligent network could then heat the offices a little more. And vice versa, let the rooms cool down a bit if there is no wind.
"Yeah, we call it virtual storage, because you cannot get power out of it when you need it, but you can only."
Oliver Gehrke and Hendrik Bindner call this a "virtual memory." Because the system can only absorb energy, but cannot release it again.
"Yeah, we are - in a few months from now, May I think is the latest date of the shipment we will get what is called a vanadium reddox flow battery"
Syslab should also get a real energy storage system. A reddox flow battery. It's not there yet, but the hall already exists - until recently Denmark's oldest nuclear reactor was located there.
"... it was Denmarks first reactor, which was build 1956/1957, I think, and - Hendrik Bindner:
Yeah, maybe we should go and have a look at that building, because it is an interesting building to look at. "
The old reactor house. It is small, the parking lot in front of it is empty.
The hall is also empty. A hole in the middle.
"This is a large hall, and what you can see in the middle here what makes it different from most toher large halls in the world that there is a huge hole in the floor, where the concrete has scraped of,"
This is where the reactor stood. Two kilowatts - a tiny one.
"... now it has been decommissioned, and for us it is ideal ... The vanadium battery will be over here, it will be seven by seven meters the containment where we will have the two eight cubic meter tanks as well as the cell stack "
The battery will be in the corner back there - Reddox Flow technology is just coming onto the market. It is more efficient than hydrogen fuel cells and more reliable than a conventional battery.
"... go back to your offices? Yeah - slamming the door - drive, end.
We hope that local networks will provide greater security of supply if the power fails - the local networks can then disconnect themselves, supply themselves for a while, and the consumer will not notice anything. "
Energy supply on site - independent of the electricity giants. With this, Denmark wants to make its electricity grid even safer. There are similar projects in Germany. As a rule, however, not from electricity grid operators. They first have to expand their networks to get up to date with the Danish standard. But that can take a while. Up to 10 years from the idea to the finished mast. The hearings and appeals of local residents against new power lines take the longest. That should be different: In November 2006 the federal government introduced an acceleration law.
"We are already actively involved, and here I can say that for my company,"
Klaus Kleinekorte from RWE Transportnetz Strom GmbH
"We are now actively involved in implementing an official approval process so that we can strengthen the coupling lines from the Eon area in the north to our RWE transport network (...) a construction project that you can read about as a necessary measure in the DENA study. "
Still, doubts gnaw. The expansion would cost 1.1 billion euros. Stretched over ten years, an average of 110 million euros every year. Write to DENA. That's not much, I thought.
But will the big electricity companies really spend that? In recent years, they have neglected their networks. The critics say that since the electricity market has existed. In 2007, two and a half billion euros are planned for maintaining the networks - that's just enough to keep the status quo.
In Denmark the cables belong to the state. In Germany, however, still the electricity companies. Not a good starting position, says Jürgen Schmid:
"That is well-intentioned, but it cannot work that way in practice because the owners of the power grids are also the owners of the power plants, and there are inevitable conflicts of interest that can hardly be resolved in this way."
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