Green Power
Prof. Dr.-Ing. Markus Zdrallek / Electrical Power Supply Technology
Photo: UniService Transfer

"Green power has no alternative for a regenerative and CO2-free energy supply world".

Prof. Dr.-Ing. Markus Zdrallek, head of the Department of Electrical Power Supply Engineering, on the energy generation of the future

Nuclear power? No thanks, was the slogan used by the anti-nuclear movement at the beginning of the 1970s to slowly force its way into people's consciousness. Coal phase-out now! is the slogan in the 21st century, because fossil fuels are increasingly damaging our planet. The 2011 Fukushima reactor accident in Japan and the young Fridays for Future movement accelerated the rolling protest of those who want to counteract climate change with renewable energies. Germany's energy transition goal of sourcing energy mainly from renewable sources by 2045 seemed to be within reach, but then Russian usurper Vladimir Putin turned off the West's gas in the wake of his Ukraine war that had begun, giving us Germans a hard winter as well. Markus Zdrallek, a scientist from Wuppertal who heads the Chair of Electrical Energy Supply Technology at Bergische Universität, knows why we are nevertheless on the right energy path. "My 100% regenerative and CO2-free world of the future looks like this," he says, "we do as much as we can with regenerative electricity, and what we can't do with regenerative electricity, we do with green hydrogen." But what is renewable electricity, anyway?

Green power from renewable sources

"In general, green electricity is defined as electricity that comes from renewable sources, i.e., generated by wind turbines, photovoltaic plants, by biomass or by hydroelectric plants. Meanwhile, we are also talking about green hydrogen. That's hydrogen produced via electrolysis, and this electrolysis is in turn fed by green electricity, i.e., renewable electricity." This electricity is almost CO2-free, the scientist explains, adding, "If we want to get to a majority renewable and CO2-free energy supply world, and at some point - our goal is also 2050- to a completely renewable and CO2-free, neutral energy supply, then this is the only way we can go." Green electricity, or green power, comes from 100 percent renewable sources. Suppliers must obtain guarantees of origin for the amount they want to sell as green power, which is also monitored by a regulatory body that oversees the electricity market. The electricity that traders buy each year is traded in Germany on a quarter-hourly basis.

Green electricity for all?

At the moment, he says, there wouldn't be enough green power if all consumers wanted to buy a so-called eco-certificate. "The way the system works," Zdrallek explains, "is that the normal electricity mix that someone buys who doesn't specifically buy a green power product is reduced by the green power components. That means that if more people buy green power now, the rest will get more coal-fired power and nuclear power, which, after all, we still have this year." But it is also true that if everyone were to buy a green power certificate, the energy suppliers would be forced to purchase 100% green power. At the same time, green power has become cheap because its generation is now competitive with coal-fired or nuclear power generation. Zdrallek explains it this way: "For example, it is said that generating a kilowatt hour of electricity in a nuclear power plant is the cheapest thing to do today and costs about 2.5 cents a kilowatt hour. But this calculation always leaves out the cost of final storage. With coal we are at 5 - 6 cents, gas-fired power plants are particularly expensive at the moment, but even before the Ukraine war gas had picked up, they are at about 10 - 15 cents per kilowatt hour. And if we talk about PV plants (photovoltaic) today, we are at power generation costs of 9 - 10 cents per kilowatt hour, onshore wind at 7 - 8 cents, offshore wind at 3 - 4 cents. I.e. renewable energy is also becoming price competitive, it is now just as cheap to generate a kilowatt hour with wind as with coal. And thus these green power certificates are also not significantly more expensive than normal electricity. But, wind power only works when the wind blows too, and with coal, it just always does."

Energy transition takes time

The energy transition is seen by experts and the public as a move away from a hierarchical power supply through power plants to a renewable and decentralized energy supply with wind and photovoltaics. "So far, we have understood the energy turnaround very much as an electricity turnaround, and we have also achieved more there than is often discussed. I can understand the young "Fridays for the Future" generation, who say we have to be even faster, we have to get out of coal," says Zdrallek, "but it has to be said that we have already come a long way. We're at about 50% renewable share of electricity consumption in Germany. 50% in the last 15 years! We were at 5% 15 years ago, and that's quite a long way. It's a marathon, and it's still going on, because we're rebuilding a huge system that we've spent decades and centuries building up and optimizing as engineers. And that doesn't happen from one day to the next." In addition, he said, we now no longer have to talk solely about electricity, but also have to consider other energy sectors. "In principle, you can say that energy consumption in Germany is divided into three thirds. One-third is electricity consumption, one-third is heating, i.e. heat, and one-third is mobility, which essentially relates to driving. And if we're at 50% renewable energy in the electricity sector right now, we're below 10% in the other two sectors." Biogas and biodiesel are too marginally used, he said, and the challenge now is to get more renewable electricity into the mobility sector. He said the issue of heat is difficult, where green hydrogen certainly has a future role to play, but the current gas shortage means we now have to get through the winter first.

Everyone can save energy

For his studies on electromobility, the expert came across a study on mobility in Germany that also gave him food for thought. It was about the driving behavior, routes, duration and paths of Germans with their own cars. "There you can read, 25% of all trips made with cars are under one kilometer." That would be trips to the bakery, to the daycare center or trips to the nearby forest to walk the dog. Zdrallek, at any rate, has since been biking to the bakery on Sundays or even walking from time to time.

Energy supply of the future

"The German government's energy concept up until the Ukraine war was that we wanted to generate 80% of the electricity regeneratively and 20% with gas-fired power plants by 2040. Now we definitely have to rethink this concept, but a completely renewable and CO2-free energy supply of the future could look like adding a lot more wind and PV generation, and we will have to. Then we need an intermediate storage medium so that we can store temporarily for the times when the wind is not blowing and the sun is not shining. And the only major storage option is green hydrogen, where we can temporarily store the large quantities from the summer for the winter. That could also be implemented to some extent in the current gas system." True, we would not be able to generate everything completely in Germany, and would also have to import from countries where the sun shines more than here. "So we could manage to set up 100% sustainable and thus become more independent," he formulates.

Existing and expanding renewable energy sources

The growing demand for green power is increasing the expansion of plants that use renewable energy sources. "We're talking about an order of magnitude of 2 million in Germany for PV systems, and I don't have exact figures for wind turbines" explains Zdrallek. At the moment, he says, that's enough to generate 50% of the country's electricity from renewable sources. Experts assume that we will have to add another three to four times that amount of PV and wind power plants in order to make the energy supply of the future 100% renewable. "That holds social explosives, one knows the discussions about new wind turbines and their locations", he gives to consider, because the energy turnaround would find everyone good, as long as no wind turbine or a high-voltage line comes too close to my environment. At this point, the only way forward is with participation models. "There are already successful citizen projects in connection with PV plants in Wuppertal, where you can participate. And if it then also yields something for oneself, then it is not perceived as so disruptive."

Oil multinationals as a role model?

The cheapest green power will soon come from Saudi Arabia. Indian engineering company L&T is currently building the Sudair solar power plant there, with a capacity of 1500 megawatts. That's roughly equivalent to the output of a large coal-fired power plant. Sudair is scheduled to go into operation later this year and will supply the cheapest solar power in the world: 1 cent per kilowatt hour. For Zdrallek, that's conceivable for Europe, too. "Our only problem with this is that there is too little sunshine in the Wuppertal summer," explains the technician. "In Saudi Arabia, you can expect four thousand full-load hours, because there the sun shines continuously on the plant for half a year. Here, we calculate with 900 full load hours, in southern Germany with 1100. There is a factor of 3 to 4 in between. That's why our costs are not one cent, but 7-8 cents, because we simply have less sun." Saudi Arabia is thus also repositioning itself to not only supply its own population with this electricity that they then generate, but then also to produce green hydrogen right away, which they want to export to Europe in the future. "The Saudis have also recognized that the fossil age is coming to an end and they still have to prepare now with the profits from their oil sales for the next 20-30 years, where that will no longer be the case." Now Saudi Arabia is not a politically easy country and that is the crux of the matter, Zdrallek explains, because wherever there are mineral resources, where our energy resources come from, i.e. Russia, Saudi Arabia or Iran, are politically sensitive countries, to that extent you have to consider whether you want to make yourself dependent on these states. "We will not manage," he concludes, "to make Germany self-sufficient in the long term. We will always be dependent on energy imports, although not as many as today."

Trade has always taken place in the world, and the mineral resources of the Middle East and Asia are now being replaced by the West with new methods of communication, technical innovations and the use of computers. Thus, we are all dependent on each other. One thing must not be forgotten: Every country has the claim to lead its population into a secure future. This also applies to Russia.

Uwe Blass (conversation of July 12, 2022)

Prof. Dr.-Ing. Markus Zdrallek heads the Chair of Electrical Power Supply Engineering in the Faculty of Electrical Engineering, Information Technology and Media Technology at Bergische Universität.

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