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How big the solar system for Germany's electric cars would have to be

Electric cars run on electricity, but not CO2-free if it is made from fossil fuels. How much solar area would e-cars need, how much Germany, how much the whole world, to generate enough electrical energy? Calculation examples and a look into the future.

The example of the Mercedes EQS makes it clear that the range of e-cars is less and less suitable as a killer argument against battery-electric vehicles, especially since the charging speed is also gradually developing in the direction of refueling speed. (The EQS charges with an average of 163 kW, so it has charged its 108 kWh battery to 80 percent in 30 minutes. It can cover a good 540 kilometers – in practice, with an average speed of more than 100 km/h).,

This means that we can once again focus on where the switch to electric drives came from: it has a good three times better efficiency in the car and it uses electrical energy - we drive with it with no local emissions and can potentially (almost) drive without CO2.,

How much solar area would we need in Germany?

But only if we generate the non-fossil electricity . For example with solar cells , which encounter less resistance from residents than, for example, wind turbines. But they take up a comparatively large amount of space. This raises the question: is the comparatively moderately sunny area of ​​Germany sufficient to supply the entire country with solar power? Because the total electricity requirement in Germany was 512 billion kWh in 2019 and if we wanted to operate all cars battery-electrically, we would need 140 billion kWh .,

Martin Doppelbauer, who at the Karlsruhe Institute of Technology (KIT) the Professorship for Hybrid Electric Vehicles has made an exciting assessment: Current solar modules provide 400 watts (peak) in full irradiation. They are typically around 1.6 square meters . In Germany, calculated with the hours of sunshine and their intensity on average per year they bring about 1000 kWh per kW peak power (kWp). On an area of ​​ 2300 km² 580 billion kWh could be generated per year - more than enough to cover the electricity requirement. Now 2300 km² is not little. That corresponds to a good 322,000 football pitches or 90 percent of the area of ​​ Saarland .,

Doppelbauer comes up with the number differently: This corresponds to the area on which Germany operates opencast lignite mines - in order to primarily generate electricity . Anyone who is familiar with the huge torn areas will quickly come to the conclusion that solar cells would cause less damage there - not to mention the CO2 emissions.

In order to all cars in Germany drive with solar power, a photovoltaic system with an area of ​​ 560 km² would be necessary.That corresponds to 78,431 soccer fields or 22 percent of the area of ​​ Saarland .,

What would the solar system for world power generation be like?

The calculation of the area required to generate the electricity requirement using solar cells can of course also be thought of globally. Based on a meme that has been circulating on social media for a long time, an article on watson.ch did it. The original image goes back to a diploma thesis at the Faculty of Physics and Geosciences at the TU Braunschweig and showed a manageable-sized square in the desert on a map of Algeria; the marked area should be enough to meet the world's electricity needs with solar cells.,

Watson took the trouble to track down Nadine May, the author of the paper , and found that May was not using solar cells but a solar thermal -Kraftwerk had expected. With the performance data and the potential yield of in different sunny regions of the world, Watson determined the size of the square on which solar cells would have to be located in the center of Australia in order to cover the world's electricity requirements. At Alice Springs in Australia's Simpson Desert, "almost the same conditions are found as in Algeria. (...) With 1899 kWh per kWp per year (5.2 per day), the conditions prevail here over a large area, which result from the mix in Algeria ( 5.0-5.4 per day) at the spot chosen by May".

The result is a square with an edge length of 437 km, which corresponds to a good 74 times the area of ​​Saarland, but which looks as modest on the map of Australia as 90 percent of Saarland does on a map of Germany.,

How does it work CO2-neutral power generation really?

Even if the idea of ​​having done the electricity generation with a large solar system is tempting, the vision for reality looks different . The study "Climate-neutral Germany 2045" by the Agora Energiewende outlines how CO2-neutral power generation can succeed in the future. We spoke to Thorsten Lenck, graduate engineer and project manager at the Agora Energiewende:

"A huge solar system in the desert and the electricity transport that would then be necessary would be technically possible. But political and economic reasons clearly speak against it. Political is the dependence on one central photovoltaic system is not desirable in another country; there are other more sensible and cheaper concepts from an economic point of view.

Another fundamental disadvantage is the temperature dependency of the performance of photovoltaic systems: a temperature that is ten degrees higher means a loss of efficiency of around four percent for solar cells."

Combination of solar energy and wind power

From the point of view of the Agora Energiewende, the cheapest option is "climate-neutral power generation, which is essentially based on a combination of photovoltaic systems and wind power. All studies show this.PV systems on several hectares of open space are now cost-competitive even without subsidies. Even some offshore wind turbines, which used to be considered expensive, now manage without subsidies. In our study "Climate-neutral Germany" we show in hourly resolution what future power generation without coal, oil and gas could look like. Solar energy and wind power form the basis of climate-neutral power generation, supplemented by reserve power plants and storage facilities. This also includes battery storage from second-life applications of car batteries. Controllable power plants are needed as a reserve, which are initially operated with natural gas and later with renewable hydrogen. It is important to keep their running times short because hydrogen production is energy-intensive and less efficient. That is why it will be important in the future for consumers to be able to use the electricity when there are peaks in demand. Cars are predestined for this because they have long downtimes in their current usage characteristics. With bidirectional charging, their storage capacity could also be used for the power grid."

Decentralized power generation saves on electricity transport

"In addition, decentralized power generation makes sense because the power consumption at the point of generation saves electricity transport. The latter is always associated with losses. Nevertheless, expanding the power grid is extremely important because electricity is not always generated where it is needed. In principle, direct current can be transported with fewer losses. For longer transport routes, it can make sense to switch from alternating current to direct current in the power grid."

How many power plants do we still need?

"We calculate with a ratio of electricity generated from sun and wind of 1:2, whereby that The opposite is true when looking at the installed capacity, because on average wind power is available much more often than solar energy. In 2045, 90 percent of our electricity could come from wind and sun, 10 percent would have to come from storage or power plants operated with renewable hydrogen in order to stabilize the grid. If we succeed in making the current demand for electricity more flexible and bringing new consumers such as electrolysers, heat pumps and e-cars to the grid as flexibly as possible, we can save some of the costs for storage and reserve power plants."

Do we have enough space to generate Green electricity?

About the "solar system square" in the desert, Lenck says in conclusion that it shows well how much space we need worldwide for renewable electricity generation". But also that even in Germany there is "sufficient space to generate the electricity with renewable energies" that we need "for electromobility, but also for hydrogen production, industry and building heating in the future".However, the expansion is snagged by the fact that "these areas are not legally available for renewable energies. After the election, the federal, state and local governments with everyone involved on site must provide these areas if we want to achieve our climate goals," says the energy expert.

Conclusion

The idea of ​​a manageable area with solar cells, which would solve the energy problem, is tempting and, at least technically, not utopian. And even if it never becomes reality, it gives an encouraging indication that power supply without fossil fuels is in principle possible.

The Agora-Energiewende has carefully calculated how this works for Germany and has come to the conclusion that a climate-neutral Germany is possible as early as 2045 - without restricting our mobility. We would then no longer be able – or would have to – drive as much as we do now, but if we get behind the wheel (which may no longer be necessary), we drive electrically. And the electricity for this comes from the socket, but is no longer generated with coal. If we wanted to produce it using solar cells, we would only need a quarter of the area that is currently wasted by opencast lignite mining.

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