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Carbon footprint of solar and wind turbines: How green is green electricity?

2019-09-21T16:34:34.630Z


Solar and wind plants produce CO2-free electricity. However, green electricity is not completely emission-free. Decisive for the climate balance is the conditions under which the modules and wind turbines are manufactured.



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Only a few meters away from the huge cooling towers of the lignite power plant Lippendorf near Leipzig extends a large solar park. On one side of the fence steams and smokes and seethes - on the other side is nothing to see, to smell, to hear.

But as clean solar parks work well: the photovoltaic is not climate neutral. Because manufacturers need a lot of energy to manufacture modules, inverters and racks. Only if it comes from renewable sources, the generated green electricity is really CO2-free. Individual companies already supply their plants with green electricity. However, it will take some time before this is the case for the industry.

The industry association SolarPower Europe expects global photovoltaic expansion of 800 gigawatts by 2023 - that's about three billion modules. In view of such figures, the energy requirement of manufacturers should not be underestimated for global climate protection.

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Made in China with higher emissions

How much energy and carbon footprint of the photovoltaic are, however, can not be quantified, because there are considerable differences between the module models. The thin-film modules, which are used almost exclusively in solar parks, perform far better on energy requirements than crystalline silicon modules known from rooftops.

The production site also plays a major role for the carbon footprint, explains Holger Neuhaus, head of module technology at the Fraunhofer Institute for Solar Energy Systems ISE. "Because of the high proportion of coal in the electricity mix, a production in China causes more emissions than one in Europe," says Neuhaus.

Last but not least, the installation location and the efficiency of the module are important factors. The more electricity a plant produces, the lower the CO2 emissions per kilowatt-hour produced. "It's complicated," summarizes the Fraunhofer researcher.

Energy expenditure quickly re-recorded

It is undisputed that solar systems prevent significantly more CO2 emissions over the course of their lifetime than their production causes, even in the worst case scenario. According to a 2015 study commissioned by the International Energy Agency (IEA PVPS) of the International Energy Agency (IEA PVPS), a roof-mounted system installed in Germany re-energized in about three years - with a lifetime of 30 years or more. Spanish plants with cadmium telluride thin-film modules need only about nine months.

With new modules, the time spans are even shorter today, as many manufacturers have significantly improved the efficiency of their processes in recent years - especially with regard to the silicon wafers from which the solar cells are made. They account for a very large part of the total energy expenditure.

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"It's very important how the wafers are sawn and how thick they are," explains Neuhaus. More and more companies are using diamond wire saws that use less silicon. This considerably reduces the material and thus the energy requirement.

Larger windmills with lower energy requirements

Wind energy plants usually provide an even better balance than photovoltaics. "Depending on the location, it takes about six to twelve months before the energy for production, installation and dismantling of the plants is recovered," says Stephan Barth, Managing Director of the ForWind Center for Wind Energy Research.

In recent years, wind turbines on land and at sea have become significantly larger and thus more powerful. However, the energy consumption has not risen to the same extent, because the rotor blades are becoming more filigree. For each kilowatt-hour of electricity produced, less energy must be used. Since the plants installed in this country generally come from European production, wind energy also has the lead in terms of CO2 emissions.

The industry is working to further reduce the wings - to save energy, but above all, to make the wind turbines bigger. "A lever for this are new control methods that can be used to reduce the mechanical loads on the systems," explains Barth. "They make it even easier to build the rotor blades."

Solar and wind energy displace coal power

The bottom line is that solar and wind energy make a significant contribution to climate protection, as a study by the Federal Environmental Agency (UBA) shows. After all, the green electricity replaces those from coal and gas-fired power plants, which emit a multiple of carbon dioxide per kilowatt-hour of generated energy.

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According to the UBA study, each kilowatt-hour of solar power generated in 2017 saved a total of 614 grams of CO2. Wind turbines on land could avoid 667 grams, those on the sea 675 grams.

Photovoltaics has relieved the German climate balance by a total of 24 million tonnes of CO2. Onshore wind energy accounted for 59 million tons and offshore 12 million tons. The amount of emissions avoided by solar and wind energy accounted for almost eleven percent of total German CO2 emissions.

Source: spiegel

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