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Corrections for coal

"The economy needs coal". This was the title of an interview with the economist Till Requate in the 50th edition of "unizeit". What does the professor of environmental and resources economics think 11 years and 50 editions later, about coal-fired power plants and the energy transition?

Power plant
© Stadtwerke Kiel AG

A modern gas-fired power plant replaces the old coal-fired power plant in Kiel. It will probably be the same elsewhere for quite some time to come.

"40 percent is very ambitious, and I am not very optimistic that this objective can be achieved by 2020." Back then, Till Requate expressed this fear regarding the climate objectives of the federal government in a unizeit interview - and has been proven correct. Instead of the targeted 40 percent CO2 reduction, in 2020 Germany will only emit 32 percent fewer greenhouse gases than in 1990. This is the conclusion of the Climate Protection Report 2018. And this is despite the fact that the targets - seen objectively - are less ambitious than it seems: due to the closure of extremely dirty power plants and industrial plants in East Germany, it was initially relatively easy to reduce the CO2 emissions significantly.

If the Kiel professor had not slightly underestimated the development of renewable energies versus the actual progress, the current report on the climate situation would be even worse. Eleven years ago, wind power cost seven to ten cents per kilowatt hour, and photovoltaic power as much as 50 cents, so experts assumed that the growth of green electricity would take longer. In fact, according to Requate, offshore power can already partially be delivered at market prices, and new installations in the photovoltaic sector deliver power at almost bargain prices of four to five cents per kilowatt hour.

"There has been a lot of progress," admits the economist, and is partially changing his previous assessment on the role of coal. In the 50th unizeit, he said "we have no other choice than to at least replace the old coal-fired power plants, and partly also to increase capacity.” In fact, according to the most recent coal compromise, the complete transition from this energy source, which currently accounts for approximately 37 percent of the total electricity supply, will only be achieved in the year 2038. "However, emissions trading is becoming increasingly effective," concludes Professor Requate, referring to figures from 2018 and 2019, when the price increased within a few months from five to more than 25 Euros per tonne of CO2. Because the number of certificates - which represent pollution rights converted into CO2 - will be reduced by two percent every year, this trend is likely to continue. In particular, electricity from brown coal, which is inefficient and thus very harmful to the climate, will become too expensive for the producers anyway in the foreseeable future, according to Requate.

On the other hand, renewable energies are still unreliable in terms of security of supply. In this regard, Requate refers to figures from the year 2018, which show electricity from wind (20 percent), solar (8 percent), biogas (8 percent) and hydro-electric power (4 percent) totalling at least 40 percent green energy. "That looks quite decent, but obscures the problem a bit," he says, pointing to another graphic. This shows the daily fluctuations depending on the type of energy, and therewith a considerable dilemma. On one December day in 2018, a terawatt hour of renewable electricity was generated in Germany, particularly due to the high winds, which represents about two-thirds of the daily requirement. In contrast, on a gloomy and windless day in January, only 0.05 terawatt hours were achieved. "There are also major differences over longer time periods," says Requate, referring to the relatively wind-free months of July and November.

However, we can certainly work to combat this. According to Requate, pumped storage power plants can already help with short-term fluctuations quite well. When prices are low on the power exchange, water is pumped upwards in order to drive turbines when prices are high. The economist also believes that so-called smart metering with intelligent measurement and control devices in households and businesses offers potential. A classic example: washing machines and dryers operate specifically when there is a lot of wind or solar power available.

But this is not enough over longer periods, so Till Requate attaches an important bridging function to gas. Despite knowing that predictions are tricky, he nevertheless dares to look ahead to the year 2040: he estimates that then, 80 percent of electricity will be from renewable sources and 20 percent from gas.

Author: Martin Geist

Rather electric than power-to-gas cars

In this country, the energy transition almost exclusively refers to the topic of electricity. But in fact, vehicle traffic and central heating are just as important. When considering everything as a whole, the experts speak of sector coupling. The Fraunhofer Institute in Karlsruhe recently presented a study on this.

Regarding vehicle traffic, the Fraunhofer Institute calculated that the electric car is the most sensible means of transport, and for heating - unspectacularly - the heat pump is best. According to the study, the second best choice for transport is the fuel cell, for which hydrogen as an energy source is produced using electricity. Only in third place is the "power-to-gas" method, with which synthetic fuels such as kerosene are produced using electricity. However, 80 percent of the energy is lost in this process, so that according to Professor Till Requate, "power-to-gas" only makes sense if there is a substantial oversupply of green electricity. "This will only be an issue in 10 to 20 years," he says, sceptical of the state political efforts to keep the power within the state, in order to generate synthetic energy sources on a large scale.

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