Renewable energy faces problems due to heatwaves
Author: Osman Cetinkaya
Nuclear and coal power plants are also affected by heat
In the past few weeks there was probably no one so happy about the heat wave as the operators of solar systems. For weeks, the sun shone over Germany for over 300 hours. The temperatures reached peaks of over 39 degrees.
Alone in July German photovoltaic plants produce more than six billion kilowatt hours of electricity – more than ever before within a month. With this amount you could supply all of Hamburg with electricity for a year.
The wind millers on the contrary are disappointed. Like the farmers, they suffer from the hot summer. The total of 30,000 wind turbines turned during the heat only with reduced power or stood completely still. Overall, the wind turbines have a potential of 58,000 megawatts, of which on July 24 not even 1300 megawatts were utilized. That’s not much more than the performance of a single nuclear power plant.
“For a lot of wind power you need a lot of wind. And this is more likely a result of weather changes” explains Christoph Podewils of the think tank Agora energy revolution. Due to the stable high-pressure area in northern Europe, there was almost no utilization of the wind farms.
In general, it can be said that the energy gained here is normally lower in summer. In total, 4.4 billion kilowatt hours of wind were produced in July. Compared to the previous year, this is a decrease of 20 percent. “You can certainly talk about a recession” says Robin Girmes, weather expert of the agency Energy Weather.
For the energy industry, the unpredictability of the weather is a real problem. More and more wind turbines and solar roofs are built, which cover almost all the demand for electricity on days with good weather, means a lots of sun and/ or wind. But as soon as the sky gets darker, the performance of the solar systems also drops significantly. The same applies for wind turbines if it is windless.
“For several weeks now, everyone’s talking about the weather. We as well, as the hot and dry summer affects power generation in Germany and Europe “said RWE CEO Rolf Martin Schmitz. For him, the heat period is the perfect argument that Germany should not only rely on renewable energies. “This unusual summer proves how important a broad energy mix is, in which every type of generation can use its strength” says Schmitz.
RWE, the largest German producer of electricity, derives its energy exclusively from conventional power plants, i.e. based on nuclear energy, gas and coal. The company often has to contend with criticism, especially through the mining of lignite.
But RWE does not just operate lignite power plants. The company also supports the energy carrier, whose enormous electricity demand causes enormous amounts of climate-damaging CO2, especially in the Rhenish lignite mining area.
According to Schmitz, lignite has been kind of insurance for the supply of energy in recent weeks: “Since lignite plants are cooled with the constant-temperature mine water of the opencast mines, they were able to perform their duties reliably even in this hot summer.”
But also on the “normal” power plants could not be fully relied on in the hot weather. The efficiency of the gas-fired power plants, more precise the percentage by which the fuel is converted into electricity, declined. And a few hard coal and nuclear power plants had to shut down their services due to low water levels too. In addition, the cooling water, which is obtained from the nearby rivers, was too hot to actually cool the factories.
Even solar energy, for which the weather was theoretically ideal, has reached its limits. This is because the efficiency of the solar modules decreases with the increase in temperature. Thus, the most powerful day of solar energy, despite the excessive hours of sunshine in July, was in May. At that time, the modules produced electricity with a power of 32,000 megawatts in sunshine and with a temperature of 23 degrees. On July 31, the hottest day of the year, however, at a temperature of 39 degrees, it was “only” 27,000 megawatts. “The warmer the module gets, the less electricity it generates” explains weather expert Grimes. In a hot summer like this, performance is about five percent below average.
Arguments of this kind are just right for Schmitz and the bosses of the other conventional energy companies. The Commission “Growth, Structural Change and Employment” has now started their work in Berlin. On behalf of the Federal Government, they should decide about the exit from coal mining. However for RWE CEO Schmitz it is very important that this step is not rash. “Such a process does not just need money and experience,” he said “above all, it needs time”.
For the coal opponents, however, the exit is rather yesterday than today. The latest protests by activists were on Saturday in front of the RWE opencast mine in Garzweiler. It will be discussed until August 22, what the future of the region will look like after a brown coal exit. Around 100 participants are expected.
And for the representatives of the renewable energy industry is a stop of the energy revolution caused by weather phenomena also out of the question. For the spokesman of the German Wind Energy Association, Wolfram Axthelm, the energy losses due to the heat period are by no means a proof that coal-fired power plants must be preserved.
“While coal and nuclear can provide less and less electricity because of missing or too warm cooling water, the sun and wind have regularly supplied a production of at least 20,000 megawatts, covering one third of the demand.” But the share of renewables still has to grow, so that it can really cover the whole demand. For this, the number of wind and solar systems must be further expanded. “Politicians must stop the standstill. They must pave the way so that the energy that will be lost due to the exit of atom energy until 2022 can be cleanly replaced with the sun and wind energy “demanded Axthelm. Just recently, construction work on renewable energy has had to be slowed down as the state cut back on subsidies.
But neither feed-in tariffs nor dark skies or heat waves can stop the increase in the share of renewable energies. Although the wind turbines seem to have contributed only weakly to the energy budget, the solar energy compensates for the balance due to the tons of sunshine. Despite the lack of wind energy, total electricity production from renewable energy sources rose by two percent in July, accounting for around 36 percent in the first half of 2018, what means that wind, solar, water and biomass plants made it for the first time to have produced more electricity than brown and hard coal fired power plants.