Rain or shine

Germany's renewable energy production defies fickle weather

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Thin (power)line between future and past. Source: Reuters

Northern Europe’s summer heat wave showed once again how sensitive wind and solar energy can be to the vagaries of weather. And proponents of the continued use of coal wasted no time calling for a slowdown in abandoning conventional fuels for power generation.

“This unusual summer shows how important a broad energy mix is, in which every type of generation can play to its strengths,” said Rolf Martin Schmitz, chief executive of RWE, Germany’s largest electrical utility. RWE relies exclusively on conventional fuels like coal, gas and nuclear.

It was a bold gambit to seize on weather conditions that are caused by too much carbon in the atmosphere to justify putting even more carbon emissions into the air.

Stilled wind turbines

The comment comes after a high-pressure front over the region, known to cause clear and sunny skies, brought wind turbines to a standstill. At one point in July, the 38,000 wind turbines with a 58,000-megawatt capacity delivered only 1,300 megawatts to the grid. Last month, the 4.4 billion kilowatt hours of wind energy produced was 20 percent less than in July 2017.

“To get a lot of wind energy, you need a lot of wind,” said think tank Agora Energiewende’s Christoph Podewils. “And that usually comes with a weather change.”

By contrast, the uninterrupted sunny weather, with temperatures hitting 39 degrees Celsius (102 degrees Fahrenheit), enabled Germany’s solar installations to produce 6 billion kilowatt hours of electricity in July – more than any other month.

Counterintuitively, high temperatures are not optimal for solar energy. Moderate temperatures lead to greater performance. “The warmer a module gets, the less electricity it produces,” said Robert Girmes from Energy Weather.

The best month for solar energy was May, when sunny weather with temperatures at a more pleasant 23 degrees Celsius led to the generation of 32,000 megawatts, while that hot 39-degree day in July yielded only 27,000. A gruelingly hot summer like this one can actually reduce performance by 5 percent.

15 p16 Wind energy production during heat wave-01

It isn’t just renewables

For that matter, the hot weather also affected the performance of conventional power plants, reducing their output. Nuclear and hard coal-fired plants often have to cut back on production because the water they need for cooling is too warm or the rivers are too low to draw from.

In any case, the continual increase in the share of renewable energy in electricity production defies the variable weather, whether heat wave or cloudy doldrums or even reduced subsidies. Wind energy may have been down this summer, but the long periods of sunshine more than made up for it, so that overall electricity production from renewable sources rose 2 percent in July.

For the first half of 2018, the share of power provided by renewable sources was 36 percent. And for the first time, electricity from wind, sun, water and biomass exceeded that from coal-fired plants.

Jürgen Flauger covers energy for Handelsblatt and Kathrin Witsch reports on economic policy. Darrell Delamaide adapted this article into English for Handelsblatt Global. To contact the authors: flauger@handelsblatt.com and witsch@handelsblatt.com.

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