In a climate-neutral energy system, in which oil and gas heating systems are replaced by heat pumps, among other things, significantly more electricity is needed, especially at low temperatures. At the same time, electricity generation is increasingly dependent on the weather, as a significantly higher proportion of electricity is produced from renewable energies (RE). In a recent study, researchers at the University of Cologne have shown how security of supply can still be guaranteed in such a climate-neutral energy system — even in extreme weather situations. With the help of weather and power plant deployment models, the two doctoral students Linh Ho and Berit Hanna Czock as well as junior professor Dr. Stephanie Fiedler investigated the reliability of the power supply with increasing RE shares in particularly extreme weather periods.
The results have been published in the expert report “Climate Neutrality 2045 — Transformation of the Consumption Sectors and the Energy System” as part of the “dena Lead Study Towards Climate Neutrality”, which was presented by the Institute of Energy Economics at the University of Cologne (EWI) at the beginning of October. The study describes a scenario for the transformation of the German energy system towards climate neutrality in 2045. According to the report, although final energy consumption will fall by about 41 percent by 2045 compared to 2018. Final energy is the energy obtained from primary energy sources such as lignite, hard coal, crude oil, natural gas, water or wind through conversion. However, the gross demand for electricity will increase significantly from today’s 580 terawatt hours (TWh) to 910 TWh. This is because transport, buildings and industry are increasingly electrified and electricity is also needed to produce hydrogen. In particular, the nine million electric heat pumps in 2045 drive simultaneous peak demand in the scenario, which must be met by the available power plants.
At the same time, conventional electricity generation from nuclear power and coal is declining, while electricity generation from wind and solar energy continues to gain importance in the long term and will cover 85 percent of gross electricity demand in 2045. However, because the wind does not always blow and the sun does not always shine, so-called flexibilities play an important role. Ideally, they absorb demand or RE feed-in peaks and thus stabilise the energy system. As part of an excursus in the “dena lead study”, the Cologne researchers looked at extreme weather situations in which it was particularly cold throughout Europe and, in addition, windless in Germany for several days. “So-called cold dark spells are particularly critical for the power supply,” says junior professor Dr. Stephanie Fiedler, who, in addition to her work at the Institute of Geophysics and Meteorology, is also Chief Energy Meteorologist at the EWI and works together with Ho and Czock in the Climate Monitoring and Diagnostics research area of the Hans Ertel Centre for Weather Research, a virtual centre for meteorological research in Germany. “These are situations of low temperatures and resulting high electricity demand coupled with low solar radiation and low wind speeds, which in turn lead to lower renewable energy generation.”
With the help of a modelling of power plant use and electricity trade, the scientists show that in the climate neutrality scenario, even in two exemplarily selected “cold dark slack periods” of the historical weather years 1997 and 2007, the entire electricity demand can just about be covered, among other things by electricity imports from other European countries. This is because in the extreme weather situations considered, European neighbours are less affected by extreme weather and can export electricity to Germany, for example from Northern Europe, France and Switzerland. To achieve this, however, the power lines between Germany and its neighbouring countries (interconnectors) must be significantly expanded.
On the German side, flexible gas-fired power plants — which in the medium term can be (partially) operated with climate-neutral hydrogen — as well as flexibly deployable large-scale batteries and pumped storage are the main options. The demand side could also contribute to the avoidance of supply gaps through its flexibility, for example by down-regulating flexible industrial processes at short notice. Private households could also use their heat storage units and the batteries of their e‑vehicles to bridge particularly critical hours. Such flexibility options are already technically possible. However, before households and other consumers become flexibility providers, appropriate incentives, for example through remuneration for flexibility, and the technical interfaces must be created.
The topic of supply security in climate-neutral energy systems will remain a research focus of the Cologne researchers in the future. Although it was possible to avoid supply gaps in the electricity supply in the two case studies. Nevertheless, the role of extreme weather events in weather-dependent energy systems needs further investigation. This is because an increase in extreme events is expected in the context of climate change. However, the impact on the energy system has not yet been systematically studied.