Renewable energy and the climate sciences

Jan Wohland is a visiting PhD student from the Forschungszentrum Jülich in Germany. On May 8, he spoke about the coupling between climate sciences and renewable energy.

The carbon budget is shrinking. We only have about 9 years left at current emission levels to have a 50 % chance of limiting global warming to 1.5 °C. Emission cuts are urgent, and transitioning to the use of renewable energy sources is a good way to mitigate climate change.

Challenges of system integration

While the economic competitiveness of wind and solar power has dramatically increased in the recent past, the integration of high shares of volatile renewables in the power system remains a challenge. In the first part of Jan’s presentation, he looked at the example case of Germany, who have seen a large growth in variable renewables in the latest years. In 2017, the share of renewable energy in the electricity mix reached almost 40 %.

Despite the increase in renewables in Germany, the country has also seen an increased cost due to “redispatch” in the latest years. The dispatch process is designed to minimize the costs of power generation, but it does not necessarily ensure physical feasibility in the grid. In Germany, this can result in a situation where cheap renewable and coal-fired generators are scheduled in the north of Germany, but with lacking transmission capacity to transfer the power to the load centres in the south. This leads to a redispatch process, in which generation is shifted in space to meet the demand. In this case, this means that the more expensive generators in the south have to be switched on, while the unused generators in the north are still being paid.

In 2016, the cost of redispatch in Germany decreased, and the underlying causes have been heavily debated. Jan and his colleagues looked into the wind generation in Germany since about 1980, and figured out that natural wind variability triggered the drop in redispatch costs in 2016. They found that 2016 was a rather weak year in terms of wind power generation, and that less variable renewable power generation lead to a reduction of redispatch costs in the order of hundreds of millions of euros. An improved understanding of wind variability is essential to optimize system design & operation.

Robustness of a fully renewable system

Several studies have shown the effect of transmission grids to smoothen the variability from fluctuating renewables. In the second part of his presentation, Jan looked at the robustness of a fully-renewable European power system and how it may be affected by climate change in the future.

Using wind fields from high-resolution climate models and a simple model of the European power system, Jan and his colleagues showed that climate change will have significant impacts on a future power system driven by wind energy. Their results led to a robust increase of backup energy, increased spatial correlation of the wind time series across Europe (leading to countries being more likely to experience generation shortfall at the same time), and finally an increase in circulation weather types usually associated with low Europe-wide wind generation.

This shows that planning and operation of renewable power systems need targeted climatic information.

Read more in Jan’s presentation below!