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Quantifying power sector flexibility in Germany and China’s Jing-Jin-Ji region, for better integration of renewables

Summary by Anders Hove, Project Director, GIZ

Electrification of energy consumption with a high share of renewable energy is one of the key pillars of the low-carbon energy transition. Many advanced economies, such as Germany, have achieved a high share of variable wind and solar in their electricity systems, but in many countries variable renewable energy still faces a variety of obstacles. And although many analysts site market design and institutional incentives as the most important factors blocking greater integration of renewable energy, within the power sector many experts continue to site technical hurdles as well. For example, in China, the distance between renewable-producing regions in western China and consumption centers in the East, as well as the high share of combined-heat-and-power (CHP) in winter months in northern China, are often mentioned to explain curtailment of wind and solar energy.

While it has long been recognized that long-distance transmission systems, coal plants, and CHP plants in Europe are operated more flexibly than those in China, it has never been easy to measure this in practice. To help policy makers, grid operators, and power sector participants understand the best path for improving flexibility, we sought to quantify the flexibility of the existing system, compare the system’s flexibility to best practices in regions with a higher share of renewables, and quantitatively analyze the costs and flexibility benefits of various strategies for improving flexibility.

In this report, A Quantitative Comparative Study of Power System Flexibility in Jing-Jin-Ji and Germany, researchers at the Energy Research Institute of NDRC and the North China Power University used five metrics to quantify flexibility in Germany versus Jing-Jin-Ji—the region comprising Beijing, Tianjin, and Hebei, altogether has a larger population and electricity load than Germany. The five metrics are the Loss-of-Load-Probability (LOLP), the probability of insufficient downward flexibility, the probability of insufficient upward flexibility, and the curtailment rate of wind and solar. We used historical data to ensure reliability, though future analysis will likely consider projected data as well.  

The overall results show that the Jing-Jin-Ji region of China lacks the flexibility of Germany’s power system. In particular, North Hebei has a relatively high loss-of-load-probability (LOLP), in both winter and summer, as well as lacking downward flexibility in both seasons. This inflexibility contributes directly to curtailment of renewable energy.

Source: NDRC, ERI, 2020

The report further compares the cost of four stylized strategies for upgrading the flexibility of the region’s power system: coal plant flexibility retrofits, upgrades to existing transmission, energy storage, and demand-side-management (better known as demand response in some countries). The model used in the study finds the greatest flexibility benefit for coal plant retrofits, which themselves can eliminate LOLP and PIDF in the regions most affected. Note that China has missed targets for coal plant flexibility retrofits in recent years.

Source: NDRC, ERI, 2020

Improved interconnections are also a cost-effective strategy, though the benefit is not quite as pronounced. Assuming renewable capacity continues to grow, improved interconnections and operational flexibility of interconnections will be necessary. Currently, the region’s interconnections are mainly used as emergency backup, to provide baseload energy, or to serve peak loads. Interconnections are not yet operated to facilitate bidirectional power flows, enable regional spot markets, or provide short-term balancing across provincial or regional boundaries.

Using energy storage costs from 2018, the report found that this was the least effective strategy, though as storage prices go down and as more renewable plants acquire onsite storage to comply with recent requirements, storage will likely play a role in the region’s future flexibilization.  

For further details and suggestions, please see the report, which is available on the website of the Sino-German Energy Partnership both in English and Chinese.

On 16 December 2020, the report’s authors will convene a workshop with experts in Beijing to discuss potential further research. Potential next steps might include expanding the analysis to cover all of Europe and all of China, including projections to 2025, and adding policy options that represent hybrids of the options considered in the report—for example, combining DSM with energy storage, or coal plant flexibilization with a small amount of energy storage.

The report was published in December 2020 within the framework of the project German Energy Transition Expertise for China. The German Energy Transition Expertise for China project is commissioned by the Federal Ministry for Economic Affairs and Energy (BMWi) and implemented by Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH in cooperation with the China National Renewable Energy Centre (CNREC), a leading Chinese think tank for advising the National Energy Administration (NEA) on formulating renewable energy and energy transition policies.

Citation: Zheng Yanan, Wang Xinnan, Anders Hove, Li Gengyin, Guo Zheyu, “A Quantitative Comparative Study of Power System Flexibility in Jing-Jin-Ji and Germany,” Energy Research Institute of the China National Development and Reform Commission (ERI of NDRC), Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ), and the North China Electric Power University, December 2020.