Carbon-neutral energy systems and the importance of flexibility options: A case study in China

China's energy system is based mainly on coal power plants, which held a share of 69% in 2017. Large numbers of coal power plants lead to air pollution and high CO2 emissions. China has high potentials for renewable energies, which could bring about the transformation of the energy system in the future. The transition of the energy system from coal-based to renewables-based is a huge challenge. A carbon-neutral energy system is based mainly on fluctuating renewable energies like wind and solar power. In order to meet the hourly demand, flexibility options are needed to balance volatile energy production. In this paper, we construct two scenarios to analyse a carbon-neutral Chinese energy system in 2060. The first scenario focusses on electricity in order to decarbonise the energy system. The second scenario uses hydrogen for the decarbonisation. We found that storage possibilities like batteries and hydrogen play a major role in both scenarios. However, the number of installed batteries was lower in the hydrogen scenario although the installed capacity of renewable energies is higher. This is due to the increased hydrogen production in this scenario, which flattens the high solar photovoltaic (PV) peak at noon. Our results highlight the importance of flexibility options in a decarbonised energy system with a high share of renewables.