Abstract: Driven by the carbon peaking and carbon neutrality goals, new forms of energy generation such as wind power and solar power have developed rapidly. To solve the problems of intermittency and volatility in the power system, it is necessary to build matched energy storage facilities. In this paper, the gravity energy storage type of taking water as the medium is defined as Water Energy Storage. A comprehensive comparison is made between different forms of energy storage available at present and in the future, from the aspects of technical principle, economy, environmental impact, and operation safety. The results show Water Energy Storage is the best form of energy storage for supporting new energy development and New Power Systems in the next period of time. This paper also explores the planning idea, regulation calculation, evaluation method, development modes, and other key technologies and relevant policies for pumped storage, hydropower expansion and cascade reservoir energy storage, and takes an outlook for their development in the future. The study would help to plan and design new energy development and New Power Systems.

Key words: water energy storage, hydropower expansion, energy storage by cascade reservoirs, pumped storage, compressed air energy storage, electrochemical energy storage