Development trend of pumped storage technology
Conventional pumped storage power stations have developed to this day, and they are developing in the direction of high water head, high speed, and large capacity. With the increase of water head speed and rotation speed, the structural size, generator motor size and plant size of the pumped storage power station will be effectively reduced, and the unit capacity of its unit will also continue to expand to meet the power grid peak shaving and accident backup requirements of large power plants such as thermal power plants and nuclear power plants.
At present, countries around the world are increasingly inclined to build variable-speed pumped storage units, mainly geared variable-speed units and continuous speed-regulating units. Variable-speed pumped storage units can provide automatic frequency control capacity, and can also improve the efficiency of power generation and pumping conditions, and realize high-speed adjustment of active power, and can also adapt to different operating heads, thereby improving the quality of power supply in the power grid, suppressing active power fluctuations in the power system, improving the hydraulic performance of the pump turbine, reducing vibration, cavitation and abrasion, and improving the operating stability of the unit.
New materials such as HT-100 grade steel and asphalt concrete have been used in pumped storage power stations in recent years. HT-100 steel can meet the design requirements of strength and elongation. It can speed up the construction speed of pumped storage power stations and coordinate with the development trend of high water head. Compared with conventional concrete panels, asphalt concrete panels have the advantages of good seepage resistance, strong adaptability to deformation, and convenient construction and maintenance. They are widely used in the upper reservoir and anti-seepage projects of pumped storage power stations. China’s Tianhuangping, Zhanghewan, Baoquan, Xilongchi and other pumped storage power stations have also adopted asphalt concrete slab anti-seepage technology. Facts have proved that making asphalt concrete face rockfill dams can save investment and protect the environment.
In addition, in recent years, unconventional pumped storage power stations have also accelerated the pace of development. The first type of unconventional pumped storage power station is a sea water pumped storage power station. As the world’s first sea water pumped storage power station, the Okinawa pumped storage power station in Japan has proved the technical feasibility of sea water pumped storage power stations. In recent years, the main focus has been on its economic effects, operating costs, corrosion resistance and environmental impact. The second type is underground pumped storage power stations, which are less affected by topographical conditions. The lower reservoir is located underground, which is conducive to site selection and investment savings. The distance between the upper and lower reservoirs of the underground pumped storage power station is short, or the underground mine is directly used, which can save investment and improve the power station’s rapid response capability. The United States has designed two underground pumped storage power stations in Hope Mountain and Summit. With technological progress, unconventional pumped storage power stations will gradually be demonstrated and applied.
The development trend of compressed air energy storage technology
The technical trend of the large-scale development of compressed air energy storage systems is mainly concentrated in two aspects, to solve the problems of the need for large-scale gas storage devices and the dependence on burning fossil fuels. In order to solve the main problems faced by the conventional compressed air energy storage system, the new compressed air energy storage system, such as compressed air energy storage systems with heat storage (AACAES), micro compressed air energy storage systems (SSCAES), and liquefied air energy storage systems (LAES), supercritical compressed air energy storage system (SCAES), compressed air energy storage system coupled with renewable energy, etc. have begun to enter the stage of research and development and demonstration application, which is the main trend of future development.
New compressed air energy storage technologies are dedicated to improving energy density and conversion efficiency, striving to get rid of the support of fossil fuels and the dependence on large air storage chambers. The compressed air energy storage system with heat storage eliminates the combustion chamber and achieves zero emissions. In the process of releasing energy, the compressed air is heated by the stored compression heat, and then the turbine is driven to perform work. The energy storage efficiency of the system can reach more than 70%. The scale of a small compressed air energy storage system is generally at the 10MW level, which breaks through the dependence of large traditional compressed air power stations on gas storage caves and has greater flexibility. There are large-scale application prospects in the urban energy supply system—distributed energy supply and small power grids. The scale of the micro compressed air energy storage system is generally in the range of several kW to tens of kW, and it has development potential in special fields such as micro power grids, control, communications, and military in remote and isolated areas. Air Liquide and supercritical compressed air energy storage systems do not require large air storage chambers. It has the advantages of large-scale energy storage, high efficiency, low investment cost, high energy density, and no need for large storage devices. It is an attractive technology. The compressed air energy storage system coupled with renewable energy can “splice” the compressed air energy storage and renewable energy coupled systems, and solve the intermittent and instability problems of renewable energy such as solar energy and wind energy, which can increase the proportion of wind power in the power grid to 80%, and there will also be considerable development in the field of biomass power generation, reducing the system’s greenhouse gas emissions and reducing the system’s dependence on natural gas supply.