Thermal energy storage system - broad development prospects
Industry definition of thermal energy storage
Energy storage refers to the process of storing energy through a medium and releasing it when needed. According to different storage media, energy storage can be divided into electric energy storage, thermal energy storage, and hydrogen energy storage. Among many energy storage technologies, thermal energy storage is one of the most promising large-scale energy storage technologies.
Thermal energy storage technology uses heat storage materials as the medium to store solar energy, geothermal heat, industrial waste heat, low-grade waste heat, etc. or convert electrical energy into thermal energy, and release it when needed. In order to solve the problems caused by the mismatch between the supply and demand of thermal energy storage in terms of time, space or intensity, and maximize the energy utilization rate of the entire system.
Compared with other energy storage technology routes such as traditional electrochemical energy storage and industrial electrical energy storage, thermal energy storage has obvious advantages in energy storage density, installed capacity, service life, and cost technology. Compared with the two mechanical energy storage technologies, compressed air energy storage and pumped hydro storage, thermal energy storage technology has many advantages, such as small footprint, low cost, no area impact, high energy storage density, and low impact on the environment.
Thermal energy storage technology is a large-capacity and large-scale energy storage method with high energy density, high conversion efficiency, and minimal application cost. It will play a vital role in building a clean, low-carbon, safe and efficient energy system, building a new power system with new energy as the main body, and ensuring the safe and stable operation of the power system.
Features of thermal energy storage technology
● Large energy storage capacity, flexible configuration, no special environmental requirements
● It has the advantages of large-scale construction and operating costs, and has obvious scale effects
● According to the needs of users, it can realize the combined supply of cold, heat, electricity and steam with various energy grades
● It can realize peak shaving and valley filling, two-way adjustment, and absorb intermittent new energy (wind power, photovoltaic, etc.) installed output for the regional power grid. It is the best solution to balance the peak and valley difference of the power grid.
● Large number of cycles, long life, and the bidirectional regulation function of the energy storage power station will not lead to a decrease in efficiency with long-term heat storage cycles
● There is no chemical reaction in the storage process, the technical parameters and process are controllable, and the system safety is high
Application of thermal energy storage
Thermal energy storage technology can be applied to the power supply side, grid side and user side.
● Grid side: At this stage, the power system presents a “double high” characteristic of high proportion of renewable energy and high proportion of power electronic equipment, insufficient frequency regulation and voltage regulation capabilities, and the system’s moment of inertia continues to decline, posing severe challenges to the power grid energy output. The thermal energy storage power generation can effectively realize the frequency modulation output power through the rotation of the steam turbine generator set to achieve the purpose of stable power supply
● User side: Thermal energy storage technology can be applied to user cold, heat, electricity integrated energy services, seawater desalination and other occasions. In the direct utilization of thermal energy, thermal storage technology has higher energy utilization efficiency than electricity storage technology. Thermal storage technology also includes the storage and utilization of thermal energy below ambient temperature, that is, cold storage technology has been maturely applied in cold chain related fields, and the market scale is also expanding.
● Power supply side: In the production output of top 10 thermal power companies in China, the thermal energy storage power generation technology changes the excess steam heat energy that occurs when the unit is running under load and converts it into heat storage, which is stored through the medium. The heat energy is released when needed, which can not only increase the peak depth of the power supply unit, but also increase the peak load capacity of the power unit. The investment and operating costs are greatly reduced, and the carbon emissions of fossil energy heat production are reduced.
The development trend of thermal energy storage
● The development trend of global thermal energy storage
Advanced countries in the world have carried out various researches on thermal energy storage and its power generation technology. High-temperature thermal energy storage and power generation technologies have been widely commercialized in Europe, America, Africa, and the Middle East. By the end of 2021, the installed capacity of global CSP plants is about 6.6GW.
The US Department of Energy’s plan predicts that the 12-hour energy storage CSP cost target in 2030 is 5 cents/KW·h, and the visible light thermal energy storage technology and industry are highly valued in developed countries.
● The development trend of thermal energy storage in China
In recent years, the scale of thermal energy storage in China has grown rapidly. In 2018, the installed capacity of thermal energy storage projects in China was 1.07GW. In 2019, the cumulative installed capacity of thermal energy storage projects in China was 32.4GW.
In 2020, a 100MW heat-conducting oil trough-type CSP station will be built in Wulatezhong Banner, Inner Mongolia, equipped with a 10-hour molten salt heat storage system. The cumulative on-grid electricity of the project is 205 million KW·h, accounting for 30.48% of the total CSP power generation in China at the same time.
In 2021, 3 experimental power stations and 9 commercial power stations have been built and connected to the grid for thermal energy storage power generation, with a total installed capacity of 521MW.
During the “14th Five-Year Plan” period, significant progress has been made in the adjustment and optimization of the industrial structure and energy structure, the energy utilization efficiency of key industries has been greatly improved, and the growth of coal consumption has been strictly controlled.
The construction of new power systems has been accelerated, and new progress has been made in the research and development, promotion and application of green and low-carbon technologies. Green production and lifestyle have been widely implemented, and the policy system conducive to green, low-carbon and circular development has been further improved.
Conclusion
Thermal energy storage systems are highly efficient in terms of comprehensive energy utilization of cooling, heating and electricity. It has outstanding advantages in heat storage capacity, large-scale construction and operating costs, operating life, safety, power generation, etc., especially in absorbing intermittent new energy (wind power, photovoltaic, etc.) installed capacity.
It plays an important role in building a new power system with new energy as the main body and ensuring the safe and stable operation of the power system. Thermal energy storage system is the backbone of large-scale energy storage in the future, has broad development prospects, and plays an important role in the energy revolution.
