Sensible heat storage is an effective way to solve the instability and fluctuation of solar thermal utilization. The common water medium was used as the medium material of sensible heat energy storage, and the heat storage tank device was used to realize the application of solar energy heat storage and release. The basic shape of the initially selected water tank was cylindrical. The conical structure of the tank bottom was optimized, and the respective heat storage change characteristics of the heat storage water tank under the three working conditions of 40°, 45° and 50° cone bottom angles were explored. Based on the unsteady laminar heat transfer model, the volume average temperature change and the maximum volume temperature change of the heat storage device were simulated by using the Fluent numerical software. The results showed that, when the cone bottom angle was 50°, the overall heat charging and discharging performance of the heat storage tank was better. When the average temperature of the heat storage tank body was 308.612 K under this parameter, the average temperature of the heat storage tank body was 0.202% and 0.053% higher than that of the heat storage tank body with a cone bottom angle of 40°and 45°, respectively. On this basis, the dynamic change law of heat storage and heat release of 50°tank was further analyzed, and the distribution characteristics of key indicators such as volume fraction and velocity field in the process of water storage and drainage inside the tank were studied. This research can provide some reference for the optimal design and engineering application of solar energy thermal storage system.

There is an increasing participation of thermal power units in peak shaving of power grid due to the national "double carbon" target and the strategic demand of energy transformation in China. The molten salt heat storage system can substantially improve the peak shaving capacity of thermal power system by absorbing or releasing heat efficiently from or into the thermal system. The key technologies of thermal power units coupled with molten salt heat storage system and the research progress of the heat storage system process flow design are combed in detail. Firstly, the formulas and physicochemical properties of commonly used molten salts are summarized. Great attention is paid to the characteristics and application prospects of the currently widely used binary and ternary nitric acid molten salts. Secondly, the critical equipment components including the thermal storage tank as well as heat exchangers used in the heat storage system are elaborated. The heat storage principle and characteristics of single-tank and double-tank molten salt heat storage methods are summarized, and the applicability of the former two methods to thermal power units' heat storage and peak shaving system is analyzed from the perspectives of system safety, cost, technology maturity and peak shaving response speed. Then, the current research status of molten salt heat exchanger is summarized, and the research achievements and shortcomings of molten salt-steam-water tube shell heat exchanger are emphatically analyzed from multiple perspectives. Moreover, the design schemes of molten salt heat storage system are sorted out emphatically for the process of heat storage system. The different design features of thermal storage systems are compared. Furthermore, some of the future work on the design of flexible-peak-shaving thermal storage system is also figured out. Finally, the design and practical application of molten salt heat storage system are prospected.

The spot market of electricity makes electricity return to the commodity attribute, which makes the market play an increasingly prominent role in the allocation of power resources. The electricity-trading mode has become an important part of the power market construction and power reform because it is conducive to promoting the consumption of new energy power generation and realizing the optimal allocation of power resources. This paper constructs technical routes for a thermal power unit in Shandong Province. The first is waste heat recovery, refrigeration scheme based on the voltage shrink heat pump and the second is deep peak shaving scheme based on the electric boiler and energy storage tank. The technical transformation scheme is providefor the thermal power unit to participating in the spot power market. The result show that energy supply capacity of the system increased by 48 MW, the cooling capacity increased by 32 MW, and the peak shaving capacity of the unit increased by 9%. In addition, the financial internal rate of return (before tax) of the project is 30.25%, and the payback period (before tax) is 4.1 years, with good profitability.

In order to improve the flexibility of thermal power units, enhance the peak shaving capability of thermal power units coupled with molten salt heat storage system, and reduce project investment, a variety of electric heating molten salt energy storage systems coupled with thermal power plant were proposed. The thermal performance, peak shaving capacity and molten salt consumption of a 350 MW unit were analyzed with EBSILON software. An optimal system for deep peak shaving was proposed. The results show that, during the heat charging process, the electric heating system demonstrates a higher cycling efficiency as 33.2%, which enables the lowest power generation load to be reduced to below 25%. The flow rate of molten salt in this system is only 6.6%~31.2% to that of a steam heating system. During the heat discharging process, the water is drawn from the inlets of No.1 and No.2 high pressure heater. The water temperature is 182.4~242.7 ℃. The molten salt-condensed water heat exchanger is self-anti-condensation. The cycling efficiency during the heat discharging process is 32.7%~33.9% at different unit loads, indicating unit load has little effect on the cycling efficiency of the peaking shaving system. The research results can guide the engineering application of the deep peak shaving technology of thermal power units coupled with molten salt heat storage.

In order to reduce the phenomenon of "wind and solar energy power abandonment" caused by the mismatch between the on-grid electricity generated by renewable energy power and coal-fired power unit, the coal-fired power unit needs to achieve the deep peak shaving to provide the grid space for renewable energy power with the continuous increase of the installed capacity of renewable energy. At the same time, the coal-fired power unit provides the ability to further consume renewable energy power. The utilization of coupling reheated steam extraction with thermal energy storage and molten salt thermal energy storage heated by renewable energy power in deep peak shaving system of coal- fired power unit is proposed. The research on large-scale renewable energy power consumption by peak shaving system of coal-fired power unit integrated with thermal energy storage is discussed. Moreover, the comprehensive coal consumption for power generation and the CO₂ emission is analyzed. The results show that, the power output of the coal-fired unit decreases from 300.03 MW to 210.07 MW when the reheated steam extraction mass flowrate is 270.70 t/h, and the maximum power of renewable energy power consumption by thermal energy storage system is 187.26 MW. When the stored heat is released, the power output of coal-fired unit increases from 300.03 MW to 348.68 MW. When the renewable energy power consumption per unit time is 187.26 MWh, the comprehensive coal consumption for power generation is reduced by 8.49 g/kWh and the CO₂ emission is reduced by 28.23 t. This study provides a guiding idea for the absorption of high-proportion renewable energy power.

Flexible transformation of thermal power units is the key to build a new power system and achieve the goal of "carbon peak" and "carbon neutrality". In order to promote the flexibility of thermal power units, the coupling scheme for small steam turbine drive and motor drive liquid compressed carbon dioxide energy storage system and thermal power unit is put forward, and the thermodynamic system model is established. Moreover, the heat consumption rate and energy utilization coefficient are used to evaluate the system, the thermodynamic performance of the system is compared and analyzed, and the optimal coupling scheme of energy storage is established. The researches show that, in the energy storage stage, condensate water is extracted from the outlet of the condensate pump, and the compressed heat is absorbed and returned to the outlet of No.7 low-pressure heater. In the energy release stage, steam is extracted from the exhaust of the middle pressure cylinder, and the expanded CO₂ is heated and returned to the No.5 low-added hydrophobic cooler, the coupling system has the best performance. The heat consumption rate is 48.308 kJ/(kW·h) lower than that of the original system, and the energy utilization coefficient increases by 0.52 percentage point. Changing the inlet temperature and the mass flow rate of CO₂ expander can quickly change the load. After coupling with the energy storage system, the peak regulation capacity of thermal power unit increases by 17.1%, when the hot water tank is configured and the maximum heat is released, the peak regulation capacity of the unit increases by 37.4%, indicating the flexibility of thermal power unit is improved.

Electric heat storage technology is an important approach to promote the utilization of electric energy, which has a broad prospect in the aspects of deep peak shaving, improving the utilization rate of new energy and protecting environment. In order to explore the adaptability of heat storage in steam heating, molten salt heat storage system and solid heat storage system are designed and compared based on specific engineering project. An optimal design scheme of molten salt heat storage system is put forward, and comparison is conducted from the aspects of system performance, economy and reliability. The result shows that, the proposed optimization scheme is beneficial to save investment, save space and simplify the system. For the electric energy storage heat supply station with simutaneous heat storage and heat discharge working conditions, the molten salt heat storage mode it is recommended, which is more stable for steam generation. Although the molten salt heat storage system is more complex and the total investment is slightly higher, it has higher heat exchange efficiency, lower power consumption, lower operating cost and higher income. If the total investment can be further reduced, molten salt heat storage technology will become the most competitive clean heating method in heat storage.

The transformation of energy production to renewable energy is the only way to achieve the dual-carbon goal. At present, the lack of peak shaving capacity and flexibility of coal-fired units hinders the large-scale consumption of renewable energy. In this paper, taking a 600 MW coal-fired unit as the research object, eight schemes for peak shaving system aided by molten salt heat storage are proposed, and the peak shaving capacity and thermal performance of each scheme are compared and analyzed through simulation calculation. The results show that, the peak shaving system can improve the flexibility of coal-fired unit, effectively regulate the output, and greatly expand the operating range. Heating by electricity causes a large amount of exergy loss, while extracted exhaust of intermediate pressure cylinder causes a small amount of exergy loss. The maximum peak shaving capacity can be obtained by the scheme of heating the molten salt directly by electric energy output by generator when charging, and heating the bypass feedwater by high-temperature molten salt when discharging, whose peak shaving depth can reach 17.83%. Moreover, the highest system efficiency and economy can be obtained by the scheme of heating the molten salt with extracted exhaust of intermediate-pressure cylinder when charging, and heating the bypass feedwater with high-temperature molten salt when discharging, of which the system thermal efficiency and exergy efficiency are 40.95% and 40.29% respectively, and the coal consumption rate is 350.01 g/(kW·h).

With the continuous progress of the work of "carbon neutrality and carbon peak", the installed scale of photovoltaic, wind power and other new energy is expanding, energy saving and consumption reduction as well as flexibility improvement become the two key tasks the thermal power units faced. Through mathematical modeling and hourly calculation analysis for the hybrid system, performance and economic characters for solar-thermal systems replacing high pressure heaters are obtained. The calculation results indicate that, using solar thermal and coal fired hybrid system can realize sharp decline of the unit coal consumption, which is a most direct and effective method for coal saving and reducing consumption, it has great significance for life prolonging of the units to be retired from active service because of high coal consumption indexes. However, the economic benefit of the system itself is insufficient. So it can be supplemented with molten salt electric heater to improve the system's frequency modulation ability and enhance the project's profitability. According to the calculation, when the frequency modulation income is not considered, the system's yield is only 6.0%, but it can be increased to 8.0% after considering the frequency modulation income. Therefore, the hybrid system has double effects in improvement of both coal saving transformation and flexibility transformation.

In order to solve the problems of high supercooling degree, low thermal conductivity and poor cycle stability of single hydrated salt phase change material, ammonium aluminum sulfate dodecahydrate was used as phase change material, Al₂O₃ and xanthan gum were used as additives to modify ammonium aluminum sulfate dodecahydrate by melt blending, and a new composite phase change material was prepared by using porous adsorption method to composite modified expanded graphite and modified ammonium aluminum sulfate dodecahydrate. The thermophysical properties, supercooling degree, cycle stability and material compatibility were analyzed. The results show that, the melting point, latent heat and thermal conductivity of the composite phase change material were 93.23 ℃, 235.40 kJ/kg and 4.086 W/(m·K), respectively. After 50 cycles, the supercooling degree was stable at 24 ℃, and after 300 cycles, the latent heat only decreased by 5.9%, with good stability. The 316L stainless steel and composite phase change materials have good compatibility, and can be used as packaging container materials. The composite phase change material has good performance and great application potential in building heating.