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 coaxial casing heat exchanger is one of the technologies to realize high efficient heat extraction in the middle and deep geothermal energy wells, and its heat transfer capacity is crucial to the sustainable development of geothermal system. Taking Guanzhong area as an example, the heat transfer model of coaxial casing heat exchanger in middle-deep geothermal wells is established considering the formation inhomogeneity, and the effects of injection temperature, injection flow rate, buried depth and other factors on its heat extraction performance are studied. The influences of injection temperature and injection flow rate on thermal reservoir temperature recovery under intermittent production condition are discussed. The results show that, the outlet fluid temperature decreases with the increasing of injection flow rate, but the heat extraction power of the whole system increases. Increasing the injection temperature can improve the outlet fluid temperature, but the system heat extraction power decreases greatly. With the increasing of formation depth, the temperature of outlet fluid and heat extraction power increase gradually. Reducing the inner pipe diameter and enlarging the outer pipe diameter can effectively improve the temperature of outlet fluid and heat extraction power. The temperature recovery ability of the thermal reservoir increases with the injection flow and injection temperature. Reducing the thermal conductivity of inner pipe or choosing double-layer inner pipe structure can reduce the fluid temperature loss along the inner tube and increase the outlet fluid temperature.

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.

Energy storage is the key technology of novel power system. As a medium and high temperature heat transfer and heat storage fluid, molten salt has the advantages of high heat capacity and good stability. It has been widely used in concentrated solar power (CSP) system, peak and frequency modification, green electricity consumption and other new energy fields. However, at present, the core components of molten salt energy storage system, such as the tanks, the electric heaters, the heat exchangers, and so on, are studied and developed based on the demand of CSP technology. The other application scenarios are not sufficiently considered. However, in different application scenarios, the working temperature range, heating and heat exchange methods have different requirements on molten salt. Therefore, the research status and technical achievements of the key technologies of molten salt heat storage are summarized. The development path of molten salt energy storage technology and its application in novel power systems are studied. According to the different application scenarios, the requirements on molten salt parameters and the suitable types of storage tanks and heat exchangers are illustrated.

In order to improve the energy utilization efficiency of high flexibility power generation system coupled with internal combustion engine and coal-fired unit, a new thermal system combined with the internal combustion engine and the coal-fired unit was proposed. By feeding the flue gas of internal combustion engine and the waste heat of cooling water into the thermal system of coal-fired generating unit, the coal consumption of coal-fired generating unit can be reduced. EBSILON software was used to model the composite system. Steam consumption rate and heat consumption rate of the coal-fired units were taken as evaluation indexes to analyze the thermal economy of the coal-fired unit under different composite schemes. The results show that, the heat consumption rate and steam consumption rate of the coal-fired unit can be significantly reduced by combining the waste heat of the internal combustion engine into the thermal system of the coal-fired unit. The closer the compound position of flue gas waste heat is to the boiler, the smaller the proportion of feed water and condensed water involved in flue gas heat exchange, and the lower the heat consumption rate and steam consumption rate of the unit. When one part of the flue gas waste heat is used to heat the high pressure heater feed water and the other part is used to heat the low pressure heater condensed water, more waste heat will be allocated to feed water, and the heat consumption rate and steam consumption rate of the unit wil decrease. After optimization, the heat consumption rate of the combustion engine and coal-fired unit combined thermal system can be reduced by 6.62% at most.

Tibet is located in the hinterland of the Qinghai-Tibet Plateau, the area above 4 000 m accounts for 85% of the total area of the region, its geothermal resources are very rich. To realize the reasonable exploitation of geothermal resources, combined with the carbon peaking and carbon neutrality strategy, the current situation of the development and utilization of geothermal resources in Tibet is comprehensively combed, and the suggestions for the future development of the geothermal industry are put forward. The analysis shows that the geothermal resources of hydrothermal and dry hot rock in Tibet have large storage capacity, good quality, and excellent power generation potential. The shallow geothermal resources are mainly distributed in Lhasa, which can be combined with heat pump technology for local heating. At present, there are still some problems in geological exploration, technical improvement, equipment development, and operation management. It is necessary to develop ORC units, build EGS experimental platform, and scientifically develop deep geothermal energy. The research shows that the development and utilization of geothermal resources in Tibet should follow the principles of "survey-based, power generation-based, heating-assisted, equipment upgrading, and cascade utilization", promote the scientific exploitation and efficient utilization of geothermal resources, improve the geothermal industry chain, and effectively improve the energy consumption structure in Tibet.

The high-temperature and high-pressure (300 ℃/10 MPa) corrosion electrochemical behavior and oxide film microscopic features of Incoloy 800H alloy aged at 675 ℃ for 0~10 000 h in alkaline environament were investigated systematically. By means of electrochemical test, long-term immersion test, scanning electron microscope/transmission electron microscope observation, Raman spectroscopy/fast Fourier transform analysis and other methods, the electrochemical activity, evolution of oxide film morphology and composition characteristics of the 800H alloy with extension of aging time were systematically studied. The results show that, the value of open circuit potential and self-corrosion potential E_corr of the 800H alloy in high-temperature and high-pressure water can be slightly increased by aging treatment, but the effect of aging time extension on the electrochemical behavior was not significant. A passive to trans-passive process was depicted. The oxide film of the 800H alloy formed in high-temperature and high-pressure water had a multilayer structure: the most outer layer was the dispersed large particle oxides composed of Fe₂O₃ or NiFe₂O₄; the middle layer was relatively compact small size oxides, mostly NiFe₂O₄ or FeCr₂O₄; while the inner layer was dense and continuous oxides, amorphous or nanocrystalline oxide containing Cr and a small amount of Fe. The 800H alloy has good corrosion resistance and surface stability in alkaline high temperature and high pressure water of 300 ℃/10 MPa.

As a clean and efficient power generation technology, solar thermal complementary combined cycle power generation (ISCC) system is concerned widely. By taking the ISCC system containing three-pressure reheat combined cycle and trough solar field as the research object, and based on the conventional trough ISCC system (using solar energy to replace the high pressure evaporator (system 1)), two new trough ISCC system are presented, namely using solar heat collection field to replace the high and medium pressure evaporators simultaneously (system 2), and using solar heat collection field to replace the high, immediate and low pressure evaporators simultaneously (system 3). Moreover, the dynamic performances of the above three ISCC systems are analyzed under the operation condition of typical day. The results show that, with proper operation strategy presented above, the three systems can not only realize safe and stable operation, but also reduce the impact of solar energy varies on the ISCC system output power. Under the operation condition of typical day, the second type of ISCC system (system 2) has better thermal performance.

In order to study the corrosion behaviors of candidate materials for superheater of supercritical boilers in high-temperature flue gas environment, three austenitic heat-resistant steels including S31042, S31035 and C-HRA-5 were exposed to laboratorial simulated coal-fired flue gas for hot corrosion tests. The tests were carried out at 650, 675, 700 and 725 ℃. On the sample surface, there were three conditions including no coating, coating with real coal ash, and coating with corrosive simulated coal ash. The test duration was 500 h. The corrosion kinetic curves of the three materials were obtained through experimental research, and corrosion behaviors of the material were analyzed by XRD, SEM and EDS. Moreover, corrosion resistance of the three materials was compared. The results indicated that, the three materials had excellent resistance to oxidation and corrosion under the conditions of no coating and coating with real coal ash. Under the condition of coating with corrosive simulated coal ash, the material corrosion intensifies and the corrosion products are layered. The temperature effect was different under different coating conditions. S31042 had the best corrosion resistance, and the corrosion resistance of S31035 and C-HRA-5 materials was comparable.

In the point cloud splicing of underground pipe gallery in power plants, an improved algorithm with 3D-Harris operator about corner detection is proposed. In this algorithm, firstly, taking multiple sets of massive point cloud data of the underground pipe gallery as analysis object, the normal information of the target detection point on the adjacent point cloud microtangent plane is obtained through principal component analysis method, thus the boundary points of the point cloud are extracted. Secondly, the covariance matrix is constructed according to the normal information of the target detection point, then the corner response intensity function is calculated and compared, and some points are selected as calculation objects to judge whether they are true corner. Thirdly, the pseudo angles are filtered out and the true angles are selected by using a pseudoangle detection method based on Gaussian curvature extreme points. At last, the fast point feature histogram method is used to match similar corners between each group, and the nearest point search point cloud registration algorithm is used to realize the splicing of multiple points and cloud in the underground pipe gallery. The results are compared with that of the conventional 3D-Harris angular point detection algorithm. It is proved that the method in paper takes less time to calculate and has a higher corner-point extraction accuracy, which can realize accurate splicing of massive point cloud of underground pipe gallery.