Geothermal power generation, as one of the main ways to develop and utilize geothermal resources, is of great significance to promote the low-carbon and clean energy structure and the realization of the “dual carbon”. Firstly, the development history of geothermal resources in the world is analyzed. Then, main geothermal power generation technologies such as dry steam power generation, flash steam power generation, binary cycle power generation and wellhead power generation technology are overviewed. On this basis, the hot dry rock power generation, thermovoltaic power generation, supercritical CO₂ cycle power generation, combined power generation technology and multi-energy eomplementary power generation technologies such as geothermal-solar, geothermal-wind, geothermal-biomass, and geothermal-ocean energy, are elaborated in detail. Finally, combining with the current situation and existing problems of geothermal power generation in China, some suggestions for the development of geothermal power generation are put forward, to provide reference for the future development of geothermal power generation.

In order to inhibit the flow separation on blade surface and improve the aerodynamic performance of the blade, the design scheme of installing vortex generator on the blade surface is proposed. Taking DU97-W-300 blade section with vortex generator as the research object, the orthogonal experimental design method is used to investigate the influences of height, length, installation angle, chord installation position, spacing and pitch of the vortex generator on the aerodynamic performance of the blade section, so as to determine the basic law of vortex generator parameter design. The results show that, the vortex generator parameters that affect the magnitude of aerodynamic performance of the blade are as follows: spacing, pitch, length, height, chord installation position, and installation angle of the vortex generator. The optimal vortex generator parameter combination law is: height of 0.75ξ (ξ is blade boundary layer thickness), length of 1.6ξ, installation angle of 20°, chord installation position is 10% blade chord length, spacing of 1.6ξ, pitch of 0.8ξ, which can increase the maximum lift coefficient of this blade by 40% and the maximum stall angle of attack by 9.5°.

In natural gas-steam combined cycle power plants, the connection section between the gas turbine and the waste heat boiler is characterized by a sharply expanded channel confined by plates with large inclination angles, which often results in unsatisfactory flow pattern and consequently leads to a reduction in deNO_x efficiency in the downstream. Installation of triple layers of deflectors is proposed to improve the flue gas flow uniformity. Computational fluid dynamics modeling approach is adopted to investigate the influences of the deflector parameters including installation arrangements, installation angle and density on the flue gas flow characteristics in the flue duct. A large vortex is clearly observed in the connection section with a vorticity up to 20 m^–1, when no deflector is installed. Installing a single layer of deflector with varying installation angles is able to decrease the size of the vortex, while installation of double layers of similar deflectors leads to a satisfactory flow pattern in the connection section. A more preferable flue gas flow pattern in the whole boiler channel is obtained by a setup of triple layers of deflectors. The optimal lengths projected horizontally are 2.25 m, 1.36 m and 0.70 m for the three-layer deflector plates, and the distances between two plates are 1.20 m, 1.40 m and 1.00 m separately. The installation angle is between 15° and 30° with uniform incrementation for the first deflector, and between 15° and 60° with uniform incrementation for the second deflector. A relative velocity standard deviation of 2.1% is obtained at outlet cross-section with the triple deflectors. The research results can provide theoretical guidance for the design of flue gas flow equalization devices

Renewable energy suffers some drawbacks such as instantaneity, instability, and the mismatch between supply and demand during the utilization. Thermochemical heat storage exhibits distinct advantages, including high heat storage density, elevated heat storage temperature, and negligible heat loss during the long-term storage. It has the capability to convert intermittent energy sources into stable moderate and high temperature heat energy to fulfill the needs of fluctuating output. The classification, basic mechanisms and characteristics of thermochemical heat storage within reaction temperature range of 400~1 100 ℃ are reviewed. Subsequently, the thermal storage performance of typical thermochemical heat storage materials, such as carbonates, hydroxides, oxides, metal hydrides, ammonia and methane are analyzed, and the structural targeted regulation and modification methods are investigated, alongside the introduction of typical demonstration projects. Following this, the reactor design and system integration of solid-gas and gas-gas reaction systems are discussed. In the last, the future research interests are deliberated and proposed in the development and industrial application of thermochemical energy storage materials.

With the rapid development of artificial intelligence, virtual reality and augmented reality technology, it is possible to realize real-time monitoring of operation state of air cooling island of direct air cooling unit by using digital virtual technology. Firstly, a three-dimensional model of the air-cooled island is established, and the operating state parameters of the air-cooled island are obtained by numerical calculation. The air-cooled island operating state database and display and query software are developed. Secondly, based on the concept of digital twin, a meteorological station is set up in the power plant to obtain real-time change data of ambient temperature, wind speed and wind direction, and the operating conditions of the unit are used as software input parameters. Finally, the operation state of the air-cooled island is calculated and displayed in three dimensions. The real-time display technology for air operation state of air cooling system based on digital twin avoids the investment and maintenance of a large number of measuring points on site, which lays a foundation for the development of intelligent power stations.

In order to improve the flow field structure of rain area in cooling tower and further increase the ventilation, on the basis of the existing flat plate type wind guide plate, this paper proposes a streamline wind guide plate with low wind resistance that can be arranged in the rain area. Under the design condition, by taking the conventional cooling tower and the reformed tower with flat plate-type air guide plate arranged at each height as the reference objects, the influences of the low wind resistance streamline air guide plate on ventilation, flow field structure and temperature distribution of the whole tower are analyzed, at five different arrangement heights (1/6, 1/3, 1/2, 2/3, 5/6 air intake height). The results show that, with the rise of the height of the air guide plate arrangement, the air distribution in each region of the tower has changed, which has a significant effect on the packing heat exchange in inner zone, so that the cooling performance of the whole tower improves at first and then declines. When arranging the streamlined wind guide plate at 2/3 height of the air inlet, the ventilation increment and the average temperature reduction at the bottom of the filler area reaches the optimal value, and the improvement effect of the cooling tower performance is the best. Compared with the conventional cooling tower, the circulating water temperature drop and the ventilation increases by 2.65% and 2.78%, respectively. In addition, the circulating water temperature drop increases by 1.2% after the tower is retrofitted with a low wind resistance streamlined air guide, compared with the flat plate with an optimal arrangement height.

To study the effect of dust on performance of photovoltaic power generation, a laboratory bench was built to collect daily power generation data of clean and polluted photovoltaic strings while monitoring meteorological data to analyze the influence of dust accumulation and weather on power generation performance of photovoltaic modules. The results indicate that, the increase in PM_2.5 mass concentration in winter and the frequent occurrence of sandstorms in spring lead to a significant accumulation of dust on surface of the photovoltaic modules, resulting in a rapid increase in cumulative power generation losses. However, in summer, due to increased precipitation, dust is difficult to accumulate on photovoltaic modules, resulting in a slow increase in cumulative power generation losses. In addition, the DTW algorithm is employed to find similar days. Firstly, the entropy method is used to calculate the weights of each meteorological parameter. Then, the DTW values corresponding to each meteorological parameter on each historical day are calculated in reverse chronological order, multiplied by their weights, and added together to obtain the comprehensive DTW value for each historical day. By comparing the comprehensive DTW values of each historical day, the meteorological similar day that is closest to the current day is selected. In order to avoid extreme weather conditions, a portion of the dataset is selected as the validation set, and the criteria for finding similar days are optimized. The data from 9:00 to 15:00 each day is divided into three time periods for analysis, and the condition that the average solar irradiance is not less than 600 W/m² is set. After optimization, the evaluation index determination coefficient of the prediction model is 0.83, and the root mean square error is 0.22, indicating a significant improvement in prediction performance. Finally, the algorithm is used to develop a cleaning strategy for the photovoltaic power plant. After comparing the cumulative power generation loss with the cleaning cost, it is determined that the power plant should be cleaned every 28 days under long-term non rainfall conditions.

Against the actual problems that the wet cooling tower is easy to hang ice at the bottom of the packing and the upper edge of the inlet in winter, a three-dimensional numerical model of the cooling tower based on the constant heat load is established. The anti-freezing characteristics of the cooling tower in severe cold weather without anti-freezing device are explored, and the variation characteristics and influencing factors of key parameters such as the water temperature distribution of packing bottom and the air mass flow at tower top outlet are analyzed. The results show that, the lower the ambient temperature, the greater the influence of the unit load on the average water temperature and the lowest water temperature at the bottom of the packing. The main factors affecting the change of the difference between the average water temperature and the lowest water temperature at the packing bottom include unit load, wind velocities and water distribution mode. Among them, the influence of water distribution mode is greater, followed by unit load, and the influence of wind velocities is less. The air mass flow at tower top outlet is positively correlated with the unit load and negatively correlated with the ambient temperature. When the ambient temperature is the same, the air mass flow at tower top outlet of the outer ring with underwater is less than that of the full tower. The water temperature inside the lower part of the windward side and the outside of the leeward side is the lowest, and the freezing risk is the greatest. When the wet cooling tower is running in winter, the anti-freezing device should be arranged on the windward side and the leeward side.

The effects of blending ratio and heating rate on co-combustion characteristics of municipal sludge and camellia oleifera shell were studied by thermogravimetric analysis, and the combustion kinetics of the samples were modeled by two methods, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). Moreover, the flammability index and comprehensive combustion characteristic index of various samples were calculated, and the interaction between the mixed fuel components during the combustion process was analyzed. The results show that, the burnout temperature of the mixed fuel significantly reduced, and the combustion stability and comprehensive combustion characteristics were significantly improved after the sludge was mixed with camellia oleifera shell. With the increase of the mass blending ratio of camellia oleifera shell from 20% to 80%, the burnout temperature decreased from 590 ℃ to 532 ℃, the burnout degree gradually increased, the mass loss increased from 63.13% to 92.19%, and the flammability index and comprehensive combustion characteristic index increased by 1.66 and 2.32 times, respectively. The interaction between the components of sludge and camellia oleifera shell mixed combustion occurred, which showed an inhibition effect in the volatile combustion stage, while a promoting effect in the fixed carbon combustion stage. The average apparent activation energies of sludge calculated by the FWO method and KAS method were 122.32 kJ/mol and 118.08 kJ/mol, respectively, and the average apparent activation energies of the camellia oleifera shell were 166.46 kJ/mol and 164.94 kJ/mol, respectively. The average apparent activation energy of the mixed samples increased with the mass mixing ratio of camellia oleifera shell.

The P-U characteristic curve of a photovoltaic array exhibits multi-peak characteristics in partially shaded environments, leading to the inefficiency of conventional maximum power point tracking (MPPT) algorithm in tracking the maximum power. To address this issue, this paper proposes a two-layer control model for photovoltaic MPPT based on an improved tuned swarm optimization (TSO) algorithm. In the upper layer, the Levy flight strategy and polynomial mutation strategy are embedded into tuna algorithm, creating the Levy-polynomial mutation tuna swam optimization (LPTSO) to search for the global maximum power point. In the lower layer, the perturbation observation method is employed to locally track the global maximum power point, thereby reducing power oscillations in local shading environments. The two-layer control model is applied to the photovoltaic MPPT simulation system, and the simulation experimental results show that, for multi-peak MPPT control, the proposed model achieves significant improvements in convergence speed, tracking efficiency, power oscillations, etc. In conclusion, the proposed two-layer control model for photovoltaic MPPT effectively addresses the issue of maximum power tracking failure in partially shaded environments.