This paper studied the simulation of methanol synthesis from CO2 and green hydrogen, and proposed an indicator of the energy storage density of CO2. Then influences of multiple variables on the performance indicators were analyzed. The results show that the systematic energy efficiency and energetic yield of methanol increase with the increase in the electrolysis efficiency, per pass CO2 conversion rate, electrolysis pressure, and initial CO2 pressure. However, these indicators decrease with the increase in the methanol synthesis pressure. The variations of the energy storage density of CO2 with these variables are opposite to the systematic energy efficiency and energetic yield. The electrolysis efficiency and per pass CO2 conversion rate are the sensitive and key variables of this process. Under the optimal conditions, the systematic energy efficiencies based on the higher and lower heating values are 68.0% and 59.6%, respectively, the energy storage density of CO2 is 6.07 kWh/kg, and the energetic yield of methanol is 0.108 kg/(kW·h), indicating the powertomethanol system using CO2 as feedstock is unsatisfactory in term of systematic energy efficiency, but has significant advantage in the energy storage density.

The abandoned mines contains abundant geothermal resources.This article takes the mine water of gob area as the research object; in order to ensure the stability of pumping temperature during the heating season, the layout and parameter sensitivity of pumpingrecharging wells of water source heat pump of abandoned mine are studied. Firstly, based on the Darcy's law and the theory of heat transfer in porous media, the twodimensional numerical calculation models of the coupled multiphysical fields of the pumpingrecharged well are established.Secondly, the pumping water's temperature variation of 14 arrangement forms of pumpingrecharging wells are analyzed while the theoretical models are employed. The most reasonable arrangement form can be selected according to the degree of the heat transfixion. Finally, when the selected pumping recharging wells'arrangement form is taken into consideration, the effects of different factors including the recharge temperature, the pumpingrecharging water's flow rate, the wells' spacing, the hydraulic slope, the aquifer thickness and the porosity on the pumping temperature are discussed. The results of the analysis show that the well placement method of triangle 4 only decreases the pumping temperature by 0.148 K at the end of the system operation, and the occurrence of "thermal penetration" is the least and the well placement method is the most reasonable. The occurrence of "heat transfixion" in the aquifer is more sensitive to parameters such as pumping flow rate, well spacing, hydraulic gradient, and aquifer thickness, while it is less sensitive to recharge temperature and porosity.

It is a promising technology to store CO2 by hydrate formation in seafloor sediments. In this paper, the evolution process of CO2 hydrate formation promoted by amino acids in natural sand system was studied by hydrate formation test in a visible reactor. The experimental results showed that the formation rate and amount of CO2 hydrates in 8 mmol/L Lmethionine solution were significantly higher than those in deionized water system; The natural sand with medium particle size had the best promotion effect on the formation of CO2 hydrate, and a large amount of CO2 hydrates were generated in it, which effectively filled the gap between natural sands; Secondly, a lot of CO2 hydrates were also generated in small size natural sand; The effect of large particle size natural sand on promoting the formation of CO2 hydrate was not obvious, and no obvious CO2 hydrate formation was found inside, only a small amount of CO2 hydrates was observed on the inner wall of the reactor.

Aiming at the problem of lack of a large number of actual fault image training samples during the fault diagnosis and modeling of offshore wind turbine blades, an image recognition method for offshore wind turbine blade faults based on small data sets is proposed. In this method, the Kmeans clustering algorithm is improved to identify blade segmentation according to the color and shape characteristics of blades and their faults in wind turbine blade images, an adaptive algorithm is designed to adjust the Canny operator parameters to identify the segmentation of early fault areas on the blade surface, and the Kmeans clustering algorithm is used to extract the color and shape features of faults and design corresponding classifiers to achieve fault classification. Simulation examples show that this method is effective for the identification of early faults on the blade surface, and can provide an accurate diagnostic model for the blade fault identification of offshore wind turbines on the basis of a small number of fault samples, which can improve the operation and maintenance efficiency of offshore wind farms.

In view of the problem that data center evaporative cooling technology limited by the ambient wet bulb temperature, a solar energy and heat pump complementary drive the desiccant wheel evaporative cooling air conditioning system in data center was proposed. The system uses the waste heat of photovoltaic modules to provide thermal energy complementary heat pump system to drive the dehumidification regeneration. According to the outdoor meteorological conditions, the system can realize three operation modes: fresh air, evaporative cooling and dehumidification & evaporative cooling. The TRNSYS software is used to simulate the thermal, power and energy consumption characteristics of the three typical regional data centers in Shanghai, Guangzhou and Kunming. The results show that in the typical daily dehumidification +evaporative cooling mode in Shanghai, Guangzhou and Kunming area, the desiccant wheel pretreatment reduced the air wet bulb temperature by 10.9 °C, 11.6 °C and 10.3 °C on average compared with the outdoor wet bulb temperature. The average typical monthly system COP values in Shanghai, Guangzhou and Kunming were 4.9, 5.1 and 3.6, respectively, and the maximum instantaneous COP value was 12.1, 11.4 and 8.1.

The wide shallow bucket foundation with concrete arc transition section is subjected to significantly larger wave loads which will easily affect the vibration response of the entire structural system. For an offshore wind turbine (OWT) supported by bucket foundation, a finite element model of the whole wind turbine was established based on the measured vibration data, and then the influence of wave loads on the vibration response of the tower top of the OWT supported by bucket foundation was simultaneously analyzed through the established finite element model. It is shown in the analysis results that the vibration response of the tower top caused by wind load is greater than that caused by wave load during the operation period. Subsequently, the influence of the wave load can be ignored compared to the wind load when the wave height is small. In addition, the impact of wave loads on the vibration response of the tower top increases with the increase of external wind speed and wave height and the corresponding impact on the vibration displacement response of the tower top is greater than the vibration acceleration.

In order to suppress the false information existing in the interactive information between microgrid (MG) and microgrid cluster operator (MGCO), a trading mechanism with the Stackelberg game is proposed, and a dynamic integrity factor is used to consider the honesty behavior of the MG. Firstly, a reward and punishment mechanism based on the reported electricity quantity and the actual trading quantity is established. Transaction price can be adjusted by credit factor. Secondly, a Stackelberg game model with MGCO as leader and MGs as followers is developed. The upper level minimizes fluctuation of power for microgrid cluster, where a contract mechanism of transaction is established to adjust basic transaction prices within the cluster. In the lower level, the cost of MG operation is minimized. Each MG acts as the follower responding to the dayahead trading price and decides the electricity of exchange power with MGCO. Finally, the study prove that the presented transaction mechanism effectively suppresses the false information.

With the largescale integration of wind power, power system subsynchronous oscillation (SSO)events occur frequently, which seriously threatens the safe and stable operation of the power grid. The accurate detection of SSO in wind power gridconnected system is of great significance to ensure the stable operation of the power systems. Most of the existing SSO detection methods are singlechannel methods, which are difficult to take into account the global SSO characteristics of the systems. Therefore, this paper proposes a SSO detection method for wind power gridconnected system based on multivariate empirical mode decomposition (MEMD). Firstly, the multivariate empirical mode decomposition is performed on the measurements of wind power gridconnected points, and then the IMF components with SSO mode are screened out via TeagerKaiser energy operator (TKEO). Then, the HilbertHuang transform (HHT) is used to identify the SSO frequency and damping ratio. Finally, the proposed detection method is analyzed by the improved 4machine 2area system simulation data, and the results verify the effectiveness of the proposed method.

Lignin is one of the main components of biomass and can be converted into renewable fuels and chemicals by catalytic hydrodeoxygenation. Extensive fundamental research has been conducted based on lignin model compounds and heterogeneous catalytic systems. However, the hydrodeoxygenation of lignin model compounds with high selectivity remains a significant challenge due to their intricate molecular structures, which are featured with hydroxyl and methoxyl groups connected to the phenyl ring, leading to diverse reaction pathways. In this paper, the factors affecting the selectivity of the product were reviewed comprehensively. First, the reaction mechanisms and pathways involved in the hydrodeoxygenation of lignin model compounds were stated. Next, the factors influencing the selectivity of the products were summarized from two aspects. One aspect is focused on the hydrodeoxygenation catalysts, including catalyst components, promoters, supports, and preparation methods; the other is associated with the reaction conditions, including reaction temperature, hydrogen pressure, time, and solvents.

In order to improve the efficiency of CO2 cycle system for electric vehicle, a transcritical CO2 system with regenerator and gas injection in the middle was constructed. The effects of Tgo, Pg, Pm, B, AT on EER, Qe and To were studied by simulation. The results show that Pgo and Pm,opt makes the EER reach the maximum value, and the relationship between the Popt and the Tgo. An increase in To can degrade system performance, The performance of the system can be improved by increasing the amount of gas injection in the middle and the superheat of the regenerator, which can increase the EER by 15.64% and 6.07%, respectively, and the cooling capacity by 27.88% and 4.78%. The increase of the superheat of the regenerator will lead to the increase of the discharge temperature of the compressor, the gas injection in the middle can reduce the discharge temperature of the compressor, when the discharge temperature of the compressor is limited, the optimization ability of the regenerator to EER and cooling capacity can be increased by 203% and 173.87%. Compared with the basic transcritical CO2 system, the optimized system can increase the EER and cooling capacity by 18.38% and 35.03%.