Phase change heat storage technology plays a crucial role in addressing the intermittent and fluctuating challenges associated with solar energy. This study presents a novel low-temperature phase change heat storage unit (GCHST) featuring a virtual boundary grid structure that enhances solar-thermal storage performance. We propose two new metrics - normalized temperature (T*) and synchronous storage-collector ratio (CSR) - to establish a robust correlation model between T* and the global heat transfer coefficient (U). Results indicate a strong negative correlation between T* and U, with distribution ranges during charging being 3.17 and 3.39 times wider than during discharging, respectively. The h(U) = 1/(U-1) varies quadratically with the coded T* values, which yielding the coefficient of determination (R2) greater than 0.9800. The sensitivities of heat storage (Pq-s) and collection (Pc) power to optical power (Po) show a marked shift at the initial melting point (48.65 degrees C) of the paraffin-phase change material (PCM), a transition that coincides with the CSR exceeding 1.00. The GCHST achieves a notably high daily integrated CSR of 0.89. This work offers novel quantitative indicators and structural insights for the design of advanced PCM thermal storage systems.

Existing theoretical models for photovoltaic (PV) modules exhibit inherent limitations, including the incomplete integration of dynamic environmental factors and disconnect between the maximum power point tracking (MPPT) mechanism and physical model. To address these issues, we developed a novel optical-electrical-thermal coupling model (G-model) based on a BP neural network algorithm. This model employs BP neural networks to predict maximum output power (Pm) of PV modules and the transmittance (tau g) of the glass cover, integrates the calculation model for total solar irradiance on inclined surfaces (GT), and a heat transfer model, enabling rapid iterative solutions under complex operating conditions. Experimental results demonstrate that the correlation coefficients (R) for the training, validation, and test sets of the BP neural network-based prediction models for Pm and tau g were all close to 1.0000, indicating a strong agreement between predicted and measured values. The prediction errors were tightly clustered around zero, confirming the high accuracy of the proposed models. The average prediction errors of the G-model for backsheet temperature (tted) and output power (P) were 1.22 % and 2.50 %, respectively, which were 62.20 % to 96.10 % lower than those of the reference models (P-model and Qmodel). Nine interaction terms - including wind speed (v) with horizontal plane direct irradiance (Gb) and wind direction (theta) with dust accumulation (m) - exhibited significant interactive effects (P-value<0.01) on tted, P, and photoelectric conversion efficiency (eta e). This study provides high-precision prediction tools and theoretical support for real-time control, fault warning, and material selection in PV power plants.

Solar membrane distillation was an effective method for addressing freshwater shortages, particularly in brackish and island areas. Traditional hydrophobic alpha-Al2O3 ceramic membrane (HCM) distillation technology offers several benefits, including low operating temperature, high desalination rates, broad application temperature range, and various driving modes. However, poor solar-driven desalination performance, characterized by water production capacity and desalination efficiency, still limits its large-scale application. To enhance desalination performance, we developed a novel HCM hot-side free-interface evaporation synergism membrane distillation (IEMD) module. We also created a comprehensive water yield (Ema) prediction model to research the water production capacity and the underlying principles of the novel IEMD module. This process utilized a combination optimization method based on quadratic backward regression and orthogonal testing. Additionally, we examined the desalination capability of the new IEMD module. The results showed that the contribution rate of HCM hot side free-interface evaporation links to Ema by 39.34 % to 63.79 %. Factors such as Qr & sdot;Tc, Tr & sdot;Tc, Qr & sdot;Qa, Tr & sdot;Qa, Tc & sdot;Qc, and Tr & sdot;Qc all significantly influence Ema, with their significance and interactions decreasing in the order listed. The optimal levels of Tr, Qr, Tc, Qc, and Qa were found to be 70.00 degrees C, 160.00 L/h, 16.00 degrees C, 270.00 L/h, and 90.00 m3/h, respectively. Under these conditions, Ema reached 2523.08 g/(m2 & sdot;h), which was 2.82 times higher than that of the traditional HCM distillation module. Furthermore, the novel IEMD module could efficiently intercept electrolyte ions, suspended solids, and salt ions in raw water, indicating excellent desalination capabilities. This study presents a promising direction for resolving the freshwater supply and demand imbalance in brackish and island areas, providing a new theoretical and engineering framework for further development.

Photovoltaic power generation was one of the fastest -growing and most promising forms of solar energy utilization, and dust deposition had an important effect on the output capacity of photovoltaic modules. However, the law and mechanism of dust deposition influence the output performance of the PV modules was still not perfect and deep enough at present. In this paper, the prediction model of the thermal boundary layer thickness (delta T) was constructed, and the influence laws of dust deposition on the total attenuation rate (rt) of the top surface and the average temperature (TW) of the backplane surface were explored. Besides, the bidirectional effect of dust deposition on the output performance was researched. The results show that the main components of the dust on the top surface of the PV modules were the quartz or aluminosilicate transported remotely by atmospheric circulation and deposited. The delta T at any position of the photovoltaic module decreased with the increase of parallel wind speed (v||) by the law of -0.49800 power function, and convective heat transfer coefficient (h) changed positively with Re by the law of 0.48752 power function. In the total solar irradiance (G) decreases period and dust deposition amount (A) was 2.024201 g/m2, the influence rate of dust deposition (r) had a maximum value of 0.015363. The dust deposition attenuation rate (rdA) and the temperature gain rate (rtE) all changed positively with A by power function law, and the increase rate of rtE and rdA eventually tends to 0 and infinity, respectively. The theoretical dust removal point of the rooftop PV modules in Hohhot Urban was 5.82661 g/m2.

The carbon dioxide heat pump (CDHP) offers efficient heating over a wide temperature range, but its heating energy efficiency under low-temperature conditions decreases obviously due to a correlation with the evaporation temperature, limiting the widespread use of CDHP in cold regions. To address this, we implemented a passive solar house with short-term heat storage capacity to raise the evaporation temperature and studied it by experimental and theoretical analysis. We introduced the concept of contribution degree (K) of solar energy to the heating performance coefficient of CDHP. The prediction models for the evaporation temperature, heating performance coefficient, and K were constructed gradually. The study optimized the operation mode of solar-assisted CDHP using the evaporation temperature partition theory and presented a method to calculate the limit distribution range of K. The result shows that the order of importance level of the significant items on evaporation temperature was ambient temperature (T-a) > direct solar irradiance on the inclined surface (G(b)) > scattering solar irradiance on the inclined surface (G(r)) > G(b)center dot T-a > T-a(2) > G(b)(2). The predicted limit distribution range of K was [0.00, 8.17]. The study optimized the operation mode of solar-assisted CDHP into three categories. It was observed that K changes positively with any single variable according to the law of a composite function composed of a natural exponential function and a quadratic function. Our study suggests a feasible development direction and offers a new theoretical and engineering basis for overcoming the large-scale application limitations of CDHP in cold regions.

The deposition of aerosol particles can significantly affect the surface transmittance of photovoltaic (PV) modules and thus reduce photoelectric efficiency. With the aid of the control variable method, orthogonal experimental design, and stepwise linear regression method, a numerical simulation study of the deposition process of aerosol particles on the surface of a PV module is carried out in this paper. The influence laws of inflow wind velocity (v), particle diameter (d), installation angle (α), and particle concentration (c) on the deposition process of aerosol particles are analyzed, respectively. The deposition mechanism of aerosol particles on the surface of the PV module is disclosed, and the prediction model of deposition rate (n) is proposed. The results show that v, d, and c all positively affect n of the aerosol particles within the value ranges of each investigation variable in this study. α positively affects n of the aerosol particles when v is less than 3.65 m s−1. α negatively affects the n of the aerosol particles when v is larger than 3.65 m s−1. The prediction model could accurately predict the n of aerosol particles. This research has a theoretical guiding significance for the formulation process of cleaning strategies for the surface of PV modules.

The mass fraction of 0.01 wt% ZnO nanofluid was prepared via the two-step method. The measurement verifies that ZnO nanofluids have better transmission characteristics in the frequency division window range of 400–1200 nm. At the same time, it has good absorption characteristics in ultraviolet and near-infrared bands, which meets the application conditions of the spectral beam-splitting module of the PV/T system. A spectral beam-splitting module of the PV/T system was designed. The simplified physical model was established in ANSYS 14.0. The flow field and convective heat transfer were simulated for different arrangements of the interlayer inlet to obtain a more ideal and uniform temperature distribution to improve the system’s comprehensive efficiency. The results show that the fluid flow in the interlayer under case II is more uniform, and the temperature field distribution is better than other arrangements. Hence, this work could provide a reference for optimising nanofluid flow within a spectral beam-splitting module.

In this paper, the effect of melting characteristics of CuO/paraffin wax composite phase change material in a spherical heat storage unit in a constant temperature water bath is investigated. Experiments were conducted in three different water bath temperatures (65 °C, 70 °C, and 75 °C). The inner surface of the sphere was fixed with two, four, and six pin-shaped fins 3 mm in diameter. The spheres were filled with different mass fractions of CuO nanoparticles/paraffin phase change materials. Experimental CCD was used to model and optimize the spherical thermal storage unit. Regression models were developed to predict the effects of various operational factors on the melting time of the composite PCM. The factors in the model included the number of pin fins in the spherical heat storage unit, the water bath temperature, and the content of added CuO nanoparticles in the PCM, and ANOVA was used to statistically validate the regression model. The results showed that the interaction between the water bath temperature and the number of pin fins had the most significant effect on the melting time. With the melting time of the phase change material as the optimized objective function, the optimized optimal working condition was six pin fins, a water bath temperature of 75 °C, and the addition of 5 wt% CuO nanoparticles/paraffin phase change material, and the actual melting time under this condition was 78.9 min, which was lower than the predicted value of 79.4 min, with an error of 0.63% between them.

为研究不同加热方式下热管的传热性能,该文设计并搭建一套具有非均匀加热功能的热管传热性能实验测试台架.实验测试加热方式(均匀加热、上表面加热、下表面加热)、加热功率和放置倾角对热管传热性能的影响.实验结果表明:加热功率和放置倾角一定,均匀加热时热管热效率最大,下表面加热时次之,上表面加热时最小;下表面加热时,热管总传热热阻最小,蒸发段传热系数最大,外壁面平均温度最低.无论采用哪种加热方式,随着放置倾角的增大,热管热效率均逐渐减小,总传热热阻逐渐增大,蒸发段传热系数逐渐减小;蒸发段液池区域外壁面温度均明显高于液膜区域;液膜区域,沿高度方向外壁面温度变化较小.

With LAMMPS software, the non-equilibrium molecular dynamics (NEMD) simulations study was con-ducted for the membrane distillation process with the hydrophobic alpha-Al2O3 ceramic membrane (HCM). It could further help to explain the macroscopic laws and phenomena that appeared in the membrane dis-tillation tests with HCM. In this study, the average temperature (Tr) of raw water and the negative pres-sure (Pcon) on the cold side of HCM were taken as the investigation variables to research the microscopic water desalination performance of HCM, transport/diffusion properties of water molecules, and related mechanisms. The results showed that the root means square displacement (MSD) of water molecules on the cold side of HCM positively changed with time by the linear trend. The height of the transmembrane energy barrier mainly depends on the atomic structure of the HCM. The diffusion type of free-state wa-ter molecules in the membrane micropores of HCM was the main ballistic-transport-like accompanied by rebound-jump. The influence level of Tr on the number of water molecules in the cold side of HCM was much greater than that of Pcon under the dynamic equilibrium state. The essential reason Tr determined the HCM molecular flux was that it changed the hydrogen bond lifetime in the microporous membrane of HCM.(c) 2022 Elsevier Ltd. All rights reserved.

Integral fin with micro-channels have been widely used in small free piston Stirling engines heater due to their high heat transfer rate, low flow loss, and high machining accuracy. A beta-type free piston Stirling engine heater with composite cross section mini channels(CCSMH) is designed for heat transfer enhancement applying to solar dish power generation system. Investigation on heat transfer performance of the heater under oscillating flow is carried out by CFD method, which is compared with smooth annular tube heater. The influence of geometry parameters on the performance of heat transfer and pressure loss is investigated. A improved performance evaluation criteria PEC is proposed for the condition of equal flow velocity to evaluate the enhanced heat transfer performance of the heater. The results show that the maximum value of the comprehensive performance evaluation index PEC can reach 3.14, the maximum mean pressure drop increment of CCSMH compared with the smooth tube heater is 38.4 Pa, which is much lower than the minimum pressure of 2.3 MPa and can be neglected.

为研究复合材料铺层结构对叶片弯扭耦合特性的影响.以功率 2 kW的风力机叶片试样为研究对象,选用碳/玻纤维不同混杂比(4∶4和 2∶6)双轴向经编织物.基于经典层合板理论及联合节点位移法,实验研究集中载荷作用下,铺层结构叶片试样形变特性,分析叶片试样弯扭耦合特性.结果表明:同种碳/玻纤维混杂时,纤维排列角度为 25°时,叶片试样等效弯扭耦合系数最佳为 0.186,而同种纤维排列角度,碳/玻纤维混杂比 4∶4的叶片试样等效弯扭耦合系数大于碳/玻纤维混杂比 2∶6的叶片试样.应变测试实验发现沿叶片试样展向,叶片试样主应变逐渐减小,弯扭耦合特性可有效改善叶根处主应变.

Biochar-based photothermal evaporators are considered to be a promising choice for low energy consumed, cost-effective and sustainable solar-driven interfacial evaporation. Here, a carbonized sugarcane (CSC) evaporator was demonstrated. Benefiting from the microstructure of CSC, the CSC evaporator modified by concentrated nitric acid possesses high solar absorption and good hydrophilicity. And numerical simulation results proved that the hydrophilic surface is more conducive to photothermal water evaporation. Evaporation rate of 1.69 kg m(-2) h(-1) and evaporation efficiency of 85% were obtained under 1.0 sun irradiation (1 kW m(-2)) by the carbonized sugarcane with a carbonization temperature of 700 ? (CSC700). In addition, further studies have found that airflow and solar radiation can work synergistically to improve evaporation rate, and the evaporation rate under 1.0 sun irradiation could reach up to 2.24 kg m(-2) h(-1) for CSC700 with airflow rate of 5.18 m/s. More importantly, CSC700 shows excellent desalination performance and durability, and the average ion rejection in the collected fresh water was 99.32%. This work presents a good strategy which can make fully use of cost-effective biochar-based photothermal evaporators to produce drinking water from seawater and brackish water.

In this study, the parabolic trough collector with heat pipe evacuated tube is used as the research object. Using the ray tracing method, this study analyzes the effect of tracking error of azimuth-elevation axis and receiver installation error on the optical performance of the collector. A test bench for the azimuth-elevation axis manual tracking device of the parabolic trough concentrator was designed and built, and the heat flux distribution at the focal plane was measured. The optical simulation results were compared with the test results to verify their accuracy, and the maximum relative error was 2.69%. The simulation results were compared with those calculated in the literature, and the maximum error was 16.23%. Simulation results show that the circumferential heat flux of the receiver is still symmetrically distributed when longitudinal incidence angles and vertical installation errors were found. The symmetry disappeared when transverse incidence angles and horizontal installation errors were found. As the tracking error of the elevation axis increases, the optical efficiency of the collector decreases, and the length of the end loss increases. For the collector in this study, the azimuth axis tracking error is less than 1.5° and the elevation axis tracking error is less than 6°, which can ensure high optical efficiency. The vertical installation error of the receiver was |Δz| <17 mm, the horizontal installation error was |Δx| < 20 mm, and the optical efficiency of the collector remained unchanged. The calculation method and results in this study can provide theoretical support for selecting an automatic tracking system with reasonable tracking accuracy and determining the allowable installation errors for the parabolic trough collector with heat pipe evacuated tube, and can also provide detailed thermal boundary conditions for the subsequent research of heat transfer performance of the receiver, which has great theoretical value.

Blades in strong wind conditions are prone to various failures and damage that is due to the action of random variable amplitude loads. In this study, we analyze the failure of 1.5 MW horizontal axis wind turbine blades. The computational fluid dynamics unsteady calculation method is used to simulate the aerodynamic load distribution on the blade. Fluid–structure coupling methods are applied to calculate the blade stress. The results show that the equivalent stress of the blade is the largest when the azimuth angle is 30°, and the maximum equivalent stress is 20.60 MPa. There are obvious stress peaks in six sections, such as r/R = 0.10 (the span length of blade/the full length of the blade = 0.10). The frequency of damage that is caused by the stress in each area of the blade is determined based on the blade damage. The frequency of gel coat cracking in the blade tips and leaves is 77.78% and 22.22%, respectively, and the frequency of crack occurrence is 87.75%, 10.20% and 2.05%, respectively. By combining the stress concentration area and the damage results, the cause of blade damage is determined, which can replace the traditional inspection methods and improve the inspection efficiency.

研究了由三维角联锁机织与双轴向经编玻纤织物增强的复合材料叶片其增强体结构对叶片弯扭耦合特性的影响,选用NACA4415为基础翼型,设计了功率为2kW、长1.9m风力机叶片,应用Ansys软件数值模拟叶片应变特性,基于节点位移法分析了铺层结构对叶片弯扭耦合特性影响,进而得出增强体结构对叶片变形特性的影响规律.结果表明:在相同集中载荷作用下,同种几何形状的叶片由挠度均随叶片展向递增,并呈非线性相关;铺层结构对叶片的弯扭耦合效应影响较明显,新型结构的三维角联锁机织复合材料风力机叶片等效弯扭耦合系数为0.0616,约为传统的双轴向经编复合材料风力机叶片的2.8倍.

为改善H型垂直轴风力机(VAWT)的气动特性,文章研究了6种翼型型线改变后的翼型对H型VAWT气动特性的影响,并进行了数值模拟计算和风洞试验.风洞试验验证了模拟计算的结果,证明了型线改变后的风力机对提高气动性有积极的作用.试验结果表明:1波浪型风机和Dimple型风机均可在一定叶尖速比(λ)范围内提高风力机的风能利用率,其中1波浪型风力机在低λ下最高可提高风能利用率13.76％,其单叶片切向力在下游区明显增大;Dimple型风力机在高λ下最高可提高风能利用率14.6％,其单叶片切向力在上游区明显增大.两种改型后的翼型均可改善流动分离,并提高VAWT的气动性能.

Parabolic trough solar thermal technology is the most cost-effective approach for concentrated solar energy applications. The concentrator thickness significantly affects the performance of the parabolic trough collector. To examine the effect of mirror refraction in the concentrator, the focal plane concentration for different concentrator thicknesses was studied using theoretical calculations, simulations, and experimental verification. A longitudinal offset of the focal plane is proposed to optimize the focal plane concentration. The deviation of the reflected sunlight depending on the concentrator thickness was found to strongly affect the concentration in the focal plane. When the concentrator thickness was increased by a factor of 5, the focal plane was 5 times as wide, the maximum energy flux density in the focal plane decreased by a factor of 5, and the optical efficiency decreased by 0.24%. The longitudinal offset of the absorber plane position was introduced to avoid local overheating of the absorber and low collector temperature by maintaining the focal plane width and maximum energy flux density in the focal plane within appropriate ranges. The experimental results showed that with optimization, the maximum energy flux density, uniformity, and optical efficiency increased by 5.75%, 3.35%, and 2.43%, respectively.

Hydrophobic alpha-Al2O3 ceramic membrane (HCM) offers excellent mechanical properties, corrosion resistance, and high-temperature resistance. Application of HCM in the membrane distillation (MD) process could expand the application scope of MD equipment and greatly lengthen the replacement cycle of the membrane. Here a prediction model of the contact angle of HCM was constructed by physical-chemical combined modification method, orthogonal method, and stepwise linear regression method to optimize the preparation process of HCM. The surface morphology, contact angle, and surface functional groups of HCM were characterized. In this work, we polished the surface of the alpha-Al2O3 ceramic membrane with 400 mesh sandpaper to copy the optimal morphology and found that the effect of grafting time on the contact angle of HCM could be abandoned. The optimal levels of drying temperature, drying time, and grafting solution concentration were 250 degrees C, 65.5 min, and 0.019 mol/L, respectively. The contact angle of HCM was 145.3 degrees corresponding to the optimal preparation process. The significance of the prediction model of the contact angle of HCM was better than 0.05, and all of the prediction errors were less than 5%. This work has an important guiding value for exploiting the optimum hydrophobic property of HCM.

纳米流体是一种新型高效传热工质,广阔的应用前景引起众多研究者的关注.综述了纳米流体的制备方法、热物性、磁性纳米流体、复合纳米流体、纳米流体数值模拟.重点介绍了影响纳米流体热导率的因素,讨论了纳米流体导热率的提高机制、磁场作用下磁性纳米流体的对流换热系数以及纳米流体数值模拟、复合纳米流体面临的挑战性问题.