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Preliminary experiment on a novel photovoltaic-thermoelectric system in summer
摘要： Compared with the PV electricity generation, the hybrid Photovoltaic-thermoelectric (PV-TE) can generate more electricity due to its ability to utilize a wider solar spectrum than the PV. The PV-TE employing micro-channel heat pipe array is a novel PV-TE-MCHP system which is capable of providing high cost performance compared to the traditional PV-TE due to the use of the micro-channel heat pipe array. In this paper, the experimental investigation of this new system in summer in Hefei city, China is presented for the first time. The comparison between this system and PV alone is made, and the details are presented. The power output, PV temperature, and the hot and cold sides temperatures of the TE are all tested. The results show that the novel system has a higher electrical output than the PV alone. The electrical efficiencies of this system during the test are all higher than 14.0% and the PV temperatures are about 20 (cid:1)C higher than the ambient temperature. Based on this experiment, the results also verify the feasibility of the new system, which will give a valuable reference for the PV-TE design.
关键词： Micro-channel heat pipe,Power output,Experimental investigation,Photovoltaic-thermoelectric
更新于2025-09-11 14:15:04
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MICRO WAVE PATTERNS BY VIBRATING-LENS ASSISTED LASER MACHINING
摘要： Surfaces with superimposed patterns offer, in many applications, numerous advantages over traditional smooth surfaces since they profoundly affect functional behavior, e.g., friction, wettability, etc. Different shapes and sizes of surface patterns were fabricated by traditional laser machining, however, micro wave patterns are difficult to generate by this process. In this paper, vibrating-lens assisted laser machining is proposed to generate such patterns and to extend its capabilities. A model, based on the traditional heat-flow principle, was built to ascertain the energy distribution in the process and predict the shape of the wavy patterns generated. A specially developed experimental setup was used for model validation. Sinusoidal wave patterns were analyzed as an example to demonstrate geometrical feature under different parameters and the feasibility of the process. The feasibility of the proposed theoretical and experimental methodologies was illustrated through a comparative analysis of experimental and simulation scenarios.
关键词： Pattern simulation,Surface topography,Vibrating-lens,Laser machining,Traditional heat-flow principle
更新于2025-09-11 14:15:04
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Laser-thermal Hardening of the Tools Set for Cold-forming Fasteners
摘要： At present the problem of increasing the wear resistance of an impact stamp tool used in the fasteners production by methods of cold forming is very acute problem. The article analyzes the possibility of laser heat hardening to improve the wear resistance of the used tool set.
关键词： production tools,laser heat hardening,fasteners,tool steels,microstructure,microhardness
更新于2025-09-11 14:15:04
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Conceptual design of a high-efficiency heat transfer circular-conical-frustum laser amplifier with amplified divergent beams
摘要： Two problems exist in the repetition rate laser system with the cylindrical laser amplifier–its inability to offer the gain required for the injected seed in the low-energy stage of the laser system, and its failure to achieve efficient heat dissipation under high gain and high repetition rate. This paper proposes a new conceptual design of a laser amplifier with a circular-conical-frustum gain medium and corresponding configuration scheme for energy storage. Under the influence of its higher field synergy, the capacity of heat dissipation possessed by the system with a frustum gain medium can be increased by 10–25% and the average temperature at the steady state can be reduced by 2–4°C. With the amplified spherical wave, the energy extraction efficiency can be improved by 5% in the low-gain state and 15% in the high-gain state, and it can be further increased by 20% under the new configuration scheme of energy storage. Thus, it can be concluded that this new configuration of laser amplifier is more suitable than cylindrical amplifier and plays an important role in miniaturizing the laser system at high repetition rate.
关键词： Divergent Beams,Field synergy,Extraction efficiency,Circular-conical-frustum,Heat transfer
更新于2025-09-11 14:15:04
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Transforming a residential building cluster into electricity prosumers in Sweden: Optimal design of a coupled PV-heat pump-thermal storage-electric vehicle system
摘要： Smart grid is triggering the transformation of traditional electricity consumers into electricity prosumers. This paper reports a case study of transforming an existing residential cluster in Sweden into electricity prosumers. The main energy concepts include (1) click-and-go photovoltaics (PV) panels for building integration, (2) centralized exhaust air heat pump, (3) thermal energy storage for storing excess PV electricity by using heat pump, and (4) PV electricity sharing within the building cluster for thermal/electrical demand (including electric vehicles load) on a direct-current micro grid. For the coupled PV-heat pump-thermal storage-electric vehicle system, a fitness function based on genetic algorithm is established to optimize the capacity and positions of PV modules at cluster level, with the purpose of maximizing the self-consumed electricity under a non-negative net present value during the economic lifetime. Different techno-economic key performance indicators, including the optimal PV capacity, self-sufficiency, self-consumption and levelized cost of electricity, are analysed under impacts of thermal storage integration, electric vehicle penetration and electricity sharing possibility. Results indicate that the coupled system can effectively improve the district-level PV electricity self-consumption rate to about 77% in the baseline case. The research results reveal how electric vehicle penetrations, thermal storage, and energy sharing affect PV system sizing/positions and the performance indicators, and thus help promote the PV deployment. This study also demonstrates the feasibility for transferring the existing Swedish building clusters into smart electricity prosumers with higher self-consumption and energy efficiency and more intelligence, which benefits achieving the ‘32% share of renewable energy source’ target in EU by 2030.
关键词： Thermal storage,Heat pump,Prosumer,Building cluster,PV optimization,Electrical vehicle
更新于2025-09-11 14:15:04
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Potential of water natural circulation coupled with nano-enhanced PCM for PV module cooling
摘要： This paper introduces a new photovoltaic module passive cooling system that works with natural cooling water circulation. The heat was removed from cooling water by a PCM-based cooling system. A special zig zag geometry of PCM container was considered to increase the heat transfer surface. At the ?rst stage of experiments, a composed oil consisting of 82 wt% coconut oil and 18 wt% sun?ower oil was used as PCM. Then, in order to increase the performance of heat transfer between PCM and cooling water, the composed oil was mixed with Boehmite nanopowder (0.009 (w/w)). The cooling performance of the composed oil and nano - composed oil was assessed by monitoring the temperature and the generated electrical power of the panel at various radiation intensities. The results reveal the reliability of the proposed system for cooling of the PV module without need to any pumping system. Moreover, the results show that using nano - composed PCM is more ef?cient than the plain one. The highest increase in the maximum produced power relative to the reference case were obtained in the presence of nano - composed oil, which were 44.74, 46.63, 48.23% at the radiation intensities of 410,530,690 W/m2, respectively.
关键词： Photovoltaic,PCM,Natural circulation,Passive cooling,Boehmite nanoparticles,Heat transfer
更新于2025-09-11 14:15:04
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Efficient thermal finite element modeling of selective laser melting of Inconel 718
摘要： In the powder bed fusion process, an accurate prediction of the transient temperature field of a part is essential to calculate the subsequent thermal stress evolution and microstructure propagation in that part. The experimental method is time-consuming and expensive since the temperature field is controlled by many process parameters. Numerical heat transfer models can be used to estimate the temperature field at any time point. However, traditional numerical simulation schemes are not suitable for the layer-wised fabrication process due to the extremely high computational cost. The computational cost mainly relies on the element number and time step size. This research provides a new efficient and part-level simulation scheme based on an open-source finite element library, which is able to adaptively refine and coarsen the mesh and solve finite element equations with multiple processors in a parallel way. Here, a new mesh strategy that aims to reduce the element number while keeping the solution accuracy is developed. The simulation speed is 12× to 18× faster compared with the traditional simulation scheme depending on the scale of the simulated domain and number of processors. Simulation results have been compared with the experimental results of an Inconel 718 component. It is shown that the testing point in the simulation experiences the same thermal cycles of the same point in the experiment. This simulation scheme can also be used to optimize the process parameters such as scanning pattern, scan velocity, and layer thickness and can be easily extended to other additive manufacturing processes.
关键词： Selective laser melting,Finite element method,MPI,Heat transfer,Adaptive mesh
更新于2025-09-11 14:15:04
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Coaxial waterjet-assisted laser drilling of film cooling holes in turbine blades
摘要： Film cooling holes (FCHs) of nickel-based single crystal turbine blades were drilled by 532 nm Nd:YVO4 nanosecond laser in coaxial waterjet-assisted environment. Microstructure of the side wall of the FCHs was mainly investigated by means of transmission electron microscopy. The average thickness of heat affected zone (HAZ) around FCHs decreases with increasing of water flow rate. The main phase within HAZ evolves from β-NiAl to β-NiAl + γ-Ni with the increase in the water flow rate. Some γ-Ni particles in the HAZ twined along (111) plane. A small portion of the FCHs are free of HAZ when drilled by coaxial waterjet-assisted laser drilling at a laminar water flow rate ≥ 3.1 m/s. There are no processing-induced defects including HAZ, microcrack, and phase transformation around the FCHs when drilled at the water flow rate ≥ 5.1 m/s. The FCHs with high surface quality can be drilled by the coaxial waterjet-assisted laser drilling. Finally, effects of fluid water on drilling quality of the FCHs were discussed.
关键词： turbine blades,film cooling holes,Coaxial waterjet-assisted laser drilling,heat affected zone (HAZ),transmission electron microscopy (TEM)
更新于2025-09-11 14:15:04
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Polarisation of Light || PHENOMENA PRODUCED BY MECHANICAL MEANS—UNANNEALED GLASS
摘要： The chapter discusses the phenomena produced by mechanical means on unannealed glass, focusing on how mechanical strain can impart a structural character to glass analogous to that of a crystal, affecting the motion of the ether within it and exhibiting chromatic effects with polarised light. It describes experiments involving straining a rectangular bar of ordinary glass and observing the light passing through it, as well as the effects of squeezing a thick square plate of glass in a vice. The chapter also explores the impact of molecular forces due to heat and cooling on glass, and the permanent, splendid effects produced by unannealed glass that has been rapidly and unequally cooled.
关键词： crystal,polarisation,light,molecular forces,unannealed glass,mechanical means,pressure,heat,strain,chromatic effects,cooling
更新于2025-09-11 14:15:04
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Heat degradation of sputter-deposited Cu(In,Ga)Se2 solar cells and modules: Impact of processing conditions and bias
摘要： We report accelerated heat degradation studies on fully encapsulated Cu(In,Ga)Se2 modules as a function of film growth parameters, in particular back contact selenization (preeSe), as well as the impact of bias (light/voltage) during heat degradation. We show that pre-Se conditions have a profound effect on the heat stability of the device, whereby reduced preeSe, while increasing initial efficiency, results in strong heat degradation, driven by a combination of reduced space-charge region and reduced minority carrier lifetime (as evident from external quantum efficiency measurements) in the light-soaked state and resulting in strong degradation of short-circuit current. This is also accompanied by a stronger increase in the shallow acceptor concentration (as measured by capacitance-voltage profiling) in the degraded state, suggesting that the SeeCu divacancy complex (VSe-VCu) is likely responsible. In this case, appearance of a high concentration of deep acceptor states accompanies increased shallow doping upon light-soaking, with the former reducing bulk lifetime and the latter further affecting electron collection due to narrow depletion width. This result suggests that bulk structural properties of the absorber film are strongly impacted by the back contact selenization conditions, making the film more susceptible to heat degradation. In the second part of this paper we show that electrical or light bias during heat exposure reduces degradation, in particular almost fully eliminating the above short-circuit current loss. This is a surprising result as usually the positive effects of bias are attributed to interfacial changes, while our results demonstrate that bulk properties can be improved as well.
关键词： Absorber,Interface,Defects,Thin film solar cell,Heat degradation,Reliability,Light soaking,Copper indium gallium selenide
更新于2025-09-11 14:15:04