Advanced Materials Research Vols. 512-515

Abstract: Aiming at expanding and extending the application of photovoltaic energy technology into a bigger scope, a kind of soft substrate with multilayer structure is designed and fabricated to be bonded with photovoltaic silicon wafer to manufacture photovoltaic system. Pure aluminum thin film is introduced in the designed structure, which consists of mainly organic polymeric materials, to improve the thermal conducting behavior and anti-corrosion properties of the whole photovoltaic system. To study the reliability of the eventual structure with photovoltaic module of silicon wafer, various loading rates are chosen to measure the nominal bonding strength between the soft substrate and photovoltaic module.

Abstract: In this article, we have explained quantum state observed in fabricating poly-silicon the thin film and calculated the crystallization procession of rapid thermal annealing as a function of light energy. Equal energy driving principle was presented, it is shown that the change in magnetic frequency leads to the conversion of magnetic field energy to annealing energy.

Abstract: The simulation model of PV module, which is based on Simulink software, the mathematical model and the equivalent circuit of PV module, is established in this paper. This PV module model can be used to show the output characteristics of PV module under different irradiations and temperatures. Moreover, this model can be extended to various parameters of PV modules and used to study parallel and serial characteristics of PV module. The output characteristics of PV module, which is affected greatly by light irradiation and ambient temperature, has obvious non-linear features. Therefore, a maximum power point tracker (MPPT) is needed. Compared with perturbation and observation (P&Q) control method and other MPPT control methods, incremental conductance (IncCond) method may be unease to be adopted because it needs a high-performance controller which is costliness. However, as IncCond method is suitable for the irradiation situation of both rapid and slow changes, it has important research meanings. Meanwhile, aiming at the disadvantage of a fixed tracking step size, a improved control method is put forward and simulated in this paper. Finally the simuliation results verify the accuracy and superiority of the improved IncCond method.

Abstract: A new structure of a-Si/ poly-Si tandem solar cell has been desiged and prepared. Amorphous silicon has been use as photovoltaic material of bottom cell. And polysilicon has been used as photovoltaic material of bottom cell.The combination of amorphous silicon and polysilicon extends the light range which can be used by solar cell. This structure improves the efficiency of solar cell greatly.

Abstract: With increasing concern of global warming, many are looking at sustainable energy solutions to protect the earth for the future generations.. This paper presents a new inverter which can be used in hybrid wind/photovoltaic grid-connected power system. This inverter allows the two sources to work separately or simultaneously depending on the availability of the energy sources. Harmonic content is detrimental for the Grid security. The introduction of the inverter can effectively reduce the harmonics generated by the system. Operational analysis of the proposed system will be discussed in this paper. Simulation results are given to highlight the merits of the proposed inverter.

Abstract: A system is designed to combine the solar disc power generation and desalination in this paper. The steam generated in the solar disc system goes into the low-parameter steam turbine to produce electricity. Then the exhaust steam heats seawater in the desalination device, acting as a low temperature heat reservoir which makes the seawater boils to dilute. A tracking system adopting the "Date-time - latitude-longitude - sunlight incident angle" match pattern is designed to track the position of the sun, in order to achieve the maximum solar power input.

Abstract: The decrease of photovoltaic (PV) cell temperature by 10 °C is expected to improve the PV electrical efficiency by 0.6-0.7% based on the reference efficiency of 15%. Different cooling liquids like air and water have been introduced to pass across the PVs to reduce the cell temperature, and thus increase the electrical efficiency. In this paper, the refrigerant R134a was used as the cooling liquid and a PV/thermal (PV/T) collector was coupled with a heat pump system acting as the evaporator, which was expected to achieve a better cooling effect and energy performance due to its low boiling temperature. A hybrid PV/T collector, made of 6 glass vacuum tube – PV module – aluminum sheet – cooper tube sandwiches connected in series, worked as the evaporator of the heat pump system. Numerical steady models were established for each component of the heat pump system and part of the PV/T collector/evaporator for predicting their energy performance under the weather data of January 14th at Tibet, China. The results showed that the maximum COP could reach up to 7.6. The daily average thermal efficiency and electrical efficiency were 0.764 and 0.104, respectively.

Abstract: Cooling of concentration photovoltaic (CPV) cells with oscillating heat pipe was investigated numerically and experimentally. Based on Reynolds-averaged Navier-Stokes approach, a turbulent model was proposed in present work. Numerical study presented the temperature distribution under different heat flux and various outdoor conditions. CPV (with 12 suns concentration) system was experimentally studied, and the results show that the oscillating heat pipe begin operation at about 62°C, and CPV system could enhance electric power with a good cooling system under a high concentration light. The oscillating heat pipe cooling system, without air fan or pump, no power consumption, gives a uniform, reliable, simple and costless cooling method, oscillating heat pipe cooling is suitable for the high-CPV system.

Abstract: The reflectance of the hexagonal array silicon nanohole structure was systematically studied using various measurements and through simulations. It was found that the hexagonal array silicon nanohole can reduce the reflectance along the entire spectrum range by approximately 6%. It is suggested that the enhancement of the electric field intensity at short wavelength is mainly due to the large surface area provided by the nanohole structure, while multiple reflections occurring in the nanohole contribute to electric field enhancement in the long wavelength range. In addition, the simulation of a hexagonal array silicon nanohole coated with a thin layer of indium tin oxide (ITO) was carried out. The results show that reflectance is greatly decreased along nearly the entire spectrum range, except from 400 nm to 440 nm, and almost zero reflectance is achieved at wavelengths from 650 nm to 750 nm. The results provide a practical guideline to the design and fabrication of a low-reflectance, and as a consequence, a high-efficiency hexagonal array silicon nanohole solar cell.

Abstract: Based on tow-diode model of PV cells, the simulation model of PV array is established. This simulation model can simulate the output characteristics of PV array according to different shading conditions. The output power-voltage curve of PV array may have multiple local Maximum Power Points (MPPs) due to the partial shading. As a result, traditional maximum power point tracking (MPPT) algorithms can easily fail to track global MPP, this can be one of main causes for reduced energy. In order to overcome this drawback, an improved global scanning MPPT algorithm is proposed. Moreover, Matlab-based model is established. It is verified by simulation results carried out that this improved MPPT algorithm is effective to track the global MPP.