Advanced Materials Research Vols. 860-863

Abstract: The paper presents the results of a comparative analysis of point-location methods for the computation of the daylight factor inside the rooms of irregular shapes with the use of hollow light guides. The daylight factor value for natural lighting provided by a set of light guides is computed in accordance with the Solovyovs procedure [; the following methods are considered as the point-location methods: the strip method and the ray-tracing method, both are modified for their use in the process of solution of the aforesaid problem. The results obtained show both the advantages and disadvantages of the aforesaid methods and allow the evaluation of the time-consumption value for both methods when applying in large rooms of irregular shapes.

Abstract: Si-based photonic crystal device such as solar cells have been developed and attract lots of attention. Whether what kind of different structures are used, two key problems are needed to investigate. One is the improvement of the optic-electric (or electric-optic) transformation efficiency. Another is the capability to modulate the light-emitting and detection wavelength for various industrial applications. The wavelength of the light emission and detection can also be further adjusted by changing the material band-gap. In this work, we develop the periodic nanoscale surface textured solar cells. The characteristics of top thin film textured solar cells is developed and estimated to see if the structure is worthy to be scaled from the modern micrometer (um) level down to the nanometer (nm) level continuously. The process of nm-scale textured Si optoelectronic device used in this work is fully comparable to the modern CMOS industry. Optimal Ge concentration in SiGe-based solar cells has been investigated qualitatively by the systemic experiments. With the appropriate addition of Ge to a SiGe-based solar cell, the short current density (Isc) is successfully increased without affecting the open-circuit voltage (Voc) and then the overall efficiency is successfully improved about 4 % than the nanoscale surface textured Si solar cell.

Abstract: Using only photovoltaic battery on solar-powered aircraft will waste energy because of its low conversion efficiency. For reusing the energy that converted into heat by photovoltaic cells, a hybrid power system is presented in this paper for solar-powered aircraft. Its a new electricity-generating method that spreading photovoltaic cells on the wing surface and arranging photothermal cells in the wing box section. Due to temperature of the back of photovoltaic battery is high, it can be used as high temperature heat source. And the lower wing surface can be a low temperature cooling source. A lightweight solar-powered UAV was used to analyze the relevant performances of pure photovoltaic powered aircraft and hybrid powered aircraft. The result shows that using hybrid system can reduce the area of wing by 4.6%, and solar-powered aircraft with a 6m or below-6m wingspan can raise the utilization rate of solar energy per unit area by adopting hybrid power system.

Abstract: In the present work, Cerium Fluoride (CeF₃) was selected as the host material because of its High density, fast response and high radiation resistance, efficient absorption and energy transfer by host (to activator). Rare earths have been used to show the process of Quantum Cutting (QC) via energy transfer process between Tb³⁺ and Yb³⁺ incorporated in CeF₃. For the synthesis of CeF₃ nanoparticles codoped with Tb³⁺ and Yb³⁺ ion, co-precipitation route was employed. Different doping concentrations were prepared to study the changes that take place in the luminescence spectra of the composition. Thus, concentration dependent study of the fluorescence of CeF₃: Tb³⁺, Yb³⁺ was carried out. These materials have great applications in solar cell devices as quantum efficiencies up to 200 % can be achieved.

Abstract: A PV power system with bi-directional inverter is proposed in this paper. The system is divided into two stages, one is power stage, which contains DC/DC converter and bi-directional inverter, the other is control stage. Both stages control schemes are by a micro-controller dsPIC30F4011. For preventing from high current harmonic caused by the two stages, a predictive current control and modulation principle are designed and operated in high frequency to reduce the current harmonic. The bi-directional inverter can operate in grid-connection (GC) mode or power factor correction (PFC) mode. But the core material of inductance will result in violent current ripple change when the inductor current promoted. So, a gain modulation is used to compensate various inductances used to reduce grid-connection current ripple. Finally, the system is implemented to verify the feasibility and performance of the proposed system.

Abstract: The global energy issues have become increasingly prominent in recent years, photovoltaic power generation as a renewable energy use pattern is widely used, but a large number of photovoltaic power generation to the grid is a big negative impact, it is necessary to predict the output power of the photovoltaic. Power system load forecasting is the reference and safeguard of the power system operation. This article analyzes the main point of the prediction of photovoltaic power system and power load system, then introduces the support vector machine (SVM) based on quantum particle swarm optimization (QPSO) to do the prediction. And then this paper proposes a generalized system load prediction system containing the photovoltaic power system.

Abstract: A novel built-in photovoltaic Trombe wall (BiPV-TW) was proposed in this paper and the air flow in a BiPV-Trombe wall was numerically simulated by CFD method. The effect of channel height on flow patterns and air velocity was analyzed. The mass flow rate of air was calculated and a dimensionless expression to calculate the air flow rate in term of a Reynolds number was correlated according to a modified Rayleigh number and the aspect ratio, H/b, which took into account both of the channel sizes and solar radiation based on a multivariable regression analysis.

Abstract: A mathematical modeling method was devoted to study the thermal performance of integral solar air collector. A mathematical model of heat transfer was set up based on one-dimension assumptions at first, and then numerical solution was brought out by using finite-difference method under one-dimension steady heat exchange. Through the MATLAB programming, the approximate solutions for the local air temperature and thermal efficiency were obtained at the quasi-steady state. After calculation, the influence of air inlet velocity, inlet temperature, solar radiation intensity and height of flow channel on the performance of collector was analyzed. It is discovered that the mathematical model is reasonable, the thermal efficiency decreases with temperature of inlet air increasing and increases with air velocity increasing, on which the solar radiation intensity have little influence. Depth of the channel and optimum flow both have a best value.

Abstract: This paper firstly analysis the principle of three-phased photovoltaic grid-connected power system. Secondly, the 20KW photovoltaic power system will be given as an example to introduce the design strategy of photovoltaic modules. Also, the photovoltaic grid-connected inverter is designed, which includes its parameters calculation and components selection. Finally, the whole photovoltaic power system is designed and verified via the experiment. The result of the experiment shows the design is reasonable and reliable. The power system can achieve full power operation and satisfy its expected goal.

Abstract: This paper analyzes the modular design method of the photovoltaic power generation system and presents a 5KW solar power inverter with variety of operating modes. Depending on the signal interface model, the hardware circuit is divided into several modules, including DC-DC main power circuit, DC-DC control circuit, DC-AC main power circuit, DC-AC control circuit and auxiliary power supply module. The circuit detail design is given and this system has been already used in the solar power stations. The circuit has a reusable and beneficial photovoltaic inverter standardized design. The experiment results prove that this system has features of reliability, easy maintenance, strong scalability and meets the requirements of the solar-energy generation system.