Abstract: Solar collectors are the key components of solar thermal utilization. The comparative tests of solar flat-plate collector (SFPC) and heat pipe evacuated tube collector (HPETC) were done in this paper. The results show that during the low temperature difference range, the heat collecting efficiency of the flat-plate collector is about 2.3 times higher than the efficiency of the heat pipe evacuated tube collector and the heat loss of the flat-plate collector is about 3.2 times bigger than that of the heat pipe evacuated tube collector. Through the analysis, two measures are proposed to improve the efficiency of flat-plate collector and reduce the heat loss in order to make it more efficient in the solar heat pump system.
Abstract: This paper presents the analysis, design, and simulation of a photovoltaic power system with bi-directional inverter, which can be controlled with a single-chip microcontroller, such as dsPIC30F4011. The bi-directional inverter can fulfill grid connection and rectification with power factor correction to regulate the dc bus to a certain range of voltages. So, it will no need energy storage elements to buffer power. But the two stage series can cause high current harmonic, so a predictive current control and modulation principle for the bi-directional inverter is designed and operated in high frequency to reduce the current harmonic. Simulation and experimental results have illustrated the discussed features and significantly demonstrated its feasibility, reliability, and stability.
Abstract: Direct liquid immersion cooling of concentrator solar cells was proposed as a solution for receiver thermal management of concentrating photovoltaic (CPV) systems. This research investigates the electrical performance of silicon concentrator solar cells under concentration, which are in both the absence of the candidate immersion liquids and also within different thickness on top. The results show that the presence of thin liquid layers results in an increase in the silicon CPV solar cells efficiencies by 8.5-15.2% from the reference value, arising from a decrease in a part of the reflected radiation and a decrease in the velocity of the surface recombination from surface adsorption of polar molecules. With an increase in the thickness of the liquid layer, the degree of the improvements to the efficiencies of the cells decreases due to more incident light is absorbed by the thicker liquid layer, which also depends to a noticeable degree on the liquid species.
Abstract: The linearly polarization photosensitivity of Si-based solar cells has been investigated. It has been shown that the angular dependence of the open-circuit voltage and light intensity are observed similar change trend. However, a contrary behavior is reported in the angular dependence of the ratio between the open-circuit voltage and polarized light intensity. Through the establishment of a theoretical model and detailed analysis, it is found that the nonlinear effects play a crucial role in the photovoltage responses of solar cells under low illumination. The angular dependence of the ratio of the open-circuit voltage to the light intensity is inversely proportional to the square of the cosine function. This work is very significant for the photovoltaic system research.
Abstract: An optimization model to get the optimal capacity of photovoltaic connected to the microgrid aimed at reducing the loss and satisfying the node voltage constraints is proposed. A microgrid with n nodes and n-1 feeders is taken as an example to set a linear programming model. Taking a microgrid with 11 nodes, first sensitivity analysis method is applied to determine the best location of the photovoltaic power, and then the optimal value of the PV power capacity is calculated by the Matlab programming. Finally, the curve of the relationship between loss and the capacity of the ptotovoltaic power is plotted through Matlab, which qualitatively verifies the feasibility and practicality of the method.
Abstract: Using methods of system analysis and patent analysis, some gratifying progress about the industrial chain, industrial scale, R&D ability, low cost had been made in the solar energy industry in China. But there are some questions such as internal and external challenges, the enterprise innovation ability needing to be improved further, output quality not being high, the emerging and domestic market being yet to be developed etc. Therefore, the effective countermeasures just like strengthening multilateral communication, building the independent innovation system, formulating the strategy of intellectual property rights and developing the domestic and foreign markets are proposed to promote the sustainable development of the solar energy industry.
Abstract: A suitable deposition method of CdS is necessary for the high performance CIGS(Cu(In0.7Ga0.3)Se2.2) solar cells. In this paper, CdS films were deposited onto glass substrates at the substrate temperture of 50°C、100°C、150°C by thermal evaporation, the effect of the temperature were presented. CdS film deposited at substrate temperture of 150°C was annealed at 150°C for 30min. All films were characterized for their morphology, structure and optical property using scanning electron microscope(SEM), X-ray diffractometer(XRD) and UV–VIS–IR transmittance respectively.The quantum efficiency of the fabricated solar cells with annealed CdS buffer layer was also enhanced at short wavelength. This new method leads to the improved performance of CIGS solar cells and also simplify the whole fabrication technology.
Abstract: This article proposes a new method for the extraction of five parameters of a solar cell using Lambert W-function with the current-voltage data. Here we select three points: the short circuit point, the open circuit point, and the maximum power point. On the basis of these we construct five equations to establish a nonlinear formula, in which the series resistance can directly be obtained. The other four parameters are calculated by series resistance. This method is confirmed by two different solar cell data in Matlab software.
Abstract: The impact of grid-connected photovoltaic power on power quality and reliability of power supply has gained more attention, with the continuous improvement of its generation capacity. This paper describes the power conditioning system of grid-connected photovoltaic power plants based on super-capacitor energy storage, which acts as the energy storage element to stabilize fluctuations in output active power of photovoltaic power generation system. Based on the configuration and principle of the power control system, a power and current double closed loop feedback hysteresis current control strategy is proposed in details, which controls the super capacitor energy storage system to absorb and complement the active power output fluctuations of the photovoltaic power generation system. The effectiveness and good operating performance of the device and control strategy are validated by simulation with PSCAD/ EMTDC.