Advanced Materials Research Vols. 608-609

Abstract: In the study, LiBr absorption refrigeration machine runs in the air-cooled condition, combined with temperature and humidity independent control and the air condition end with radiant cooling, improving the system operation mode. Calculation and simulation were carried out to study the performance of the system, and effects of the cooling air inlet temperature and flow rate, refrigerant water outlet temperature on system performance, which will have the important theoretical significance for the development and application of the minitype solar lithium bromide unit.

Abstract: Because of shortages of energy and environmental carrying capacity limits, China will launch a solar photovoltaic energy. In 2011, the Chinese Government provides the strong policy for the development of photovoltaic industry, including “Inter solar China”, “The Twelfth Five-Year Plan of PV Industry” and so on. Due to the policy encouragement, by the end of 2011 projects completed formally is up to 2.7GW. China’s PV market has finally officially launched, it is expected that China will become the world's leading PV market in 2012. Therefore, this paper made an original creative analysis on comprehensive benefits of solar energy photovoltaic industry in China, and evaluated based on comprehensive evaluation system, and finally got economic, social and ecological benefits of the solar PV industry. The conclusions show the ecological optimal efficiency, so seeing the PV industry is to the benefit of future generations, the power industry of the future.

Abstract: The method that dividing a year into multiple time periods and calculating the optimum tilt angle of PV panels in every period is proposed. Calculation software is developed using Labview language. Taking some region in Liaoning province for example, the yearly radiation under fixed inclination, two inclinations and three inclinations every year are compared. The capital investment and increased revenue in the case of fixed inclination, adjusting the bracket twice a year and adjusting the bracket three times a year are compared. The calculation results show that adjusting the angle twice a year and adjusting it three times a year can increase the overall yield 4.03% and 4.39% respectively. The test platform is built up. And the experiment results show that the generating capacity of the 8th unit after angle adjustment increases significantly comparing with that of the 5th unit under fixed inclination.

Abstract: According to GB /T 4271-2007 in regard to the temperature control requirements, we have designed a set of closed loop temperature control system, it uses two levels of temperature control, and it uses LabVIEW PID kit and an external controllable silicon module for secondary heating fine-tuning, the whole system ensures that the solar heat collector inlet temperature stability at the setting value ± 0.1 °C.

Abstract: The photo-thermal performance tests of heat conduction oil were made in an all-glass evacuated solar collector tube under solar irradiation. The influences of solid particles (carbon powder, copper foil, aluminum foil) with different mass fraction and sizes on insolation temperature and irradiation were investigated. The mechanism of convective heat transfer enhancement of solid particles in oil was discussed. The results show that copper foil particles oil can improve average insolation temperature 14°C. The carbon powder-oil insolation temperature is the highest, it is 3.3°C higher than copper foil-oil’s and 7°C higher than aluminum foil-oil’s in the same mass fraction; The appropriate mass fraction of copper foil particles is 3%-3.2%, and continue to increase particles mass fraction the temperature did not change significantly.Within millimeter-scale range,the convective heat transfer enhancement is related to particle size, the effect of different sizes copper foil particles on oil temperature is 1-4°C; Solar irradiation of carbon powder-oil and copper foil-oil are lower and their photo-thermal conversion properties show better than that of aluminum foil-oil in the insolation experiment.

Abstract: Introducing a kind of bidirectional switch type five level inverter, and put forward the compound control scheme which repetitive control and PI adjustment are combined. And a detailed analysis of the repetitive control algorithm. Through the Matlab/simulink to simulate under different control modes. The results show that, the five-livel inverter which using repetitive PI control, its output grid-connected current waveform stability, harmonic distortion rate is small, and can real-time tracking the network voltage.

Abstract: This paper investigates the operation of a PV unit which is connected via a three-phase voltage-source inverter to the grid. The PV grid-connected control system is mainly related to a few key issues that are characteristics of photovoltaic cells, maximum power point tracking and grid-connected control of three-phase inverter. The control strategy of the three-phase PV grid-connected system is analyzed and studied by simulative experiment in this paper. A mathematical model of solar cells is established. Then the algorithms based on perturb & observe to track maximum power point is used. The structure of three-phase PV grid-connected system is introduced, and the current control method with Space Vector pulse width modulation (SVPWM) is examined and compared to other current control methods. The p-q theory is used to achieve uninterrupted compensation of the reactive power of the system. Simulative results on Matlab/Simulink software illustrate the reliability and superiority of this control strategy.

Abstract: Models for computing daily global radiation for Lanzhou of China were developed. The development of the models was based on the analysis of global and daily sunshine duration data during 10 years. Estimated values were compared with measured values in terms of statistical error tests such as mean percentage error (MPE), mean bias error (MBE), root mean square error (RMSE). The model performing best was selected. The global solar radiation estimated from the best model was compared with measured values. It was determined that the predicted values have good agreement with the measured values at high daily global radiation.

Abstract: As the world economic development, environmental problems are increasingly serious and renewable energy use by the peoples of common concern. Beijing as the capital of China, is a densely populated city, the increasingly serious environmental problems, the energy consumption also increases, which not only affects people's daily life, but also influence the whole nation's image. The development of solar photovoltaic (PV) generation in Beijing has certain inevitability; its development is mature day after day. But in the course of its development there still exist various problems, therefore, the development of photovoltaic power generation system in Beijing also need further perfect and corresponding support.