Diurnal and environmental characterization of solar photovoltaic panels using a PC-AT add on plug in card

This article describes the development of an instrumentation system for characterizing photovoltaic panels. It uses an add on card (which contains DAC, ADC and digital input/output ports) in conjunction with a PC-AT. The panels in a field are selected in succession through a set of relays actuated by the digital output port. The selected panel is loaded in discreet steps by a transistor loading circuit which is activated by the digital to analog convertor to trace the most significant portion of the I-V curve. The data shows that the power output is invariably lower than that specified by the manufacturer. The reasons for drop in output have been analyzed. It is shown that these effects can be represented by the curvature of I-V characteristic at the maximum power point (OP). The loss of power due to accumulation of dust and the increase in temperature of the panels can be significant.     

使用索引提升数据库性能

影响到数据库性能的最大因素是索引,建立合理的索引可以大幅度的提升数据库性能,这里以SQL SERVER为例,我简单的介绍一下索引的相关知识,以及如何设置合理的索引提高数据库性能.     

银粉振实密度对晶硅太阳能电池电性能的影响

晶硅太阳能电池是利用最广泛的太阳能电池,但是,其光电转换效率远低于理论最大值(31%)。本文首先采用化学还原法制备出高分散的微米(D₅₀=2.78μm)和亚微米(D₅₀=0.56μm)球形银粉,然后将微米银粉和亚微米银粉按一定的比例进行混合,并借助XRD、SEM、EDS等测试方法研究了银粉的振实密度对前电极栅线的横截面结构、表面形貌以及电池接触界面结构和电性能的影响。结果表明,混合银粉的振实密度高于纯微米或亚微米银粉的振实密度,当亚微米银粉在混合银粉中质量分数为15%时银粉的振实密度最高。且当银粉的振实密度最高时,前电极栅线的横截面结构、表面形貌和电池的接触界面结构最优,电池的电性能最佳。综上,银粉的振实密度对电池的电性能有重要的影响。