Chosen diagnostic methods of photovoltaic modules
Solar modules under ordinary working condition are exposed to amount of degradation factors which deteriorate their properties. The most important degradation of PV modules during operation are optical, electrical and thermal degradation. The result of these factors is performance degradation of the modules, or even can caused their fault. It is important to find the cause of the fault and its timely removal. The choice of convenient diagnostic method can reduce financial losses and increases safety of photovoltaic power plant. The example of tests performed on PV modules by using infrared (IR) thermography and, potential induced degradation (PID) are presented in this paper.
Integrated micro tesla magnetic sensor for detecting photovoltaic cells failure
Recently more attention on the failure of PV systems has been paid and more reports have been found in PV related papers. Various methods to detect failure of PV module have been developed; They are visual method, I-V characteristic method, electroluminescence (EL) method, UV fluorescence method, signal transmission method, IR thermography method, photoluminescence (PL) method. However, each method has some limitations. Developing a new alternative diagnostic method of PV cells will be required for efficient operation of PV system. The proposed method uses μ-tesla magnetic sensor (MI-CB-1DM) to detect failure in a PV cell. The experimental design carried out in this study covered two stages. In the first stage, we developed a method for detecting faults in PV cells using the μ-tesla magnetic sensor method. In this second stage a calculation will be made to determine the current level due to the failure of the PV cell. The results show that Bx at the lower busbar in the degraded module has smaller magnetic density than the upper busbar. No obvious difference can be seen in the Bx and By profiles between the normal and degraded cells.
Sustainable production of toxin free marine microalgae biomass as fish feed in large scale open system in the Qatari desert.
Mass cultivation of microalgae biomass for feed should be cost effective and toxin free. Evaporation loss in Qatar can be as high as 2 cm/d. Hence, production of marine microalgae biomass in Qatar would also require mitigating water loss as there was only very limited groundwater reserve. To address these issues, a combination of four growth conditions were applied to a 25,000 L raceway pond: locally isolated microalgae strain was selected which could grow in elevated salinity; strain that did not require silica and vitamins; volume of the culture would increase over time keeping denser inoculum in the beginning, and evaporation water loss would be balanced by adding seawater only. A local saline tolerant Nannochloropsis sp. was selected which did not require silica and vitamins. When the above conditions were combined in the pond, average areal biomass productivities reached 20.37 g/m(2)/d, and the culture was not contaminated by any toxic microalgae.