To investigate characteristics and estimate propulsion performance of a high-density radio frequency plasma with a very small diameter, we have developed the Small Helicon Device (SHD) and measured an electron density n e , an ion velocity v i and an emission intensity of Ar II under various conditions such as a discharge diameter (down to 3 mm), a mass flow rate and a gas species. Using quartz discharge tubes with inner diameter (i.d.) of 3, 10, 20 mm with an Ar gas, n e of (2.5-6) × 10 12 (estimated from optical measurement), ∼2.5 ×10 12 and ∼ 2.0 × 10 12 cm −3 , respectively, at −40 mm downstream from an excitation antenna was obtained. Using the 20 mm i.d. tube with a H 2 gas, v i ∼ 40 km/s was achieved in the presence of the magnetic field gradient.
Performance loss rates of five different photovoltaic (PV) technologies operating under Thailand's climate have been derived from the first 3-year data. Although ambient temperature throughout the year in the tropics is relatively constant, we found remarkable seasonal variations in performance loss of the PV modules. The performance loss rates in rainy and dry seasons were severe, while those in summer were relatively slight. The soiling had great effect on the PV performance in the dry season, while the temperature was a key factor in the summer. The high module temperature in the summer caused high temperature loss but it also provided positive effect of recovering performance of thin film Si modules. In the rainy season, with less amount of irradiance and high humidity at the module surface the PV modules showed the highest performance loss rate. Our findings can be used to develop a better operations & maintenance (O&M) strategy for PV systems in the tropics, e.g., proper cleaning of PV modules during the dry season.
(2017) The impact of cracks on the performance of photovoltaic modules. In: PowerTech, 2017 IEEE Manchester. IEEE. ISBN 9781509042371 This version is available at Abstract-This paper presents a statistical approach for identifying the significant impact of cracks on the output power performance of photovoltaic (PV) modules. Since there are a few statistical analysis of data for investigating the impact of cracks in PV modules in real-time long-term data measurements. Therefore, this paper will demonstrate a statistical approach which uses two statistical techniques: T-test and F-test. Electroluminescence (EL) method is used to scan possible cracks in the examined PV modules. Moreover, virtual instrumentation (VI) LabVIEW software is used to predict the theoretical output power performance of the examined PV modules based on the analysis of I-V and P-V curves. The statistical analysis approach has been validated using 45 polycrystalline PV modules at the University of Huddersfield, UK.
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