Engineering topics
Publications and source records attributed to Kurtz, S.
This report summarizes the current status of the CPV industry and is updated from previous versions to include information from the last year. New information presented at the CPV-8 conference is included along with the addition of new companies that have announced their interest in CPV, and estimates of production volumes for 2011 and 2012.
To sustain the commercial success of photovoltaic (PV) technology it is vital to know how power output decreases with time. Unfortunately, it can take years to accurately measure the long-term degradation of new products, but past experience on older products can provide a basis for prediction of degradation rates of new products. An extensive search resulted in more than 2000 reported degradation rates with more than 1100 reported rates that include some or all IV parameters. In this presentation we discuss how the details of the degradation data give clues about the degradation mechanisms and how they depend on technology and climate zones as well as how they affect current and voltage differently. The largest contributor to maximum power decline for crystalline Si technologies is short circuit current (or maximum current) degradation and to a lesser degree loss in fill factor. Thin-film technologies are characterized by a much higher contribution from fill factor particularly for humid climates. Crystalline Si technologies in hot & humid climates also display a higher probability to show a mixture of losses (not just short circuit current losses) compared to other climates. The distribution for the module I-V parameters (electrical mismatch) was found to change with field exposure. The distributions not only widened but also developed a tail at the lower end, skewing the distribution.
Light-to-dark metastable changes in thin-film photovoltaic (PV) modules can introduce uncertainty when measuring module performance on indoor flash testing equipment. This study describes a method to stabilize module performance through forward-bias current injection rather than light exposure. Measurements of five pairs of thin-film copper indium gallium diselenide (CIGS) PV modules indicate that forward-bias exposure maintained the PV modules at a stable condition (within 1%) while the unbiased modules degraded in performance by up to 12%. It was additionally found that modules exposed to forward bias exhibited stable performance within about 3% of their long-term outdoor exposed performance. This carrier-injection method provides a way to reduce uncertainty arising from fast transients in thin-film module performance between the time a module is removed from light exposure and when it is measured indoors, effectively simulating continuous light exposure by injecting minority carriers that behave much as photocarriers do. This investigation also provides insight into the initial light-induced transients of thin-film modules upon outdoor deployment.
We report the discovery of 6.035 GHz hydroxyl (OH) maser flares toward the massive star-forming region IRAS 18566+0408 (G37.55+0.20), which is the only region known to show periodic formaldehyde (4.8 GHz H{sub 2}CO) and methanol (6.7 GHz CH{sub 3}OH) maser flares. The observations were conducted between 2008 October and 2010 January with the 305 m Arecibo Telescope in Puerto Rico. We detected two flare events, one in 2009 March and one in 2009 September to November. The OH maser flares are not simultaneous with the H{sub 2}CO flares, but may be correlated with CH{sub 3}OH flares from a component at corresponding velocities. A possible correlated variability of OH and CH{sub 3}OH masers in IRAS 18566+0408 is consistent with a common excitation mechanism (IR pumping) as predicted by theory.