Wind Power Persistence Characterized by Superstatistics

Mitigating climate change demands a transition towards renewable electricity generation, with wind power being a particularly promising technology. Long periods either of high or of low wind therefore essentially define the necessary amount of storage to balance the power system. While the general statistics of wind velocities have been studied extensively, persistence (waiting) time statistics of wind is far from well understood. Here, we investigate the statistics of both high- and low-wind persistence. We find heavy tails and explain them as a superposition of different wind conditions, requiring q-exponential distributions instead of exponential distributions. Persistent wind conditions are not necessarily caused by stationary atmospheric circulation patterns nor by recurring individual weather types but may emerge as a combination of multiple weather types and circulation patterns. This also leads to Fréchet instead of Gumbel extreme value statistics. Understanding wind persistence statistically and synoptically may help to ensure a reliable and economically feasible future energy system, which uses a high share of wind generation

Stromspeicher : Radikal organisch = Power storage : radically organic

Lithiumionenbatterie, Bleiakku und Co. sind für den Sprung von der konventionellen zur flexiblen, gedruckten organischen Elektronik wenig geeignet. Polymerbasierte, organische Radikalbatterien bieten einen effizienten Ausweg

Nanostructured organic radical cathodes from self-assembled nitroxide-containing block copolymer thin films

This contribution describes the formation of nanostructured thin film organic radical cathodes. First, the self-assembly of poly(styrene)-block-poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA-b-PS) diblock copolymers is detailed. In order to improve the nano-morphology of the immiscible PTMA and PS domains, the effect of thermal and solvent annealing is investigated. The formation of thin films with different morphologies such as cylindrical or lamellar nanostructures is observed depending on the processing conditions. The electrochemical properties of the nanostructured films are further investigated to assess the redox activity of the PTMA domains. Cyclic voltammetry of PTMA-b-PS diblock copolymers, either in dissolved or thin film supported configuration, confirms the reversible redox behavior of the nitroxide radical. Galvanostatic cycling of the thin film nanostructured cathodes reveals good capacity retention with fast charge/discharge response resulting from efficient charge and ion transfer as well as structural integrity. Such nanostructured organic radical cathodes provide opportunities for the fabrication of new generation nanostructured organic radical battery architectures

The effect of 25 M versus 50 M course length on backstroke performance – An analysis of national and international swimmers

Background: The aims of the present study were (i) to examine effects of course length (25 m versus 50 m) on backstroke performance and (ii) to analyse the changes in 25 m and 50 m courses backstroke performance across years during the 2000- 2013 period, for both women and men at national (Switzerland) and international (finals of the FINA World Championships) level. Methods: Backstroke swim performances were analysed for 53,849 swimmers ranked on the national Swiss high score list, and for 624 swimmers competing in the finals of the FINA World Championships, in 50 m, 100 m, and 200 m races, during 2000- 2013. Analysis of variance was used to compare swim speeds for different groups, and linear regression was used to determine statistical significance of temporal trends. Results: National and international athletes were on average 4.3% faster on short courses than on long courses, for both sexes and over all race distances. Sex-related differences in swim speed were greater on short courses than on long courses for international athletes over all distances, and for national athletes in 200 m races. Swim performance improved for both international (r2=0.61–0.90, p=0.004-0.04) and national swimmers (r2=0.32–0.65, p=0.001- 0.04) in short- and long course events. Sex-related differences in backstroke swim performance showed no change over time. Conclusions: These results indicate that elite backstroke swimmers were significantly faster on 25 m courses than on 50 m courses, irrespective of sex and race distance. International and national swimmers improved performance in short- and long-course races during the 2000-2013 period. Further studies are required to determine whether course length has similar effects on other swim styles