A new Markov-chain-related statistical approach for modelling synthetic wind power time series

The integration of rising shares of volatile wind power in the generation mix is a major challenge forthe future energy system. To address the uncertainties involved in wind power generation, modelsanalysing and simulating the stochastic nature of this energy source are becoming increasinglyimportant. One statistical approach that has been frequently used in the literature is the Markov chainapproach. Recently, the method was identified as being of limited use for generating wind time serieswith time steps shorter than 15–40 min as it is not capable of reproducing the autocorrelationcharacteristics accurately. This paper presents a new Markov-chain-related statistical approach that iscapable of solving this problem by introducing a variable second lag. Furthermore, additional featuresare presented that allow for the further adjustment of the generated synthetic time series. Theinfluences of the model parameter settings are examined by meaningful parameter variations. Thesuitability of the approach is demonstrated by an application analysis with the example of the windfeed-in in Germany. It shows that—in contrast to conventional Markov chain approaches—thegenerated synthetic time series do not systematically underestimate the required storage capacity tobalance wind power fluctuation

3D pin-by-pin power density profiles with high spatial resolution in the vicinity of a BWR control blade tip simulated with coupled neutronics/burn-up calculations

Pellet cladding interaction (PCI) as well as pellet cladding mechanical interaction (PCMI) are well-known fuel failures in light water reactors, especially in boiling water reactors (BWR). Whereas the thermo-mechanical processes of PCI effects have been intensively investigated in the last decades, only rare information is available on the role of neutron physics. However, each power transient is primary due to neutron physics effects and thus knowledge of the neutron physical background is mandatory to better understand the occurrence of PCI effects in BWRs. This paper will focus on a study of local power excursions in a typical BWR fuel assembly during control rod movements. Burn-up and energy deposition were simulated with high spatial granularity, especially in the vicinity of the control blade tip. It could be shown, that the design of the control blade plays a dominant role for the occurrence of local power peaks while instantaneously moving down the control rod. The main result is, that the largest power peak occurs at the interface between steel handle and absorber rods. A full width half maximum (FWHM) of +/- 2.5 cm was observed. This means, the local power excursion due to neutron physics phenomena involve approximately five pellets. With the VESTA code coupled MCNP(X)/ORIGEN2.2 calculations were performed with more than 3400 burn-up zones in order to take history effects into account. (C) 2011 Elsevier B.V. All rights reserved