Wind power integration, negative prices and power system flexibility - An empirical analysis of extreme events in Germany

This article analyses the flexibility of the German power market with respect to the integration of an increasing share of electricity from renewable energy sources. Flexibility limiting system components, which cause negative prices are explained and illustrated for the German market. Then, the decision of the European Energy Exchange in Leipzig (EEX) to allow negative price bids is explained. Empirical data show the flexibility of conventional generating capacities in Germany during the considered time frame from October 2008 until November 2009. Of the 71 hours with negative spot prices, ten hours were significantly negative with prices of at least -100€/MWh. These extreme hours are analysed in greater detail by the examination of the different system components. Thereby, load, wind power infeed and conventional generation by fuel type are observed as well as the market for negative tertiary reserve as indicators for market tightness. It will be shown that although the market situations were severe, under current conditions it could have been much worse under certain circumstances. Furthermore, the long-run implications of an increasing RES-E share on the conventional generation capacity are discussed. The article concludes with an outlook on additional power system flexibility options.Electricity markets, negative prices, renewable electricity integration, wind power

Loss induced collective subradiant Dicke behaviour in a multiatom sample

The exact dynamics of $N$ two-level atoms coupled to a common electromagnetic bath and closely located inside a lossy cavity is reported. Stationary radiation trapping effects are found and very transparently interpreted in the context of our approach. We prove that initially injecting one excitation only in the $N$ atoms-cavity system, loss mechanisms asymptotically drive the matter sample toward a long-lived collective subradiant Dicke state. The role played by the closeness of the $N$ atoms with respect to such a cooperative behavior is brought to light and carefully discussed.Comment: 14 pages, 6 figures, submitted to EPJ

Stationary entanglement induced by dissipation

The dynamics of two two-level dipole-dipole interacting atoms coupled to a common electromagnetic bath and closely located inside a lossy cavity, is reported. Initially injecting only one excitation in the two atoms-cavity system, loss mechanisms asymptotically drive the matter sample toward a stationary maximally entangled state. The role played by the closeness of the two atoms with respect to such a cooperative behaviour is carefully discussed. Stationary radiation trapping effects are found and transparently interpreted.Comment: 1 figure, submitted to Phys. Rev. Let

One Who Was Known to Become Irascible

To Rear Admiral Stephen B. Luce (1827-1917) belongs the credit for the concept of a Naval War College and for its establishment on Coasters Harbor Island, Newport, in 1884

The Navy, Newport and Stephen B. Luce

The annals of Newport for the last half of the 19th century until the First World War deal chiefly, if not exclusively, with the brilliance of the summer society

Flow curvature effects on dynamic behaviour of a novel vertical axis tidal current turbine: numerical and experimental analysis

The paper deals with performances analysis of vertical axis turbine to exploit tidal marine currents. Flow curvature effects on performences of a novel vertical axis turbine have been investuigated. It has been shown that the flow curvature effect allows to design properly an accurate airfoil shape to increase turbine performances