Technical and Economic Assessment of Storage Technologies for Power-Supply Grids

Fluctuating power generation from renewable energies such as wind and photovoltaic are a technical challenge for grid stability. Storage systems are an option to stabilise the grid and to maximise the utilisation factors of renewable power generators. This paper analyses the state of the art of storage technologies, including a detailed life cycle cost comparison. Beside this, benefits of using storage systems in electric vehicles are analysed and quantified. A comprehensive overview of storage technologies as well as possible applications and business cases for storage systems is presented.

Topological entropy and orbit growth in link complements

In this article, we exhibit certain linking properties of periodic orbits of $C^{1+\alpha}$ flows with positive topological entropy on closed 3-manifolds M. It is shown that any such flow contains a link L of periodic orbits and a horseshoe K in M\L, such that all periodic orbits in K are unique in their homotopy class in M\L (among periodic orbits in M). Moreover, the entropy of the flow can be approximated by the entropies of such horseshoes K. A version of that result for chords is obtained. Our main motivation comes from Reeb dynamics, and as an application, we address a question by Alves-Pirnapasov, and obtain that the topological entropy of a 3-dimensional, $C^{\infty}$-generic Reeb flow can be approximated by the exponential homotopical growth rates of contact homology in link complements.Comment: 52 pages, 1 figur

A novel model for smectic liquid crystals: Elastic anisotropy and response to a steady-state flow

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in J. Chem. Phys. 145, 164903 (2016) and may be found at https://doi.org/10.1063/1.4965711.By means of a combination of equilibrium Monte Carlo and molecular dynamics simulations and nonequilibrium molecular dynamics we investigate the ordered, uniaxial phases (i.e., nematic and smectic A) of a model liquid crystal. We characterize equilibrium behavior through their diffusive behavior and elastic properties. As one approaches the equilibrium isotropic-nematic phase transition, diffusion becomes anisotropic in that self-diffusion D⊥ in the direction orthogonal to a molecule’s long axis is more hindered than self-diffusion D∥ in the direction parallel to that axis. Close to nematic-smectic A phase transition the opposite is true, D∥ < D⊥. The Frank elastic constants K1, K2, and K3 for the respective splay, twist, and bend deformations of the director field n̂ are no longer equal and exhibit a temperature dependence observed experimentally for cyanobiphenyls. Under nonequilibrium conditions, a pressure gradient applied to the smectic A phase generates Poiseuille-like or plug flow depending on whether the convective velocity is parallel or orthogonal to the plane of smectic layers. We find that in Poiseuille-like flow the viscosity of the smectic A phase is higher than in plug flow. This can be rationalized via the velocity-field component in the direction of the flow. In a sufficiently strong flow these smectic layers are not destroyed but significantly bent.DFG, 65143814, GRK 1524: Self-Assembled Soft-Matter Nanostructures at Interface

Rabinowitz Floer homology, leafwise intersections, and topological entropy

We study dynamical properties of contact manifolds using methods from Floer theory. In the first part of this thesis we exhibit examples of contact structures on spheres of dimensions greater than $5$ having positive topological entropy. We give two different types of constructions, each requiring a different approach, each leading to positive entropy. The first approach uses the algebraic growth of wrapped Floer homology and its invariance properties under some class of contact surgeries. By carrying out a suitable series of those surgeries we then obtain contact spheres $(S^{2n-1},\xi)$ of dimensions $2n-1>5$ such that the topological entropy of every Reeb flow on $(S^{2n-1},\xi)$ is positive. Those spheres admit an exact filling by a domain that is homotopy equivalent to a bouquet of spheres. In dimension $5$ this approach leads also to the construction of a contact structure on $S^{3} \times S^{2}$ such that all its Reeb flows have positive topological entropy. The second approach uses the Floer homology of perturbations of the Rabinowitz action functional. This allows us in particular to show that there exist contact spheres in dimensions greater then $5$ that are exactly fillable by a domain diffeomorphic to a ball and such that the topological entropy of every Reeb flow on it is positive. In the second part of the thesis we define a version of Rabinowitz Floer homology for hypertight contact manifolds in symplectizations and prove versions of conjectures by Sandon and Mazzucchelli on the existence of translated points and invariant Reeb orbits. Furthermore we give a proof of the existence of non-contractible Reeb orbits on hypertight contact manifolds that admit positive loops of contactomorphisms