Possible mechanisms of electronic phase separation in oxide interfaces

LaAlO3/SrTiO3 ad LaTiO3/SrTiO3 interfaces are known to host a strongly inhomogeneous (nearly) two-dimensional electron gas (2DEG). In this work we present three unconventional electronic mechanisms of electronic phase separation (EPS) in a 2DEG as a possible source of inhomogeneity in oxide interfaces. Common to all three mechanisms is the dependence of some (interaction) potential on the 2DEG's density. We first consider a mechanism resulting from a sizable density-dependent Rashba spin-orbit coupling. Next, we point out that an EPS may also occur in the case of a density-dependent superconducting pairing interaction. Finally, we show that the confinement of the 2DEG to the interface by a density-dependent, self-consistent electrostatic potential can by itself cause an EPS.Comment: 4 pages and 4 figures, Proceedings of the International Conference "Superstripes 2014", 25-31 July 2015, Erice, Ital

Method for size optimisation of large wind\u2013hydrogen systems with high penetration on power grids

Wind power generation is growing rapidly in many locations around the world. Power systems are able to absorb large amounts of wind capacity, but operational problems arise when the wind power penetration becomes high. Such factors as voltage dips, frequency variations, low power system stability, low reactive power and power flow imbalances reduce the economic value and represent a barrier to the unlimited development of wind energy. Hydrogen production from wind power that is not matched with hourly electricity demand appears to be an attractive storage option capable of providing a balancing service to the electricity generators and suppliers for mitigation of the negative impacts due to the random nature of wind. Because of its multi-functionality, hydrogen can be used directly as a fuel, mixed with methane, or transmitted through pipelines to the users. The aim of this paper is to produce useful suggestions for the planning, development and sizing of wind\u2013hydrogen systems by taking into account the local and regional resources, demands, constraints and opportunities. This study considers both the economic and technological variables and describes an optimisation method (OM) for analysing power systems in which part of the electricity generated by a grid-connected wind plant is used to produce hydrogen by electrolysis. An example application of this OM has been developed for a specific geographical area located in central Sicily. Our results identify the potential and the limitations connected to cases that use excess wind power to produce hydrogen for civil applications