Efficient Operation of Modular Grid-Connected Battery Inverters for RES Integration

Grid-connected battery storage systems on megawatt-scale play an important role for the integration of renewable energies into electricity markets and grids. In reality, these systems consist of several batteries and inverters, which have a lower energy conversion efficiency in partial load operation. In renewable energy sources (RES) applications, however, battery systems are often operated at low power. The modularity of grid-connected battery storage systems thus allows improving system efficiency during operation. This contribution aims at quantifying the effect of segmenting the system into multiple battery-inverter subsystems on reducing operating losses. The analysis is based on a mixed-integer linear program that determines the system operation by minimizing operating losses. The analysis shows that systems with high modularity can meet a given schedule with lower losses. Increasing modularity from one to 32 subsystems can reduce operating losses by almost 40%. As the number of subsystems increases, the benefit of higher efficiency decreases. The resulting state of charge (SOC) pattern of the batteries is similar for the investigated systems, while the average SOC value is higher in highly modular systems

Brand champion behaviour: Its role in corporate branding

yesBrand champions are responsible for encouraging employee commitment to the corporate brand strategy. They strongly believe in and identify with the brand concept—the company’s selected brand meaning, which underpins corporate brand strategy implementation. We conducted research to explore why and how brand champion behaviour operates within companies implementing a new corporate brand strategy. Against a backdrop of growing interest in brand champion behaviour in corporate branding research, we grounded our study in social identity theory and rhetorical theory from change management literature. Our findings show that articulating a compelling brand vision, taking responsibility, and getting the right people involved are the most widely used strategies by brand champions. We uncover how rhetorical strategies within brand champion behaviour generate employee commitment to a new corporate brand strategy. The dimension of brand champion behaviour that is effective depends on the type of brand evolution, involving shifts in the brand concept. We make suggestions for further studies underpinned by social identity theory and rhetorical theory to investigate brand champion behaviour processes within companies introducing a new corporate brand strategy

Coarsening of Finite Element and Boundary Element Spaces

In this paper, we will present composite boundary elements (CBE) for classical Fredholm boundary integral equations. These new boundary elements allow the low-dimensional discretisation of boundary integral equation where the minimal number of degrees of freedom is independent of the, possibly, huge number of charts which are necessary to describe a complicated surface. The applications are three-fold: (a) The coarse grid discretisation by composite boundary elements allow the use of multi-grid algorithms for solving the fine grid discretisation independently of the number of patches which are necessary to describe the surface. (b) If the accuracy requirements are moderate the composite boundary elements allow the low-dimensional discretisation of the integral equation. (c) A posteriori error indicators can be applied already to a low dimensional discretisation, which do not resolve the domain, to obtain a problem-adapted discretisation.

Magnetization switching of submicrometer Co dots induced by a magnetic force microscope tip

We have applied magnetic force microscopy (MFM) with an in situ electromagnet to study the switching of the magnetization of submicrometer Co dots fabricated by means of electron-beam lithography. By using the MFM tip as a local-field source, the magnetization of individual single-domain Co dots could be reversed. Micromagnetic simulations show that the switching process is induced by the stray field of the MFM tip. Furthermore, the external field that is necessary to support switching of the dot depends on the tip-dot separation