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International Conference on Innovative Applied Energy    

E-Proceedings ISBN: 978-1-912532-05-6

St Cross College, University of Oxford, United Kingdom



Computational analysis of vanadium redox flow batteries for centralised storage applications in low-voltage grids



G. Heyer, C. Zugschwert, T. Roediger and K.-H. Pettinger

University of Applied Sciences Landshut, Technology Center Energy, Wiesenweg 1, Ruhstorf an der Rott, Germany



Paper Abstract

Historically low-voltage grids (LVG) were built and operated as distribution systems without decentral energy sources. A high amount of decentral power suppliers due to renewables can cause imbalance between the energy supply and demand. Ultimately LVG operators need to extend the grid in order to maintain the power quality. The use of a centralised energy storage system can increase the electrical self-sufficiency of a LVG segment and therefore can substitute local grid extension measures. Vanadium redox flow batteries (VRFB) are of special interest for long term applications because of the reusability of the electrolyte. The liquid electrolyte is stored in tanks, which enables a retreatment of the electrolyte. Compared to smaller VRFBs in decentralised applications, central storages offer economic scale-up effects of components and maintenance. In addition, it is possible to improve the return on investment by active participation in the market for secondary control power. The approach followed here is based on an energy system simulation including an electric VRFB model and individual load profiles. The simulations exhibit the VRFB power flow within a complex grid environment and the effects on the grid performance e.g. utilisation of the operating resources and self-sufficiency in the grid segment.
For analysing the effect of VRFBs in a LVG, all consumers and sources in the grid territory need to be defined using individual load and photovoltaic power profiles. These profiles serve as inputs for the energy system simulation. Within the simulation an VRFB model and a control strategy for the battery are combined. The experimental characterisation on cell level and of a VRFB system will provide the data for the electrical VRFB modelling and parameterisation. Two different research approaches will be investigated within the energy system simulation. The first approach analyses the use of VRFBs in decentralised systems and is congruent to the home storage concept for solar energy. The second approach considers only one centralised battery in the grid territory. Decentralised energy production and the demand of grid participants are balanced. Both research approaches offer the potential for different evaluation criteria e.g. load coverage, self-sufficiency and therefore provide the opportunity to define technical and economic benefits of VRFBs in these applications. The output of the simulation are VRFB power profiles, which are evaluated in a load flow calculation. The load flow calculation is based on a model of grid topology and shows the utilisation of grid components and the power quality. Due to the comparison of the historical grid usage before and after photovoltaic integration, with the two introduced approaches the performance of the LVG can be evaluated.
Future impacts of the work presented will be an improved and validated commercialisation concept for centralised VRFBs. Adapted local marketing strategies for decentralised power generation units are defined and evaluated. Furthermore, the avoidance of additional local grid extension measures due to the use of centralised VRFB systems can be analysed. The evaluation of energy systems in LVG in combination with the commercialisation concept shows a holistic approach for the prospective use of VRFBs. 

Paper Keywords
Vanadium redox flow battery, VRFB, low-voltage grid, LVG, holistic energy system simulation, self-sufficiency, electrical energy storage, costs for engery storage, centralised storage applications, centralised electrical energy storage systems, grid stability problems.
Corresponding author Biography

Christina Zugschwert, born in 1993, has a Bachelor’s Degree in Energy Industrial Engineering and a Master’s Degree in Electrical Engineering, both from University of Applied Sciences Landshut. In 2017 she began to work as a research engineer at the University of Applied Sciences Landshut. At the Technology Center Energy her tasks include the investigation of different applications for redox flow batteries by the computational analysis of energy systems in the research team of Prof. Karl-Heinz Pettinger and Prof. Tim Rödiger.

The International Conference on Innovative Applied Energy (IAPE’18)