23 rd International Conference on Electricity Distribution Lyon, 15-18 June 2015 Paper 0750 CIRED 2015 1/5 DEVELOPING A REDOX FLOW BATTERY WITH SPANISH TECHNOLOGY. PROJECT REDOX2015 Luis SANTOS Raquel FERRET Alberto IZPIZUA Maddi SANCHEZ Maria RIVAS Carlos SANCHEZ EDP – Spain ZIGOR – Spain TEKNIKER – Spain ISASTUR- Spain lsantos@edpenergia.es rferret@zigor.com alberto.izpizua@tekniker.es maddi.sanchez@tekniker.es maria.rivas@isastur.grupoisastur.com carlos.sanchez@isastur.grupoisastur.com 1. INTRODUCTION Project REDOX2015 is an example of the efforts to improve performance of one storage technology: Vanadium redox flow batteries. The objectives of the project were two: to develop a VRFB by Spanish partners and to increase knowledge in new components for the next generation of VRFB. The project consortium was made by EDP Spain, ZIGOR, ISASTUR , Oviedo University, TECNALIA, IREC, INCAR and TEKNIKER. The project is funded by the Economy and Competitiveness Ministry of Spain with FEDER funding from the European Commission (IPT-2011-1690-900000). This paper describes key findings of the first objective of the project in designing, manufacturing and deployment of the battery connected to the grid. 2. DESIGN OF REDOX2015 BATTERY The main challenges in the design of the REDOX2015 Redox Flow Battery have been related mainly to the stack design and more precisely to the design of the frame to avoid the shunt currents between cells and the design for an uniform distribution of the flow rate in all cells of the stack. Fig 1 Vanadium Redox Flow Battery diagram Concerning the design of the frame, two important issues have been considered, the electrical one and the fluidic one. The electrical subject deals with avoiding the shunt currents. It has been made an electrical model in SIMULINK based on the Fig. 2 to calculate the resistance needed in the electrical path [1]. Fig. 2. Circuit analog model for a Stack of N single cells The results of this model have been the starting data for designing the serpentine at the inlet and the outlet of the cell. In this design it is very important the relationship between the resistance and the pressure drop that is produced. Therefore, simulations with CFD (computational fluid dynamics) are highly important for serpentine design and to ensure that it does not increase the pressure drop in a large way. Besides that, two additional effects have been analyzed with CFD. On one side, the distribution of the electrolyte along the carbon felt and, on the other side, the uniform distribution of the flow into the cells. To do that, the serpentine pressure drop and the distribution of the flow along the carbon felt have been simulated with a single cell model. It is highly important the distribution of the electrolyte on the carbon felt where dry zones are dead zones that do not work. The figure below shows one of the results of electrolyte flow distribution. It can be seen that there is not any dead zones and that the biggest pressure drop is in the carbon felt. This means that predominant pressure drop does not happened in the serpentine.