Design aspects and early experiments of a Vanadium Redox Flow Battery cell test facility: measurements and methods for scaling up

Redox Flow Batteries (RFBs) development and future success depend on the research on new active materials, namely electrolytic solutions, membranes and electrodes, typically conduced on small single-cell device [1]. However, also the technological development plays a fundamental role in view of the successful design of large RFB systems [2]. This work presents the design, construction and early operation of a single-cell medium-size (5 cm x 8 cm) Vanadium Redox Flow Battery (VRFB) cell test facility, dubbed VRFB-CTF Fig. 1a) suitable to test materials and geometries in easly controllable and adjustable conditions. VRFB-CTF is also capable of testing small VRFB stacks. The test bench has been designed and built to accurately measure the main thermal, hydraulic, electric, and energetic quantites affecting the performance of VRFBs [3]. By extrapolating such measurements, the performance of large-scale RFB stacks can be estimated by means of analytical formulations built on similitude concepts. VRFB-CTF layout has been conceived for high accessibility with the pump for circulating the solutions located apart. The hydraulic circuits are equipped with valves for fast maintenance operation and the reservoirs are hermetically sealed with their residual volumes filled with inert gas to prevent vanadium species contamination from atmospheric oxygen. The plant is fully instrumented with electrical, thermal and fluid-dynamic probes. Charge and discharge power control is provided by a Power Conditioning System (PCS) that can be controlled both locally and remotely by a Flow Battery Management System (FBMS). The latter has been designed and built around a desktop computer with a compact data acquisition interface in LabVIEW enviroment that allows fully customizable high-level SCADA-like (Supervisory Control And Data Acquisition) data management and experiment control (Fig. 1b). Instrumentation includes a multichannel electrochemical impedance spectroscopy (EIS) analyzer. Measurents provided by VRFB-CTF have already been used to address criteria and metrics for the design of industrial-scale RFBs [4].