Enhancing the efficiency of kW-class vanadium redox flow batteries by flow factor modulation: An experimental method

Abstract

The paper presents a control method of the electrolyte flow factor in kW-class Vanadium Redox Flow Batteries that minimizes transport losses without affecting the battery's electrical performance. This method uses experimental data acquired on a 9 kW/27kWh test facility at varying operating conditions. The effects of overpotentials on the polarization curves are then modeled as nonlinear electrical resistances that vary with the stack current, state of charge and electrolyte flow rates. Our analysis of these variables shows that the optimal performance is found if the flow factor is modulated during operation according to stack current and the battery state, so as to minimize the overall flow-dependent losses. The optimal profiles have been identified as functions of the battery's operating conditions. Based on these results, a dynamic control for the electrolyte flow rates has been implemented at a software level (i.e. without modifying the hardware of the test facility), which is capable of maximizing the round-trip efficiency and exceeds the performance achieved with a constant flow factor strategy, as proposed in previous literature. The implementation of the optimal flow rate control requires a preliminary test campaign to collect performance data, which are then used in the control protocol to manage the battery's operation. This scheme is easily implementable at a software level in other industrial redox flow batteries.

Non‐Solvent Induced Phase Separation Enables Designer Redox Flow Battery Electrodes

“…Advances in zero-gap reactor architecture and thinner electrodes to ameliorate ohmic losses have led to significant performance enhancement at the lab scale; [14,17] furthermore, reactor design and stack topology are continually progressing to satisfy larger-scale energy demands. [18][19][20][21][22] However, the fundamental challenge remains to simultaneously enable ample surface area for redox reactions, high permeability to reduce the pressure loss, and augmented mass transfer to minimize concentration overpotentials-all while using materials that are fabricated using continuous, low-cost, and sustainable manufacturing techniques. Accordingly, research efforts have focused on tailoring RFB electrodes, both in terms of surface functional groups and microstructural arrangements.…”

Impacts of Renewable Energy Resources on Effectiveness of Grid-Integrated Systems: Succinct Review of Current Challenges and Potential Solution Strategies

“…Furthermore, capacities of practical BESS in green grids today range from small scale of rated power in few kW [184] to large scale in several MW [185]. In addition, apart from peak shaving of power on electrical grids, BESS are further employed for performing other key functions on the grid, such as arbitrage, which by extension reduces power curtailment due to the fluctuating renewable energy source; transmission and distribution upgrade deferrals; as well as black start, which entails using energy stored in the grid to warm up big generating plants at start-up prior to the onset of power generation [186].…”

Comparative Study of Kilowatt-Scale Vanadium Redox Flow Battery Stacks Designed with Serpentine Flow Fields and Split Manifolds

“…A number of studies have been reported on the performance of kilowatt (kW) scale VRFB stacks in the literature. Extensive focus has been given to the electrolyte flow rate strategies and range [9][10][11][12][13][14][15][16][17], shunt current losses [17][18][19][20][21][22] and engineering aspects of flow battery stacks [23][24][25][26].…”