scholarly journals Thermodynamically Rigorous Description of the Open Circuit Voltage of Redox Flow Batteries

2021 ◽  
Author(s):  
Nicolas Hayer ◽  
Maximilian Kohns
Keyword(s):  
Activity Coefficients ◽  
Open Circuit Voltage ◽  
Renewable Energy Sources ◽  
Measurement Data ◽  
Open Circuit ◽  
Power Grids ◽  
Nernst Equation ◽  
Rigorous Approach ◽  
Redox Flow Batteries ◽  
Flow Batteries

Redox flow batteries (RFBs) are considered an outstanding candidate for the integration of renewable energy sources into the existing power grids. A key property of RFBs is the open circuit voltage (OCV) corresponding to the currentless equilibrium state. In the literature, the Nernst equation describing this property is often simplified by neglecting the activity coefficients. In this work, using a thermodynamically rigorous approach, we show that activity coefficients have a significant influence on the OCV of the Iron-Cadmium and All-Vanadium RFBs. Moreover, this influence varies with the state of charge. Therefore, activity coefficients should not be neglected in the Nernst equation. We show that when doing so, the resulting offset in OCV is actually comparable to typical voltage losses occurring during operation. Hence, fitting kinetic parameters to measurement data of voltage losses can lead to ambiguous results if only the idealized OCV, obtained by neglecting the activity coefficients, is used in that evaluation. Therefore, the implementation of a thermodynamically rigorous model has the potential to significantly improve state-of-the-art models for RFBs.

scholarly journals Vanadium Redox Flow Batteries: A Review Oriented to Fluid-Dynamic Optimization

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 176
Author(s):  
Iñigo Aramendia ◽  
Unai Fernandez-Gamiz ◽  
Adrian Martinez-San-Vicente ◽  
Ekaitz Zulueta ◽  
Jose Manuel Lopez-Guede
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Fluid Dynamic ◽  
Renewable Energy Sources ◽  
Vanadium Redox Flow Battery ◽  
Redox Flow Batteries ◽  
Design Flexibility ◽  
Flow Batteries ◽  
Exchange Membrane ◽  
Vanadium Redox

Large-scale energy storage systems (ESS) are nowadays growing in popularity due to the increase in the energy production by renewable energy sources, which in general have a random intermittent nature. Currently, several redox flow batteries have been presented as an alternative of the classical ESS; the scalability, design flexibility and long life cycle of the vanadium redox flow battery (VRFB) have made it to stand out. In a VRFB cell, which consists of two electrodes and an ion exchange membrane, the electrolyte flows through the electrodes where the electrochemical reactions take place. Computational Fluid Dynamics (CFD) simulations are a very powerful tool to develop feasible numerical models to enhance the performance and lifetime of VRFBs. This review aims to present and discuss the numerical models developed in this field and, particularly, to analyze different types of flow fields and patterns that can be found in the literature. The numerical studies presented in this review are a helpful tool to evaluate several key parameters important to optimize the energy systems based on redox flow technologies.

scholarly journals Redox Flow Batteries: Materials, Design and Prospects

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5643
Author(s):  
Igor Iwakiri ◽  
Tiago Antunes ◽  
Helena Almeida ◽  
João P. Sousa ◽  
Rita Bacelar Figueira ◽  
...  
Keyword(s):  
Renewable Energy Sources ◽  
Energy Sources ◽  
Future Perspectives ◽  
Major Step ◽  
Redox Flow Batteries ◽  
Different Types ◽  
Flow Batteries ◽  
Vanadium Redox ◽  
Interesting Alternative ◽  
Intense Research

The implementation of renewable energy sources is rapidly growing in the electrical sector. This is a major step for civilization since it will reduce the carbon footprint and ensure a sustainable future. Nevertheless, these sources of energy are far from perfect and require complementary technologies to ensure dispatchable energy and this requires storage. In the last few decades, redox flow batteries (RFB) have been revealed to be an interesting alternative for this application, mainly due to their versatility and scalability. This technology has been the focus of intense research and great advances in the last decade. This review aims to summarize the most relevant advances achieved in the last few years, i.e., from 2015 until the middle of 2021. A synopsis of the different types of RFB technology will be conducted. Particular attention will be given to vanadium redox flow batteries (VRFB), the most mature RFB technology, but also to the emerging most promising chemistries. An in-depth review will be performed regarding the main innovations, materials, and designs. The main drawbacks and future perspectives for this technology will also be addressed.

scholarly journals Optimization of Method and Components of Enzymatic Fuel Cells

2019 ◽  
pp. 143-146
Author(s):  
Ibukun Akinsola ◽  
Aderemi Babatunde Alabi ◽  
Muibat A Soliu ◽  
Taiye Akomolafe
Keyword(s):  
Fuel Cells ◽  
Open Circuit Voltage ◽  
Short Circuit ◽  
Renewable Energy Sources ◽  
Electrical Power ◽  
Short Circuit Current ◽  
Electrical Energy ◽  
Open Circuit ◽  
Biofuel Cell ◽  
Carbon Electrodes

Enzymatic fuel cells produce electrical power by oxidation of renewable energy sources. An enzymatic glucose biofuel cell uses glucose as fuel and enzymes as biocatalyst, to convert biochemical energy into electrical energy. The applications which need low electrical voltages and low currents have much of the interest in developing enzymatic fuel cells. The cell was constructed using three different materials with different electrodes (Bitter leaf and Copper electrodes (BCu), Bitter leaf and Carbon electrodes (BC) and Water leaf and Carbon electrodes (WC)). The short circuit current and open circuit voltage were measured in micro-ampere (mu A) and milli-volt (mV) respectively at 30 minutes interval over the period of 12 hours (from dawn to dusk). The results which show that fuel cells constructed using bitter leaf with carbon electrode has the highest open circuit voltage, short circuit current and generated power of 162.8~mV, 1.65~ mu A and 268.62~nW respectively at 720~mins is obtained from the plots generated by the use of Microsoft Excel. The results show that all short circuit currents, voltages and powers generated increases with time and this is as a result of the exposure to solar radiation during the period of taking the measurement.

Open-Circuit Voltage Comes from Non-Equilibrium Thermodynamics

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Diego del Olmo ◽  
Michal Pavelka ◽  
Juraj Kosek
Keyword(s):  
Open Circuit Voltage ◽  
Open Circuit ◽  
Electrochemical Reactions ◽  
Equilibrium Thermodynamics ◽  
Nernst Equation ◽  
Vanadium Redox ◽  
Mixed Potentials ◽  
Thermodynamic Derivation ◽  
Zinc Air Batteries ◽  
Non Equilibrium

AbstractOriginally derived by Walther Nernst more than a century ago, the Nernst equation for the open-circuit voltage is a cornerstone in the analysis of electrochemical systems. Unfortunately, the assumptions behind its derivation are often overlooked in the literature, leading to incorrect forms of the equation when applied to complex systems (for example, those with ion-exchange membranes or involving mixed potentials). Such flaws can be avoided by applying a correct thermodynamic derivation independently of the form in which the electrochemical reactions are written. The proper derivation of the Nernst equation becomes important, for instance, in modeling of vanadium redox flow batteries or zinc-air batteries. The rigorous path towards the Nernst equation derivation starts in non-equilibrium thermodynamics.

Redox Flow Batteries for Energy Storage: A Technology Review

2017 ◽  
Vol 15 (1) ◽  
Author(s):  
Ruijie Ye ◽  
Dirk Henkensmeier ◽  
Sang Jun Yoon ◽  
Zhifeng Huang ◽  
Dong Kyu Kim ◽  
...  
Keyword(s):  
Energy Storage ◽  
Electrode Materials ◽  
High Efficiency ◽  
Storage Systems ◽  
Low Cost ◽  
Renewable Energy Sources ◽  
Active Species ◽  
Energy Storage Systems ◽  
Redox Flow Batteries ◽  
Flow Batteries

The utilization of intermittent renewable energy sources needs low-cost, reliable energy storage systems in the future. Among various electrochemical energy storage systems, redox flow batteries (RFBs) are promising with merits of independent energy storage and power generation capability, localization flexibility, high efficiency, low scaling-up cost, and excellent long charge/discharge cycle life. RFBs typically use metal ions as reacting species. The most exploited types are all-vanadium RFBs (VRFBs). Here, we discuss the core components for the VRFBs, including the development and application of different types of membranes, electrode materials, and stack system. In addition, we introduce the recent progress in the discovery of novel electrolytes, such as redox-active organic compounds, polymers, and organic/inorganic suspensions. Versatile structures, tunable properties, and abundant resources of organic-based electrolytes make them suitable for cost-effective stationary applications. With the active species in solid form, suspension electrolytes are expected to provide enhanced volumetric energy densities.

scholarly journals Developing Shunt-Current Minimized Soluble-Lead-Redox-Flow-Batteries

2021 ◽  
Author(s):  
Rathod Suman ◽  
Satya Prakash Yadav ◽  
Musuwathi Krishnamoorthy Ravikumar ◽  
Satish Patil ◽  
Ashok Shukla
Keyword(s):  
Power Density ◽  
Discharge Current ◽  
Coulombic Efficiency ◽  
Specific Capacity ◽  
Open Circuit ◽  
Redox Flow Batteries ◽  
Flow Batteries ◽  
Discharge Parameters ◽  
A Charge ◽  
Charge Discharge

Abstract Shunt currents in membraneless soluble-lead-redox-flow-batteries (SLRFB) are observed in open-circuit condition and found to depend on size of the stack, manifolds, flow rates and charge/discharge parameters. Ramifications of shunt currents on the performance of membraneless SLRFB stacks with internal and external manifolds are reported. In the case of stacks with 3, 5 and 7-cells and internal manifold design, the charge current for the middle cell decreases by 3.3%, 6%, and 8.5%, while the discharge current increases by 2.6%, 5.5%, and 6.6% , respectively, for 3 A charge/discharge current. By contrast, no such adverse effect is observed for external manifold design. The current – potential studies show that while the stacks comprising 3 and 5-cells deliver a maximum power density of 35 mW/cm2, which declines to 15 mW/cm2 for the 7-cell stack with internal manifold design, while the power density remains invariant at 50 mW/cm2 for stacks with external manifold design. An 8-cell stack of 12 V, 50 mAh/cm2 specific capacity and 273 Wh energy storage capacity with 64% energy efficiency is also reported which shows good cyclability over 100 cycles with 95% coulombic efficiency when cycled at 20 mA/cm2 current density for 1h duration.

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