Variable Porous Electrode Compression for Redox Flow Battery Systems

Vanadium redox flow batteries (VRFBs) offer great promise as a safe, cost effective means of storing electrical energy on a large scale and will certainly have a part to play in the global transition to renewable energy. To unlock the full potential of VRFB systems, however, it is necessary to improve their power density. Unconventional stack design shows encouraging possibilities as a means to that end. Presented here is the novel concept of variable porous electrode compression, which simulations have shown to deliver a one third increase in minimum limiting current density together with a lower pressure drop when compared to standard uniform compression cell designs

Variable Porous Electrode Compression for Redox Flow Battery Systems

Vanadium redox flow batteries (VRFBs) offer great promise as a safe, cost effective means of storing electrical energy on a large scale and will certainly have a part to play in the global transition to renewable energy. To unlock the full potential of VRFB systems, however, it is necessary to improve their power density. Unconventional stack design shows encouraging possibilities as a means to that end. Presented here is the novel concept of variable porous electrode compression, which simulations have shown to deliver a one third increase in minimum limiting current density together with a lower pressure drop when compared to standard uniform compression cell designs

Gas Transition: Renewable Hydrogen’s Future in Eastern Australia’s Energy Networks

The energy transition for a net-zero future will require deep decarbonisation that hydrogen is uniquely positioned to facilitate. This technoeconomic study considers renewable hydrogen production, transmission and storage for energy networks using the National Electricity Market (NEM) region of Eastern Australia as a case study. Plausible growth projections are developed to meet domestic demands for gas out to 2040 based on industry commitments and scalable technology deployment. Analysis using the discounted cash flow technique is performed to determine possible levelised cost figures for key processes out to 2050. Variables include geographic limitations, growth rates and capacity factors to minimise abatement costs compared to business-as-usual natural gas forecasts. The study provides an optimistic outlook considering renewable power-to-X opportunities for blending, replacement and gas-to-power to show viable pathways for the gas transition to green hydrogen. Blending is achievable with modest (3%) green premiums this decade, and substitution for natural gas combustion in the long-term is likely to represent an abatement cost of AUD 18/tCO2-e including transmission and storage

Enhanced Reactant Distribution in Redox Flow Cells

Redox flow batteries (RFBs), provide a safe and cost-effective means of storing energy at grid-scale, and will play an important role in the decarbonization of global electricity networks. Several approaches have been explored to improve their efficiency and power density, and recently, cell geometry modification has shown promise in efforts to address mass transport limitations which affect electrochemical and overall system performance. Flow-by electrode configurations have demonstrated significant power density improvements in laboratory testing, however, flow-through designs with conductive felt remain the standard at commercial scale. Concentration gradients exist within these cells, limiting their performance. A new concept of redistributing reactants within the flow frame is introduced in this paper. This research shows a 60% improvement in minimum V3+ concentration within simulated vanadium redox flow battery (VRB/VRFB) cells through the application of static mixers. The enhanced reactant distribution showed a cell voltage improvement by reducing concentration overpotential, suggesting a pathway forward to increase limiting current density and cycle efficiencies in RFBs

Multiphysics Flow Battery Modelling and Optimisation

Efficient and effective energy storage technologies are a key element of digital power networks. Batteries offer versatile capabilities, and flow batteries are well suited to large-scale applications due to inherent technical advantages. Their efficiency, capacity and power density, however, is hindered by mass transport limitations. Availability of reactants must be maintained to reduce parasitic overpotentials and maximise electrolyte utilisation. This is a coupled mechanical-electrochemical problem as pressure differentials and associated losses from pumping power must also be considered. This thesis optimises flow battery system performance using computer aided design of cell architecture innovations. Flow-through vanadium redox flow battery cells charging at high state of charge were simulated in COMSOL with two- and three-dimensional multiphysics models developed and validated against published data. Trapezoidal and annular sector shapes, where cell width is reduced towards the outlet, were compared to conventional rectangular geometry. These shapes were employed to increase electrolyte velocity from inlet to outlet, thus improving the delivery of active species as reactants are depleted. The radial design raised the minimum reactant concentration in the cell by 66%, and improved flow uniformity when compared to the trapezoidal design, at the cost of an increased pressure differential. Wedge-shaped cell designs, where the thickness is reduced instead of the width, were then simulated with variable porous electrode compression. Results showed 1% improvement to operating cell voltage. Laboratory experiments demonstrated a 15% higher energy efficiency and extended usable capacity with no parasitic pressure drop increase using this design.Static mixers were then used to address concentration gradients. The redistributing of reactants within the flow frame showed a 60% improvement in minimum V3+ concentration and a corresponding 1% cell voltage improvement by reducing concentration overpotentials. This innovation was then combined with a wedge-shaped cell to take advantage of variable compression with higher flow rate mixed electrolyte at the outlet. Results showed a 2% voltage improvement by addressing concentration overpotential associated with mass transport limitations. This was achieved with a lower pressure drop, demonstrating how mechanical design can optimise flow-through battery cells to reduce losses from pump energy while increasing the availability of active species where required

Mass Transport Optimization for Redox Flow Battery Design

The world is moving to the next phase of the energy transition with high penetrations of renewable energy. Flexible and scalable redox flow battery (RFB) technology is expected to play an important role in ensuring electricity network security and reliability. Innovations continue to enhance their value by reducing parasitic losses and maximizing available energy over broader operating conditions. Simulations of vanadium redox flow battery (VRB/VRFB) cells were conducted using a validated COMSOL Multiphysics model. Cell designs are developed to reduce losses from pump energy while improving the delivery of active species where required. The combination of wedge-shaped cells with static mixers is found to improve performance by reducing differential pressure and concentration overpotential. Higher electrode compression at the outlet optimises material properties through the cell, while the mixer mitigates concentration gradients across the cell. Simulations show a 12% lower pressure drop across the cell and a 2% lower charge voltage for improved energy efficiency. Wedge-shaped cells are shown to offer extended capacity during cycling. The prototype mixers are fabricated using additive manufacturing for further studies. Toroidal battery designs incorporating these innovations at the kW scale are developed through inter-disciplinary collaboration and rendered using computer aided design (CAD)

Effets du cobalt sur les communautés de diatomées en cours d’eau

International audienceLe cobalt est un métal essentiel qui constitue l'atome central de la vitamine B12. Dans les eaux naturelles, il est présent à l’état de trace (généralement inférieur à 1 μg/L). Toutefois, dans le contexte actuel de transition énergétique, l’intensification de son extraction entraine une augmentation de ses concentrations dans l’environnement, et en particulier dans les milieux aquatiques, au cours de la dernière décennie. L'objectif de cette étude est donc d'examiner les effets de dose du cobalt et de durée d’exposition croissante sur les diatomées périphytiques. Pour cela, des biofilms matures colonisés sur des lames de verre dans l’eau du Gave de Pau ont été exposés à des concentrations croissantes de cobalt (0, 6, 30 et 60 μg/L) pendant 28 jours dans les Rivières Pilotes du Pole d’Études et de Recherche de Lacq (PERL). Les biofilms ont été collectés avant contamination et après 1 heure, 1, 3, 7, 14, 21 et 28 jours d'exposition afin d'analyser la concentration en cobalt bioaccumulée, la biomasse, la teneur en chlorophylle a, la densité et la mortalité des diatomées ainsi que les métabolites produits. Le cobalt était accumulé principalement sous forme intracellulaire dans les biofilms. La quantité de cobalt bioaccumulé était corrélée à la concentration dans l’eau jusqu’à 21 jours d’exposition, confirmant une exposition croissante des organismes au métal. Après 14 jours d’exposition, une diminution de la biomasse et des teneurs en chlorophylle a proportionnelle aux concentrations d’exposition a été mesurée. Concernant les densités de diatomées, une inhibition nette de la croissance était visible pour les concentrations nominales de 30 et 60 μg/L, en particulier après 21 et 28 jours d’exposition. La mortalité, toutefois, restait dans des taux acceptables (généralement <10%). Ces résultats indiquent que le cobalt est susceptible d’impacter négativement les communautés de microalgues dans les milieux à proximité de sites d’extraction et d’activités industrielles, avec des conséquences possibles sur les niveaux trophiques supérieurs

New sensitive tools to characterize meta-metabolome response to short- and long-term cobalt exposure in dynamic river biofilm communities

International audienceUntargeted metabolomics is a non-a priori analysis of biomolecules that characterizes the metabolome variations induced by short- and long-term exposures to stressors. Even if the metabolite annotation remains lacunar due to database gaps, the global metabolomic fingerprint allows for trend analyses of dose-response curves for hundreds of cellular metabolites. Analysis of dose/time-response curve trends (biphasic or monotonic) of untargeted metabolomic features would thus allow the use of all the chemical signals obtained in order to determine stress levels (defense or damage) in organisms. To develop this approach in a context of time-dependent microbial community changes, mature river biofilms were exposed for 1 month to four cobalt (Co) concentrations (from background concentration to 1 × 10−6 M) in an open system of artificial streams. The meta-metabolomic response of biofilms was compared against a multitude of biological parameters (including bioaccumulation, biomass, chlorophyll a content, composition and structure of prokaryotic and eukaryotic communities) monitored at set exposure times (from 1 h to 28 d). Cobalt exposure induced extremely rapid responses of the meta-metabolome, with time range inducing defense responses (TRIDeR) of around 10 s, and time range inducing damage responses (TRIDaR) of several hours. Even in biofilms whose structure had been altered by Co bioaccumulation (reduced biomass, chlorophyll a contents and changes in the composition and diversity of prokaryotic and eukaryotic communities), concentration range inducing defense responses (CRIDeR) with similar initiation thresholds (1.41 ± 0.77 × 10−10 M Co2+ added in the exposure medium) were set up at the meta-metabolome level at every time point. In contrast, the concentration range inducing damage responses (CRIDaR) initiation thresholds increased by 10 times in long-term Co exposed biofilms. The present study demonstrates that defense and damage responses of biofilm meta-metabolome exposed to Co are rapidly and sustainably impacted, even within tolerant and resistant microbial communities