Flow Batteries for gridscale energy storage Joep Pijpers 1
Discharge Time Why Flow Batteries? Power Quality Upgrade deferral Renewables Integration Bulk Power Management Pumped Hydro Flow Batteries Below Ground CAES Seconds Minutes Hours NaS, NaNiCl Sealed Battery Other Sealed Batteries (Liion, Pbacid) Flywheels 1 kw 10 kw 100 kw 1 MW 10 MW 100 MW 1 GW System Power Flow batteries can provide high power output and long discharge times at lowcost, anywhere
Schematics of a Flow Battery System Active Materials: Negolyte Tank Cell Stack Posolyte Tank Redoxactive compounds (Posolyte, Negolyte) Cell Stack: Membranes Electrodes Bipolar plates Balance of Plant (BOP): Power Conversion Pumps, tanks, piping Control and power conversion hardware Decoupling power and energy capacity makes for flexible design High footprint envisioned for stationary storage applications
How could a Flow Battery System look like? Source: Lockheed Martin
Requirements for a successful flow battery technology 1. Low cost (in terms of Levelized Cost of Storage) 2. Safe LCOS = (σ CAPEX t σ O&M t σ Charging t ) σ kwh s t 3. Environmentally benign 4. Low foot print
The incumbency: allvanadium Flow Batteries Pros: Wellestablished technology Good durability Decent energy density Source: www.echemion.com Cons: Corrosive electrolytes Crossover across membranes must be managed Vanadium is expensive Companies: Vionx, Sumitomo, UniEnergy Technologies, Primus Power, Solibra, GEC, etc Hokkaido, Japan (2013 pilot) Sumitomo, 40 MW, 60 MWh
The incumbency: ZincBromine Flow Batteries Pros: Many years of development Very cheap active materials High voltage (~1.8V, good energy density) www.echemion.com Cons: Bromine highly corrosive reduced lifetime, expensive BOP complicate regulations, customer perception Zinc plating at negative electrode only partial decoupling of power and energy capacity danger of membrane pinching by dendrites Companies active: Gelion, Redflow,
Levelized Cost of Storage: flow batteries vs. Lithium Application Power (MW) Duration (h) LCOS Vanadium FB ($/kwh) LCOS ZincBr FB ($/kwh) LCOS Lithium ($/kwh) Peaker Replacement 100 4 0.210.41 0.290.32 0.280.35 Distribution 10 6 0.180.34 n/a 0.270.34 Microgrid 1 4 0.270.41 n/a 0.360.39 Source: Lazard, 2017 At 2017 costs, flow batteries exhibit similar LCOS values relative to lithium ion batteries for long discharge applications
Project decrease of CAPEX cost: flow batteries vs. Lithium Source: Lazard, 2017 In light of decreasing costs of Lithium batteries, flow battery research should focus on using significantly cheaper materials
Cost breakdown Vanadium Flow Batteries Source: Fraunhofer Institute, 2016 Materials dominate cost, especially vanadium ore/processing and stack components (membrane, electrode, etc)
Novel developments: focus on cheaper materials Ligand A A. AspuruGuzik, M. Aziz, Nature, 505, p195, 2014 e Metal Ion Ligand B Sun Catalytix Lockheed Martin Coordination complexes as active material Status: prototype (250 kw / 1 MWh) realized 2017 Harvard University and others Allorganic redox active materials Status: significant academic research
Novel developments: focus on cheaper materials J. Power Sources, 310, 111, 2016 Source: Fumatech Aalto University Finland Allcopper redox chemistry Status: Albufera Energy involved in commercialization Future research project: INEEL and Fumatech Electrodialysis using abundant salts Status: innovation on membranes needed
Guiding Questions (1) What are the main technological challenges of redox batteries? Focus on cheaper materials, for electrolytes and stacks Durability often yet unproven (membranes, electrolytes) Of the different redox batteries, which are the most suitable to be used as an interconnected energy storage system to the network? Lowest cost technology will dominate. Safety also important, but is related to cost What basic research topics are necessary and relevant to make redox batteries more competitive? Cheaper materials: lowcost effective electrolytes (aqueous!), membranes, stack components, etc What is the environmental impact of this technology? Material abundancy not expected to be a problem (compared to Co, Li) Corrosive substances may pose a SHE risk Footprint of flow battery systems will be large Possibility of H 2 released in atmosphere due to parasitic reactions
Guiding Questions (2) What challenges exist in the integration, monitoring and maintenance of these batteries? End customers may be riskaverse: a flow battery may be more complex to operate than a large Liion system Controls systems need to be developed specifically for flow battery operation MTBF (Mean Time Between Failure) values for some flow battery components doe not exist. Development of reliability engineering Cost and application models need to be more refined Human resources need to be developed for FB operation and maintenance What implementations should a country like Mexico do to be competitive in the manufacture of this battery technology and which one (s) are the most attractive redox battery technology (s)? Develop its own flow battery research programs Engage with international flow battery companies to explore the possibility of manufacturing in Mexico
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Flow batteries based on Electrodialysis Animal plant cells: high concentration K ions inside cell, high concentration of Na ions outside cell E K = RT zf ln([k ] out [K ] in ) Typical cell: 5mM K outside cell and 140mM K inside cell: E K = 85mV Proposal: dissociate water into H and OH ions using bipolar membranes E H = RT zf ln([h ] acid [H ] base ) For 1M acid and 1M base production, E H = 830mV Bipolar membrane H H H C A OH OH OH