Flow Batteries for grid-scale energy storageJoep Pijpers

1

Why Flow Batteries?

Pumped Hydro

Below Ground CAESFlow Batteries

NaS, NaNiCl Sealed BatteryOther Sealed Batteries

(Li-ion, Pb-acid)

Flywheels

1 kW 10 kW 1 MW100 kW 10 MW 100 MW 1 GW

System Power

Dis

char

ge T

ime

Seco

nd

sM

inu

tes

Ho

urs

Power QualityUpgrade deferral

Renewables Integration

Bulk PowerManagement

Flow batteries can provide high power output and long discharge times at low-cost, anywhere

Schematics of a Flow Battery System

Balance of Plant (BOP):

• Pumps, tanks, piping

• Control and power conversion hardware

Active Materials:

• Redox-active compounds (Posolyte, Negolyte)

Cell Stack:

• Membranes

• Electrodes

• Bipolar plates

Cell Stack Posolyte TankNegolyte Tank

Power Conversion

• 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

1. Low cost (in terms of Levelized Cost of Storage)

2. Safe

3. Environmentally benign

4. Low foot print

𝐿𝐶𝑂𝑆 =(σ𝐶𝐴𝑃𝐸𝑋𝑡 + σ𝑂&𝑀𝑡 + σ𝐶ℎ𝑎𝑟𝑔𝑖𝑛𝑔𝑡)

σ𝑘𝑊ℎ´𝑠𝑡

Requirements for a successful flow battery technology

The incumbency: all-Vanadium Flow Batteries

Pros:

• Well-established technology

• Good durability

• Decent energy density

Cons:

• Corrosive electrolytes

• Cross-over across membranes must be managed

• Vanadium is expensive

Companies: Vionx, Sumitomo, UniEnergyTechnologies, Primus Power, Solibra, GEC, etc

Source: www.echemion.com

Hokkaido, Japan (2013 pilot)

Sumitomo, 40 MW, 60 MWh

The incumbency: Zinc-Bromine Flow Batteries

Pros:

• Many years of development

• Very cheap active materials

• High voltage (~1.8V, good energy density)

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,

www.echemion.com

Levelized Cost of Storage: flow batteries vs. Lithium

Source: Lazard, 2017

Application Power (MW)

Duration (h)

LCOS Vanadium FB

($/kWh)

LCOS Zinc-Br FB

($/kWh)

LCOS Lithium($/kWh)

Peaker Replacement 100 4 0.21-0.41 0.29-0.32 0.28-0.35

Distribution 10 6 0.18-0.34 n/a 0.27-0.34

Microgrid 1 4 0.27-0.41 n/a 0.36-0.39

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

In light of decreasing costs of Lithium batteries, flow battery research should focus on using significantly cheaper materials

Source: Lazard, 2017

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

Sun Catalytix – Lockheed Martin

Coordination complexes as active material

Status: prototype (250 kW / 1 MWh) realized 2017

Ligand A

Metal Ion

e–

Ligand B

Harvard University and others

All-organic redox active materials

Status: significant academic research

A. Aspuru-Guzik, M. Aziz, Nature, 505, p195, 2014

Novel developments: focus on cheaper materials

Aalto University Finland

All-copper redox chemistry

Status: Albufera Energy involved in commercialization

Future research project: INEEL and Fumatech

Electrodialysis using abundant salts

Status: innovation on membranes needed

J. Power Sources, 310, 1-11, 2016

Source: Fumatech

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: low-cost 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 H2 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 risk-averse: a flow battery may be more complex to

operate than a large Li-ion 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

Thank You!

15

Flow batteries based on ‘Electrodialysis’

Animal plant cells: high concentration K+ ions inside cell, high concentration of Na+ ions outside cell

𝐸𝐾+ =𝑅𝑇

𝑧𝐹ln(

[𝐾+]𝑜𝑢𝑡

[𝐾+]𝑖𝑛

)

Typical cell: 5mM K+ outside cell and 140mM K+

inside cell: EK = -85mV

Bipolar membrane

H+

H+

H+

OH-

OH-

OH-

Proposal: dissociate water into H+ and OH- ions using bipolar membranes

𝐸𝐻+ =𝑅𝑇

𝑧𝐹ln(

[𝐻+]𝑎𝑐𝑖𝑑

[𝐻+]𝑏𝑎𝑠𝑒

)

For 1M acid and 1M base production, EH+ = 830mV

C---------

A+ + + + + + + + +