ict_redox-flow-battery.pdf

8/10/2019 ICT_Redox-Flow-Battery.pdf

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F R A U N H O F E R - I N S T I T U T F R C H E M I S C H E T E C H N O L O G I E I C T

REDOX FLOW BATTERY


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Scalable energy storage

In the future, scalable electricity storage devices with an out-

put range of 100 kW to 5 MW will be increasingly necessary,

forming decentralised, network-integrated storage systems

that make better use of the network capacities and avoid

bottlenecks. Within the desired output range, vanadium redox

ow batteries have a high development potential with regard

to the target costs and scalable set-up.

Technology

Vanadium redox ow batteries are based on the principle

of chemical energy storage, in the form of dissolved redox

couples in external tanks. Electricity is generated in a separate

power module. During discharge the electrodes are continually

supplied with the dissolved substances from the holding

tanks, and once these are converted the resulting products are

returned to the same holding tanks. As the storage capacity

depends chiey on the quantity of electrolyte solution, and the

efciency is over 75 %, this type of storage has potential forlarge scale application. Vanadium redox ow batteries have a

similar energy density to lead batteries, however their service

life is almost ten times longer.

Current research topics

At the Fraunhofer ICT a prototype of a vanadium redox ow

battery has been developed, with which various developments

in the elds of electrode materials, membranes and electro-

lytes can be exibly tested. Different redox ow batteries and

their materials can be compared in a test design, and the

advantages and disadvantages of the different systems can

be determined.

System and unit set-up

The developed concept targets the practical integration

of a vanadium redox ow battery in the existing electricity

network, as a storage device for uctuating energies from

wind or photovoltaic plants.

A storage device with a power of 2 MW consists, for example,

of eight blocks, each containing seven stacks. Each stack is

made up of 100 individual cells and has an electrical power of

35 kW at a current density of 80 mA/cm

2

. The active electrodesurface in this example is 3600 cm2per cell. A 2M vanadium

solution in 3M sulphuric acid is used as an electrolyte.

EFFICIENT USE OF RENEWABLE

ENERGIES

The amounts of energy generated in wind and solar energy plants often fa l l short of requirements . The

storage of e lectr ica l energy, part icular ly for large appl icat ions, has therefore become one of the greatest

chal lenges faced by the energy technology sector. Due to increas ing appl icat ion of f luctuat ing renewable

energy sources i t has become a key technology. To compensate for the increas ingly temporary imbalances

between generat ion and demand, innovat ive solut ions are required in network construct ion and in the

power output and balancing energy reserves . A better adjustment of the capacity of the reserves to meet

the changing demands can be achieved when decentral ised storage devices are appl ied, which are

scalable in terms of power output and the amount of energy s tored.

R E D O X F L O W B A T T E R Y


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It is possible to switch between energy storage and energy

supply by changing the direction of electricity. In practice this

task is carried out by power electronics, which allow access

times in the region of s to ms.

The unit has a modular construction, and through control

valves and several pumps it can consistently achieve a

technically and economically viable operating range. A further

advantage of the modular construction is, for example, the

possibility to separate individual stacks for maintenance.

The missing output is compensated during this time by the

remaining stacks. The overall efciency remains at over 70 %.

Progress achieved beyond conventional technology

Work is focused on the optimisation of the energy and power

density, to reduce the costs and complexity and create a

market-ready energy storage device.

Modular construction of a newly developed long-term

storage device

Power and amount of energy are independently scalable

Optimal operation through anticipatory regulation and load

management

Efcient and cost-optimised energy conversion

Uninterruptible electricity supply with low self-discharge

Our offer

We support users, developers, manufacturers or component

suppliers for redox ow batteries with the design and speci-

cation of their energy supply.

In particular we offer:

Material synthesis, treatment and characterisation

Development, production and testing of electrolytes

Production and characterisation of electrolyte additives

Design and construction of prototypes

Beside comprehensive electrochemical laboratory facilities

we offer you broad electrochemical know-how.

Schematic representation of the processes in a

redox ow system.


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Fraunhofer-Institut fr

Chemische Technologie ICT

Joseph-von-Fraunhofer-Strae 7

76327 Pnztal (Berghausen), Germany

Director

Prof. Dr.-Ing. Peter Elsner

Phone +49 7 21 46 40-0

Contact

Applied Electrochemistry

Dr. Jens Tbke

Phone +49 7 21 46 40-343

Fax +49 7 21 46 40-318

[email protected]

www.ict.fraunhofer.de

R E D O X F L O W B A T T E R Y

ict_redox-flow-battery.pdf

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