StorEn Technologies

A vanadium flow battery is a type of rechargeable battery in which the energy is stored chemically in a liquid electrolyte contained in two tanks, unlike conventional batteries that store their reactive materials within their cells.

Each tank contains a different electrolyte formulation: one for the positive reaction, the second one for the negative one. The liquid electrolytes are pumped through the cells, generally grouped together in a block known as stack or cell stack. The two flows of electrolyte never mix as they are separated in the cells by an extremely thin membrane that only allows selected ions to flow through. The cells also contain an array of very stable porous carbon electrodes, where critical reactions take place.

In each side of the stack, the cells are connected electrically in series by bipolar plates, i.e. conducting plates that have positive electrolyte on one side and negative on the other. Therefore, the stack voltage (V) is the sum of the voltage of the individual cells. E.g. a 10-cell stack has ten times the voltage of a single cell.

The stack power (in kW) is also the sum of each cell power. The power of each cell is governed by the battery chemistry, temperature and cell dimensions, among others.

However, the energy (in kWh) of the battery is dictated by the amount of electrolyte in the tanks. Higher volumes of electrolyte will store more energy, and provide the same power for longer, thus increasing the power ratio of the battery.

Therefore, flow batteries are unique in being able to independently scale the power and the energy or duration and to meet the demands of any given application. Longer durations will grant reduced cost/kWh.

Vanadium flow batteries have demonstrated key fundamentals that are intrinsic to the technology such as:

• Over 20,000 cycles (3X longer than lithium) or 20+ years of operation.

• Scalable by just increasing the quantity of electrolyte stored in the tanks.

• No ghost-effect due to recharging when not fully discharged.

• Absence of self-discharge even if left unused for long periods of time (as opposed to lithium batteries).

• No damage if left completely discharged for long periods of time.

• Exceptional sturdiness if overcharged up to a 400% and can easily resist to charge and discharge tensions up to twice the nominal one.

• The electrolyte does not need replacement because it does not contaminate over time. When the battery needs replacement, the old electrolyte can be used in the new battery or its vanadium content extracted for alternative use.

• The large availability of vanadium, with 82% coming from the reprocessing of industrial waste such as oil refining and steel foundries, hence from “circular” economy. The vanadium coming from mining or primary production accounts for approximately 18% of the supply.

StorEn R&D activities focused on improving the electrochemical performance of the modules. As a result, four PCT patents were filed at WIPO, and then extended internationally covering all major countries in the world.

Our R&D delivers:

• Improved electrical performance and power density of the stack due to the use a novel design and innovative materials in the stack. This will grant a considerable reduction in the size and cost of the power side of the batteries.

• Improved module design to reduce internal components. This will grant a reduction in manufacturing costs and enhanced duration and reliability.

• Innovative systems to control leaks to extend maintenance intervals and reduce maintenance costs.

• Innovative formulation of the electrolyte to increase the modules’ energy density. This will reduce the size, weight and cost of the batteries.

After successfully deploy batteries in Australia and Canada, StorEn is now moving into volume manufacturing.