Comment: How flywheel technology can bring public charging up to speed

With the International Energy Agency reporting the current rate of growth in the electric vehicle market could cut oil consumption by 6 million barrels a day by 2030, it is self-evident that EVs are a key enabler to achieving net zero emissions by 2050. But for them to make their contribution requires considerable growth in public charging infrastructure.

While home charging is common, many consumers are reluctant to switch to EVs without a public charging infrastructure to rival the current filling station network, with 42 per cent citing this concern in a McKinsey study. The study also found charging speed to be the top priority for potential EV owners. However, ultra-fast charging often exceeds grid capacity, especially in remote highway locations between large towns and cities – the very places that people want to be sure they can charge on long journeys. Upgrading the grid is ideal but costly and time-consuming, posing challenges for charging network operators and hindering investment.

At Zooz Power, we’ve spent over five years developing, refining, and perfecting a cost-effective, readily deployable, modular solution of power boosting existing public chargers, now installed at several locations worldwide. Called ZOOZTER-100, it supports sites with two to eight ultra-fast DC chargers and features what we believe is the best technology for rapid charging and discharging cycles.

Our system rapidly supplies high-power surges to meet the intense, short-duration energy demands typical of ultra-fast electric vehicle (EV) charging stations. ZOOZTER-100 actively enhances the power infrastructure by delivering stored energy at high rates for immediate consumption. It charges itself using grid power and then "flashes" this stored energy to the EV charging station when a vehicle is plugged in, significantly reducing charging times. The charging accelerator system contains eight flywheels, each capable of providing 12.5 kW for 15 minutes, totalling 100 kW for 15 minutes.

The flywheel is a kinetic energy storage device where energy is stored in the rotation of a dreidel-shaped rotor. Made of high-strength, fatigue-resistant steel, the rotor is not a solid piece but a lamination of steel plates. This structure allows strict control of the quality of the plates before assembly, and prevents crack formation between the different plates, ensuring maximum safety.

During charging, the steel flywheel - running at 17,000 rpm inside a sealed vacuum chamber using magnetic bearings to minimise windage and friction losses - drives a generator to temporarily supplement grid power. This enables rapid DC fast charging rates that exceed the grid's capacity alone. When not charging, the flywheels are engineered to stay at maximum speed for efficiency. The built-in power management system optimizes power and capacity to minimise energy losses while ensuring high availability for EV charging. In standby mode, the flywheels use minimal electricity to maintain high speed.

Flywheels are a time-proven technology, and the refinements we’ve engineered in-house make them an ideal solution for this application. While batteries, including those built using second-life lithium-ion cells, can perform a similar function, our flywheels offer several distinct advantages. Durability is critical because EV chargers have a high utilisation rate, and batteries can only deliver a limited number of charge/discharge cycles before needing replacement, whereas our flywheels are designed for 200,000 cycles over 15 years.

Moreover, because our flywheel technology is engineered to deliver the rapid bursts of high-power needed to support ultra-fast charging, it is capable of C-rates up to eight times greater than batteries can deliver. It is this capability that is most suited to the duty cycles of public chargers, where power demand from EVs has many short duration spikes. And we can deliver this without having to worry about dendrite formation within battery cells or reaching the limits of thermal management which create flammability risks in battery technology. Additionally, end-of-life considerations are important, as batteries are challenging to recycle and leave some materials as waste, whereas our flywheels are made from recyclable steel and do not rely on critical and costly minerals such as nickel, cobalt, and lithium.

It is certain that the grid upgrades fundamental to making public charging networks around the world as fast, convenient, and widespread as consumers want will come, and that’s something we all want to see. But it will take a long time, and that’s why right now, today, we are supporting the improvement and expansion of charging infrastructure with cost-effective, robust, and sustainable technology for sites where grid power alone is not yet enough.

Ilan Ben-David is co-founder & Chief Technical Officer at Zooz Power