Qnetic begins low-speed tests of Pulsar flywheel prototype

Inside a steel cylinder, a carbon fiber rotor spins in a vacuum at speeds above 11,000 rpm, held off its central shaft by magnetic bearings so that almost nothing rubs. That is the heart of Pulsar, a flywheel storage prototype that Sacramento-based Qnetic has begun testing at its technology center in Shanghai. The unit is still in low-speed testing. It has not yet been installed on a grid.

The principle is old, the materials are new. Surplus electricity pushes the rotor to high speed, and the energy is stored as motion. When power is needed, a generator turns that motion back into electricity and the rotor slows. The heavier and faster the rotor, the more energy it holds, which is why the strength of the carbon fiber matters so much to the company. Flywheels have mostly been used for short bursts, lasting minutes or even seconds, such as backup power for telecom sites and data centers. Qnetic wants to push them into long-duration storage on the grid.

The case against lithium-ion batteries is the one Pratt keeps returning to. Batteries are typically cycled once a day, and they weaken with every cycle. Five years ago, when Qnetic was formulating its concept, large containerized battery systems were just becoming mainstream, and Pratt says batteries were then "too expensive" with degradation as the main problem. He argues that many billions have since gone into battery chemistry without solving cycle life and calendar life. Qnetic's bet is that a flywheel can cycle repeatedly without losing capacity.

The evidence so far is early. Qnetic reported in September that Pulsar completed its first 100 continuous charge-discharge cycles with zero faults or capacity degradation, a first test rather than a lifetime record. Separately, the motor produced 130 kW at 97.3% efficiency. The company has set up a factory and headquarters in Sacramento for low-volume production, and the Sacramento Municipal Utility District (SMUD) is to test Pulsar in a pilot under an initiative run by the Electric Power Research Institute, with a start targeted for the first half of 2027.

For a utility, the promise is a unit that can be cycled every day for years without the wear that batteries show. The planned design would reach 500 kWh, which is four hours of storage at a nominal 125 kW. But that growth depends on a stronger rotor that is still being developed, and Pratt acknowledges that the company is breaking new ground with composite rotors and that capacity and economies of scale remain hurdles. Competitor Amber Kinetics is also developing a version of its 32 kW units for above-ground deployment in steel shipping containers. Whether Pulsar reaches the grid will be decided by the 2027 pilot, not by the lab.