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Storing energy with flying metal objects

Pentadyne twirls weights in the air, and it makes electricity.

You can store energy in chemical batteries. Pentadyne Power stores it in moving objects.

The Chatsworth, Calif.-based company has created and sells uninterruptable power supply (UPS) for data centers and large power consumers that stores energy kinetically. A 25-pound mass spins in a vacuum chamber at a high speed. When a utility needs a jolt of electricity, kinetic power is converted to electrical power. When it's not needed, the mass just spins to conserve its energy.

The company uses a relatively small mass to avoid potential mishaps (imagine what would happen if a large mass came unstuck from its moorings) and efficiency gains can be made through speeding up rotation.

"Kinetic energy equals mass times velocity squared. So doubling mass doubles energy storage, but doubling the rotational speed increases energy storage exponentially," the company's Web site reads.

The mass also levitates on a magnetic field like high-speed trains. This reduces mechanical failure as well as friction. The system has advantages over batteries because, among other reasons, maintenance is lower and the performance does not degrade over time, according to Pentadyne.

Utilities and data centers buy UPSes to keep their own power output level and prevent surges.

The power coming from the company's VSS+dc power supplies does decline from when it first provides energy to when energy is no longer required. That is, it puts out more energy in the first five minutes it is engaged than twenty minutes later. (Batteries do the same thing but generally have longer staying power.) To increase power, utilities can add more power supplies.

Energy storage devices, along with clean coal, are part of a market that is attracting investors but also eluding any easy answers. Conventional batteries improve with performance over time, but not at a regular rapid pace like semiconductors. Utilities are also clamoring for UPS devices because renewable energy sources like solar power fields and wind farms don't produce power at level, regular rates. Thus, everyone is looking for new ways to solve this problem.

Another notable company in the field of UPSes is Deeya Energy, which has a device called a flow battery. In flow battery, new electrolyte flows through the battery and the old stuff moves out, thereby eliminating the charge cycle.

Ben Rosen (who funded Compaq way back when) and Rustic Canyon Partners are investors in Pentadyne.