Solar, wind, and other intermittent renewable energy sources have a major barrier to widespread adoption: the electric grid has no storage. The grid is essentially an enormous production center with no warehouse. Until that problem is solved, these clean technologies can never fully replace coal, nukes, and other on-demand sources.

Fortunately some innovative solutions are starting to gain traction, including this mechanical energy storage system from Massachusetts-based Beacon Power. The company’s first 20-megawatt plant went online at the beginning of this year with 8 megawatts of storage capacity in Stephentown, NY, with full capacity to come soon.

This initial application is frequency regulation on the grid, smoothing out spikes and dips in power demand and output, a function normally performed by conventional power plants. But backup up renewable sources like solar panels (say, when a cloud momentarily passes in front of the sun) is an obvious next step.

The company’s modular system, based on flywheels, seems scalable to just about any size, from a single-flywheel system providing storage and backup for a solar installation, to groups of flywheels connected in clusters—which can in turn be interconnected on the grid, as in the Stephentown plant. I’d like to see a residential version of one of these providing uninterruptible power for home solar and wind installations. Grid? We don need no steenking grid!

Click the video above for a demo of how it works.