Rocks, Rails and a Big Hill Are All You Need to Store Renewables

©. ARES train full of rocks

We love renewable energy, but it can be hard to store. That's why people are building better batteries, flywheels, big balloons in lakes and other expensive new technologies.

And then there is Ares, an idea with real potential. It's basically a couple of shipping containers full of rocks. When your renewable sources like wind and solar are all pumping out more power than you can use, you use the excess to push the train full of rocks up a hill. When you need the power, you let the train roll down the hill, and the electric motors turn into generators. That's it. Rocks.

Ares demo unit

© ARESAarian Marshall in Wired reports that an installation of ARES' technology is going to be coming down the tracks soon.

In April, the Bureau of Land Management approved an ARES—that’s Advanced Rail Energy Storage—project, conceived by a Santa Barbara-based energy startup called, well, ARES. By 2019, ARES operations head Francesca Cava says, the facility will occupy 106 acres in the excellently-named town of Pahrump, Nevada....The Nevada project has a power capacity of 50 megawatts and can produce 12.5 megawatt-hours of energy. That’s relatively large, especially compared to a lot of battery storage projects.

This is such a wonderfully low-tech idea that I thought I would see if my favorite low-tech website, the excellently-named Low Tech Magazine had heard of it. And of course they had, and they wrote about it back in 2013.

ARES is a great low-tech project that deserves praise for its sustainable thinking. One problem might be that climbing slopes is not what trains are good at, while it is the vertical distance travelled that matters. The consequence is that the method requires a lot of space. A 50 MW rail energy storage system needs an eight kilometre track on an eight percent grade with 32 vehicles, each weighing 300 tonnes.

ARES-Technology from Advanced-RES on Vimeo.

Over on VOX, David Roberts explains in greater detail how it can be used not only as storage, but to smooth out power fluctuations in the grid.

ARES systems do not respond quite as fast as batteries (five to 10 seconds, as opposed to effectively instant), but the company claims its capital costs are far lower. Also, rail cars and concrete slabs, unlike batteries, do not degrade over time.

It is such a wonderful, simple idea, dumb as pushing a rock up a hill. We need more thinking like this.