Water battery: Riverbank Power brings new twist to pumped storage

I have a feature in today’s Toronto Star about a local company called Riverbank Power, founded by a former wind developer who’s determined to open up opportunities for large-scale energy storage across North America. Riverbank does pumped hydro storage, but not like conventional projects that require the right geography and topology (i.e. a large natural reservoir hundreds of metres over lake level).

Riverbank depends more on geology. It looks for brownfield sites that are located next to a large body of water and transmission lines (with adequate capacity). It then digs a few deep holes to figure out the rock conditions. If the rock is hard and if the site meets all other conditions, it will excavate massive caverns 600 metres below the surface that can safely contain 3.8 billion litres of water.

Sounds crazy ambitious, eh? It is, but it’s also something that’s done all the time by the mining industry. The technology is there and the excavation techniques are well proven. After digging such caverns, Riverbank would install four 250-megawatt hydro turbines next to them, then dig four connecting shafts up the surface that open up into a lake or large river.

The idea is to let the water drain down into the caverns to generate power during times of peak electricity demand. The design would allow 1,000 MW of generation over six hours. The water, temporarily stored in the caverns, would then be pumped back up to the surface during off-peak demand when electricity is cheap or when wind-energy is ample but not needed. John Douglas, founder and CEO of Riverbank, has crunched the numbers and figures such a facility could be built within five years and, as a peaker facility, would be competitive with natural gas-fired generation. He sees it as a way of unlocking the value of renewables without having to use natural gas plants as shadow generation.

Why is this better than conventional pumped storage? For one, there aren’t many locations around North America that are ideal for pumped storage that haven’t already been built. Those that are available are too remote and would involve the flooding of huge swaths of land, something that’s heavily frowned upon — moreso these days. The remote ones also require transmission, which adds huge cost to the projects (and complexity — i.e. nimbyism) and often makes the power they generate uneconomical. Riverbank, however, can choose to build close to heavily populated areas where the power is needed, close to transmission, close to water, and in willing communities, as long as the rock conditions are right. The actual site is also underground, with the exception of a big-box building that functions as a substation.

Riverbank has signed agreements to build in Maine (on the site of a decommissioned nuclear plant, the Maine Yankee) and New Jersey. It has shortlisted 15 ideal sites and plans to build on five of them, including one in Ontario that hasn’t been announced, by 2014. Former Ontario premier David Peterson is Riverbank’s chairman, and it’s biggest financial backer is New York-based investment giant BlackRock Inc.

It will be interesting to see the kind of traction this company gets over the next few years, particularly under a pro-renewables Obama administration.

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