Advances in wind power have made well-sited turbines a very cost-effective method of generating power—when they're working. The variability of wind in even the best of sites, however, can cause wind farms to go from nothing to producing a power output that exceeds demand. This variability has made figuring out how to smooth out the energy produced with wind a major topic of research.

At the annual meeting of the American Association for the Advancement of science, a panel on energy storage included a talk by Igor Shvets, a researcher at Trinity College in Dublin. Shvets is involved in the planning for an audacious scheme called Spirit of Ireland that would turn large areas of the west coast of that country into a renewable energy powerhouse. If the plan is rolled out to its full extent, Ireland could even end up sending its electricity under the Irish Sea to the UK.

Western Ireland lies on the Atlantic, and receives a steady supply of wind. According to Shvets, that wind has, over time, stripped off the best soil from many of the rugged areas of coast. As a result, it's not very productive agriculturally, and is sparsely inhabited. All of that makes it a perfect site for on-shore wind, which is substantially cheaper to build and maintain than the offshore turbines that Europe's high population density often requires.

None of that, of course, helps with wind's intermittent nature. But the low population and poor soil should enable Spirit of Ireland to implement a form of energy storage via a technique called pumped hydro.

Pumped hydro is mature technology that's in use in both the US and Europe. All it requires are two reservoirs at different altitudes. When energy supplies are high, water is pumped into the upper reservoir. When electricity is needed, the water is allowed to drop back into the lower one, generating hydropower in the process. It's somewhat limited, however, by the need to have two appropriately sized reservoirs and a steady supply of water. As a result, the largest facility in Europe holds only nine Gigawatt-hours (Gwhr) of power.

Spirit of Ireland has identified 60 potential sites for the upper reservoirs, and most of them can hold about 100Gwhr, many quite a bit more. The lower reservoir? That would be the ocean, which obviates any issues with a steady supply of water. In the four regions that Spirit of Ireland is studying, the steady winds that have eliminated the best soil have left behind a largely impermeable layer of rock that should prevent the salt water from seeping away from the reservoirs in significant volume.

In most cases, the valleys the project has identified are within a few kilometers of the ocean, but several hundred meters higher. In several locations, a single spur of land has enough large valleys to support several reservoirs. The plan is to build earthen reservoirs that fit into the landscape, and to bury the pipes that lead from the reservoir to the ocean, along with the entire pumping/generator station. It will also use relatively low power lines that can be supported with wooden poles, which will also minimize the change in the landscape.

The general plan is that wind power won't be placed directly on the grid. Instead, it will be aggregated and fed into these reservoirs, which will convert it into a consistent, baseline power source. The reservoirs will also hold enough of a buffer that, in all but fairly unusual events, power won't be disrupted—Shvets suggested that problems would probably arise about once every five years, based on historic wind patterns.

If the project can scale up fast enough, Shvets thinks that electricity can become an export product for Ireland. The UK, he pointed out, has a lot of coal and nuclear plants coming to the end of their life expectancies, and will have to replace them while facing a European mandate to increase the use of renewable power. This may raise the price of electricity there, and make running some DC power lines under the Irish Sea a viable option.

Will all of this work? Everything about it is pretty mature technology, so there's technically no reason why it shouldn't. The thing that strikes me as as the biggest concern is the one thing we don't have any experience with: the large scale storage of salt water in elevated reservoirs. There would seem to be a significant chance that it will seep into the local environment, with results that are difficult to predict.

Even with that caution, it's a very intriguing plan. The world will eventually have to learn to power itself in a sustainable manner, and storage will almost certainly need to play a role in whatever comes next. This is the first idea I've seen that efficiently scales energy storage to the sorts of levels that are likely to be needed.