Storage critical to future grid

Around the world, development of renewables has been speeding up, even if — in most regions — wind and solar energy continue to meet just a small proportion of energy needs. Still, every megawatt of capacity added somewhere is a good thing, another dent in our massive daily fossil-fuel budget, right?

Yes and no. While the efficiency of wind turbines and solar photovoltaics have improved, there’s one thing engineers in the renewables industry can’t do: make the wind blow and the sun shine whenever power is needed.

For now, that means relying on coal- or gas-fired power, or nuclear power, to fill in the gaps. Faced with the challenge of reducing carbon emissions, though, we’ll eventually need other alternatives for backup power.

The ideal solution would be to find viable, affordable ways to store surplus energy from clean sources for later demand. The good news is, there are a variety of promising technologies available to us. The question is whether they’ll be able to adequately ramp up in time to assure future energy security.

In New York, Beacon Power has been building a flywheel-based energy storage plant that could provide up to 20 megawatts of stored energy capacity to balance the state’s energy frequency regulation needs. Originally set to begin operations in late 2010, however, the plant has yet to be completed, although the main holdup as of December was with the adjacent electrical substation being constructed by the local utility company.

Once finished, the Beacon plant in Stephentown would be the world’s first grid-connected flywheel energy storage plant. We’ll need a whole lot more to stabilize energy supplies globally.

Of course, there’s the DESERTEC project, a hugely ambitious program to build concentrating solar power (CSP) plants across North Africa that would be connected via new transmission lines to the electricity grids in Africa, the Middle East and Europe. As the project’s backers point out, all the world’s deserts collect enough solar energy in six hours to more than meet our annual energy needs. And CSP has the added dual benefits of being able to provide energy for desalination, and to store surplus energy in heat storage tanks that could be used to drive steam power at night.

DESERTEC could, in theory, provide a better form of clean energy storage than electric cars, another proposed solution for providing energy when renewables aren’t producing. While electric car batteries could prove a valuable way to store energy on a distributed basis, they are overall “primarily additional electricity consumers” rather than electricity producers, the DESERTEC website points out. The goal, for now, however, is for DESERTEC to meet 15 per cent of Europe’s energy needs by 2050. That leaves 85 per cent to be met by other means.

Supergrids that could link  wind and solar to pumped hydro storage are another potential way to smooth the ups and downs of intermittent renewables. But, as with the DESERTEC project, numerous policy and cost considerations need to be resolved before the first new transmission lines can start being installed.

On the other hand, reversible heat engine/heat pumps such as those developed by the UK’s Isentropic could help speed up energy storage development more quickly. Capable of operating at a smaller scale than pumped hydro, these types of pumps could be rolled out more quickly and easily, and could prove a vital element in a future of microgrids and microstorage. So too could zinc-bromide batteries like ZBB Energy’s. (In fact, the company has already signed contracts with a solar energy firm and a petrochemical producer in China.)

In short, the faster we start implementing energy storage technologies — both small- and large-scale — the more reliable our fast-growing renewable energy sources will be.