Those Intermittent Renewables - Part 2

To store power for the grid, we'll need some bigger batteries.
Credit: Heather Kennedy

"We believe energy storage is the next big thing," says Craig Horne, CEO of EnerVault, a Sunnyvale startup. His company is developing a battery that could help solve a renewable energy problem (check out our previous post): how to keep electricity flowing when we need it, even as more of it comes from sources we can't control. Horne was a panelist at a UC Berkeley-Stanford sponsored CleanTech Conference about energy storage held last week at Berkeley's Lawrence Hall of Science.

Proponents of energy storage think it has a key role to play in the future energy grid. A network of storage systems could act as a kind of shock-absorber, balancing the spikes and troughs of production that can come from solar and wind power. For example, if we had a way to store the power generated by wind turbines during a storm, we could release it later when demand gets high, making the power supply more constant.

We all use batteries daily – in cell phones or electronics – so it’s clear we already have the technology to store electricity and use it later. Unfortunately, that technology doesn't scale up very easily; batteries that can store enough energy to help smooth the grid are expensive, though company's like Horne's are hoping to change that. (For more on the challenges facing battery technology in particular, check out the QUEST TV story, Waiting for the Electric Car).

Batteries are just one strategy on the table, however; there are lots of ideas for how to store power at a large scale. One that's already in use in California is pumped-hydroelectric storage, which uses excess power to pump water from a low reservoir to a higher one. To get the energy back, you let the water flow the other direction, turning turbines to generate electricity as it drops in elevation. Compressed air energy storage (CAES), features a similarly clever use of the laws of physics, using excess power to compress air, which then releases energy as it expands later.

Another scheme includes using the sun – but in this case, it’s used to heat molten salt, which retains heat for a long time and can generate power even after the sun stops shining. Even electric cars could become a storage device if they become widespread, using their relatively small, distributed batteries to help feed power back to the grid at peak times.

So why aren't these technologies already being used all over the place?

"There are three obstacles to storage: Cost, cost, and cost," jokes Haresh Kamath, a Senior Project Manager at the Electric Power Research Institute, and also a panelist at the conference. Energy storage on the scale we'd need with the technology we have today is prohibitively expensive.

That may start to change, however. The stimulus package includes about $600 million for energy storage demonstrations, a 30% investment tax credit that applies to energy storage projects, and $2 billion for battery development and manufacturing. Venture capital firms are looking to invest. And there's a bill currently before the California legislature that encourages utilities to invest in and build storage.

Those injections of money and attention may be enough to get more energy storage projects off the ground – or at least get people thinking about them. Hopefully the conversations will keep going, and going, and going...

For more on the conference and specific storage technologies, check out this FAQ over at Earth2Tech.

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