Could air solve our energy storage challenge?

An energy future that’s both secure and low-carbon means more than just lots of solar panels and wind turbines: it will take lots of energy storage as well. Without a reliable, affordable and wide-scale means of storing energy, the intermittent power from sun, wind and tidal sources just won’t be able to support the infrastructure we have today.

Batteries are the obvious first choice, but the current technology isn’t sufficient yet. As Donald Sadoway, a leading researcher in energy storage and a professor at the Massachusetts Institute of Technology, told Time magazine, “We need radical breakthroughs, so we need radical experiments.” The right breakthroughs, he said, would “send chills down the spine of the carbon world.”

Bloom Energy made a big splash in 2010 with the release of its advanced fuel cell, the Bloom Energy Server. Since then, the company has begun offering fuel-cell storage as a service as well as a product, but it remains to be seen whether the so-called Bloom Box will be the game-changer the company claims it to be.

So if batteries and fuel cells aren’t yet “ready for prime time” at a grid scale, which other energy storage technologies show promise? It could be compressed air energy storage (CAES) and, in particular, a type of CAES under development by a New Hampshire-based firm called SustainX.

SustainX’s technology has earned enough interest from both the National Science Foundation and the US Department of Energy to garner $5.4 million in funding. And, just this week, the company secured another $14.4 million from GE Energy Financial Services and other investors. It’s also won the support of the global generation and distribution firm AES, which is working with SustainX to help it develop a full-scale demonstration plant that could store enough energy to power up to 1,000 homes.

While CAES has been used for more than 100 years to drive telegraph dispatches or power clocks, its limitations have kept its from being applied at a wider, more useful scale. One of the problems has long been heat: when air is compressed to store energy, it heats up, and dissipated heat that’s not recaptured means wasted energy and a loss of efficiency. SustainX claims its technology keeps the air at near-constant temperatures (isothermal) during both compression and expansion, making it more efficient that other systems. And by storing air in standard, off-the-shelf industrial gas cylinders above ground instead of in underground salt domes, as do the world’s two existing CAES operations, SustainX says its approach offers the additional advantages of being both scalable and transportable to wherever energy storage is needed.

It all sounds highly promising, though — as usual — the proof will depend on how well the technology performs at a large and commercial scale. However, considering the problems with conventional chemical-based energy storage in batteries, the financial challenges surrounding hydrogen fuel-cell storage and the physical risks associated with pumped water energy storage, mechanical systems based on air or gravity could show real potential for helping to resolve the grid-scale energy storage conundrum.