Li-titanate storage balances Indianapolis power grid

Battery stack shacks to back renewables?

Battery-tech firm Altairnano, best known to Reg readers as the developer of kit which might soon drive genuinely practical electric cars, has now produced a really big battery pack for use by power companies. This week Altairnano announced its first sale of the mega-battery gear, to power giant AES.

The lithium-titanate storage units in question are a pair of 250 kilowatt-hour stacks, each rated for a maximum output of 1 megawatt (under which load they would be drained, obviously, in less than 15 minutes). The two stacks and ancillary power converters, control hardware etc. fit into a truck trailer-sized shed, now hooked up to an AES-owned substation in Indianapolis. The whole unit could power a typical US household for just eight days, but that's not what it's for. It's meant to be used in shorter cycles, ironing out dips and peaks created by other supplies and loads on the grid.

"This two-megawatt validation project is one of the final steps in our move towards commercial deployment of grid-scale energy storage," said Chris Shelton, the bod in charge of such matters at AES. "Fast-responding, high-efficiency energy storage systems such as these will create a more resilient grid and allow for increased use of variable generating sources such as wind and solar."

The Altairnano battery stack shack has already gone through comprehensive tests, and can apparently cope easily with being switched rapidly from full discharge to full charge and back again repeatedly. This is the great virtue of the new lithium-titanate kit - it can charge (and, evidently, discharge) much faster than ordinary batteries without damage. This means that an electric car fitted with Altairnano's batteries can be charged up in minutes* rather than the hours required by almost every existing electrovehicle, making such cars serious contenders against fossil-fuelled ones. Today's news also has serious implications for those - like Google, the Danish windpower base etc. - who'd like to see a future electric transport fleet used to balance the grid while plugged in for charging**.

It now appears that the new, tougher batteries could help solve some of the terrible problems caused for power grids by erratic supplies such as wind, wave and solar. Recent research suggests that gas turbine backup for these renewable generators could be very expensive, problematic and carbon-intensive, so this could be good news for the greenly-inclined.

Just how well the lithium-titanate gear stacks up against alternative power storage methods like pumping water uphill remains to be seen, especially throughout its lifecycle (including disposal or recycling). Battery stacks seem likely to face some of the same objections as pumped storage too, in that ones able to cope with multi-day windless, cloudy calms would be prohibitively expensive.

One might also note that the other vision of a fossil fuel-free, all-electric future, in which the grid would be largely nuclear powered, would still need some balancing capability. Current nuclear power stations don't like being thrashed up and down in load factor. Though human demand swings are less severe and unpredictable than the changes to be expected in renewable supplies, an all-nuclear grid would still need some storage.

Whichever way the future goes, then, it seems that lithium-titanate gear is likely to play some part in it. Tech detail on the AES project for those interested is here (pdf). ®


* Charging up a battery car this fast couldn't be done using domestic mains wiring, as it can't carry such a load. An industrial three-phase outlet is required for a quick charge, though you can do a slow trickle topup from a domestic socket. However, fast-charge outlets wouldn't be hard to install at forecourts.

** A plugged-in lithium-titanate car would plainly be a more valuable resource for the grid than a li-ion or lead-acid one. But such cars would probably be plugged in a lot less often. The vehicles of the numerous non-garage-owning classes, parked on the street overnight, would only ever be connected quite briefly at the forecourt - so denying the grid any serious chance to benefit from their existence.

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