Austin Energy is looking at all the angles for storing electricity on the grid.

Got a battery? Put it to use storing energy – and use it as a filter to keep "blips" on the grid from messing up the city's semiconductor factories, or keep factories running at top efficiency.

And if you're going to pay for storage, might as well sell the power back at the best price you can get, rather than saving pennies per kilowatt-hour on baseload power to keep the household refrigerator humming. Why not use it to replace gas turbines kept running – so-called "spinning reserves" – to keep the grid stable in the rare event that peak demand threatens to push it into brownouts?

All that is going to take a lot of different types of batteries, from cargo container-sized to those small enough to sit in a home's basement. (Storage will be one of the primary topics of discussion next week at The Networked Grid taking place November 4 in San Francisco.)

Or it may take bigger storage containers, like a reservoir for water that can be pumped uphill when power is cheap and spin a turbine when it's expensive, or giant underground salt caverns filled with compressed air that can make a gas turbine run at double efficiency.

Those are all parts of Austin Energy's storage scheme, said John Baker, Austin Energy's chief strategy officer. It will be complicated, he said, but the utility has little choice in the matter.

Austin has set a goal of getting 30 percent of its power from renewable sources by 2020, and is planning a city loan program for homeowners that want to putsolarpanels on their roofs. All that solar and wind power doesn't flow consistently, or sometimes at all, making storage a priority, he said (see Grid Energy Storage: Big Market, Tough to Tackle).

But storing electricity is expensive. The cheapest batteries on the market, high-temperature sodium sulfur batteries, cost about $3,000 a kilowatt-hour – about 10 times as much as pumped hydro and compressed air energy storage systems, which can take decades and billions of dollars to build (see Top Ten Smart Grid: Energy Storage).

A host of technologies, from lithium-ion, advanced lead-acid and zinc-based flow batteries to fuel cells, flywheels and ice-making air conditioners, are trying to bring down their prices (see IceCycle: A Retrofit). Austin Energy is looking at many of them, Baker said last week at the Clean Energy Venture Summit in Austin.

The utility does have a smart grid playground of sorts to work with. The municipal utility of Texas's capital city doesn't have to split itself up into generation, transmission and retail arms like Texas' deregulated investor-owned utilities, and its decisions are ratified by the city council, which is already boosting renewable energy in a big way.

And the Pecan Street Project – a proposed smart grid showcase seeking millions of dollars in Department of Energy stimulus grants – has partners including General Electric, Microsoft, IBM, Cisco, Oracle and Dell that want to prove they can manage and control such a complicated storage system (see Green Light post).

"If we can start looking at having some control over it, we have the capability of bringing some resource on that doesn't affect the end use... but does represent a balancing source for the utility," Baker said.

Take the cargo container-sized flow batteries from Premium Power, now being tested at Austin Energy substations in a project with the Electrical Power Research Institute.

"Part of what we're trying to do is see where some of these technologies can play more roles," Baker said. Flow batteries could balance out the quality of power being delivered from the substations they're stationed at, as well as keep reserves free to reduce peak loads, he said.

"Also, if strategically located next to industrial customers with very high need for clean power," like server farms or semiconductor plants, "it doesn't take a large outage to take their process down – it takes a blip," he said. "If we can screen some of those blips out of that, we have two value propositions out of that equation."

The same goes for inverters, which convert direct current from solar panels into alternating current for household and grid integration. New inverters could help balance frequency and voltage on distribution grids, Baker said.

Voltage sags and dips can account for efficiency losses of around 5 percent on distribution grids, and the United States uses about 1.5 percent of its generation capacity to keep grid frequency stable. Those are both markets that clever storage systems could sell into, Baker said (see Green Light posts here and here).

Adding batteries to solar-powered homes could also play a role in stabilizing the dips and peaks that come when clouds pass overhead. Add enough solar-powered homes to a neighborhood, and those fluctuations can cause serious problems (see Rooftop Solar, Batteries Included).

Storage that's distributed throughout a neighborhood distribution grid could help balance the power in that area, he said. That's a concept that utilities including American Electric Power are looking into (see Utility to Try Backyard Storage).

But that brings up the question of how utilities and homeowners will negotiate issues of control over those storage systems, as well as who should pay for what share of that functionality, he said.

"Where's the benefit accrued, who sees more value in it – the utility or the customer? These are things that still need to be analyzed," he said.

Photo of an Austin Energy worker via Austin Energy.


Interact with smart grid industry visionaries from North American utilities, innovative hardware and software vendors and leading industry consortiums at The Networked Grid on November 4 in San Francisco.