Utility energy storage no longer just giant batteries

If you need more evidence that energy storage is much more than lithium ion batteries, take a look at the latest smart-grid utility storage projects.

The Department of Energy on Tuesday announced that $620 million in stimulus funding is going to 32 smart-grid programs, which will be coupled with another $1 billion in private money. A total of $770 million from government and industry sources in the next few years will go to energy storage, giving a number of storage technologies a dose of real-world experience. (See this PDF for details.)

(Credit: PG&E)

Notable in the list is the prominence of compressed-air energy storage and flow batteries, two technologies rarely discussed just a few years ago. Also in the mix are flywheels and using batteries for distributed energy storage in communities.

It's unlikely that all the DOE-aided projects will immediately prove to be commercially viable. But storage has clearly emerged as a key component in the vision of the smart grid. A number of start-ups are developing technologies they hope can address a specific storage application or undercut pumped hydro, considered the cheapest form of utility storage, on price. With pumped hydro, water is pumped uphill and released at peak times to run a generator. But its use is limited by geography.

Many of the 16 Energy Department power storage grants were focused on storing wind power, which is a variable source of energy. In California, for example, utility Pacific Gas & Electric plans to store the power generated by wind turbines at night, when turbines are most productive in underground caverns. During the day, when grid demand is higher, the air is released and passed through a turbine to make electricity.

The advantage of underground compressed air storage is that it can be cheaper than batteries and can store many hours worth of energy. PG&E forecasts that its Kern County, Calif., project can deliver 300 megawatts of power for 10 hours, enough to supply tens of thousands of homes.

Another novel technique is using metal tanks to store compressed air, a technology being developed by a Dartmouth College spin-off SustainX. The compressed air is released to run a hydraulic motor that drives a generator to make electricity.

Flow batteries, meanwhile, use tanks of liquid electrolyte solutions. When the two liquids interact, there is a chemical reaction that creates a flow of electricity.

An advantage of this approach is that store large amounts of energy and discharge relatively quickly, according to the Electricity Storage Association. One project will use technology from Premium Power, which makes tractor trailer-size zinc flow batteries to maintain a steady frequency on the grid and supply power during times of peak demand.

Different strokes
The variety of technologies points to the range of energy storage applications. Flywheels from award winner Beacon Power, for example, can absorb and discharge megawatts' worth of power to the grid but only in 15-minute bursts. Still, flywheels are getting more attention because they are a nonpolluting replacement to the natural-gas plants now used to smooth out short-term fluctuations in grid frequency, according to the company.

Click on the image for a slide show of different energy storage technologies.

(Credit: AEP)

Large batteries, too, will be further tested for grid storage. Duke Energy plans to use multiple battery types for 20 megawatts' worth of power delivery at the Notrees Windpower project in Texas. The "hybrid" battery system is being designed for two tasks: to smooth out short-term grid fluctuations and to supply hours' worth of power during the day, according to a Duke Energy representative.

Utility Portland General Electric in the next two years plans to install five batteries from auto battery supplier Ener1 to supply enough juice to power 400 homes for about an hour. Alternative chemistries, including lead carbon batteries from East Penn Manufacturing, will also be used.

One project will test the viability of used car batteries for grid storage. Lithium ion plug-in car batteries from A123 Systems will be used to supply 25 kilowatts for two hours in 20 community energy storage projects. The performance of lithium ion batteries degrades after many years in a car, but there is still sufficient storage and power for grid applications, utility executives say.

[fokkwp]

"Pacific Gas &#38; Electric plans to store the power generated by wind turbines at night, when turbines are most productive in underground caverns."<br /><br />Ah, I was wondering when those underground wind turbines were most productive.

[Mergatroid Mania]

Interesting stuff. I'm surprised that, considering they can store compressed gas in underground chambers, why don't they line one of the chambers, dump tons of electrolyte into the chamber, a couple of mountainous electrodes and tada...one giant battery. <br /><br />I would think an electrolyte would store electricity more efficiently than compressed air.

[stewartm0205]

Another way is to control demand. We can connect fridges, air conditioners, and electric space heating to intelligent plugs that would respond to signals from the utility to either turn off or reduce consumption. For a few dollars we could replace hundreds of dollars of storage.

[NocturnalCT]

I heard from a friend who lives in CA that PG&#38;E has some of that type of technology available. The problem is that they don't provide an incentive to users. So by installing this equipment you allow PG&#38;E to power down your AC while your neighbor who said 'no thanks' gets to keep his AC at full blast. Not very attractive. So to compensate PG&#38;E should offer a lower electricity rate, not just when they do cut your power but at all times. Or some other kick-back mechanism.

[dacopper]

Can't say if same is true for electricity, but PG&#38;E does provide intensives at least for gas. A couple of months ago I got a letter from them informing me because my gas consumption was below some threshold for several months straight, they were giving me credit towards my next bill (sorry, don't remember exact numbers).

[whitesoflr]

Companies are now offered the opportunity of reduced electric charges by voluntarily participating in load-shedding programs where the utility can call on the company in times of high demand and request that they shed load.<br /><br />A voluntary program is a great idea. But when you talk of letting the utility turn off a fridge or an AC inside a private residence you're getting quite "big-brother" for me.

[UpajOs]

Screw 'em. That sounds like a truly leftist solution: The pie is only so big, so we'll need to ration it. How about baking a bigger pie, instead? The utilities' job is to supply gas and electricity. Build nukes -- lots of 'em -- and don't mess around with my lights, refrigerator or air conditioning.

[Hunnter2k3]

Flywheels have always been my favorite for energy storage.<br />It is such a simple thing to build for low energies.<br />And with a little knowledge of basic physics, chemistry and electronics, it is pretty easy to build high energy systems too.<br /><br />The idea of mini energy storage facilities is a nice idea as well.<br />A lot of energy goes to waste simply because it isn't stored efficiently, or at all.

[NocturnalCT]

I thought that underground compressed air storage seems quite attractive. I'd be concerned about leakage when natural caverns are used. Another problem is there's never a good cavern around when you need one. So an option may be to simply drill a hole straight down and line it with a thin coat of concrete or plastic or both. The Earth will provide pressure resistance, the coating keeps the air in.<br /><br />This could work on both large and small scale. Use a simple post hole boring machine to drill 'tanks' in your back yard. Use a TBM (tunnel boring machine) type machine to drill a much larger vertical hole for utility size storage.

[farrago]

If using compressed air, why not use off peak energy to pump water into raised reservoirs and then let it flow down and turn a turbine when at peak requirements.<br /><br />T

[UpajOs]

That's been done for decades in locations around the world. See more in the English Wikipedia article, "Pumped-storage hydroelectricity".

[FrankKush]

Websites such as yours has info on proposals and plans. Do you keep track of defunct projects such as in air and CO2 storage?<br />An example is the project in IOWA - is it still on? <br />http://www.greentechmedia.com/green-light/post/in-iowa-compressed-air-to-be-source-of-electricity-351/<br /><br /><br />Also can you comment on overall efficiency claims with a "hydraulic pump" instead of 90% efficient centrifugal compressors - Re. http://sustainx.com/isothermal_cycling.html<br />"A key aspect of the SustainX technology is the use of isothermal (constant temperature) compression and expansion of the gas, as opposed to the adiabatic (no heat transfer) compression and expansion employed by other CAES techniques. Thermal efficiencies in excess of 90% have been achieved experimentally for the compression and expansion cycles, as compared to ~50% thermodynamic efficiencies for adiabatic techniques over the same pressure range."<br /><br />Could this change everything?<br />Carnegie Mellon University battery generates interest, $5M grant<br />... Rogers said the house-sized battery would handle massive amounts of energy<br />for about one-tenth the price of other methods. The battery...<br />www.pittsburghlive.com/x/pittsburghtrib/news/pittsburgh/s_654844.html<br /><br />Other batteries can store large amounts of energy, but they rely on such items as molten sodium and sulfur. Some must be kept hotter than 1,000 degrees Fahrenheit.<br /><br />"Because we're using water ... the cost is an order of magnitude less," Whitacre said.

[guest18934367]

A thought...I think this is a pretty good idea, but what happens if there's an earthquake and the cavern is cracked? Do we lose all the energy stored in it? Might seem to be a big waste, but maybe that risk is acceptable (place the cavern in less earthquake prone areas, reinforce it heavily, etc.)?