Tackling Climate Change
In search of a better battery
by Scott Gates
Electricity remains tricky to manage. When it’s created, it must be immediately moved to where it can be used. When it’s needed, it must be instantly on hand. Yet there’s no sure-fire way to store it, unlike water or natural gas.
Due to this “use it or lose it” factor, engineers have long sought methods to stockpile electricity. In recent years, the need for energy storage has grown — from supplementing renewable energy sources like wind farms to powering the latest hybrid electric vehicles. All of this has sparked new efforts to find the better battery.
“Energy storage could solve so many problems and help control electric rates,” remarks Bob Gibson, senior program manager with the Cooperative Research Network (CRN), an arm of the National Rural Electric Cooperative Association (NRECA). “The potential is enormous.”
Large-scale energy storage was first used in the United States in 1929, when a 31-megawatt pumped-storage hydro facility came online. Pumped-storage hydro involves pumping water uphill to a reservoir during times of low electric use, such as at night. The next day, when people are active and electricity consumption peaks, the water is released through turbines to convert that “stored” energy back into usable power.
About 3 percent of the nation’s total electricity is generated using this method, according to the U.S. Department of Energy. Most pumped-storage hydro plants were built from the late 1950s to the late 1980s, which taps almost all of the technology’s potential — there are few prospective sites for new installations.
A twist on this idea stores compressed air in large underground caverns. When power is needed, the air gets released to blast turbines into action. (Compressed air storage plants can operate, burning an air/natural gas mix, for roughly 12 to 24 hours or more.) PowerSouth Energy Cooperative, a generation and transmission cooperative (G&T) based in Alabama, operates the only compressed-air storage facility in the United States.
But this method shares the same limitations as its water-driven predecessor. “Pumped-storage hydro and compressed-air storage are only feasible near special geographic features,” notes Gibson. “Batteries, on the other hand, can be put anywhere.”
Bigger, Better Batteries
To date, large-scale battery arrays haven’t offered a good energy storage option for co-ops — they’re expensive, don’t hold a charge for long, and can have short lifespans. But as technology improves, many see the “better battery” as a major breakthrough waiting to happen.
Batteries used for large-scale energy storage range from glorified lead-acid versions (what’s in your car) to more advanced nickel-cadmium batteries (such as those running a cordless drill). A recent CRN study analyzed these and other battery types to find the best for co-op use.
“We looked at all of the different options out there,” explains Dale Bradshaw, a consultant to CRN. “The head-and-shoulders winner, with the lowest up-front cost, longest life, acceptable efficiency, and low environmental impact, appeared to be the zinc-bromide battery.”
As a result, CRN plans to put zinc-bromide batteries to the test through a proposed research project with four electric co-ops that could win federal funding before the end of the year. Each co-op would demonstrate how the batteries could be used in different ways, in different parts of the country.
Columbia, S.C-based Central Electric Power Cooperative would use batteries to, among other things, flood the power grid with stored energy when outages occur. The co-op could also supply electricity to the grid during times of peak electricity use, trimming their “peak” and reducing demand charges — expensive natural gas-fired generators would be switched on otherwise.
Tampa, Fla.-based Seminole Electric Cooperative plans to use batteries to store solar power. The co-op’s photovoltaic solar array typically provides the most power at noon or 1 p.m. By storing that energy at noon, the G&T can put it to use later in the day when more electricity is needed but clouds have moved in.
Kaua’i Island Utility Cooperative and Kotzebue Electric Association, which respectively serve parts of Hawaii and Alaska, would deploy batteries to manage the intermittency of renewable generation. If wind energy was stored at night, that power could then be used during the day — when there’s a bigger demand for electricity but breezes may not cooperate. These co-ops could also use batteries to ensure service reliability, feeding power to consumers when parts of the system experience outages. As a result, both co-ops will reduce the use of expensive oil-fired generators during periods of high demand.
“We think this could be one of the biggest breakthroughs of the last 20 years,” claims Bradshaw. “What we’re doing now could have a major impact on co-ops in the future. It’s one of the rare opportunities where we can begin to stabilize the price of electricity, hopefully slowing down increases in rates.”
On the Road
Though there’s great potential for large, utility-scale batteries, better batteries are also needed on a smaller scale, especially if electric vehicles are to become mainstream.
“It’s really great that electric cooperatives got involved in this technology early on,” comments Alan Shedd, an engineer with NRECA who has logged thousands of miles behind the wheel of a co-op-owned PHEV. “Participating co-ops deserve a lot of credit for getting out there and making this initiative happen.”
PHEVs take traditional hybrid cars a step further by using larger, more powerful lithium-ion batteries that can be charged overnight from a standard 110-volt outlet. Batteries alone power the cars over short distances; a gas engine kicks in for longer hauls. As a result, PHEVs can average between 120 and 150 mpg on trips less than 40 miles.
The Palo Alto, Calif.-based Electric Power Research Institute (EPRI), of which electric co-ops are members, recently noted that a dramatic increase in the number of plug-in hybrid electric vehicles on the road over the next 20 years could reduce total U.S. carbon dioxide emissions by 9 percent. EPRI estimates that 100 million PHEVs would do the trick; there were 247 million registered vehicles on the road in 2007, according to the U.S. Department of Transportation.
One roadblock is — you guessed it — the batteries. Lithium-ion batteries powering PHEVs are similar to what’s used in cell phones and laptops, although they’re not fully proven in cost-effective automotive applications. But things are looking up: a report by the California Air Resources Board found manufacturers “making impressive technical progress worldwide,” improving longevity and safety.
What’s more, General Motors is set to roll out a plug-in vehicle next year. The Chevrolet Volt will rely on rechargeable lithium-ion batteries for its electric power, and could achieve up to 230 mpg in the city, according to early GM estimates.
CRN has recently partnered with Ford, which received a $30 million U.S. Department of Energy grant to develop its electric fleet. Ford plans on releasing its own plug-in hybrid electric vehicle in 2012. The partnership could answer important questions such as how the new vehicles will affect co-op electric grids — the transmission and distribution lines connecting power plants to consumers.
“If PHEVs were to be used on any widespread scale, it could create some very unique challenges for distribution systems,” cautions Barry Lawson, NRECA manager of power delivery. “We must take measured, careful steps with anything related to developing technology. New energy storage technology and equipment, both large scale and in PHEVs, have the potential to provide benefits to the electric utility system, but it must be done in a reliable, safe, and affordable manner.”
Gates writes on consumer and cooperative affairs for the National Rural Electric Cooperative Association, the service arm of the nation’s 900 electric cooperatives.
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