Xcel Energy of Minnesota announced February 28th 2008 that they have signed to acquire the NGK sodium-sulfur batteries in the 50 kilowatt size. That’s right 50kw per module, and Xcel is getting 20 modules totaling 1 megawatt. As regular readers know, storage is the key to making the wind and other variable renewable energy sources practical. What stands out about this announcement is this is the first application for wind storage. The module kit as ordered will hold enough electrical potential to power an equivalent of “500 homes for 7 hours.”

Sodium-Sulfur NaS Battery

The sodium-sulfur (NaS) is already installed in a few U.S. locations and several in Japan. The full unit as ordered weighs in at 80 tons and is about the size of a pair of semi trailers. The planned location is Luverne Minnesota, due to be set up by S&C Electric Co., and will be feed from the Minwind Energy Farm, with an expected completion about October 2008.

The partners in the project include Xcel Energy, the University of Minnesota, the National Renewable Energy Laboratory, the Great Plains Institute, and Minwind Energy. Xcel is leading the testing as an “emerging technology and energy storage devices” effort to support its Smart Grid strategy whose goal is a modern upgraded grid that allows for easy integration of renewable sources of power. A pending grant of $1 million from the Minnesota Renewable Development Fund is up for approval this spring.

NaS Modular Unit

NaS is one of the oldest technologies in battery chemistry. By the 1960s, Ford Motor Company pioneered the modern design in hopes of powering early electric automobile designs. NGK and Tokyo Electric have refined it for power grid applications. NaS is actually a quite advanced technology. The anodes and cathodes are not vulnerable to the corrosive effects that plague lead (Pb) acid batteries, which makes the NaS battery very long lasting. The NaS is about 5 times more energy dense by volume than Pb acid.

Over the years, Tokyo Electric and NGK have installed enough battery storage in Japan for 155,000 homes. In the U.S. the latest installation is by AEP who installed a unit large enough to supply 260 homes with the idea that it would charge at night and discharge onto the grid by day during peaks, so leveling the demand and reducing costs. The math that AEP uses offers a postponement of substation upgrades of $10 million by 7 years and reduces the blackout chances against the installed cost of $2.5 million. The battery then can be moved and when expired, recycled.

NGK offers these specifications. About a 1/3 area of installation compared to Pb acid. 75% efficiency in the charge/discharge system. 15 year durability from a 2,500 cycle life. NaS discharges no gases or fumes, works silently, and doesn’t vibrate.

The down side is these things need to be hot. At 300 degrees C the active materials are liquid and work smoothly while the electrolyte remains solid, and internal resistance is low. But these characteristics make for excellent performance. The battery can be used continuously as reversible charging and discharging can take place. Hot, for sure but well insulated the units are very good fits for stationary installations that need large capacity.

Peak Load Battery Application

Other ideas beyond wind are being considered. The ability to buy power off peak and use it during high peak offers large users a way to cut costs. Today the batteries are still quite expensive. At $2,500 per kilowatt they cost about 110% of a new coal plant per kw. Industry people say the one source and limited production of today replaced by mass production can greatly reduce the costs.

One of the more curious quotes comes from Imre Gyuk the head of the U.S. Department of Energy who said, “Stick it any place you can stick it.” I take that to mean that the biggest batteries ever can make a big difference in the total generating capacity required to run a modern economy.


Comments

9 Comments so far

  1. Store Power in Super Batteries | on March 23, 2009 9:53 PM

    […] Japan, where NaS batteries are made, enough have been installed to power the equivalent of at least 155,000 homes. Later this year or next, American Electric Power, a major utility serving 11 midwestern states, […]

  2. Store Power in Super Batteries | Smartlogix Technologies on March 23, 2009 11:16 PM

    […] Japan, where NaS batteries are made, enough have been installed to power the equivalent of at least 155,000 homes. Later this year or next, American Electric Power, a major utility serving 11 midwestern states, […]

  3. bw on March 26, 2009 5:25 AM

    Xcel Energy of Minnesota announced February 28th 2008 that they have signed to acquire the NGK sodium-sulfur batteries in the 50 kilowatt size.
    When it comes to the capacity of batteries you should talk about kWh i.e. kilowatt hours, the product of power and time not kW which is only power. You can get 50 kW of an ordinary car battery but only for a short time.

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