Block’s Indicator of Sustainable Growth

by Ray Block

 Wind energy in both Europe and the US is becoming a major source of alternative energy. The American Wind Energy Association (AWEA) reported on December 22 2008 that at the end of September, the US wind energy industry had reached an installed capacity of over 21 GW (21,000 MW), passing Germany in size to become world leader in wind generation.

US progress has been very rapid when you realise that since 2006, the American wind industry has doubled from a previous installed capacity of 10,000 MW. Growth of this order will continue in coming years, with the US Department of Energy believing that by 2030, the US wind industry will be supplying 20 per cent of the country’s electricity.

Wind energy will become much larger as an energy source, with the ability of combining batteries to store wind power. Xcel Energy is one of two US utilities, which are testing a sodium sulphur (sulfur) battery to store wind energy. They are trying it out in a 1,100 megawatt facility of wind turbines in Southern Minnesota. The utility reckoned that the experiment was worthwhile, because “the wind doesn’t always blow, and even worse, it often blows strongest when people aren’t using much electricity, like late at night.”

The smart grid software start up GridPoint has been mandated to employ its software to control the flow of power between an 11 megawatt wind farm and NGK’s one megawatt battery. For renewable energy such as intermittent wind, the sodium sulphur battery is going to be judged a great success. That’s because wind turbines only generate power when the wind blows, meaning they need backup, or “firming” power, such as peaking natural gas.

With the Japanese battery, the need for other peaking power is reduced. The use of batteries allows wind power to be stored when prices for power are cheap, and sold at peak prices in the afternoon to create a win win for wind power.

The (NAS) battery is made up of “twenty 50-kilowatt modules. The battery is roughly the size of two semi trailers and weighs approximately 80 tons. The battery is able to store about 7.2 MW hours of electricity, with a charge/discharge capacity of one megawatt. When the wind blows, the batteries are charged. When the wind calms down, the batteries supplement the power flow. Fully charged, the battery could power 500 homes for over 7 hours.”

Currently, the battery is solely produced by NGK Insulators of Japan in partnership with TEPCO (Tokyo Electric Power Co. There is a demonstration project of the NAS battery at Japan Wind Development’s Miura wind farm in Japan.

The battery originated in the US in the 1960s for use in electric vehicles, when General Motors intended to produce electric cars, and even Ford had an attempt at electric cars in the late 1980 using the battery.. While it wasn’t suitable for this use because of its operating temperatures of 300 to 350C, and the highly corrosive nature of the sodium polysulphides, the Japanese from 1983 onwards have been researching the unit with its suitability for large scale stationary use in grid storage.

The unique properties of the battery remains its high energy density, high efficiency of charge/discharge (89-92 per cent efficiency), long cycle life, and ability to be manufactured from inexpensive materials.