Utility Scale Energy Storage

For electric powered automobiles, Lithium Ion batteries appear to be state of the art, for now. For large-scale energy storage, something "bigger" is necessary. While we are waiting for redox flow cell technology to mature, Sodium Sulfide (NaS) batteries appear ready to step in and provide enough heavy-duty electrical storage for utility load-leveling. Brian Westenhaus at New Energy and Fuel looks at NaS battery storage and comes away hopeful.

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 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.___NewEnergy

Large scale energy storage is important for several reasons:

1. Demand is higher in the day and early evening than overnight. This makes night-time power cheaper, if you have the means to store it and use it during peak demand.
2. Large scale storage helps to smooth out transient supply:demand mismatches in the grid.
   
3. Large scale storage helps compensate for temporary grid power outages when located at hospitals, industrial plants, high rise buildings (elevators), city traffic light systems, etc.
4. Large scale storage allows much greater scaling and utilisation of renewable energy power generation, such as wind and solar.

As time goes by, and large scale storge gets better and cheaper, we will find that the economics of power systems works out much better with large scale storage in the mix.

More information on NaS batteries at Energy Blog.