solar.coolerplanet.com
August 07, 2009
Salt Lake City-based Ceramatec, Inc, is in development of a battery that solar energy users outside the grid could use to store energy from their solar panels for most of a day, and its size and configuration – almost fitting in the palm of a hand, without lead and sulfur – promises safer, more manageable energy storage.
The battery runs on a sodium-sulfur mix, which is reportedly more energy intensive than typical lead-acid batteries, and has a 92-percent charge/discharge rating, allowing grid-tied solar energy users to store energy from their solar panels during off-peak hours (typically midnight to 7 a.m.) and use them when kW-hour electricity costs soar during the day.
It would potentially allow non-solar users to do the same, providing the batteries don't catch on to the extent that their use tips the on-peak/off-peak paradigm and draws the wrath of utility companies nationwide, most of whom have carefully calculated peak loads with plant operations.
Ceramatec has also reportedly found a way to make the battery run at less than 200 degrees Fahrenheit, thanks to a ceramic membrane between the sodium and sulfur which inhibits positive sodium ions, leaving the electrons to create a high-energy current. Of course, the sodium compound is corrosive, so it's probably not something you would give your kids.
The batteries, which can be ramped to store up to 20 kW-hours of electricity and are attached to a disk, will be ready for market testing in 2011, and will sell for about $2,000. The size alone is a radical departure from the 12-volt, deep-cycle (RV, marine and golf cart) batteries currently on sale for alternative energy storage, which measure about 25 inches by 40 inches (and roughly 10 inches deep), weigh 50 pounds, and cost about $2,500.
At 20 kW hours – most of an average household's electricity use per day – they look very promising. American households typically use about 33 kW hours a day, or 1,000 kW hours a month, so the battery's storage capacity could easily take an energy-conscious household through a typical day, with some caveats (no dishwasher or combined TV/computer operations, for example).
Off-grid households relying on alternative energies like solar typically use deep-cycle batteries, wired in tandem, to store energy for periods when the sun doesn't shine. This gives them a distinct advantage over the grid-tied, who either have to wait out a power failure or rent a generator. Batteries also help loads to run at a constant voltage, while still allowing solar panels or wind turbines to charge as much as possible.
On the negative side, existing deep-cycle batteries are large, full of lethal components like lead and sulfuric acid, heavy, and require regular maintenance. They are also the first part of a solar electric system to wear out.
Newer models, adapted to alternative energy storage, may have a useful lifetime of up to 20 years, and offer 2,100 cycles (complete discharge to recharge), or 4,000 cycles to half-capacity, but they are still large, heavy and dangerous, and may not last as long as the solar panels they serve. In fact, battery failure is often the largest contributing factor in a solar array's failure to deliver according to its rated capacity.
If Ceramatec's battery delivers as promised, it would be an ideal, and less cumbersome, solution to solar energy storage, though most users will likely want a lifetime rating (beyond the 92-percent charge/discharge tag) when asked to fork over two grand.
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