Energy Storage and Conversion
Wednesday, March 12, 2008 at 07:27AM
Toby Considine in Microgrids and Distributed Systems, Re-thinking things, Zero Energy Buildings

It’s not all about electricity. It’s not all about the grid. Local energy storage and conversion will play a big part in our future.

Energy storage is much more than batteries, and does not wait on new battery technology. Heat wells can run absorption chillers and thus eliminate a portion of some electrical loads. Water storage, as the ranch I grew up did with windmills, can provide potential energy of electrical buffering.

Trane began selling ice making capacity to office buildings decades ago. An Ice Maker that runs all night on cheap power can air condition all day with almost no power. The failure of the Public Utilities Commissions to require clearing markets in energy for each time of day is the biggest barrier to adoption. It may not look like a row of car batteries, but this type of solution gets energy from the grid, stores it until needed, and expends it when grid prices are high.

A Scandinavians project painted the streets white and black, and used the black to gather heat for a piping system under the street, pumped down by convection into a heat well underground for optimized hating in winter. Same project dissipating heat in winter under the white pavement to create a second thermal pool underground that is significantly cooler than normal - to help cool the next summer.

Thermal gradients of less than 25 degrees can run new computerized Stirling engines - and thus convert waste heat to power. This type of generator, originally marketed for high-end yachts, can generate electricity from waste flue heat. It may not be a lot, but it can be enough to take a home’s base load off grid—or slowly charge house batteries. Battery efficiency is almost irrelevant in such a scenario.

Even electricity is convertible. Batteries are DC. Most devices in your house (except white boxes) actually use DC. When running off a house battery today, you may lose 15 per cent converting to AC. You probably lose the same or more converting back to DC in the little "vampire taps" and "wall Warts" and internal power supplies of your electronics. Eliminating the double conversion gains back more "battery efficiency" then most anticipate from the next 20 years of research.

The problem is the lack of standards for DC electrical distribution within your house. The international electrical energy conference in Paris last summer proposed using existing consumer electronics standards. Some of you know the USB power supplies Blackberries have used for years. USB power outlets are one of the proposed plug standards. While some see this movement as far-fetched, others see it as a chance to establish a common plug standard across North America, Europe, and Asia.

Once some use of DC power in the home, requiring standards, rather than not-invented-yet technology, is adopted, it makes other technologies cost effective as a secondary effect. Solar generates DC power – and so would become more useful in exactly the same was as batteries. Cost effective storage batteries bring even home wind power into the main-stream.

DC solutions are only useful for the home or office. We still need AC to drive power over distance, so the grid will always remain AC. This makes local storage quite different from storage by the power company.

Benefits will come from re-thinking the processes by which we manage the entire energy life cycle, not by bolting on renewable technologies onto the head-end of the giant broken robot that is the power grid.

Article originally appeared on New Daedalus (http://www.newdaedalus.com/).
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