Big Australian Balls

Over at The Ergosphere, there's an interesting post proposing that alternative energy is civil defense.

What with one thing and another, we all live in potential disaster areas and I've long thought that we don't emphasize civil defense enough in this country. Though one can argue over the details of what makes for a more robust infrastructure, I would hope that all of us agree on the need for it. Check it out.

More pleasant to think about (unless you're James Kunstler) is this post regarding a reconception of marine power.

...the high cost of oil is rekindling interest in sail. Modern materials and automation have reduced the labor requirements to use it. Roller-furling jibs are one thing, but computer-controlled parafoil kites are a whole new game. Flying well above the waves, these kites can capture more power than even the highest topsail of a clipper ship. With favorable winds, even large cargo ships can see substantial fuel savings, greater speeds or both.

I had a rather cursory link to this concept last Earth Day, but the Ergosphere's coverage puts mine to shame. He devotes much more time to the idea of power kites that generate useful levels of electricity regardless of wind direction. Now, some of you may remember Cousteau's old wind turbine ship, the Alcyone, and wonder why we need anything as cumbersome and Rube Goldbergesque as a kite. The answer can be found in this wonderful paper, The Case for Transport Sail Craft.

One of the big advantages of kites over conventional rigs, rotating cylinders, and wind turbines is the relative freedom from heeling moment. This will allow us to attach kites to most commercial ships without significant modifications. Another advantage is dynamic sheeting, or the ability to fly patterns in the sky to maintain relative winds at the kite that are several times stronger than the wind on the deck.

So much to learn and so little time. It's humbling. But what about those titular Australian balls? Relax, we're almost there. This will call for a slight change of tack, but we'll still be in peak oil survival waters. They're powerballs. Solar power, specifically.

Australia's Green & Gold Energy is preparing to market what they call SunBalls to the Australian consumer. I have to say, the individual units are sort of cute, in an R2-D2 kind of way. But cute is irrelevant when what you're paying for is juice. By that standard, and assuming that the company's claims stand up to scrutiny, these power units will be freaking beautiful.

An example from their FAQ...

What's different about the solar cells used in the SunBall™ Solar Appliance?

The SunBall™ Solar Appliance uses 35 - 38% efficiency triple junction solar cells normally only used in space. Close cousins of our solar cells power the two Mars rovers Opportunity and Spirit. Flat panels solar cells normally rate around 15%.

Why not just use these high efficiency cells in flat panels?

The cells cost around $10 / cm2. 1 m2 of these cells would cost around $100,000 so don't expect to see them in flat panels unless you happen to live on Mars or in a space station.

How does the SunBall™ Solar Appliance use these cells yet cost less than flat panels?

The SunBall™ Solar Appliance uses an optical acrylic Fresnel lens to capture the light from an area 500 times that of the solar cell and focus it onto the triple junction solar cell. This lens costs a lot less than using silicon solar cells to cover the same area. This is the first cost reduction effect we use in the SunBall™ Solar Appliance. In the SunBall™ Solar Appliance a 1cm2 (1cm x 1cm) concentrator cell (~$10) does about the same work (kWh output) as about 2,000 cm2 (45cm x 45cm) of typical silicon solar cells (~$120).

Focusing the sun 500 times sounds like the solar cell would burn up from the heat. How does the SunBall™ Solar Appliance stop this from happening?

The triple junction solar cells we use in the SunBall™ Solar Appliance are specially designed to handle this amount of concentrated sun light whereas normal silicon solar cells are not. We also mount the solar cells on a massive heat spreader which transfers the heat into the SunBall™ Solar Appliance's aluminium hemisphere shell which serves as a heat radiator. This heat radiator is 180% larger than the solar collection area, is always in the shade and cooled by passing winds much more easily than flat panels. While 500 suns sound massive it is really only a heat load of about 30 watts per solar cell. The rest is just good thermal engineering.

As an example 500 cm^2 of Fresnel lens will connect 50 watts of power at 1,000W/m^2 or 0.1W/cm^2. The Fresnel lens will loose / reflect about 8% or 4 watts leaving 46 watts beaming to the cell which then converts say 40% to electricity. That leaves 46 * 0.6 = 27.6 watts to be spread and dissipated by the passive heat management system.

This separated and broken down heat load is then very thermally manageable and no way as difficult to handle as the massive heat load found on dish and trough type concentrators which have to depend on pumped cooling liquid to stop their cells from being damaged and/or melted into expensive glass.

Great stuff, eh? If you're even slightly interested in home power, I would urge you to give their website a closer look. Don't miss their calculator feature.

I know we've all had our hopes raised and dashed a few times in regard to affordable solar power, but don't let that crimp and sour you. Hope is good for the heart.

posted by Justin on 11.01.05 at 11:55 AM





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