Solar Power

[via Gilder Technology Newsletter] Wired writes about Bill Gross’ Sunflower Solar Concentrator:

Gross turned that bigger-is-better thinking upside down. By combining Internet-age technology, clever design, and inexpensive Chinese manufacturing, he realized that a radically downsized solar concentrator could retain all the efficiencies of its giant cousins and also fit on a roof. It was the PC paradigm all over again.

Gross’ R&D team tried at first to avoid silicon entirely, converting concentrated sunlight into electrons with a Stirling heat engine, a superefficient refinement of the steam engine. When that proved too difficult to bring to market, the engineers set it aside and reluctantly turned back to silicon. They tried dozens of configurations to maximize the stream of photons: 8-foot parabolic dishes, arrays of 500 tiny motorized mirrors, ridged Fresnel lenses mounted in gleaming aluminum tubes. By the start of 2004, there were two contending designs: a clamshell-style reflective dish that closed up in high winds and a grid of moving mirrors.

Then, in a weekend flash of inspiration, a young Caltech physics grad named Kevin Hickerson figured out how to reduce the number of motors needed to move 25 mirrors independently, a major cost factor. Instead of two motors for each mirror – the traditional approach – Hickerson’s solution requires only two motors for any number of mirrors. The key is a mathematical curve known as the conchoid of Nicomedes (named for the ancient Greek mathematician, who discovered it). A grid of ball bearings arrayed to match the conchoid is attached to a frame inside the Sunflower. As the motors move the frame, the bearings control each mirror’s position individually.

The resulting Sunflower 250 is heavy enough to stay put in high winds, but light enough to be lifted by two installers. To take full advantage of outsourced manufacturing, it’s sized to fit into a shipping container; commercial units could be transported to your favorite big-box retailer’s rooftop direct from the Shenzhen factory.

Atanu also pointed me to this BBC article on China’s plans for its new cities:

Internationally renowned designer, sustainability architect and author of Cradle to Cradle, William McDonough, argues that we can only think of our future cities if we think about what our intention is as a species…Mr McDonough’s ideas for the Next City are about to be played out in China where his company has been charged with building seven entirely new cities.

Waste is energy in Mr McDonough’s Next City vision; methane is used to cook food. A quarter of the city’s cooking will be done with gas from sewerage. “The energy systems will be solar energy. China will be largest solar manufacturer in the world,” says McDonough.

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Rajesh Jain

An Entrepreneur based in Mumbai, India.