Is Natural Light Better Than Solar?

SAN FRANCISCO — PTW Architects, the firm that designed the famed Swim Cube at the Beijing Olympics, considered putting solar panels on top of the building.

The company, though, found that it worked better todynamically adjust the polymer shell around the building to let insunlight and heat. The outside of the building is coated with athree-meter thick mesh of pillows from a material called ethylenetetrafloroethylene (ETFE) that can be inflated or deflated to let inlight, or deflect glare.

"The ETFE pillows were more efficient in saving energythan what could have been done by putting PV panels on the roof," saidJohn Bilmon, managing director at PTW.

In all, the design of the building cut power by 35percent. A good portion of that came from letting sunlight in naturallyto heat the water.

Other fun Swim Cube facts: The building is square toorder to compliment the round Bird’s Nest stadium nearby. Squarebuildings represent earth while round ones represent heaven. The bluecolor also complimented the red stadium.

In all, the building was made from 22,000 steel beams,each one different from any other. Although the building was a straightsquare, none of the beams run along conventional straight lines. "Thebeams never ever followed straight lines," he said. The beams wereconnected by sticking them in, Tinkertoy-like, into 1.5 meter widesteel nodes. The firm was going to assemble these structures at thefactory but found it was cheaper to just hire people on site to do it.

The firm studied bubbles extensively to come up withthe shell. Bubble studies can be traced back to Lord Kelvin, who notedthat bubbles are round when exposed to air but connect to each otherthrough flat surfaces. Kelvin designed 12 and 14 sided polygons todemonstrate how bubbles efficiently fit together.




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