By Brian Dumaine, assistant managing editor
Architecture firm SOM rises to the challenge of designing the most energy-efficient tower, a 71-story building in China.
The Holy Grail of modern architecture is to design a zero-energy building, or ZEB.
ZEBs use solar, wind, and geothermal systems to produce at least as much energy as they tap from the grid. In some cases, a building's owner can sell the excess electricity generated by the structure back to its utility, reducing overall demand for power generated by coal and other greenhouse-gas-emitting plants.
Yet ask any architect and you'll get an earful on the design challenges of ZEBs. (Skyscrapers don't have much roof space for solar panels, for example.) In fact, there are only eight nonresidential ZEBs in the U.S. -- all of them tiny.