The National Aquatics Center, which was put into use on Monday, is an architectural achievement that literally embodies the theme of "water" -- it will host water events, looks like water bubbles and is even nicknamed the Water Cube.

The structure takes that theme even one step further. It demands very little water and actually helps recycle it. It is also a "green" venue with advanced energy-saving technologies.

"In designing the venue, we took into consideration the 'Green Olympics' concept by applying advanced energy-saving technologies," said Zheng Fang, one of the Water Cube's designers.

The outer surface and roof facade of the rectangular venue can collect 10,000 tons of rain water, 70,000 tons of clean water and 60,000 tons of swimming pool water per year. And the venue can also save 140,000 tons of recycled water a year.

The venue's membrane structure, covered by ETFE (Ethylene Tetrafluoroethylene) air cushions, is not only the first of its kind in China and the world's largest and most complex ETFE project, but it is also an economical and water-saving creation.

"Through the half-transparent membrane, sunshine can heat the water in the pools, which will also save heating energy," Zheng said.

"The blue-colored material is much lighter than conventional glazing structures with the same lighting effect. So the cost of its supporting steel structure was reduced considerably as well."

The Water Cube's outer wall is composed of 3,000 irregular "bubbles", which make up the ETFE membrane structure. The ETFE membrane has good ductility and is crush resistant. It is also resistant to fire and intense heat.

Over the past 20 to 30 years, ETFE was used in 600 to 800 architectural structures in Europe.

It was dubbed "king of plastics" and was originally used in the aviation industry.

"The membrane's lifespan is over 30 years and we designed the whole venue to last for at least 100 years," Zheng said.

The membrane is also self-cleaning. Since the material's friction coefficient is small, dust does not easily attach to the structure. Even if dust does collect, as long as it rains, the surface will be washed.

Located on Beijing's central axis at the North Fourth Ring Road, the venue will host swimming, diving and synchronized swimming events during the Games, with 42 gold medals on offer.

The venue's complex design presented great challenges for builders since there is no precedent.

"The unprecedented design of the venue left us no rule or standard to apply," said Sun Hongzhuang, the Water Cube's construction project manager.

"During the construction process, we had to solve difficulties in the steel structure, membrane structure or even the interior environment," he added.

Because it is a completely enclosed swimming center, there arose the potential problem of high humidity.

"With sustainable development as its design principle, a strict temperature and humidity control system was built with recycled hot water to supply an air-conditioning system in the living area and the swimming pool," Sun said.

"In addition, other cooling methods, such as outdoor and indoor air recycling systems, solar energy and double-deck ventilation devices successfully maintain comfortable temperatures and stable humidity of between 50 and 60 percent."

The venue will be able to seat 17,000 spectators with 6,000 permanent and 11,000 temporary seats.

Some human-oriented facilities have also been taken into consideration.

"A floor heating system has been used to ensure the floor isn't cold and the athletes can walk comfortably from the warm-up pool to the competition pool," said Kang Wei, president of the National Aquatics Center Company Ltd, the venue's owner.

"For the spectators, we will set up more water selling spots than other venues to ensure people do not rush for water during the break. The toilets will also be very close to the stands."

A colorful box

Thanks to LED lights inside the center, the Water Cube will appear more than just blue in color. This week, with the lights adjusted, the box turned green, red and pink at night.

"Colorful lights will be turned on during the holidays and during the Games," Kang said.

The first test events, the China Open Swimming Competition, began yesterday.

The event has attracted 376 swimmers from 36 countries and regions.

(China Daily February 2, 2008)