Another problem is the heat. Solar panels' dark surfaces absorb sunlight, raising their temperature to as much as 80 °C. The heat affects some solar-cell technologies more than others. Some of the most efficient solar panels also produce less power when they get hot. Because of these trade-offs, it's not obvious which panels will work best at the Masdar site, Abu-Zaid says. At the test plot, sensors track how much various panels heat up, how effective different cooling strategies are, and how power output changes with temperature, among other factors.

Such data gathering will continue as the city grows. Its designers and engineers will measure both energy consumption and energy production. They will track water consumption down to the individual fixture. At Masdar headquarters, designers may use RFID tags in security badges to gather information on the way ­people use water and energy. Such measurements will allow designers and engineers to compare the real performance of the city with the performance predicted by laboratory tests and simulations.

Reality Check
In the early 1960s, while the United States was rushing to put a man on the moon, electric fans and lights were still unheard-of in Abu Dhabi, according to Mohammed Al Fahim, a native of the emirate who has written a rare history of the place. That was not long after oil was discovered there, and well before the money started flowing. Al Fahim is from one of the wealthiest families in the area, yet both his sister and later his mother died because of a lack of basic health care. Now life expectancy in Abu Dhabi is virtually the same as in the United States. Before, the locals survived on water from brackish wells; now they drink fresh water from new desalination plants. The fragile and highly flammable palm-frond huts that housed most people have been replaced by gleaming glass-and-steel skyscrapers.

In many ways, the development of Abu Dhabi over the last few decades has reflected a frenetic effort to catch up with the developed world. Now, because of projects such as Masdar City, the emirate has a chance to race ahead. But in terms of urban development, it appears to be very much at a crossroads. In a few years, while the citizens of Masdar City will be pinching kilowatt-hours and using waterless urinals, go-carts will be screaming around a new track at a Ferrari theme park nearby, kids will be shrieking as they plummet down water slides at a new water park, and massive air conditioners will be roaring as they cool a new 700-store supermall. It's all part of a 2,500-hectare development that will dwarf the 640-hectare Masdar City.

The two developments are competing visions for the future of Abu Dhabi. If the Masdar project doesn't justify itself financially, it could indeed be just a green playground for the rich, an environmental theme park that is largely irrelevant for the development of sustainable technology on a broader scale. But if it is profitable, it could be a driving force for sustainable urban design. Then the oil-rich developers in the UAE and elsewhere might have a reason to build more green cities and skip constructing another ski slope in the desert. And developers worldwide will follow.

Kevin Bullis is Technology Review's Energy Editor.