Neighboring heating and cooling zones can also affect one another to create complex and unpredictable feedback loops, especially as the number of zones increases. United Technologies’ J. Michael McQuade recalls what happened when his company designed what was supposed to be an intelligent heating, ventilation, and air-conditioning management system for a new building in Paris. The system was designed to coördinate 3,000 different zones. “When that building was first put together, it was a significant energy consumer, and it took a revamp of the integrated control systems to get it right,” McQuade says.
If zero-emissions buildings are to be economical, Scofield says, the designs will have work from the start. “If you don’t get it right,” he says, pointing to the fiasco at Oberlin, “every correction you make is so much more costly than getting it right the first time.”
Masdar City will be raised on concrete stilts to make room for a personal rapid-transit (PRT) system that will replace buses and trains with smaller vehicles designed for four people. Masdar’s planners expect the system to use less energy than conventional mass transit, and they say it will be more convenient, too.
In a PRT system, several small vehicles, often called pods, are kept waiting at each station. An individual or a small group boards one and selects a destination; the pod proceeds automatically to the destination without stopping. In a typical design, each vehicle resembles a battery-powered golf cart, only it’s completely enclosed and somewhat bigger–and it lacks a steering wheel. The vehicle follows a track, which is connected to stations by on-ramps and off-ramps, and a computer controls how the pods enter and exit the stations: the ramps allow individual pods to make stops while others continue along the main track at top speeds. Simulations suggest that the systems could run with as little as half a second between vehicles.
But although PRTs look promising, they haven’t caught on. That’s in part because an early PRT-like system built in the 1970s in Morgantown, WV, gave the idea a bad name, says Jerry Schneider, an emeritus professor of urban planning and civil engineering at the University of Washington in Seattle and a longtime advocate of PRTs. “People would get on the vehicles and they wouldn’t stop,” Schneider says of the system, a transit line with automated cars for about 20 people. Technology has improved since then, he says, but there hasn’t been a significant real-world demonstration of the updated systems.
Two demonstration programs are on the way. The first, which will transport passengers to a new terminal at Heathrow International Airport near London, will open later this year. Tests of that system are already under way. And the first stage of the system at Masdar City, to be built by the Dutch firm 2GetThere, is scheduled to be in place for the opening of the Masdar Institute this fall.
The Test Bed
Sameer Abu-Zaid isn’t breaking a sweat. It’s 39 °C with 74 percent humidity, but he says it’s a nice day–much cooler than the summer in Abu Dhabi, when temperatures can reach 49 °C. Abu-Zaid, who’s originally from Jordan and was most recently a manager at a semiconductor equipment manufacturer in Silicon Valley, will manage Masdar City’s power and distribution infrastructure. “All of these modules have been tested at the factories,” he says as he gives a tour of one of the first visible signs of the city, a test site where he’s putting 41 arrays of solar panels from various manufacturers through their paces. “But they have been tested under standard test conditions: 1,000 watts per meter squared, 25 °C. Nice air-conditioned space. It is totally different here.”
Dust from the desert quickly coats the panels, effectively dimming the light that reaches them. Abu-Zaid has learned that just four months of dust reduces the output of the solar arrays by more than 20 percent–information he’ll use to decide how often to wash the panels, balancing power loss against water consumption.