Isegoria

Rapidly growing China is looking to build Pop-Up Cities, “bright green metropolises” that don’t make the mistakes of existing cities:

These new megacities could evolve into sprawling, polluting megaslums. Or they could define a new species of world city. Unlike New York or London, they are blank slates — less affluent, perhaps, but also free from legacy designs and technologies tailored to the world of the 19th and 20th centuries. That is a huge advantage. It took Boston 20 years and more than $14 billion just to reroute a freeway underground. New York can hardly install a second network of water pipes. Most of Los Angeles is too spread out for fast public transit or combined heat and power plants. And because these cities are so isolated from agricultural land, most of the food that locals eat gets shipped hundreds of miles. “Shanghai today is making 90 percent of the mistakes that American cities made,” Burdett argues — spreading out, building up single-family homes, replacing naturally mixed-use neighborhoods with isolated zones for living, shopping, and working, and connecting it all with car travel. But fixing these problems is still possible.

Dongtan, outside of Shanghai, is meant to be such a green city:

Their first decision was big. Dongtan needed more people. Way more. Shanghai’s planning bureau figured 50,000 people should live on the site — they assumed a green island should not be crowded — and the other international architects had agreed, drafting Dongtan as an American-style suburb with low-rise condos scattered across the plot and lots of lawns and parks in between. “It’s all very nice to have little houses in a green field,” Gutierrez says. But that would be an environmental disaster. If neighborhoods are spread out, then people need cars to get around. If population is low, then public transportation is a money loser.

But how many more people? Double? Triple? The team found research on energy consumption in cities around the world, plotted on a curve according to population density. Up to about 50 residents per acre, roughly equivalent to Stockholm or Copenhagen, per capita energy use falls fast. People walk and bike more, public transit makes economic sense, and there are ways to make heating and cooling more efficient. But then the curve flattens out. Pack in 120 people per acre, like Singapore, or 300 people, like Hong Kong, and the energy savings are negligible. Dongtan, the team decided, should try to hit that sweet spot around Stockholm.

Next, they had to figure out how high to build. A density rate of 50 people per acre could mean a lot of low buildings, or a handful of skyscrapers, or something in between. Here, the land made the decision for them. Dongtan’s soil is squishy. Any building taller than about eight stories would need expensive work at the foundation to keep it upright. To give the place some variety and open up paths for summer wind and natural light, they settled on a range of four to eight stories across the city. Then, using CAD software, they started dropping blocks of buildings on the site and counting heads.

The results were startling. They could bump up Dongtan’s population 10 times, to 500,000, and still build on a smaller share of the site than any of the other planners had suggested, leaving 65 percent of the land open for farms, parks, and wildlife habitat. A rough outline of the city, a real eco-city, began to take shape: a reasonably dense urban middle, with smart breaks for green space, all surrounded by farms, parks, and unspoiled wetland. Instead of sprawling out, the city would grow in a line along a public transit corridor.

That was the easy part. From there they needed to design ways to make efficient use of resources:

A power scheme started to take shape. Dongtan’s plant would burn plant matter to drive a steam turbine and generate electricity. What to burn, though? They could have planted miscanthus, a tall, feathery grass. It sprouts fast and burns clean. But if Arup planted miscanthus fields, it would sacrifice lots of land to a single purpose. Then it struck them: rice husks. China already grows mountains of rice, and farmers just trash the husks. Dongtan could take a useless byproduct and use it to light the city.

Instead of building the plant far away and out of sight, Arup would put it up near the city center, capture waste heat, and pipe it throughout the town. With good insulation and smart design, the plant could heat and cool every building in Dongtan. “We can get something like 80 percent efficiency in our fuel conversion,” says Chris Twinn, the Dongtan team’s energy chief. “The Prius is probably only 20 percent efficient. The rest is wasted. Why are we satisfied with that?”

I’m not sure how burning rice husks for energy will work out, but piping heat makes good sense in a dense, urban environment — as long as you maintain the pipes.

Some of the additional ideas seem perfectly reasonable; some do not:

Arup investigated hollowing out the hills at the edge of the city and installing underground “plant factories” — stacked trays of organic crops, growing under solar-powered LEDs, that seem to yield as much as six times more produce per acre than conventional farming. Arup would run twin water networks throughout the city: one that supplies drinking water to kitchens and another that supplies treated waste water for toilet flushing and farm irrigation. Trucks delivering goods from across China would park at consolidation warehouses on the edge of the city, then load up shared, zero- emission delivery trucks to reduce traffic and save gas. Waste would be either recycled or gasified for energy, and the captured heat would be converted into more power; no more than 10 percent of the city’s trash would be permitted to end up as landfill. To invite in cooling summer breezes, block winter winds, and reduce demand for heat and air-conditioning, they would position trees strategically and persuade the client to twist the city grid slightly off a traditional north-south axis (a feng shui idea that has become an almost inviolable rule of Chinese city planning).

I’d love to see an analysis of the costs and benefits of some of these ideas.