4 nov 07 | The Sunday Times

City Salvation

By Hugh Pearman

From pigs grazing on the roof to colossal solar power stations, future buildings will be clean and self-sustaining. Hugh Pearman gives the low-down on high-rise eco-habitats and looks at the greening of existing cities

We are getting tantalizingly close to the holy grail of human habitation. Since the future for all of us is urban - more, bigger, taller, denser cities - the challenge is this: can we make those cities self-sustaining, able to generate all their own carbon-neutral power, harvest and conserve all their water, produce good food efficiently, recycle all their own waste? Can the 21st century city be the salvation of the planet, relieving pressure on natural resources, as James Lovelock has suggested? The good news is that it can be. But we're not quite there yet.

The technology we need already exists. It needs refining, and above all applying. But we're well on the way. Photovoltaic panels, which convert the energy of daylight into electricity, have been around since the early 1960s. They have steadily got better and cheaper and are now close to being a mass market product. Wind power is almost as old as humanity (think sailing ships and windmills), but there have been huge strides recently in the efficiency of wind turbines. Increasingly, they will sprout in towns and cities as well as remote moorland and estuaries. In Seville, there is already a solar power station that drives power-generating steam turbines, just as coal, gas and nuclear power stations do. We're still not too clever when it comes to storing such intermittently produced power. But that is being worked on too.

Invisible undersea power stations powered by pistons responding to the swell of the oceans are now being tested. In the UK, the previously isolated Orkney Islands have become the centre of this emerging technology. All these things will feed clean power to the cities of the near future.

And for the cities of today, it is already possible to build a self-sufficient skyscraper that can harvest the sun and wind to generate all the power it needs to sustain itself, while around its base is all you need to store the power, recycle the waste, clean its water and so forth. The trouble is that a true zero-energy 1,000ft tower could cost 10 times as much as a conventional one. But ease targets slightly and it is affordable. Thus the world's most sustainable skyscraper to date, the Pearl River Tower, is going up right now, in Guangzhou, China, for completion in 2009.

Designed by Gordon Gill and Adrian Smith, it started out as a competition project. It won, but economic reality then intervened. The tower was not allowed its own power plant supplied by waste methane. But by taking a lot of its ideas - such as turning the facades into huge sculpted air intakes for integral wind turbines, and also into a power-generating photovoltaic skin - the Pearl River Tower will use at least 60% less energy than its conventional equivalent. And remarkably, the extra capital cost will be recouped in lower running costs in just five years. The shrewd Chinese like that.

China knows well enough the consequences of all the coal-fired power stations it is building and all the cars that are replacing bicycles, particularly as the 2008 Olympics are threatening to take place in a toxic chemical atmosphere. Is there hope? Possibly, in the form of the planned eco-city of Dongtan, at the mouth of the Yangtze.

Dongtan is designed by the engineers Arup as the world's first true eco-city. An overspill of Shanghai, it will be sited on 8,600 hectares of agricultural land amid sensitive wetlands. Yet its impact on the area will, they say, be pretty close to neutral.

It will generate all its own power from sun, wind, water, biofuels and recycled waste. Food will come from double-decker organic farms, public transport will be hydrogen-powered and zero-emission, while electricity will be from a hydroelectric plant (of the kind, one hopes, that does not destroy too much wildlife).

Dongtan will be high-density but resolutely low-rise. Buildings will bristle with vegetation. Wind turbines and solar panels will be everywhere. With all its waterways, Dongtan will be a modern Venice, the prototype for three more Chinese cities. But how much more difficult will it be to build a high-rise eco-city, for instance, in the desert?

Abu Dhabi, which has much more oil wealth than Dubai, turned to Britain's Norman Foster to design its eco-city. And Foster looked to Yemen and its extraordinary ancient walled cities of tall, tightly packed mud-brick towers for inspiration for the new planned city of Masdar, which will cover 6 million square metres. As in Dongtan, zero-emission public transport will be a short walk from everyone's front door. But where will all the power come from? Abu Dhabi gets a lot of sun and wind, so a vast photovoltaic solar-power plant is planned, plus lots of wind farms. As with Yemen's ancient cities, agriculture will take place in surrounding plantations. Where they will get all the water remains a mystery. Plus they will have to find ways to store the power generated in daytime. It's not easy but it's doable.

Another international superstar, Rotterdam's Rem Koolhaas, got to the starting block first with a historically inspired city for the emirate of Ras al Khaimah. The RAK Gateway, as it is known, suggests an alternative to the mad sprawl of Dubai and other Gulf states.

New eco-settlements are all very well, but half of us live in existing cities that are far from sustainable. We're not going to close them down. So ingenuity will be needed to improve them.

Among existing cities the shining example is Curitiba in Brazil, master planned since the late 1960s by a visionary architect-planner, Jaime Lerner. As the rest of the urban world tore itself apart with ring roads and motorways, Lerner took an unfashionable, balanced approach to the car. Maybe if public transport was really good, there would be less need for cars. And maybe where lots of people gathered on foot, cars could be kept out. So it has proved.

The value of the Curitiba experiment is the pioneering way it anticipated the needs of cities in the early 21st century. And it shows that it's never too late to make changes. The city could not afford an expensive metro, so instead it made buses so frequent and regular that they might as well be trains.

Closer to home, David Marks and Julia Barfield, inventors of the London Eye, have come up with a neat urban wind-generating device, the Beacon, which they foresee dotted around on virtually every street corner. Meanwhile, we could all save ourselves shed-loads of money and carbon if we could afford to fit solar water heaters and photovoltaic panels to all our existing houses. If our government was serious about its carbon targets, it would introduce far more generous tax breaks to encourage us to do just that. Dongtan will very probably happen, but at the same time city sprawl of many times its size, and none of its eco-credentials, will continue to mushroom all round Shanghai and cities like it. In India there's an eco-city initiative under way in Bangalore. That's it, for an entire continent. And what is Russia doing? Putin-land, rich in oil and gas, is plonking down conventional skyscrapers to rival Dubai.

So we have a way to go. But here's a thought: it seems to me that eco-cities will be a lot nicer to live in than where we live now, and we'll all want to flock to them. In the end, consumers as much as politicians may demand truly green cities.