Urban retrofits

How to make a city green -- without tearing it down

By Michael Fitzgerald
June 28, 2009
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As the world warms, it’s also getting more urban - more than half the world’s population now lives in and around cities. So when it comes to sustainable living, cities pose a growing challenge.

In one sense, cities have a lot going for them - good public transit, efficient power distribution, and a density that means you often don’t need cars to get around. Plus, living and working in tall buildings rather than spread-out exurbs saves a huge amount of energy per person. But cities also have one big problem: they’re already built. We can invent all the green technologies we like, but we can’t tear down blocks full of drafty old structures and start from scratch - to say nothing of the networks of streets lined with wiring, pipes, and tunnels that might be decades, even centuries old. The problem is especially acute in older cities such as Boston.

So how to improve the cities we’ve got? The answer: retrofitting. In the past several years, engineers, urban planners, and entrepreneurs have come up with imaginative new ways to take what we now know about living more energy-efficiently, and grafting that technology onto cities without clearing away what’s already there. Here are some ideas already being tried, including some that might work in Boston.

Bicycles use sweat power, not fossil-fuel power, which means they’re a favorite of green-transit planners everywhere. But unless you’re a dedicated cyclist, you don’t always have your bike with you when you need to make a quick jaunt. Enter bicycle-sharing programs, which offer racks of public bikes that can be used for one-way rides around town. Though such programs have mostly failed over the last 20 years, France is starting to break through: in 2005, the city of Lyon deployed a successful program, and Paris then adapted it. A one-year pass in Paris (about $40) buys access to 20,000 bicycles available at 1,500 stations throughout the city. The bikes cost nothing for the first 30 minutes, after which a sliding scale of rates apply. Some two dozen cities, notably Barcelona and Washington, D.C., now offer some sort of bike-sharing program, often subsidized by advertising.

The power grid that delivers our electricity might be complex, but it’s not too bright. Think of it as that phone in grandma’s house - you know, the one that doesn’t give you caller ID, let alone receive text messages or video of your friend’s graduation party. If it were smart, it could communicate with your house, and vice versa. At the household level, this means you’d know exactly which appliances are hogging power, and how to manage them more efficiently. At the city level, a smarter grid could change how power gets consumed, in part by charging more money at high-demand times. You could even sell excess renewable power back to the grid. A few pioneering cities and utilities already have smart grids under way - in Boulder, Colo., the utility Xcel Energy is piloting smart meters that let consumers see up-to-the-second statistics on their power usage, and change temperature and other usage settings automatically.

Masdar City, an experimental “post-petroleum” city being built in Abu Dhabi, will feature the world’s first city-scale personal rapid transit project - a small underground tunnel system of battery-powered four-person vehicles, or podcars. Similar schemes are being tried at London’s Heathrow Airport and in a test in Uppsala, Sweden. All these podcars use wheels, which means they need tracks, so cities like Boston might be better served by magnetic levitation technology, similar to that used in high-speed trains. Unimodal Systems, a California company, has built a prototype mag-lev podcar system at NASA’s Ames Research Center, and it says the system is light enough to use utility poles as support. It’s been a long time coming for podcars - a podcar project at West Virginia University in Morgantown was funded during the Nixon administration, and is still shuttling students around campus.

As cities sprout new alternative transit ideas, like car-share companies and bike-sharing services, one problem looms: they don’t necessarily connect very well, especially as you get farther away from downtown. Well-planned small hubs could link these services, much the way urban train stations connect buses, subways, and taxi stands. Bremen, Germany, has created a system that connects bus and train stops, bikes, taxis, and car-sharing services, so residents can get around more easily without owning a car. An integrated payment system means they can make the whole journey with just one card, or even a cellphone. Other “mobility hubs” are being organized in cities such as Washington, Sao Paolo, Cape Town, and Chennai, India. Proponents also envision online smart maps that link every means of publicly available transit, with GPS-based estimates of travel time.

Efficient new buildings are great, but not if you need to knock down existing buildings to construct them. Instead, developers are starting to “re-skin” older concrete buildings, adding new thermal covers to reverse concrete’s normal tendency to capture heat in summer and release it in winter. Careful re-skinning might cut energy usage by as much as half, and the new skin can also house better pipes, ducts, and cables. Berlin is leading the way here, re-skinning a complex of 40-year-old buildings with 16,000 apartments. An office building in Manchester, England, was reskinned with photovoltaic cells. Even iconic buildings can be re-skinned, in a sense: the Empire State Building is being retrofitted from the inside, adding triple-paned windows and mechanical updates that should yield $4.4 million in annual energy savings without changing its appearance. One problem with these projects is that they are hard to repeat, so a Toronto nonprofit called Zerofootprint has created a $1 million prize for re-skinning designs that can be easily scaled up in urban areas.

For homeowners who want to switch to solar power, one of the biggest obstacles is the cost: an average of $25,000 for a set of roof panels. Cities like San Francisco sweeten federal subsidies to cut these costs by about half, but that’s still a lot of money. Now private companies like SolarCity and SunRun give consumers a different way to get solar power: for a down payment of as little as $1,000, homeowners can “lease” panels for a monthly fee based on electricity usage. While these installers have focused mostly on the sunny West Coast, SunRun also started a panel-leasing program in Massachusetts earlier this year.

Michael Fitzgerald is a writer living in Millis.