Look up for answers to our urban problems

April 20, 2002

The trees along Cherry Creek are blossoming in the spring breezes, so barring the stray snowstorm or two, winter's over. I am pleased to tell you that I never had to turn the heat on at home.

My high-rise condominium near downtown has heating and cooling for the whole building, which works by keeping a loop of circulating water at a steady temperature. Individual units have heat pumps, which take energy from the water loop to warm my air when it's cold and I turn on the heat, and put it back when I turn on the air-conditioning.

In a brand-new energy-efficient building, though, it just never got cold enough inside for me to flip the switch to "heat." Early one Saturday morning, when it was barely zero outside, the indoor temperature dropped to 65 degrees or so and I put on a sweater. But even then, by mid-morning the A/C was coming on occasionally.

Actually the way the system works is neater than that. When my sunny southeast corner is too warm, and my heat pump is putting my BTUs into the water loop, the person living on the chilly northwest corner warms his home partly with my sunshine.

The energy bill for the building is $80,000 annually, but that's for 72 households, perhaps 100 people, plus three floors of retail, commercial and parking. My share comes to about $650 a year. I spent most of my adult life in outstate Minnesota, where our big drafty barn of a house averaged $350 a month in utility bills year-round.

I'd already been thinking about this when I ran across the claim by environmentalist Lester Brown that a modern wind turbine takes up a quarter of an acre and can generate $100,000 worth of energy a year.

Steve Roalstad of Xcel Energy confirms that a one-megawatt turbine can produce 2.5 million kilowatt-hours of electricity a year, in a suitably windy place, and its footprint is about a quarter-acre, though in a big wind farm the turbines have to be farther apart to minimize wind turbulence.

Well. My building occupies only a little more than a quarter-acre of ground. Does that mean we homeowners could put a one-meg turbine on the roof and be a net exporter of energy?

Practically speaking, no. The building isn't engineered for that kind of stress, zoning regulations would prohibit it, and living right under it would be noisy. There are windier places, too. But we command enough space to do it.

Here's another question. Could we feed ourselves on our quarter-acre? Julian Simon, in Ultimate Resource 2, cites the example of an Illinois produce farm, or perhaps I should say factory, that produces enough calories to feed from 500 to 1,000 people on barely more than an acre. Of course it takes artificial light (but theoretically we have energy to spare; see above).

It wouldn't make economic or ecological sense for urban apartment dwellers to be raising wheat and rice in their window boxes and chickens in the bathtub. The building wasn't designed for it, regulations prohibit it.

Yet if everybody as a matter of course raised what food they could indoors, and buildings were designed with that expectation, my 60 running feet of outside wall lined floor-to-10-foot ceiling with growing stuff could feed me and several other people. And if I'd grown up doing it, I'd know how to do that kind of intimate gardening, just as I grew up knowing how to cook.

It's interesting that fewer and fewer people do know how to cook, except for those who do it as a hobby just as others garden. The preparation of food is gradually being concentrated and automated, just as its production has been over the past century.

We're not crowded in our aerie. I know my next-door neighbors, but not everybody on my floor, though the number of units on a floor runs from four to eight. Now and again I meet someone on the elevator, about as often as I used to meet someone when I was outside raking leaves or shoveling Minnesota snow.

Yet our population density of 100 people on a quarter-acre is the astonishing equivalent of 250,000 per square mile. At that density, five times Manhattan's (or Monaco's) everybody in Denver could live in a narrow band of prime real estate along Cherry Creek and leave more than 100 square miles of what's now the city for park and wilderness (and factories and wind turbine farms, for that matter).

We're not going to do that, of course. Not everybody wants or needs to live in a high-rise building, no matter how private and spacious it is. I wouldn't if I had young children. But knowing that it is possible to do so -- and, in theory at least, to be self-sufficient in food and energy besides -- made me think that maybe the way to live lightly on the land is to get as far above it as possible.