Newspaper article International Herald Tribune

The Power of a Hot Body

Newspaper article International Herald Tribune

The Power of a Hot Body

Article excerpt

What could be more selfless than sharing heat from the tiny campfires in your cells?

As I waited with a throng of Parisians in the Rambuteau Metro station on a blustery day, my frozen toes finally began to thaw. Alone we may have shivered, but together we brewed so much body heat that people began unbuttoning their coats. We might have been penguins crowding for warmth. Idly mingling, a human body radiates about 100 watts of excess heat, which can add up fast in confined spaces.

Heat also loomed from the friction of trains on the tracks, and seeped from the deep maze of tunnels, raising the platform temperature to around 70 degrees Fahrenheit, almost a geothermal spa. As people clambered on and off trains, and trickled up and down the staircases to Rue Beaubourg, their haste kept the communal den toasty.

Geothermal warmth may abound in volcanic Iceland, but it's not easy to come by in central Paris. So why waste it? Savvy architects from Paris Habitat decided to borrow the surplus energy from so many human bodies and use it to supply radiant under-floor heating for 17 apartments in a nearby public housing project, which happens to share an unused stairwell with the metro station. Otherwise the free heat would be lost by the end of the morning's rush hour.

Appealing as the design may be, it isn't feasible throughout Paris without retrofitting buildings and Metro stops, which would be costly. But it is proving successful elsewhere. There's Minnesota's monument to capitalism, the huge Mall of America, where even on subzero winter days the indoor temperature skirts 70 from combined body heat, light fixtures and sunlight cascading through ceiling windows.

Or consider Stockholm's busy hub, Central Station, where engineers harness the body heat issuing from 250,000 rail travelers to warm the 13-story Kungsbrohuset office building 100 yards away. Under the voluminous roof of the station, people donate their 100 watts of surplus natural heat, but many are also bustling around the shops and buying things, emitting even more energy.

This ultra green body-heat design works well in Sweden, a land of soaring fuel costs, hard winters and ecologically minded citizens. First, the station's ventilation system captures the commuters' body heat, which it uses to warm water in underground tanks. From there, the hot water is pumped to Kungsbrohuset's heating pipes, which ends up saving 25 percent on energy bills.

Kungsbrohuset's design has other sustainable elements as well. The windows are angled to let sunlight flood in, but not heat in the summer. …

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