Picture this:
It’s 7:30 a.m. on a cold winter morning in downtown Stockholm and a sea of Swedish nationals are flooding Central Station to catch a train to work. Thanks to the busy shops and restaurants and the body heat being generated by the 250,000 commuters, the station is nice and toasty. Well, this heat used to be lost by the time the morning rush hour ended. Now, engineers have learned a way to harness it and transfer it to a newly refurbished office building down the block.
Says Karl Sundholm, a project manager at Jernhusen, a Stockholm real estate company, and one of the creators of this new system:
“They’re cheap and renewable…this is old technology, but used in a new way…It’s just pipes, water and pumps, but we haven’t heard of anyone else using this technology in this way before.”
Here’s how the system works:
The heat generated by the commuters is captured by the station’s ventilation system and used to heat water in underground tanks. The water is then pumped through pipes to the 13-story Kungbrohuset office building, roughly 100 yards away, where it is incorporated into the main heating system. The company expects to lower the energy costs in their office building by as much as 20% per year. And building the new heating system, including installing the necessary pumps and laying the underground pipes, only cost the firm about $30,000.
According to Sundholm:
“It pays for itself very quickly,” he adds. “And for a large building expected to cost several hundred million kronor to build, that’s not that much, especially since it will get 15% to 30% of its heat from the station.”
While drawing on a crumpled napkin during a coffee break two years ago Sundholm and his colleague Klas Johansson stumbled upon the idea:
“[The excess body heat] was previously just let out into the air. We thought we could do something with it,” says Johansson, head of Jernhusen’s environmental division. Both men are optimistic about the possible future uses of the technology: if they can figure out how to harness excess body heat on a mass scale, it could offer a significantly cheaper way to heat homes and reduce carbon emissions. Sundholm says the aim is to one day transfer body heat generated in residential areas at night to office buildings in the morning, and back again in the afternoon. “It could even be our next project.”
Obstacles:
One obstacle for total success is that the buildings need to be close together for the engineering to work:
“It is very hard to move low-temperature heat very far. The buildings would have to be very close together by 100 to 200 yards and they would have had to really do some magnificent engineering to make sure they were not using more energy to pump the hot air over in the train station into the office building,”
Says Lester Lane, director of Carnegie Mellon University’s Green Design Initiative. Lane also says:
“countries like the U.S., where energy is not as expensive as it is in Sweden, may not see the same financial benefits after investing in the insulation, pipes and pumps. Also, if people don’t regularly turn up to the train station or other high-density place where the energy is derived from, there won’t be enough body heat to fuel the heating systems”.
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