The excess body heat of commuters is used to heat a Stockholm office building.

At least not when someclever Swedish engineers figured out a wayto harness the excess body heat of thousands of busy commuters moving through Strockholm's Central Station to warm an entire office building.

The station's ventilation system includes heat exchangers that convert all that excess warmth into hot water. That water is then pumped to the nearby building, where it reportedly reduces energy costs by as much as 25%.