Body heat used to warm office

Imagine using the body heat of commuters to heat up an office. This would be a very useful step; imagine harnessing the energy of a large crowd and using this to effectively save other means of generating energy. The technology described is fairly simple, using pumps, pipes, and ventilator aggregates; the crowd being used to generate energy is already there through the commuters in a Swedish train station. Read the story:

A Swedish state-owned firm has found a cheap, eco-friendly source of energy to warm one of its offices: body heat from a quarter million commuters steaming through Stockholm's central train station.
Body heat already warms the station itself but the surplus, currently let out in thin air, will be redirected to provide as much as 15 percent of the heating in a planned 4,000 square meter office building, real estate firm Jernhusen said.