Body heat already warms the station itself, but the surplus, currently let out into the air, will be redirected to provide as much as 15 per cent of the heating in a planned 4,000-sq-m office building, real estate firm Jernhusen said.

'We had a look at it and thought, 'We might actually be able to use this',' said Mr Karl Sundholm, project leader at Jernhusen, which owns the station.

'This feels good. Instead of just airing the leftover heat out, we try to make use of it.'

Jernhusen markets the building as 'environment-smart' and aims for its energy consumption to be half that of a corresponding building.

The bodily warmth from the central station will be redirected to heat up water. The investment will be around 200,000 Swedish kroners (S$45,000), Mr Sundholm said.

'The ventilator aggregates are already there, and even some of the pipes. All we need to do is complement with a few pumps and pipes,' he said.

REUTERS