Paris flats to be heated by warm Metro passengers

As London gets back to normal after a 24-hour Tube strike expected to cost the city almost £50m, it emerges that Parisians have found a novel way to use their underground rail network to actually save money.

A block of low-income flats in the middle of the city, near the Centre Pompidou, is to be heated with warmth generated by Metro trains and passengers - a neat use of what would otherwise be wasted energy.

Paris Habitat-OPH, owners of the apartments, will capitalise on the year-round 14-20ºC average temperature of Rambuteau station to heat water in specially-laid pipes. The water will then circulate through the flats’ underfloor heating system.

Dr Patrick James, an expert from Southampton University, told the Guardian: "It's a huge source of free, zero-carbon heat so it couldn't make more sense. I guess the only problem will be if there's a train strike in the winter, in which case they'll need a back-up source of heat."

While the idea is novel, it is not unique: the same system is used in Stockholm's central station, heating a nearby office block.

Not only is the scheme impeccably green, it will also save money – a win-win situation. But there is one catch for anybody hoping to replicate it in the UK: the cost of tunnelling down to find the underground is prohibitively expensive.

The Paris scheme can only go ahead – with construction starting next year – because it will make use of an existing, disused, stairwell. Pipes will run between the station and the flats using this route. ·