London Underground is to start an experiment to use the heat trapped in the Northern Line tube tunnels to warm up homes on the surface.
The heat on the tube network is one of those perennial issues that crops up each summer and we get the usual lamentation about how difficult it is to deal with the deep level tunnels.
And indeed, it is difficult to effectively deal with them as there is limited capacity to remove the heat that is dumped into them by the trains. As I have noted in the past, various ideas are being deployed to either remove the heat, or better still — reduce the heat created by the trains in the first place.
However, one of the other side factors in removing heat from tunnels is what to do with it — just blow it into the sky, or can something more productive be done with that waste warmth?
That is what is now being tried — a communal heating system in Islington is to start pulling heat from a London Underground ventilation shaft. Along with heat from a nearby electricity sub-station, the two sources should provide heat for around 500 homes.
The scheme will be run through Islington Council’s Bunhill Heat and Power heat network, which already supplies more than 700 homes with heating. The network has 1.4 miles of pipes which carry the heat to local housing estates and a leisure centre. Heat from the London Underground will be captured and added to this network.
Now, it might occur to you that the tubes are hottest in summer, which is when the homes above are least likely to want heating up. As it happens, if the tunnel temperature can be reduced during the winter months, and maybe draw some of the stored latent heat out of the surrounding soil, then that builds up a buffer of capacity in the soil to absorb more heat in the summer.
So, extracting heat in winter, can indeed help reduce tunnel temperatures six months later.
This particular scheme is not likely to affect tunnel temperatures, as it is simply making use of an existing ventilation shaft. If that waste heat could be sold in the future — then it might make it economic to build more ventilation shafts, say in the City of London where offices can use the warmth to preheat hot water supplies (etc) and that would improve matters for the rest of us deep underground.