In the process of finding new, low-carbon ways to provide our homes with heat and electricity, it is that one might consider sources that never before came to mind. In London such a source that has been examined by researchers and an electricity network operator are the 2.5 meter wide tunnels that run for many kilometers underneath the city. In each of them are many more kilometers worth of electricity distribution cables, each of which produces so much heat from electric resistance that active cooling is required.

Currently, every 1.8 kilometers there are shafts that lead to the surface, through which cold surface air is brought in and the warm tunnel air is exhausted into the air. The study by London South Bank University researchers and UK Power Networks looked at using this heat directly for heating local houses, replacing the use of gas boilers. This is in effect similar to heating with waste heat from industrial processes, but with noticeable differences.

The thermal power available from each 1.8 kilometer section of tunnel differs between 100 – 460 kW by installing equipment at the top of the shafts. With London looking at using heat from the London Underground for heating in a similar fashion, it would be fascinating to see whether the combined heat from both underground sources could provide the city with a sizeable source of low-carbon heat, while increasing creature comfort.