This seems like a good time to raise that pumping heat into the surrounding soil doesn't work forever. For a home aircon it might be OK, however the London Tub

This seems like a good time to raise that pumping heat into the surrounding soil doesn't work forever. For a home aircon it might be OK, however the London Tube is having serious problems with this where many of the tube tunnels have warmed from around 14C to nearly 30C (57-86F) over the last 100 years. Leaving many of them quite hot. The surrounding ground around the tubes has warmed up and effectively heat soaked. Heat is generated from a number of sources including diesel engines however apparently a large portion of the heat is generated by braking for each station. They've improved that by using electric regenerative braking now which in some cases can dump the power into other trains that are accelerating at the same time. Some of the newer trains now also have air conditioning inside the trains, while that helps inside the train it doesn't help outside the train where even more heat is dumped. Anyway for more information there is a good youtube video I can't find right now, so you could read this instead: https://www.forbes.com/sites/lauriewinkless/2017/06/22/sweating-on-the-underground-why-are-tube-tunnels-so-hot/#3aaca8cd5234 https://www.forbes.com/sites/lauriewinkless/2017/06/22/sweat... https://www.ianvisits.co.uk/blog/2017/06/10/cooling-the-tube-engineering-heat-out-of-the-underground/ https://www.ianvisits.co.uk/blog/2017/06/10/cooling-the-tube... https://en.wikipedia.org/wiki/London_Underground_cooling https://en.wikipedia.org/wiki/London_Underground_cooling