> Cooling the stations is not an engineering challenge. Installing and operating huge chillers is a solved problem. Not correct in context. You cannot successf

> Cooling the stations is not an engineering challenge. Installing and operating huge chillers is a solved problem. Not correct in context. You cannot successfully chill air without having a place to vent the resulting waste heat. Where, in deep tube lines, to vent the waste heat, is _not_ a solved problem. It _is_ an unsolved engineering challenge. The heat has been accumulating there for decades. As detailed here https://en.wikipedia.org/wiki/London_Underground_cooling https://en.wikipedia.org/wiki/London_Underground_cooling https://news.ycombinator.com/item?id=38364027 https://news.ycombinator.com/item?id=38364027 https://news.ycombinator.com/item?id=38363476 https://news.ycombinator.com/item?id=38363476