[TheCoelacanth]

> 20 feet underground will be about 50 F year-round

Is that the case in India? I was under the impression that while underground temperature is consistent across seasons, it does vary considerably across climates, with warmer climates generally having higher underground temperatures. For example, while much of the central US has underground temperatures around 50F, southern Florida, California and Arizona have areas with temperatures in the upper-70s[1].

[1] https://www.builditsolar.com/Projects/Cooling/EarthTemperatu...

[kibwen]

I can believe the ground temperature is higher nearer to the equator. At the same time, you don't need the ground temperature to be very low, just low enough for the heat exchanger to function. Alternatively, you can dig deeper until you hit a lower temperature.