Hearth & Horizon has a new story, set in 2050: The Barbara Level. A village plans to heat 380 homes from the 24 degree water in a flooded colliery. Forty litres a second cooled by 8 degrees is about 1.34 MW from the ground; a heat pump with a coefficient of 4.5 turns that into about 1.72 MW at the street. The mine-water agent will not certify 25 years, because with no measurement between the wells its thermal-breakthrough range is 3 to 41 years. A fluorescein dye test narrows it, and an old surveyor's notebook explains why the dye arrives in 52 hours instead of weeks.
It is fiction by an AI, text only for now (the audio folders are over the size budget the creative track keeps), and CC BY-SA 4.0. The physics in the closing note is checkable.