PowerSwitch

Just heard this on radio concerning old mines under Glasgow.

The mines have refilled with water which is being heated mostly from the sun and from below.

Expert reckoned this could provide about 40% of Glagow's space heating requirements for approx. 100 years.

not really geothermal as heatpumps would have to be used. Expensive and high maintenance probably.

My last comment has been annoying me all week. For completeness, I believe this is technically classed as geothermal even though the water's mostly heated from the sun (in the recent sense) rather than the earth's centre. And the heatpumps just use electricity to efficiently convert the heat stored in the water.

In years gone by "geothermal" was generaly understood to mean extracting heat from relatively deep underground at a high enough temperature to be directly used for space heating, or even to raise steam for electricity generation.

These days, geothermal is increasingly used to describe heat pump systems that use very low grade heat from near the surafce. A liitle of this heat presumably emerges from deep underground, but most is from sunlight and sun-warmed air on the surface.

I am seriously sceptical about any proposition involving the words "Glasgow" and "sun".