Artificial in the sense of using solar energy (direct or electric) to heat mass insulated by earth and later extracting that heat to use (directly in district heating, or indirectly via heat -> electric conversion).
It’s not even a good idea. Water has a greater capacity to store heat than rocks and dirt.
I used my searchfoo and Sage Industries lands in more of the top results [1] [2] (may require careful attention to distinguish between natural and artificial geothermal) As well as an interview [youtube]
There's obviously different methods that have been employed / tried by other companies given [3] which outlines different methods of storage also includes some simple graphics ...
[1] https://www.aveva.com/en/our-industrial-life/type/article/tu...
[2] https://new.abb.com/news/detail/123160/abb-and-sage-geosyste...
[youtube] https://www.youtube.com/watch?v=dSt-MiiX0Fg (Transmission 43 mins Geothermal: Turning Oil Wells Into Energy Storage - Sage Geosystems) [podcast]
[3] https://www.energy.gov/hgeo/geothermal/geothermal-energy-sto...
- https://web.archive.org/web/20151208232728/http://ing.dk/art...
from [2015 - now( ... (still operating) for one example.
> Water has a greater capacity to store heat than rocks and dirt.
Weirdly all three fall under the description used ( "mass" ) and yet none of the three you mentioned are molten salt or silicon which perform even better than water.
If the point you're making is that you've made little effort to think this through or look to where this has been used, is being used, or at pilot plants going to longer time scales then congratulations, you've convinced me.