I wonder if a water well used for lawn irrigation could be converted to geothermal?
It's a low-maintenance system, says Kivioja. The company uses cheap, low-quality sand that's been rejected by builders instead of high quality river-sand which is used in vast quantities for construction, leading to a global shortage.
"There's no wear and tear involved with the [heat exchange] pipes and the sand. The fan is the only moving part and it's easy to replace if necessary," says Kivioja.
Sand is a very effective medium for retaining heat over a long period, storing power for months at a time. And there are other benefits too. "The sand has a very long lifetime: it can heat up and cool off any number of times," says Kivioja. "It will get denser after a while so needs less space. At that point we can add more sand."