Directional drilling?

The advantages are:

The capital costs from 0,1 EUR pro kWh for the storage
Less use of filling martial, graut, lower cost
No insulation material necessary in top of storage
Drilling length up to 300 m
Use of standard pipe/hose, lower cost
Storage can be built under already used perimeters, building, parking lots sun collector areas etc.
Lower impact during construction, less mud and handling of surplus soil
Faster than conventional drilling.
It is possible to avoided layers with ground water, stone baring layers etc.
Directional drilling is applicable in the range of 60-300 horizontally and 2-40 m vertically.