- High initial capital required - funding
- Political consensus (highly desirable)
- Nation wide development (cascading use)
- Site location
- Unjustified fears and misconceptions (about smells, earthquakes, water contamination…)
- Super deep well drilling developments
- Short-cut flows and deep seepage from area
- Possible ground subsidence (risk reduced by re-injection and site location)
- Micro-seismic effects during initial hydro fracture phase
- Solid waste disposal (construction phase)
- Thermal pollution (eliminated by re-injection)
Smells are normally associated with natural geothermal fields (H2S, NH3, CH4). Gaseous emission can be prevented. Eventually this may only be an issue in the drilling stage.
What is pumped up is re-injected down
All activity takes place well below the water table.
Micro-seismic activity is manifested mainly by low frequency noise (like in a far away quarry). This is noticed in the initial fracturing stages, and usually only by instruments.
The bore diameter is negligible compared to the rock formation. Earthquakes were never caused by geothermal utilization.
Ground subsidence (few cm) occurs when non porous igneous rock has to be fractured heavily and at relatively shallow depths, or where naturally hot-aquifers are heavily depleted. It is never catastrophic but very gradual (detectable over a number of years). It is reduced by re-injection of fluids. Its effects could be eliminated altogether by developing the field partly under the seabed.