Mine water as a Renewable Energy Resource - Promoscene

Minewater as a Renewable Energy Resource
Hydrothermal modelling revealed results are very site
dependent. The Freyming-Merlebach mine was selected
for further analysis. Of the 8 shafts two (Vouters2 and
Cuvelette-Nord) reach the lowest gallery at 1250m depth.
The modelling for a single shaft suggests that the water
temperature is strongly dependent on the ratio between
the shaft diameter and the height of the water column. For
a 7.5 m diameter shaft (Vouters2) a steady temperature is
established along the water column, while for a diameter
1m is used
Due to variable hydraulic losses in the network, the
use of 3 separate types of pump, for production,
circulation and re-injection.
For heat exchangers and pumps, titanium components
instead of stainless steel (notably 316L type) due to the
presence of NaCl and other chloride brine.
PVC and high density polyethylene coated pipes for
mine water transportation.
Ongoing monitoring of water level and the installation
of a stand-by pump in order to prevent accidental
contamination of the sandstone aquifer
Chemical monitoring of the mine water (at least every
3 months).
Cost benefit analysis
In order for the capital investment and likely return for
initiating a mine water project to stand a chance of being
viable the following elements are necessary:
•
Close proximity of the mine to the heat production
plant (within 1 km)
• Heat demand ≥ 40 GWht
per year
•
The use of existing shafts (no new well drilling)
Table 2.2 gives some indicative costs.
Investment Costs (M€)
Heating plant and geothermal loop assuming pre-existing infrastructures 0.7
Shaft equipment 1
Piping for new installations for providing medium temperature hot water 4
Total 5.7
Maintenance Costs/year
Equipment 0.1
Energy 0.6
Contingency (20%) 0.15
Total 0.85
Income (assuming a sale price of 45€/MWh and a 40GWh installation) 1.8