| Title | Environmental Impacts of Low Enthalpy Direct Uses - the Geothermal District Heating Case |
|---|---|
| Authors | Pierre Ungemach |
| Year | 2008 |
| Conference | International Summer School |
| Keywords | |
| Abstract | Reclamation of low grade geothermal heat deposits is most often achieved by extracting the heat stored in tepid and hot water sources, within the 10°C to 100°C temperature range, either straightforwardly or via heat exchangers. It addresses a wide spectrum of so-called direct uses, from balneological/medicinal/recreational, agricultural, industrial process heat, space heating, heat pump, and, last but not least, district heating utilisations. In most instances, geothermal heat is mined from an exhaustible source, which arises the problematic of reservoir life and sustainable reservoir development and management. The foregoing portray an overall context which is resource specific, site specific and process specific. The forthcoming will focus on the geothermal district heating segment, deemed illustrative of a key development issue, as it challenges the most severe environmental constraints and regulatory frameworks, prevailing in sensitive, densely populated (sub)urban environments. In so doing it is assumed: (i) that a Mining Law exists, categorising low enthalpy fluids as a mineral resource, thus subject to the Mining Code, and to awarding exploration/exploitation concessions/leases by an ad-hoc State Mining Authority, according to the scheme depicted in Fig. 1 (Ungemach and Ventre, 1997); (ii) that disposal of geothermal (liquid, gaseous, solid) waste complies with the Environmental Law and regulatory framework in force, with respect to toxic and, environmentally sensitive, gas abatement, solid filtering, heat depleted brine processing and (re)injection, safety, noise and clean air tolerance thresholds; (iii) that the previous formatting encompasses the whole of the well exploratory/development, drilling/completion/exploitation, and abandonment sequence. The foregoing are illustrated by the Paris Basin district heating commissioning/exploitation/monitoring/abandonment protocols, which benefit from a twenty five year backup experience and thirty four heating grids operating to date. |