Energia geotérmica

Caderno Lab. Xeolóxico de Laxe Coruña. 2004. Vol. 29, pp. 97-117

Recursos geotérmicos e seu aproveitamento em Portugal Geothermal resources and applications in Portugal
MARTINS CARVALHO, J.1 e CARVALHO, M. R.1

Abstract Geothermal energy can be used under a number of several technologies, depending on its occurrence and namely on the configuration of consumers. Nowadays, geothermal operations can be divided in the following basic categories: (i) Electricity production, (ii) Direct uses, (iii) Geothermal heat pumps (GHP), and (iv) Hot Dry Rock and related Enhanced Geothermal Systems. The geology of Portugal determines different conditions for geothermal energy occurrences. In the mainland, where crystalline rocks outcrop over 60% of the area, thermal waters are related with active faulting. Twenty-seven springs have discharge temperatures between 25ºC and 75ºC and are used in balneotherapy. Three small, low enthalpy operations for direct use at existing hotels are operating normally, and a dozen of feasibility studies already carried out demonstrate adequate conditions for further operations. In the sedimentary basins, particularly in the Lisbon area where important heat consumers are located, Lower Cretaceous reservoirs with temperatures up to 50ºC are adequate for small multipurpose geothermal operations, but technical and economical difficulties are known. The already studied potential for developing geothermal heat pumps over proven aquifers is high all over the country. However, no reports are available on the application of this technology. In the volcanic Azores Archipelago, the geological and market conditions allow high enthalpy electricity producing operations in some islands. In S. Miguel, the largest island, one plant operates regularly since 1980 and a second after 1994. The total production capacity of 3+13MWt is installed. At Terceira Island a drilling campaign is in due course aiming to install 12 MWt.

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Martins & Carvalho

CAD. LAB.