Geothermische Technologieentwicklung Geologische und energietechnische Ansatzpunkte

Dieser Report fasst Ergebnisse aus der Startphase des Projekts Nutzbarmachung klueftigporoeser Speichergesteine zur abnehmernahen geothermischen Energiebreitstellung zusammen. Klueftig-porooese Speichergesteine sllen zur Waermegwinnung nutzbar gemacht und eine entsprechende Technologie entwickelt werden. Dadurch wird das Angebotspotenzial geothermischer Energie wesentlich erweitert. Ziel des Projektes ist es, das Fuendigkeitsrisiko geeigneter Horizonte, d.h. primaer gering ergiebiger aber kontrolliert stimulierbarer Speichergesteine zu reduzieren. Aufbauend auf Kenntnissen des geomechanischen Stoffverhaltens (Bohrloch und Labor) werden wirtschaftliche Stimulationsverfahren entwickelt. Fuer die Betriebsphase wichtige Untersuchungen des Lagnzeitverhaltens dieses Speichertyps werden druch Erfassung der Kinetik der chemischen Reaktionen an den Poren- und Kluftoberflaechen durchgefuehrt. Folgende Themenkomplexe sollen untersucht werden: (a) Petrophysikalische Charakterisierung und Verbreitung der Zielhorizonte, (b) ihre Nutzbarmachung mit Betrachtung bohrtechnischer und geomechanischer Aspekte sowie (c) technischer Betrieb und energiewirtschaftliche Konsequenzen aus der Nutzung klueftigporoeser Speichergesteine. Es werden die Grundlagen fuer eine standortvariable Erdwaermenutzung entwickelt. (orig.)An overview of the available technologies to convert geothermal energy to electricity and their range of application is presented. Geothermal power plants and geothermal heating systems are compared from technical and economic points of view. Reservoir temperature, steam content, fraction of non-condensable gases, corrosion and scaling potential as well as the productivity of a geothermal field determine the choice of the type of power station appropriate for a specific geothermal field. Direct steam and flash steam plants are used when geothermal fluid temperature is above 150 C. The plants benefit from fluids with small fractions of non-condensable gases and low corrosion and scaling potential. Binary power plants work with a secondary fluid and require geothermal fluid temperatures of at least 80 C. Higher temperatures improve their efficiency sugstantially. The working fluid is selected according to the temperature range in the geothermal reservoir. Since the impact of the geothermal fluid is limited to the brine supply system and the heat exchanger, binary systems can use geothermal fluids with high concentrations of dissolved gases and high scaling or corrosion potential. Geothermal heating systems and geothermal power plants use the same primary energy, however, they differ in the products they supply to the energy market, in the management and in the basic economic data. While space heating is clearly taylored to the customer, the design of geothermal power plants is largely independent of specific users. Three issues affect the decision for a certain energy conversion technology: -geological conditions, i.e. flow rate, temperature and enthalpy content of the geothermal fluids determine which products can be offered, - local demand, i.e. consumer needs at specific sites decide which products will find a ready market - economy, i.e. production costs and local market conditions control the profitableness of the investment. The technical feasibility of the use of geothermal energy for space heating and electricity generation is demonstrated in many places of the world. In Germany, however, the level of development of the two systems differs strongly: geothermal heating systems have been operated successfully for several years, while geothermal power plant technology is still incipient. Further developement of this technology is indispensible to assure its availability in the future. (orig.)SIGLEAvailable from TIB Hannover: RR 6134(2000,23) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman