Direct uses of earth heat

Abstract

Potential resources and applications of earth heat in the form of geothermal energy are large. World‐wide direct uses amount to 7072 MW thermal above a reference temperature of 35°C. District heating is the major direct use of geothermal energy. Equipment employed in direct use projects is of standard manufacture and includes downhole and circulation pumps, transmission and distribution pipelines, heat exchangers and convectors, heat pumps and chillers. Direct uses of earth heat discussed are district heating and cooling, greenhouse heating and fish farming, process and industrial applications, combined and cascading uses. The economic feasibility of direct use projects is governed by site specific factors such as location of user and resource, resource quality, system load factor and load density, as well as financing. Examples are presented of district heating in Reykjavík, Klamath Falls, Melun l'Amont and Svartsengi. Further developments of direct uses of geothermal energy will depend on matching user needs to the resource, and improving load factors and load density.

Direct Utilization of Geothermal Energy

“…Aboveground pipelines have been used extensively in Iceland, where excavation in lava rock is expensive and difficult; however, in the USA, below ground installations, either direct buried or in utilidors are used to protect the line from vandalism and to eliminate traffic barriers. A detailed discussion of these various installations can be found in Gudmundsson and Lund [4] and in Lund [5].…”

“…Heat pumps utilizing very low-temperature fluids have extended geothermal developments into traditionally non-geothermal countries such as Canada, France, Switzerland and Sweden, as well as areas of the mid-western and eastern U.S. Most equipment used in these projects are of standard, off-the-shelf design and need only slight modifications to handle geothermal fluids [4,5].…”

Γεωθερμικη Ερευνα Χαμηλης Ενθαλπιας. Μελετη Του Γεωθερμικου Πεδιου Ν. Κεσσανης

“…Στο τέλος του 1984 η εγκατεστημένη θερμική ισχύς στην απ'ευ θείας χρήση σ'όλον τον κόσμο ήταν περίπου 7.072 MWt σύμφωνα με τη μελέτη του Geothermal Resourses Counsil (GRC)(Gudmundsson 1985) ενώ η εγκατεστημένη γεωθερμική ηλεκτρική ισχύς στα τέλη του 1985 ήταν 4.764MWe (Di Pippo, 1985).Το δίκτυο μεταφοράς του γεωθερμικού ρευστού από τη γεώτρηση πα ράγωγης μέχρι τον τόπο ανάκτησης της θερμότητας αποτελεί σημα ντικό κομμάτι του όλου εξοπλισμού. Η θερμοκρασία του γεωθερμι κού ρευστού πολλές φορές φθάνει τους 200°C και οι μηχανικές κα ταπονήσεις του εξοπλισμού, λόγω της θερμοκρασίας και της δια-στολής είναι σημαντικές.…”