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 Reykjavik, 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.