Geothermal reservoirs: From vapour dominated to conductive systems

Abstract

Geothermal reservoirs are part of the system needed to produce electricity using geothermal fluids. The temperatures in the reservoirs are important for choosing the type of plant. It is also important to know the principal type and amount of fluid that the reservoir can provide. Temperature and pressure in the reservoir will determine whether the fluid is liquid or vapour and whether the system is predominantly conductive or convective. In this work we describe the different types of systems, from the vapour systems where the observed temperatures are highest, up to systems used with geothermal heat pumps that exploit differences in temperature between the soil and the atmosphere. In the last part of the work we present a low-enthalpy geothermal reservoir, located near an old building of the Évora University at Alentejo, in the South of Portugal, that is used to climatize the rooms located in the cloisters of the building. We present the device and some problems related to the exploitation of this reservoir.