Dry-Steam Power Plants

Dry-steam plants were the first type of geothermal power plant to achieve commercial status. Large dry-steam reservoirs have been discovered only in two areas of the world: Larderello and The Geysers. The general characteristic of a dry-steam reservoir is that it comprises porous rock featuring fissures or fractures, either occluded or interconnected, that are filled with steam. The mechanism of fluid behavior in a dry-steam reservoir is complex and several models are proposed. These mechanisms are depicted schematically. The study cites close correlation between the observed temperatures in dry-steam reservoirs and the temperature that corresponds to the maximum enthalpy for saturated steam. A dry-steam reservoir owes its existence to a combination of highly fortuitous circumstances. The connection between the wells and the powerhouse for a dry-steam plant is relatively simple compared to a flash-steam plant. Furthermore, this chapter presents an example that helps to treat the problem of deciding on the optimum wellhead pressure for a dry steam plant receiving saturated vapor at the wellhead. The major equipment items found at dry-steam plants are quite similar to those used at a single-flash plant. The list is drawn for dry-steam plants with annotations applied only for items that differ from those at single-flash plants.