GEG Power is acting as development partner and investor through the Geoneer venture, an international partnership. The business is built on the experience of complete turn-key wellhead geothermal power plant development technology independent.
There are “three basic types of geothermal power plants: dry steam, flash steam, and binary. All are an option for the development activities by GEG Power and the Geoneer venture.
Each power-plant configuration features different energy-conversion efficiencies and different operating requirements that influence sustainable management approaches for the associated geothermal resources. Operational characteristics influence reservoir performance, thus requiring proactive management of both the plant and reservoir.
Variety in power-plant designs affords developers the opportunity to optimize the geothermal resource of interest and meet the needs of the application and end users. Differences in efficiencies and operating requirements ultimately impact power-plant capital costs.”, so the GeoVision report by the U.S. Department of Energy from 2019.
Initially focused on offering flash-condensing-type geothermal power plant technology, GEG has since expanded its offering and capabilities to build and deliver back-pressure units and binary-cycle units.
Single-flash condensing technology
Single flash turbines are the most common turbine type in geothermal power plants utilising condensers. The two-phase flow of a geothermal fluid is piped from the production well to the separator, where the fluid is separated from the steam. The liquid is disposed into the reservoir through a reinjection well. The steam flows from the separator through a turbine and electrical power is generated in the generator, coupled to the turbine. The steam then enters the condenser, where it is condensed at sub atmospheric pressure. This condenser provides cooling with cooling water circulating through a cooling tower.
(Source: Gudmundsson, Y., Hallgrimsdóttir, Wellhead power plants, ARGeo Proceedings 2016)
Back pressure
The back pressure power plant is in many ways similar to the condensing power plant, except there is no condenser and cooling system. A two-phased flow (mixture of geothermal steam and liquid) is piped from the production well to the separator, where the liquid is separated from the steam. The liquid is disposed into the reservoir through a re-injection well. The steam flows from the separator through a turbine and electrical power is generated in the generator, coupled to the turbine. The steam then exhausts to ambient atmospheric pressure in the steam exhaust. The condensate is then pumped to the re-injection well and injected with liquid from the separator. The pressure of the stream exhaust from a back pressure power plant is above atmospheric pressure and the steam is not condensed. Since the steam is not condensed, the entire cold end not required and therefore, the cost of back pressure power plants is considerably lower than the conventional condensing power plant, but the available power form the well is not as efficient in condensing or ORC plant.
(Source: Gudmundsson, Y., Hallgrimsdóttir, Wellhead power plants, ARGeo Proceedings 2016)
Organic ranking cycle (Binary)
The binary power plants are significantly different from the back pressure and condensing power plants. The reservoir fluid flows through from the production well to a vaporizer. The binary working fluid is heated and evaporated in the vaporizer and preheater and piped to the turbine. The binary fluid impels the turbine and electricity is generated in the generator, coupled to the turbine. The slightly superheated binary fluid exits the turbine at lower pressure and enters the condenser where it condenses back into liquid form. A feed pump circulates the condensed binary fluid to the preheater and then again to the vaporizer, repeating the process. The geothermal fluid is injected back into the reservoir through a re-injection well. The condenser requires cooling which may be provided by either water (wet cooling) or air (dry cooling).
(Source: Gudmundsson, Y., Hallgrimsdóttir, Wellhead power plants, ARGeo Proceedings 2016)