GEG Power is acting as developer, co-investor and also as a supplier of modular geothermal power plant technology. The business is built on providing turn-key wellhead geothermal power plants in sizes ranging from 0.5 to 35 MW per unit. They can be set up in units according to the project’s needs & output specifications.

There are “three basic types of geothermal power plants: dry steam, flash steam, and binary.

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)

Development Approach

Green Energy Geothermal (GEG) is providing turn-key wellhead geothermal power plants in sizes ranging from 0.5 to 11 MW per unit. They can be set up in units according to customer needs & output specifications.

GEG’s condensing single flash plants utilise turbines and components reliably sourced from trusted international suppliers in a single or twin configuration, handling a pressure range from 4 to 18 bar_a.

Remote access and optimised power

The modular design by GEG’s engineering and scientific experts allows for electricity generation from remote or stranded wells that are outside of the topographical reach of larger traditional plants.

Utilising individual wellhead power plants enables optimum energy generation regardless of differing well outputs and characteristics.

Alternative to traditional power plants

Geothermal wellhead units are an option to large-scale plant development allowing a more efficient use of capital to connect power units to the grid. The high speed of delivery will provide early revenues to offset development costs, may replace diesel cost for drilling rigs, and mitigate risk on the resource assessment.

Power farms & rapid deployment

As well as independent unit implementation, GEG wellhead plants can be deployed in larger numbers for cultivation of ‘power farms’ to be operated long-term. Interconnecting several plants together can replace traditional large-scale plants.

GEG’s unique wellhead solution can be deployed and online within 12-14 months from ordering allowing for faster return on investment.   Scope of supply GEG supplies its geothermal wellhead plants on a turn-key basis with specific elements depending on the type of plant chosen for the project.

  • Steam system
  • Modular plant (including gen-set, cooling towers and related systems)
  • Electrical, control and protection system, ancillary and auxiliary systems

Scope of services

  • Shipping, supply, installation and commissioning of entire plant
  • Design & engineering, quality management
  • Supervision of GEG sub-contractors
  • Procurement to site and preparation of installation and operating manuals
  • Testing and commissioning
  • Training of operators

Additional supply and services

  • Steam system and separator for dry steam as replacement for two-phase alternative solution
  • Main step-up transformer substations
  • Diesel Generator systems
  • Civil works, incl. excavation, plant fencing with gates, trenches, drains and flood protection
  • Operation & maintenance