GE Energy, working with the Italian ENEL Group, has been awarded a turnkey contract to expand an existing geothermal generating plant at Berlin, in the department of Usulatan, El Salvador. The contract was awarded following a sealed bid competition with the supplier of the existing plant.

The Berlin geothermal plant is one of two operated by LAGEO SA. Between them they generate some 23% of the country’s electric power.

At Berlin, the geothermal wells that supply steam to the turbines are 3000 meters deep, tapping into strata where the temperature is a constant 300°C. After use, the condensed stream is returned to the aquifer.

GE Energy is taking responsibility for conceptual and detailed engineering and supply of the complete plant extension, on a turnkey basis. In El Salvador local partners will take responsibility for construction and erection phases of the work.

Major components of the expanded facility are a model SDFG2-22 Steam Turbine, specially developed for geothermal use; an electrical generator; step-up transformers and substation; station control system; condenser, vacuum generator, air cooled refrigeration towers and circulating water pumps; and a power house to contain the turbogenerator.

Ecoimagination at work
Geothermal generation has perhaps the least impact on the environment of any large scale generating process. Non-condensable gases are stripped out from the condenser by means of ejectors and a liquid ring compressor which is driven by the steam turbine. The plant imposes a small imprint, and compared to other thermal generating plants its output of greenhouse gases is virtually zero.

GE Energy has over 35 years of experience in the design, supply and support of geothermal plants, many of them in partnership with ENEL. The LAGEO contract is the first to be awarded outside Italy. The major components are designed and manufactured by GE Energy specifically for geothermal applications.

Geothermal Steam Turbine, model SDFG2-22
The machine specified for the Berlin expansion is double flow type, and incorporates features that will optimize performance and reliability under the conditions encountered at the site. It is capable of sustained efficiency over a wide range of inlet pressure variations, has reaction blades designed to operate efficiently even under off-design conditions, and can be adjusted for wide variations in pressure. The two exhaust sections are equipped with a 22-inch last stage bucket to maximize kinetic energy recovery. Special materials and coatings, developed over years of operation of similar units under similar conditions, have been selected to protect turbine components against corrosion and water droplet erosion.

Direct Contact (Mixed Flow) Condenser
Experience has proven that a mixed flow type of condenser provides optimum service in direct steam geothermal applications. The greater part of the condensation effect takes place in a horizontal duct; the process is completed in a vertical column which also refrigerates non-condensable gases, for extraction.

A challenging location
The mountainous terrain, and the physical size and weight of the turbine, will require careful planning of access routes to the site – with possible civil works improvements along the way. Work will be carried out while the existing plant is in full production, and will require a Performance Test before acceptance by the owners.