Large-scale wind and solar farms are the most visible aspect of the global transition to sustainable energy, but there is another important source of clean, reliable power hidden beneath our feet. Geothermal energy is already the most important source of power in Iceland, now countries from Indonesia and the Philippines to Turkey are rapidly developing their own geothermal resources.
feedwater pump installed in geothermal power plant in Turkey
Sulzer’s main feed pumps installed in a Binary Cycle Geothermal Power (Image Source: Exergy International srl)

Process enhancement

The energy for a geothermal power plant comes from hot water or brine extracted from deep underground aquifers. Traditional plants require water temperatures of at least 350°F (180°C) to create the steam used to run the station’s turbines. More recently, however, the geothermal industry has perfected an alternative approach that can operate at lower temperatures, greatly expanding the range of possible generating sites.

Binary cycle power stations pass hot brine from the geothermal borehole through a heat exchanger, where it heats a working fluid. This has a lower boiling point than water, allowing the plant’s turbines to operate efficiently at the lower geothermal temperatures. After the turbine, the working fluid is cooled and condensed, then returned to the heat exchanger to complete the loop. On the geothermal side, the cooler brine exiting the heat exchanger is re-injected into the ground.

Handling the working fluid in a binary cycle power station requires highly specialized pumping technology. The pump used to return the working fluid to the heat exchanger must be able to work with a very low net positive suction head (NPSH) and develop a high head to provide the right conditions at the inlet of the gas expander turbine. 

SJD CEP pumps ready to be shipped out in Sulzer factory
The SJD-CEP pumps ready to be shipped out of the factory

Performance by design

The pump chosen for Exergy’s most recent project was one of the largest from Sulzer’s SJD CEP range of multistage canned vertical pumps. The selected pump has a unique double suction first stage, which ensures safe operation at low NPSH values, while, through its bowl diffuser configuration, it can also develop a high differential head per stage. Achieving the high head required for the application with fewer stages results in a smaller pump that is easier to integrate into the plant design. For the customer, fewer stages also means lower purchase, spare parts and maintenance costs.

Exergy was already confident that the Sulzer design would meet its performance expectations; an identical design has been in operation for several years at another of the company’s projects in Turkey. The key challenge for the latest build was ensuring every component of the project could be manufactured and delivered to exceptionally tight timescales.

Andres Mercader - Tendering Manager, Sulzer Pumps

Rapid construction

In common with other renewable energy installations around the world, geothermal power plants often benefit from government financial support. Accessing that support requires facilities to be up and running before pre-agreed deadlines, leading to tight construction schedules. 

To meet the delivery deadline, Sulzer drew on its global manufacturing and supply chain capabilities. All parts were then inspected, assembled and tested in one of Sulzer’s facilities focusing and specializing in vertical pumps. The standard, modular design of the CEP pumps proved especially beneficial here, as high-precision casts and components are shared by several Sulzer facilities across its global supply chain locations.

After assembly, the pump was tested with water at full speed using a calibrated lab test motor. Upon successful completion of the test, the motor was replaced with the smaller job-specific motor, since the isopentane working fluid used at the power plant is significantly lighter. Despite the challenging timeframe, the completed unit was delivered to the customer ahead of schedule, helping to ensure the plant could begin generating power before its deadline.

Our mission is to shape technical innovations and deliver high quality services that enable our customers to transform a heat source into clean, sustainable and efficient power. To attain this target our projects depend on reliable, high-performance components from leading specialist suppliers, Sulzer has once again met our expectations and helped us to meet a very tight schedule.

Marco Frassinetti - Sales Director at Exergy
  • SJD-CEP vertical multistage can condensate extraction pump
    SJD-CEP vertical can condensate extraction pumps, are specified wherever limited NPSH is available, either due to system constraints or liquids operating near to their vapor pressure, typically for condensate extraction and heater drain pump applications.
Contact us