Compared to traditional thermal power generation, ORC plants operate at much lower temperatures around 105°C to 185°C. Rather than using steam to drive a turbine, a secondary organic fluid with a lower boiling point is heated by the geothermal fluid via a heat exchanger. The organic fluid expands into a gas and powers a turbine and generator, producing renewable energy. Following this, it is condensed and reheated as part of a closed loop.

Sulzer has built a reputation as a premier supplier of hydrocarbon feed pumps for ORC geothermal applications. Its VS6 pumps are adept at circulating the condensed organic fluid within the closed loop process and are being specified for geothermal projects globally.

Sergio Periz, Tendering Manager at Sulzer Pumps Spain, explains the challenges: “While the organic fluid in ORC processes is noncorrosive, its lower boiling point and higher vapor pressure mean that the fluid is constantly trying to escape the pump. Fortunately, Sulzer has the pump technologies and expertise to overcome these unique challenges so the VS6 mechanical sealing system is highly specialized.

“ORC plant project lead times are typically short - usually less than two years – so we may have only a month or less to prepare our tender. Our response times are critical, as are the lead times for the pumps, despite the highly technical nature of these projects.”

The ability to quickly design a solution was demonstrated during a recent project in Turkey. Sulzer was approached to provide several types of VS6 hydrocarbon pumps to retrofit an existing ORC geothermal plant. The customer wanted to minimize costly modifications to existing infrastructure and set a zero tolerance 82% efficiency rating for Sulzer to achieve.

Sergio continues: “In a brownfield project like this, it’s about adapting a pump to the existing dimensions, which entails changing parts like flanges. The pressure limits of the existing pipework must also be respected. This is all while ensuring that the pump meets the required head to make the application viable. Of course, we were able to deliver the units, meeting the agreed efficiency rating and other customer requirements.”

While retrofits present unique engineering challenges, Sulzer is also supporting new-build ORC geothermal plants. The company recently won an order in the US to supply VS6 pumps to multiple carbon-free installations that are being built. Harnessing both wind, solar and geothermal energy, the plants produce no emissions, signposting how these facilities will operate as part of a net zero future.
Beyond individual projects, Sulzer provides long term service support to national-scale geothermal plant operators, accelerating the transition to renewable energy globally.

Sulzer’s Services division recently signed a five-year customer service agreement with PT Pertamina Geothermal Energy Tbk (PGE), the geothermal energy subsidiary of Pertamina. Under the agreement, Sulzer is providing strategic maintenance support for rotating equipment at PGE’s geothermal power plants throughout Indonesia.

Together, the plants offer a total capacity of 330 MW – enough to power around 620’000 homes. Sulzer’s repair technologies, outage optimizations, equipment overhauls, turbomachinery life extensions and technical advisory services thus play an important role in the long-term reliability of this important resource.

The opportunity to harness geothermal energy exists around the globe, and the abundance of heat stored in the Earth from its formation over 4.6 billion years ago ensures we have potential access to clean energy long into the future. Capitalizing on this largely untapped resource relies on the expertise of engineering companies that can deliver highly reliable, specialized solutions within the condensed timeframes of geothermal projects. With its recent successes and pump technologies, Sulzer is demonstrating the deep expertise that makes it a leader in the industry.