Turbine technology | The power of two
Italy based Exergy International, specialist in advanced geothermal binary power plants, has unveiled a new evolution of its proprietary Radial Outflow Turbine (ROT) technology. Called the Gemini turbine, the new configuration combines the power of two turbines into a single high capacity unit, delivering up to 60 MW for geothermal applications.
Conceived of and developed entirely in-house by Exergy’s turbine team – having its roots in an idea originated by Exergy turbine engineer Giorgia Ruffato – the company says “the Gemini sets a new benchmark for efficiency, scalability, and competitiveness in large-scale geothermal power generation, making it the ideal match for next-generation Enhanced and Advanced Geothermal Systems.”
The new turbine features a dual-inlet design that allows the working fluid to enter symmetrically from both sides and expand radially outward through a central rotor disk equipped with dual mirrored rotor stages. After its radial expansion, the fluid converges toward a central exhaust flange for discharge.
In this new configuration, stator blades are mounted on lateral stator disks, while the rotor is supported in a between-bearings arrangement, replacing the traditional overhung setup. This structural advancement significantly enhances the
Gemini turbine. Source: Exergy
turbine’s mechanical stability, reduces vibration, and improves operational reliability. According to Exergy, the Gemini turbine’s “unique configuration” delivers a series of technical, operational and economic advantages, “providing
real value for developers and operators”: ● ability to handle very high volumetric flows (exceeding 50 m3
/s) on a single shaft;
● isentropic efficiency above 90%, equivalent to multi-turbine systems in one compact machine;
● simplified plant layout and reduced mechanical complexity;
● shaft locking system allowing easy and fast maintenance;
● reliability based on Exergy’s proven ROT technology (>550 MWe installed worldwide);
● up to 30% lower power plant cost than conventional multi-turbine configurations;
● reduced erection and civil works, with smaller footprint; and
● improved project economics with faster return on investment.
Exergy says the Gemini turbine opens up new possibilities for harnessing geothermal resources with very high flow rates more efficiently, replacing traditional configurations that use two ROT turbines operating in parallel. It provides a “competitive, cost-effective, and high- performance solution for large-scale geothermal power plants in the 30–60 MW range.” Gemini is said to be particularly suited to next-generation geothermal systems based on EGS and AGS technologies, which are emerging as “the most promising frontier of global geothermal development”, enabling power generation in regions previously considered unsuitable for geothermal projects. Exergy points out that since 2017, investment in next-generation geothermal technologies has risen sharply — from negligible levels to nearly US$2 billion raised in 2024 (Wood Mackenzie) — driven by both private and public sector support.
According to the International Energy Agency, global geothermal capacity could exceed 800 GW by 2050, supplying around 8% of the world’s electricity — “confirming geothermal energy as a key pillar in the world’s clean-energy future,” says Exergy.
Extended life for Bruce
Bruce Power has signed an exclusive agreement with Siemens Energy Canada for new high-pressure steam turbines for its four Bruce A nuclear units. As part of Bruce Power’s Project 2030 and life-extension asset management projects, the upgrades are expected to increase output by more than 30 MW per unit, delivering an additional 125 MW in total. The turbine replacements, building on Bruce Power’s existing “strategic alliance agreement” with Siemens Energy, are due to
be completed between 2028 and 2031. “Upgrading a power plant is the fastest way to get more energy onto the grid,” said Arne Wohlschlegel, Managing Director of Siemens Energy Canada. “When this upgrade is complete, Bruce Power will be able to deliver more clean energy throughout Ontario and extend the life of this plant for another 30 years.”
The new turbines will replace machines originally manufactured by C.A. Parsons in the UK (now part of Siemens Energy).
Bruce steam turbine. Photo: Bruce Power Modernising Opatovice
previously completed similar projects at Opatovice TG5 and TG3.
Opatovice CHP plant.
Pilsen based Doosan Škoda Power has been awarded a contract for steam turbine modernisation at unit TG6 of the Opatovice cogeneration plant, Czech Republic, having
The TG6 scope encompasses supply of a new condensing turbine and condenser, repair of the existing generator, installation of new district water heaters, and extensive work on piping and steel structures. Doosan Škoda Power is delivering the project as an EPC contractor, on a “turnkey” basis. “The most challenging aspect was devising a comprehensive solution that would both increase the operational efficiency of unit TG6 and respect the spatial limitations of the
30 | March 2026 |
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Sales Manager at Doosan Škoda Power. “A crucial factor was also the need to adhere to a very demanding schedule for the planned outage of the district water heating system.” Opatovice is undergoing major modernisation with the objective of progressively phasing out coal and replacing it with gas-fired combined cycle. The modernised steam turbines are designed to operate optimally both in the current coal-fired mode and in a future gas-fired combined cycle configuration, with the aim of guaranteeing “stable and uninterrupted heat supplies for the entire region throughout the transition.”
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