Serbia Advances Geothermal Drilling for the Mišeluk District Heating Plant in Novi Sad Serbia is moving forward with plans to develop a geothermal district heating system in Mišeluk, a rapidly urbanizing area of Novi Sad. The project is intended to place geothermal energy at the centre of a new low-carbon heating network, supported by solar power and natural gas backup. Exploratory drilling and construction of the heat distribution network are being carried out by JKP Novosadska toplana, Novi Sad’s public district heating utility. The initiative is supported through the United Nations Development Programme’s “Geothermal Energy in Serbia” programme, with financial backing from Slovakia. The Mišeluk project is important not only because it could provide a new renewable heat source for Novi Sad, but also because it demonstrates how geothermal energy can be integrated into urban development from the earliest planning stages. Rather than retrofitting a geothermal system into an establi...
image : a thematic view of a geothermal turbine "blade"
Geothermal power is entering a new phase. Two of the most important announcements in the sector point to larger, more standardized, and more commercially viable binary geothermal systems: Exergy’s Gemini Turbine and Ormat’s Ormega100. At first glance, both machines promise major gains in scale, but they are not trying to solve the same problem in exactly the same way. Gemini is built around a high-capacity radial outflow turbine architecture that can deliver up to 60 MWe per shaft, while Ormega100 is designed as a 100 MW binary surface power unit intended to accelerate enhanced geothermal system commercialization.
For project developers, utilities, and data-center buyers looking for firm clean power, the comparison matters because it reveals two competing ideas about how geothermal should grow. Exergy is emphasizing turbine architecture, efficiency, and mechanical simplification; Ormat is emphasizing standardization, autonomous operation, and a larger single-unit power block. In practical terms, Gemini asks how to make a geothermal turbine more efficient and compact, while Ormega100 asks how to make geothermal deployment larger and faster to commercialize.
What Gemini is
Exergy unveiled Gemini as a milestone in its proprietary Radial Outflow Turbine, or ROT, technology. The company says the turbine combines the power of two turbines into a single high-capacity unit and is capable of reaching up to 60 MW, while Exergy’s own website states that Gemini advances ROT technology with up to 60 MWe per shaft and over 90% efficiency. A geothermal industry article further explains that Gemini uses a six-stage expansion model and can deliver slightly above 50 MW of mechanical power at the shaft, with gross electrical output around 50 MW and net output just over 40 MW after auxiliary loads in one modelled configuration.
That matters because geothermal binary plants often face a tradeoff between output, size, and complexity. Exergy’s Gemini is designed to reduce the need for multiple turbines operating in parallel, which can simplify plant layout, lower mechanical complexity, and improve overall economics. Exergy-linked material also says the configuration can handle very high volumetric flow rates, uses a symmetric dual-entry design, and can reduce power plant cost by up to 30% versus conventional multi-turbine arrangements. For developers targeting large geothermal reservoirs, that makes Gemini attractive not just as a turbine, but as a plant-optimization strategy.
What Ormega100 is
Ormat introduced Ormega100 on June 8, 2026 as a geothermal power plant design capable of producing 100 megawatts of electricity. Reuters reported that the company describes it as the largest geothermal power plant design in the industry and said it is dependent on advanced geothermal technologies that Ormat is currently testing. Ormat’s announcement also ties Ormega100 directly to enhanced geothermal systems, or EGS, which use injection into deep rock formations to access heat beyond traditional hydrothermal reservoirs.
Ormat says the new unit is a standardized, modular, and autonomous binary power block intended to reduce time to operation by up to 30% and support the needs of data centers and hyperscalers. The company also says the design uses field-proven plain bearing technology, targets more than 90% turbine efficiency, and is engineered for 10 years of operation before major maintenance. In other words, Ormega100 is not just about size; it is a system-level attempt to turn geothermal into repeatable infrastructure that can be rolled out at scale.
Capacity and scale
On raw capacity, Ormega100 wins the headline number because it is designed for up to 100 MW from a single unit. Gemini, by contrast, is positioned at up to 60 MWe per shaft, though Exergy also frames it as a high-capacity replacement for configurations that would otherwise require two turbines operating in parallel. That means Gemini is a large single-shaft solution, but Ormega100 is a larger system-level block intended to push geothermal into a new scale bracket.
Still, capacity alone does not tell the full story. The key question is whether the plant is optimized for a specific geothermal resource or for broader commercial replication. Gemini appears to be particularly strong where very high flow rates and compact turbine architecture are central design constraints. Ormega100 is framed more as a standardized deployment platform that can pair with EGS developments and provide a repeatable 100 MW surface solution.
Efficiency and performance
Exergy repeatedly emphasizes efficiency as one of Gemini’s biggest advantages. The company and related reporting say the turbine achieves over 90% efficiency and brings together the output of two turbines into a single configuration, which can reduce equipment count and mechanical losses. A technical article adds that the design offers a symmetrical dual-entry flow path, a central rotor disk, and a shaft-locking system that improves maintenance practicality.
Ormat also claims more than 90% turbine efficiency for Ormega100, but its pitch is less about turbine novelty and more about platform-level reliability and autonomy. The company says the unit is designed for fully unmanned operation and uses standardized modular construction to accelerate deployment. So while both products claim high efficiency, Gemini’s selling point is especially strong on thermodynamic and mechanical innovation, whereas Ormega100’s selling point is operational repeatability and project execution.
Design philosophy
The two turbines reflect different philosophies. Gemini is rooted in Exergy’s Rotary Outflow Turbine lineage and appears aimed at improving how high-flow geothermal energy is converted inside the turbine itself. It is a machine-level innovation that tries to extract more value from the working fluid by using a compact, symmetric, high-capacity architecture.
Ormega100 is more of a power-block innovation. Ormat is vertically integrated across geothermal development, drilling, construction, ownership, and operations, and that structure allows the company to standardize a large binary unit around its broader project pipeline. The result is a design philosophy centered on industrialization, where repeatable equipment and autonomous operation are just as important as turbine mechanics.
Deployment and market fit
Gemini looks especially relevant for large geothermal plants in the 30 to 60 MW range, and Exergy-linked material says it is ideal for next-generation geothermal systems based on EGS and advanced geothermal systems. That makes sense because such projects often need compact but powerful surface equipment that can handle high flow rates efficiently. The smaller number of rotating assemblies could also make integration easier for developers trying to keep footprint and complexity under control.
Ormega100 is aimed at a broader commercial target: large baseload projects, hyperscalers, data centers, and EGS deployments that need a bigger standardized surface unit. Reuters noted that geothermal is attracting new interest from technology companies seeking reliable electricity for AI growth, and Ormat has already positioned Ormega100 as part of that demand story. In this sense, Ormega100 is as much a market-access product as a technical one.
Image : Ormat’s turbines in numerical description
Maintenance and operations
Maintenance is one of the clearest differentiators between the two approaches. Gemini’s dual-entry, compact arrangement is presented as mechanically simpler than using two separate turbines, and the design’s shaft-locking feature is intended to make service easier and faster. Exergy also emphasizes lower plant complexity and reduced civil works, which can translate into lower lifecycle cost and faster returns.
Ormega100, meanwhile, is marketed around autonomous operation and long maintenance intervals. Ormat says the unit is built for 10 years of operation before major maintenance, which is a strong signal to utilities and hyperscale buyers that reliability is central to the product’s value proposition. That gives Ormat an edge in operational simplicity, while Gemini appears stronger on mechanical elegance and project simplification.
Exergy claims Gemini can reduce power plant cost by up to 30% compared with conventional multiturbine setups. That claim is tied to lower equipment count, less assembly work, reduced civil construction, and a smaller overall footprint. In project economics, that combination can matter as much as efficiency because geothermal developments are highly sensitive to capital cost and the difficulty of reservoir-specific engineering.
Image: an image showing 3D pictures of the Gemini Turbine
Ormat’s economic logic is different. Ormega100 is designed to reduce timeline to operation by up to 30%, and Reuters says the company expects construction after pilot validation to take 18 to 24 months. For a geothermal developer, faster commercialization and standardized execution can lower financing risk, shorten payback timelines, and improve bankability. So Gemini appears cost-competitive at the turbine and plant-design level, while Ormega100 is trying to improve economics through standardization and speed.
Which one is better
There is no universal winner because the best choice depends on project goals. If a developer wants a highly efficient, compact turbine architecture for a large geothermal site with very high flow rates, Gemini looks compelling. If the goal is to deploy a large, standardized, autonomous binary block that can support EGS scale-up and serve industrial buyers, Ormega100 has the stronger commercial story.
In a strict one-to-one comparison, Ormega100 leads on headline capacity, while Gemini leads on turbine architecture innovation and plant simplification. Both claim high efficiency, both are aimed at next-generation geothermal, and both are meant to help geothermal move beyond smaller, site-specific projects into a more scalable model. The real difference is that Exergy is refining the turbine, while Ormat is industrializing the power block.
The bigger trend
These two announcements show where geothermal is heading. The industry is no longer only talking about resource discovery; it is now talking about repeatable surface equipment, large binary units, autonomous operation, and standardized scaling. That shift is important because geothermal has long struggled with project complexity, site specificity, and high upfront cost.
Gemini and Ormega100 represent two credible answers to that challenge. Gemini suggests geothermal can become more competitive by making the turbine itself smarter and simpler. Ormega100 suggests geothermal can become more competitive by making the plant block larger, faster to deploy, and easier to replicate. Together, they mark a meaningful step toward geothermal power systems that are not only clean, but also industrially scalable.
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