Windstory #27 - OptiGen: the startup that wants to revolutionise the drivetrain of direct-drive wind turbines (II)
The Spanish startup OptiGen has presented an innovative drivetrain design for direct-drive wind turbines. We have spoken with them to bring you all the details.
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This is the second part of the feature on OptiGen, the startup that wants to revolutionise the drivetrain of offshore wind turbines. Read the first part here.
For the review of this article, I have relied on the kind collaboration of Windtechs, a consultancy and Market Intelligence firm specialised in wind turbine technology.
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OptiGen: revolutionising the drivetrain of direct-drive wind turbines
Principle of operation
In the following image, the principle of operation of the technology can be seen. There is also an animated version, which illustrates the process more clearly, available at this link.
As can be observed, the rotor rests on a set of wheels which, thanks to their elastic supports, absorb the deformations and vibrations generated during operation.
According to OptiGen, this design makes it possible to maintain the stability of the air gap (the distance between the rotor, which carries the permanent magnets, and the stator, where the copper windings are housed).
And why is it important to maintain the air gap?
In the event of excessive deformation, the air gap can collapse, meaning that the windings and the magnets come into contact. In such a case, the damage to the generator would be extremely severe. For this reason, in traditional generators, in addition to closely monitoring the relative distance through sensors, the stator and rotor are designed with very high structural stiffness, which entails a significant increase in generator weight, increasing exponentially with turbine power.
In the OptiGen system, the air gap is always kept stable thanks to the proximity of the wheel-and-rail system located next to it. This also makes it possible to reduce the length of the air gap and, consequently, to decrease the amount of magnets required.
The main question they receive today is clear: will the wheel–rail system be able to withstand 25 years of operation?
“The calculation methods traditionally used for bearings indicate that, with our design, we triple the required service life,” explains Santiago. “But those methods cannot be applied directly to our system.”
For this reason, two partners of the European consortium, Marine Resources and Fraunhofer IWES, are developing new calculation methodologies inspired by crane systems and yaw mechanisms used on large oil platforms, which yield even longer lifetime projections. Tests have recently started that will serve to validate the theory.
“If this is confirmed, we believe that the industry will end up adopting this solution, not only because of the savings in initial costs, but also because of its reliability, ease of repair, and the possibility of extending the service life of turbines. It is what large rotating platforms in the oil sector have done, from whom we have much to learn, as they have been dealing with this type of problem at sea for a long time.”
In the offshore environment, equipment is designed for maintenance intervals longer than 30 months, and OptiGen will be no exception. It will feature automatic lubrication systems and remote monitoring, which will make it possible to detect anomalies and plan interventions while minimising the impact on availability.
Although it is a disruptive technology, Santiago stresses that a large part of the wind turbine remains unchanged. “We are actively working on reducing risks and confirming its benefits. What we are doing is introducing a substantial change, but on a simple and reliable technological base, within a commercial market where it has already proven its effectiveness.”
When asked about the main technical challenges of their design, Santiago is clear: “The biggest challenge, by far, is rolling contact fatigue (RCF). It is essential to guarantee reliability, especially in the rails,” he explains.
Once that point is overcome, everything comes down to applying safe and methodical engineering. “It is about analysing all failure modes and properly sizing the components. It should not be a major problem, because everything we use in our mechanical system already exists in the railway industry.”
LightWind project
OptiGen’s proposal will soon cease to exist only on paper. Thanks to Horizon Europe programmes and collaboration with a consortium of eight partners from six European countries, brought together under the LightWind project, the company has secured a €3 million grant to develop this technology.
In addition to OptiGen itself, the consortium participants are:
Euro-Funding (project management and financing)
TNO (applied research in energy transition)
CREADIS Sp. z o.o. (engineering and manufacturing)
Fraunhofer Institute for Wind Energy Systems IWES (wind energy research and testing)
X1 Wind (floating wind platforms)
Hellenic Centre for Marine Research (environmental sustainability in offshore)
Marine Resources (offshore technologies and marine resource management)
CINEA (project support from the European Commission)
The LightWind project aims to bring OptiGen’s technology from TRL 2 to TRL 4, with the goal of demonstrating its viability and quantifying its advantages compared to current designs.
For those who may not be familiar with it, TRL 4 corresponds to the validation of components in a laboratory environment. You can consult the different TRL levels here.
The project envisages carrying out two laboratory tests:
One to validate rolling contact fatigue.
Another to study the complete mechanical system at a 1:10 scale. It was designed by Idom.
The tests, which began in early 2026, will run through the summer. The results will be decisive in confirming the design methodologies and guaranteeing the viability of the technology at large scale.
Potential impact on the offshore sector
The company’s initial estimates indicate that its technology could reduce costs by 25% in the nacelle, tower, substructure, and foundations, whose design is heavily conditioned by the weight of the rotor–nacelle assembly. This has a particularly relevant positive impact on floating wind.
A 15 MW turbine has the hub at around 140 metres height, and at that scale every tonne counts. “The lower the turbine weight, the lower the tonnage required for the tower in fixed-bottom wind or for the structure in the case of floating wind,” explains Santiago. “Not only for flotation reasons, but above all for stability and dynamics.”
“We estimate that an optimised version of the OptiGen system can reduce the total turbine weight by up to 35%,” Santiago says. “We do not expect to achieve that reduction in the floater, but in any case we would be talking about a huge volume of steel or concrete, since even in the lightest designs the floater at least triples the weight of the turbine. To this advantage we must add savings in the mooring system, as well as in the costs associated with transport and installation.”
But according to Stefan Keller, co-founder and co-CEO, the greatest advantage lies in operation and maintenance: “The system is very easy to inspect thanks to its open design, which also allows all mechanical and electrical components to be replaced or repaired in situ, without the need for large cranes, jack-up crane vessels, or towing to port in the case of floating wind.”
“Projects such as Hywind or Kincardine have had to replace bearings or entire generators, towing the turbines back to port and stopping production for months,” Santiago recalls.
According to the company’s preliminary calculations, the reduction in CAPEX, together with lower operating costs, would make it possible to reduce the LCoE by 10%.
Testing and prototypes
One of the most delicate issues in the development of a new technology is the scale of the prototypes. A 1:10 model may be sufficient to validate the concept, but it does not always reproduce the same behaviour as a real turbine.
Santiago acknowledges this: “We are following the procedures established by DNV standards for the development of new technologies. The strategy, inspired by NASA methods, consists of progressively getting closer to reality, in a robust way and while optimising resources.”
Jumping directly to a full-scale prototype would be risky and costly, he explains. For this reason, the team is working gradually, moving step by step through increasing levels of technological maturity (TRL).
“With LightWind we will reach TRL 4, and with a future 1:2 scale prototype we will reach TRL 5. Then we plan to carry out a test with a turbine to validate operation under real operating conditions, adapting an existing turbine. There is still a long way to go to TRL 9, the level of commercial reliability, but each phase is designed to learn and reduce risks,” they explain.
For now, talking about a full-scale prototype would be premature. “It is too early to think about full scale,” Blai admits. “At those levels it will be essential to have an OEM or a partner with strong financial capacity. For the moment, we are leaving the door open to discuss that step later on.”
Next steps
Looking ahead, the OptiGen team has a clear roadmap: “In less than five years we expect to have a first pilot turbine at scale in operation,” explains Santiago. “From there we would start commercialisation, and within a ten-year horizon we expect the technology to be fully deployed in the sector, with growing demand.”
There is no single route to market. “We are open to different options: from licensing the technology to manufacturers or OEMs, to developing a complete drivetrain in-house”, he adds. “Each route has its own challenges and capital requirements, but the final objective is the same: that operators and developers are the main beneficiaries of the CAPEX and OPEX savings offered by our system.”
OptiGen’s technological roadmap envisages a progressive increase in power. The next step will be to scale the design to a 22 MW platform, and subsequently reach 30 MW.
In fact, the company expects that by the end of the LightWind project in 2027, the 15 MW design will be optimised and the new higher-power versions will be presented.
Funding round and future
The start-up is preparing for a new stage of growth. In the coming weeks it will announce a pre-seed funding round valued at €600,000, aimed at driving technological development over the next two and a half years.
“The capital will be used to strengthen the team, carry out tests, validate our theoretical models and cover engineering activities that we need to outsource, as well as general and structural expenses,” explains Blai.
In parallel, OptiGen will continue to rely on public funding. To date it has secured more than €3 million in grants and subsidies, which has allowed it to progress without the need for significant private investment. “Thanks to those funds we have been able to build two initial test benches, which are essential to reach TRL 4,” he details.
Beyond the Horizon project
The company obtained a grant from Acció Startup Capital in 2024 and, more recently, has been selected as a beneficiary of Neotec (CDTI). In 2026 it is preparing the application for a new Horizon Europe project that would allow it to reach TRL 5. “The project is already broadly defined and we are finalising the list of partners that could participate,” he adds.
More information
And for Windletter paid subscribers, access to the draft of the full interview.
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