Windstory #28 - Saitec Offshore Technologies’ floating prototype, two years later
Saitec Offshore Technologies’ DemoSATH prototype has now surpassed two years of operation. We have spoken with them to learn both about the lessons learned and the future outlook
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Saitec Offshore Technologies’ floating prototype, two years later
It has now been practically two and a half years since Saitec Offshore Technologies installed its DemoSATH floating wind turbine prototype in the BIMEP (Biscay Marine Energy Platform) test area, off the coast of Bizkaia.
And almost four years since I had the opportunity to visit it at the Port of Bilbao (very close to home), when it was still waiting to be transported to its final location. I told the story then in the now almost historic edition #12 of Windletter (sorry, only in Spanish).
I remember that visit with special excitement. I believe that was the first time Windletter left home to do “field work”. Thank you, David Carrascosa, for the invitation and for taking the time to explain everything to me in detail. With a bit of luck, this 2026 will bring some other edition with field work.
In October 2024, we reviewed the prototype’s first year of operation. At that time, the message was clear: the SATH platform had demonstrated viability and good performance in one of the most demanding environments in the European Atlantic.
Today, with more than two years of real operation behind it and a much more solid operational database, Saitec Offshore’s narrative has evolved. It is no longer only about withstanding the blows of the Cantabrian Sea, but about turning that experience into a competitive advantage that enables the commercial viability of the platform. And we spoke to David again to find out more details.
What we knew in 2024: viability validated under real conditions
DemoSATH, a double-hull concrete barge-type platform equipped with a 2 MW Senvion MM82 turbine, was connected to the grid in September 2023, becoming the first floating wind turbine in Spain to inject energy into the electricity system.
Its location, BIMEP, although perhaps not an area with a major wind resource, is very interesting for testing the technology: 85 metres of water depth, significant wave conditions which, according to Saitec data, exceed 1.5 metres 42% of the time (as a reference, in the North Sea this is around 30% of the time), and recorded waves of up to 10.78 metres.
In that context, the first-year data were especially relevant:
98% of the time, pitch and roll motions (that is, the pitching and rolling of the assembly) remained below 2.5º.
No turbine shutdowns attributable to the platform were recorded.
Operational stoppages occurred only during wind speeds above 25 m/s, just as in an onshore site.
During this time, the design combining the horizontal double hull, damping plate, and SPM (Single Point Mooring) turret-type mooring system inherited from Oil & Gas has shown that stability was not only a design hypothesis, but an operational reality.
DemoSATH, two years later: more production, more data, and less uncertainty
A second year of operation has provided continuity, more data, and more testing hours. In addition, and although this is not the main objective of a prototype, DemoSATH recorded a 26% increase in annual energy production (AEP) compared to the first year. According to the Saitec team, this is the result of two main factors:
Exceptionally favourable wind conditions.
Greater team experience in the integrated management of platform–turbine dynamics.
Saitec says that monitoring, data acquisition, and data management has been one of the challenges that has surprised them the most: “We have found the task of processing monitoring data strikingly labour-intensive,” the company explains. “The collection, validation, and processing of data has required more effort than expected during the design phase, an aspect that is often underestimated in demonstration projects.”
In terms of technical validation, the real results have remained close to the simulations. “There are always small divergences between models and reality, but they are within reasonable ranges.” The models appear to have slightly underestimated actual energy production, while some hydrodynamic design loads have turned out to be more conservative than those measured in the field.
The latter is especially relevant because it opens the door to a certain margin for optimisation in future designs without compromising integrity.
“Our most important asset is the characterisation of the platform’s dynamic behaviour under different metocean conditions and turbine operating regimes,” Saitec explains. “By establishing the analytical relationships that govern these variables, we have acquired a predictive capability that is fundamental for optimising future designs, reducing fatigue in the loads, and improving the overall profitability of the technology.”
An onshore turbine in a floating offshore environment
One of the critical points for this testing phase, and one that also greatly sparks my curiosity, is how a turbine originally designed for onshore use has performed when installed under marine conditions on a floating platform. It is a 2 MW Senvion MM82 that Saitec acquired refurbished and retrofitted to adapt it to the marine environment.
After two years, the assessment is more than positive: “Its behaviour under wave conditions is considerably similar to performance on land, demonstrating the stability of the SATH platform even under adverse conditions.”
The decision to use passive ballast systems, reducing mechanical complexity, has minimised failure risks. Added to this is the single point mooring with passive alignment, which allows the platform to behave like a weather vane against wind and waves, reducing dynamic loads on the tower and mooring lines.
In a context where some pioneering floating projects have had to carry out major corrective interventions, the fact that after two and a half years the turbine is still operating in good condition is especially significant.
O&M and bankability: less towing, more in situ intervention
From the operation and maintenance point of view, the experience has reinforced a clear priority: maximising remote diagnostics and preventive maintenance.
Reducing the number of trips out to the turbine offshore is a direct lever for OpEx optimisation. In addition, Saitec points to the future integration of solutions that allow major component replacement (MCR) to be carried out in situ as a strategic line, avoiding towing-to-port strategies, which involve high costs and long periods of downtime.
“We are proactive when it comes to major component replacement. Assuming that failures may be due to various factors, we are integrating innovative design solutions into the SATH platform to eliminate or significantly reduce the logistical costs associated with major offshore interventions,” they add.
SATH 15+: from demonstrator to industrialisation
Of course, these years of data and lessons learned have been key in the design of the SATH 15+, the version of the platform adapted for 15 MW turbines or more.
If DemoSATH has served to validate the behaviour of the technology under real conditions, SATH 15+ is already being born with a clearly commercial purpose, with the focus placed on industrialisation and on reducing LCOE.
The experience accumulated at sea “has been incorporated into the current design, orienting it more clearly towards market needs and the economic challenges of floating offshore wind,” SAITEC tells us.
The design keeps its essence (stability, hydrodynamic response, concrete as the base material) but incorporates optimisations aimed at:
Standardisation and modularisation.
Simplification of construction sequences for serial production.
Reduction of critical operations that allow industrialised manufacturing with a high degree of replicability.
Lower dependence on specialised port infrastructure, especially relevant for emerging markets where ports present limitations in draught, surface area, or load capacity.
“This approach makes it possible to directly reduce CAPEX costs associated with manufacturing, assembly, and commissioning, as well as planning and execution risks,” Saitec adds.
The challenges of scaling to 15 MW turbines
Scaling towards turbines of 15 to more than 20 MW, which is already emerging as the new standard in commercial projects, poses challenges that directly affect platform design, the structural integrity of the complete system, and economic viability.
One of the main challenges is stability control, since the aerodynamic loads from the wind and the hydrodynamic actions of waves and currents must be managed simultaneously. “The combined response of the turbine and the platform becomes a critical aspect of the design,” which requires precise analysis and control of movements.
The increase in power also implies higher loads and structural demands, which must be addressed while guaranteeing robustness and fatigue performance without penalising the structure, given its direct impact on CAPEX and LCOE. To achieve this, integrated analyses using aero-hydro-servo-elastic tools are required in order to reflect the real behaviour of floating wind turbines.
At the construction and logistics level, high-power turbines require minimising offshore operations and prioritising onshore activities, which makes it necessary to design solutions compatible with ports that have limitations in draught, surface area, or lifting capacity.
At the same time, in operation and maintenance, higher production per unit increases the economic impact of any unavailability, making movement control, operational stability, and intervention efficiency key factors.
Concrete as a competitive advantage
Concrete has proved to be a material with great strength, high durability, significantly lower operation and maintenance (O&M) costs due to the reduced need for offshore interventions, and a high local content, since it is widely available in many regions and can be produced close to ports.
Unlike other materials, which are more exposed to the volatility of global markets, concrete maintains greater stability in terms of availability and costs.
“We believe it is a key bet for the markets where floating offshore wind is being developed, representing a strategic opportunity,” Saitec comments. “Concrete offers a clear competitive advantage, since the production, batching, and prefabrication of concrete can strengthen existing local industries (cement, aggregates, construction), creating technical and skilled jobs close to ports.”
Market: from enthusiasm to natural selection
At a global level, floating wind has moved from the initial euphoria to a phase of greater realism. “At Saitec Offshore we remain focused on projects that are committed to a reliable and robust technology, where we can contribute our differential value with SATH technology.”
Their current focus is on participation in pre-commercial and commercial projects, with specific tenders that are taking place in different countries.
At the same time, they are positioning themselves in the supply chain, reserving spaces in strategic ports where they can “incorporate SATH platform manufacturing plants, which can supply the demand that will be generated in the coming years.”
In terms of real traction, Saitec identifies the United Kingdom (especially Scotland), France, and Norway as markets with defined revenue frameworks and advanced permitting. China is pushing in supply chain and large-scale prototypes, while Japan, although it is beginning to materialise commercial milestones, continues to face cost challenges.
Spain, for its part, remains in a phase of regulatory waiting. The opening of the public consultation for the first competitive procedure is a necessary step, but insufficient if it is not accompanied by a predictable timetable. “If we want industry, we need certainty and speed.”
When asked whether pre-commercial wind farms with a small number of units should have been prioritised in Spain, Saitec is clear: “yes, pre-commercial wind farms would have brought a great deal of value in Spain, but not as a substitute for large scale, rather as a parallel route to reduce technological and permitting management risks, and to prepare the supply chain ahead of the commercial leap.”
Where they see Saitec Offshore in 5 years
Over the next 5 years, Saitec’s stated objective is to have built a pre-commercial wind farm with large offshore turbines and to have been selected as the technology in at least one large-scale project.
The key will be to turn the DemoSATH experience into bankability evidence: data, reliability, procedures, and risk mitigation. In addition, the design must demonstrate cost competitiveness.
Floating wind is going through a phase of consolidation. It is no longer about proving that it is possible, but about proving that it is competitive, financeable, and scalable.
Four years ago, DemoSATH was an ambitious experiment facing the Cantabrian Sea. Today it is a test bench that has reduced technical uncertainty and has fed the design of a platform oriented towards the market.
In a sector where technological natural selection is already under way, the difference between a concept and a commercial solution is measured in real operational data. And in that field, Saitec has already accumulated more than two years of evidence.
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Disclaimer: The opinions presented in Windletter are mine and do not necessarily reflect the views of my employer.