Gazelle Floating Wind Platform Cost Estimates

Gazelle floating wind platform cost estimates show that the concept aims to reduce the levelized cost of energy (LCOE) for deep-water wind farms to the $50–$70 per megawatt-hour range, though no commercial-scale project has yet published a final, verified cost figure. The estimates come from engineering studies and developer statements, not from an operating farm, so they should be treated as projections rather than confirmed prices. This article explains what those estimates cover, how they compare to other floating platforms, and what the numbers actually mean for a wind farm budget.

Formula

The calculator above gives a rough planning estimate for a floating wind farm using a generic semisubmersible platform similar to Gazelle. The first output, estimated LCOE, is the levelized cost of energy in US dollars per megawatt-hour. It starts at 60 USD/MWh for a 15 MW turbine in 200 m water depth, then adds 0.02 USD/MWh for each additional meter of depth (because mooring and anchoring costs rise) and 1.5 USD/MWh for each additional MW of turbine capacity (because larger turbines require a larger platform and heavier structure). The second output, estimated CAPEX (capital expenditure), is the total upfront cost in million USD. It uses a simplified model: each turbine costs about 1.2 million USD per MW of capacity, plus a fixed 25 million USD per platform for steel, fabrication, assembly, and installation. The third output, estimated annual OPEX (operating expenditure), is the yearly operating cost in million USD: 0.08 million USD per MW per year plus 1.5 million USD per turbine for maintenance, crew, and insurance.

Worked Example

Using the default values from the calculator – 15 MW turbine, 200 m depth, 10 turbines – the estimated LCOE is:

60 + (200 – 200) * 0.02 + (15 – 15) * 1.5 = 60 + 0 + 0 = 60 USD/MWh.

The estimated CAPEX is:

10 * (15 * 1.2 + 25) = 10 * (18 + 25) = 10 * 43 = 430 million USD.

The estimated annual OPEX is:

10 * (15 * 0.08 + 1.5) = 10 * (1.2 + 1.5) = 10 * 2.7 = 27 million USD per year.

These numbers match the calculator outputs. They are illustrative only – a real project would need site-specific data for steel prices, port availability, and installation vessels.

Background: What Is the Gazelle Platform?

Gazelle is a floating wind platform concept developed by the French company BW Ideol, which specializes in floating foundations for offshore wind. The platform is a semisubmersible design – a ring-shaped steel hull that floats partially submerged, with a turbine mounted on a tower in the center. Unlike a spar or tension-leg platform, a semisubmersible is stable because of its wide waterplane area and can be assembled in a port and towed to the site without specialized heavy-lift vessels. The Gazelle name refers to a specific generation of BW Ideol’s platforms, which evolved from their earlier “Damping Pool� design. The key innovation is a central moonpool that damps wave motion, reducing the platform’s motion and allowing the turbine to operate in higher waves.

BW Ideol has deployed a full-scale demonstrator, the Floatgen turbine, off the coast of France, which has been operating since 2018. That project uses a 2 MW turbine on a 30-meter-wide platform. Gazelle is a larger, next-generation version designed for 10–15 MW turbines. The company has also licensed its technology to other developers, including a project in Japan and a proposed farm in the Mediterranean. As of 2025, no Gazelle platform has been installed at commercial scale, so cost estimates come from engineering models and bids for demonstration projects.

How Cost Estimates Are Built

Cost estimates for floating wind platforms are divided into three main categories: capital expenditure (CAPEX), operating expenditure (OPEX), and the levelized cost of energy (LCOE). CAPEX includes the cost of the steel hull, the mooring system, the anchor, the turbine itself, and the installation – towing the platform to site and connecting the cables. OPEX covers maintenance, crew transfers, spare parts, insurance, and port lease. LCOE is the total lifetime cost divided by the total energy produced, expressed in USD per MWh. It is the standard metric for comparing energy projects.

For Gazelle, the main cost drivers are:

• Steel and fabrication: A 15 MW platform requires roughly 3,000–4,000 tonnes of steel, depending on the design. At current steel prices (around $800–$1,200 per tonne), that translates to $2.4–$4.8 million for the hull alone.
• Mooring and anchoring: In 200 m water depth, a semisubmersible typically needs three to six mooring lines, each with a drag anchor or suction pile. Costs range from $1–$3 million per turbine for the full mooring system.
• Turbine cost: A 15 MW offshore turbine costs roughly $15–$20 million, which is about 40% of the total CAPEX.
• Installation: Towing the platform and connecting the dynamic cables can cost $2–$5 million per turbine, depending on vessel availability and weather.

BW Ideol has stated that their platform design reduces steel weight by about 20% compared to earlier semisubmersibles, which directly lowers material cost. They also claim that the damping pool reduces platform motion, which can increase energy production by allowing the turbine to operate in higher wave heights – effectively lowering LCOE because more energy is produced per year.

How to Choose a Floating Platform: Gazelle vs. Alternatives

When comparing floating platforms, developers look at four key metrics: steel weight, motion performance, installation complexity, and scalability. Gazelle’s main advantage is its simplicity – it is a ring-shaped hull that can be built in any shipyard and towed with a standard tugboat. This makes it attractive for sites far from shore, where installation vessels are expensive.

Alternatives include:

• Spar platforms: These are long, vertical cylinders that float upright with a deep draft (100+ m). They are very stable but require deep water and are difficult to assemble in shallow ports. The Hywind project in Scotland uses spar platforms.
• Tension-leg platforms (TLPs): These use taut mooring lines that hold the platform vertically, reducing motion. They are lighter but require complex anchors and precise installation. The WindFloat project uses a semisubmersible, not a TLP.
• Barge platforms: These are simple, box-shaped hulls that float on the surface. They are cheap but have high motion, which limits turbine size. The SATH platform is an example of a barge design.

Gazelle sits in the semisubmersible category, competing with WindFloat (Principle Power) and the OC4 design. The choice depends on water depth, wave climate, and local fabrication capacity. In rough waters, a TLP or spar may be more stable; in moderate waters, a semisubmersible like Gazelle is often cheaper because it can be assembled onshore.

Common Problems and Misconceptions

One common misconception is that floating platforms are inherently more expensive than bottom-fixed ones. In shallow water (less than 50 m), that is true – bottom-fixed monopiles are cheaper. But in water deeper than 60–80 m, floating platforms become competitive because the cost of a fixed foundation grows exponentially with depth, while a floating hull cost is nearly constant. Gazelle’s cost estimates are specifically for deep-water sites where bottom-fixed is not feasible.

Another issue is the “damping pool� – the central well in the platform that reduces motion. Some critics argue that the pool adds weight and complexity, but BW Ideol claims it reduces the platform’s pitch and roll by up to 50% compared to a flat deck, which allows the turbine to run longer. This is a key factor in the LCOE estimate: more operating hours means more MWh per year, lowering the cost per unit.

A third misconception is that the cost estimates are final. They are not. The $50–$70/MWh range is a target that assumes mass production – building hundreds of platforms in a standardized way. The first commercial project will likely be higher, perhaps $80–$100/MWh, because of learning curve and supply chain issues. The estimates also do not include grid connection costs, which can be significant for deep-water sites far from shore.

Cost Comparison with Other Floating Platforms

Industry-wide, floating wind LCOE is currently estimated at $100–$200/MWh for early projects, with a target of $50–$80/MWh by 2030. Gazelle’s estimates fall at the lower end of that range, but they are not unique. The WindFloat platform, used in the WindFloat Atlantic project in Portugal, has published an LCOE of around $100/MWh for a 25 MW farm. Hywind Scotland, a spar-based project, reported an LCOE of about $150/MWh. Gazelle’s advantage is its lighter hull – BW Ideol claims a steel weight of about 1,200 tonnes for a 10 MW platform, compared to 3,000+ tonnes for a comparable spar. That directly reduces material cost.

However, the damping pool adds a fabrication step – the pool requires a special mold or welding jig – which may increase labor cost. The net effect is uncertain until a large project is built. The calculator above uses a generic semisubmersible cost model; actual Gazelle costs could be 10–20% lower if the weight reduction is realized.

Safety and Environmental Considerations

Floating platforms have a good safety record, but there are specific risks: mooring line failure, which can cause the platform to drift; dynamic cable fatigue; and collision with vessels. Gazelle’s design includes redundant mooring lines and a motion monitoring system. The damping pool also acts as a safety feature – it reduces the platform’s motion in extreme waves, which lowers the risk of structural damage.

Environmental concerns are similar to other offshore wind: impact on marine mammals during pile driving (though floating platforms use suction anchors, which are quieter), bird collisions, and electromagnetic fields from cables. The main advantage of floating platforms is that they can be placed in deeper water, where they are less visible from shore and may have less impact on coastal ecosystems. The steel hull is recyclable at end of life, but the dynamic cables and mooring chains are harder to recycle.

Frequently Asked Questions

What is the actual cost of a Gazelle platform?

There is no public, verified cost for a full Gazelle platform because no commercial-scale unit has been sold. The Floatgen demonstrator (2 MW) cost about €25 million ($27 million) including installation, but that was a one-off. For a 15 MW platform, engineering estimates suggest a hull cost of $10–$15 million, with the total installed cost (turbine + hull + mooring) around $30–$40 million per turbine. These are projections, not invoices.

How does Gazelle compare to bottom-fixed offshore wind?

Bottom-fixed wind in shallow water (less than 50 m) has an LCOE of $40–$60/MWh, which is lower than Gazelle’s estimate. But bottom-fixed is not possible in deep water. At depths of 100–200 m, a fixed foundation would cost more than the turbine itself, making floating platforms the only option. Gazelle’s target of $60/MWh is meant to be competitive with bottom-fixed in the long run, but that will require mass production.

What is the damping pool and why does it matter?

The damping pool is a central well in the platform that is open to the sea. When waves hit the platform, the water in the pool moves up and down, dissipating energy and reducing the platform’s motion. This is similar to a tuned liquid damper in buildings. The benefit is that the turbine can operate in higher wave heights – typically up to 6–8 m significant wave height – which increases annual energy production by 5–10% compared to a platform without a pool.

Are Gazelle cost estimates realistic?

They are optimistic but not impossible. The $50–$70/MWh range assumes a learning curve similar to what bottom-fixed wind achieved in the 2010s. The key uncertainty is the supply chain – building hundreds of steel hulls requires shipyard capacity that does not exist yet. If steel prices rise or installation vessels are scarce, the cost could double. Conversely, if the design is standardized and produced in series, the cost could fall below $50/MWh.

Can Gazelle be used for hydrogen production?

Yes, but that is not part of the platform’s core design. A floating wind farm could power an electrolyzer on a platform or on a nearby floating vessel to produce green hydrogen. The cost of hydrogen would depend on the LCOE of the wind farm – at $60/MWh, hydrogen could cost around $3–$4 per kg, which is competitive with fossil hydrogen in some markets. However, this is a separate project concept, not a standard Gazelle configuration.

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in t | Turbine capacity | MW | 15 | 1 | 30
in d | Water depth | m | 200 | 50 | 1000
in n | Number of turbines | - | 10 | 1 | 100
out lcoe | Estimated LCOE | USD/MWh | 60 + (d - 200) * 0.02 + (t - 15) * 1.5 | 0
out capex | Estimated CAPEX | million USD | n * (t * 1.2 + 25) | 0
out opex | Estimated annual OPEX | million USD | n * (t * 0.08 + 1.5) | 0