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Thought Leadership / November 10, 2023

Platform Manufacturing: Crossing Chasms in a Single Jump

By Adrian Haworth

Value Engineering is a common technique in many industries to align component costs with customer priorities. In the context of an offshore wind farm, the customer’s primary focus is on the electricity generated, whether it is fed into the grid or used for processes like hydrogen production. For offshore wind, the cost of the wind turbine generator (WTG) is the most critical. However, currently for a floating offshore wind project, the platform and mooring system which supports the WTG is higher. We at Gazelle Wind Power (Gazelle) believe this cost needs to be reduced and lower than that of the WTG.

According to the National Renewable Energy Laboratory (NREL)’s 2021 Cost of Wind Energy Review, substructure and foundation accounted for $36.5 of the $133 per megawatt-hour (MWh) levelised cost of energy (LCOE). In contrast, the WTG accounted for 22.7 $/MWh, or 17.1% of the overall LCOE.

The NREL report states that the WTG for floating offshore wind is roughly $1301 per kilowatt (kW), while the substructure and its mooring systems costs $2,089/kW of capacity. With these costs for a 15MW unit, the WTG assembly would cost an estimated $19.5 million, while the platform costs just over $31 million.

This current discrepancy is to be expected considering that WTGs have been in production for decades, with hundreds manufactured each year, leading to significant cost-reducing innovations. In contrast, platform designs currently being used for floating offshore wind draw on experience from the oil and gas industry, which historically builds structures as one-offs without focusing on capital expenditure (CAPEX), instead emphasizing uptime and output. To undercut the WTG’s cost, innovation is crucial.

Gazelle’s platform takes inspiration from the shipping sector, where centuries of development have optimised steel thickness, automated welding, and refined manufacturing systems to a fine art. This is evident in the fact that steel in a single-skinned bulker constitutes around 30 – 40% of the total price of a new build. By applying a similar approach to manufacturing a Gazelle platform, one can reasonably expect similar costs. With steel at $1000 per metric ton (t), the platform weighing less than 2500t should cost between $6.2 million to $8.3 million. Even when factoring in mooring system costs, the substructure and foundation can be less expensive than the WTG.

Another key aspect borrowed from shipbuilding is modularisation. Many ships are constructed in sections, often in different shipyards, before final assembly and launch. Gazelle’s platform modules can be produced in most modern shipyards and transported to a suitable port for final assembly and launch. This approach minimises supply chain bottlenecks and maximises opportunities for local content.

In contrast to the shipping industry, and many other floating offshore wind platforms, Gazelle’s platform does not include costly engines or ballasting systems that take time and expense to install during assembly. Additionally, the Gazelle platform does not have a control system. This not only keeps manufacturing costs low but also reduces final assembly time in the port to a minimum. The target for this is three days, eliminating the need for a vast assembly space in the port. As British politician David Lloyd George once said, “Don’t be afraid to take a big step if one is indicated. You can’t cross a chasm in two small jumps.” While early floating platform designs have demonstrated the feasibility of floating offshore wind, there remains a chasm in LCOE that must be crossed. Simply replicating the original designs will not allow floating offshore wind to complete with fixed-bottom wind. Innovation is essential, and next generation platforms are already showing the chasm can be crossed.

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