Most of the world’s offshore wind flows away from the coast, beyond the reach of bottom-fixed turbines. Floating foundations are expected to grow to a footprint of 10,000m2 and weights between 4,000t and 16,000t, requiring considerable infrastructure to transport.
Floating wind offers the fastest route to 2030 emissions targets. Building bigger and in greater volumes than ever before, it faces the challenge of creating a smooth production line from design to water: lowering energy costs and increasing project viability.
The sheer space required to build floating foundations will be a challenge for existing fabrication facilities; a fact that is likely to open the market to new entrants across the globe. Floating foundations are expected to grow to a footprint of 10,000m2 and 16,000t in weight, so need considerable infrastructure to handle.
As the sector matures, these modules will need to be fabricated, transported and launched in locations all over the world. This will require feats of engineering never before seen in the renewables sector – and further intensify pressures on time and space.
As turbines reach higher, innovations such as the SK6,000 will allow assembly to continue next to the quay, where it is most efficient. When maintenance events occur, our gantry solutions allow for fast repair at the turbine site, avoiding downtime while a suitable crane vessel is found.
Our offshore services team has transferred some of the world’s largest structures between land and sea; constantly innovating to find a way into the water that is most efficient, safe and cost-effective.
Complex floater designs and high volumes will combine to place significant time pressure on fabricators. To solve this, the industry will need to think big; manufacturing on a worldwide scale.
Fabricating floating foundations will present significant real estate challenges for existing facilities. The scale of foundations also limits the number and type of fabrication facilities that can be used.
There are limited dry docks of suitable size to get these structures in the water, neither is a slipway launch appropriate for such huge objects. So, fabrication sites will need a large draft, or the yard space needed to support crane launching.
As the market opens up to these new entrants, the right modularized construction approach will be crucial to a project’s success. Designing modules so that they can be built, transported and shipped in the most efficient way shortens overall schedules and lowers whole-project costs.
Our work helps customers to manage all this through a single point of contact; diversifying the supply chain and allowing fabrication to take place where specialist workforces are most abundant. This allows more work to take place in parallel, by experienced teams, with the fewest interfaces.
“Offshore wind development has to date focused on prototype projects with limited scope and highly varied designs. Through standardized design principles and modularized mass manufacturing strategies, construction can take place in parallel and economies of scale can be enjoyed that will lower the capital investments needed - making offshore wind more viable for more countries.
To achieve the goal of launching one floater per week, every element of the fabrication, logistics and construction chain must be fundamentally re-imagined. A daunting task – but luckily, one that has been tackled successfully before in many industry sectors.”
Ensuring an efficient production line at ports to keep projects moving will be a critical step in the floating wind industry reaching a mature model. To achieve this, facilities will need to put in place additional infrastructure to load-in, store and load-out components.
Due to their size, large real estate areas with good maritime access and sufficient ground capacity will be needed. Amongst the key criteria to meet will be the space to handle the increasing size of floating foundations, which are expected to grow to a footprint of 10,000m2 with weights of up to 16,000t.
It will be a challenge to find enough ports worldwide that can provide this, and infrastructure upgrades will be contingent on a reliable pipeline of projects being planned. However, with the right equipment, facilities located almost anywhere can enter the floating wind market.
Project-based upgrades that can deliver the required capabilities using operational rather than capital expenditure will be preferred. Mammoet can help to achieve this in an efficient and cost-effective manner, providing additional port space and lifting capability without interrupting existing activity.
We have helped major ports to develop their facilities with offshore wind in mind, providing additional space and ground reinforcement to marshal and store offshore wind components. Also, through innovations such as our SK6,000 crane, we provide temporary lift capacity, on-site only when it is needed.
“80% of world’s offshore wind is actually away from the shore, i.e. above seas deeper than 60m. This resource could power the world ten times over.
These floating foundations can easily be 100m x 100m in size, so storing them on land is realistically not an option. Which means that they will have to be installed using just-in-time manufacturing processes that the renewables sector has not yet needed to use.
However, plenty of expertise from elsewhere in heavy industry can be transferred quickly and easily. For example, the transfer of smaller floating foundations such as spars, our large ring cranes can be used to create a smooth production line between quay and barge.”
With weights of anything between 3,000t and 16,000t, the launch of floating substructures is far from simple. The key challenge is to find a safe, cost-efficient and scalable method for placing large units in the water.
One common approach has been the use of semi-submersible vessels, with components rolled onto the vessel using SPMTs. However, the time needed to prepare floaters for launch is significant, so this approach may not be cost-effective at scale, due to the time the vessel would lie idle.
A hybrid approach could be used, whereby the floater is lifted from both land and sea and lowered onto the water directly at the quay side. However, the use of several equipment types to perform lifts heightens the risk of a critical path failure, and so is not seen as a workable industrialized method.
One way to achieve this effectively and safely is through the use of a heavy lift crane. This approach allows smaller foundations to be placed directly into the water; cutting down several shifts of work to a single day.
This approach has a number of other benefits: it mitigates the impact of swell on launching and requires a shallower draft than semi-submersible options, opening up more locations. It also reduces the requirement for specialized fastening and equipment when launching foundations.
“To realize the full potential of floating wind, we must find the most efficient methods of constructing wind parks at scale. Standardizing floater types and methods of launching will play a large part in this.
Floating wind farms will allow us to de-carbonize our energy supplies quickly, but to get these massive objects in the water faster their transportation must be built right into their design. This is where engineered heavy logistics comes in.
Our SK6,000 crane can lift and launch spar foundations directly into the water, reducing the need for land-based storage and shaving weeks off wind farm construction schedules – and all from operational budgets.”
Floating wind turbines are growing in size, height and weight as developers seek larger power yields from higher wind speeds. So much so, that they are rising beyond the reach of all but the tallest cranes.
In fixed foundation offshore wind, jack-up vessels install turbines nearshore. But the water depth of floating wind projects – often between 80m and 100m – are too deep for jack-up vessels to operate in.
The complex engineering required to assemble floating turbines from a floating crane vessel rules this out as a viable long-term solution. Positioning jack-up vessels at port is also problematic, as they will soon be too short to build the tallest offshore turbines and would lie dormant for long periods between load-outs.
What’s more, modern 1,000t nacelles need to be installed 170m in the air; sometimes as far as 55m from the quay edge. This means that even when assembling from dry land, one of the world’s largest crawler or super heavy lift cranes will be required to complete the job.
Using Mammoet’s LR 13000, PTC or SK ranges of cranes allows ports and developers to shift spending on lift procedures into operational rather than capital expenditure. This can turn the smallest of ports into a functioning heavy lift terminal that exists for as long as the project does.
“Offshore wind farms occupy increasingly remote waters, raising the costs of their maintenance. Floating offshore wind farms will reach into deeper waters still.
Hub heights already lie beyond the reach of many crane vessels - and the general trend is upwards. Maintenance of these turbines at sea is complex – even towing them to land is tough, since land-based cranes that could service these turbines are often scarce as well.
Modular lifting systems deployed to floating wind farm sites provide insurance against circumstances where a crane vessel is not available.”
It is estimated that around 25% of floating wind turbines will have a maintenance incident during their lifetime, creating significant pressures on budgets. With thousands of turbines being installed in the coming years this is a key consideration for the industry.
Hub heights reaching 170m will put turbines beyond the reach of many crane vessels, making repair at sea a costly operation with a significant risk of delay. The work involved in freeing a turbine and bringing it to port can make this method unviable, too.
Here, the challenges encountered during installation of the turbine are encountered in reverse; for example, the proposed port may have poor infrastructure, or be busy with other projects. So, alternative ways of conducting maintenance on the turbine in situ are needed.
Luckily, the floating wind sector can benefit from established solutions that have been tried-and-tested in other industries. Mammoet offers specialized expertise in performing repairs to offshore assets in situ and has developed modular solutions that offer important advantages for floating wind.
Our 200t module lifting system uses the turbine itself as a means of support and can be deployed from even small fishing ports. This makes it possible to execute turbine maintenance, quickly, cost-effectively, and without the need for a crane vessel at all.
