Close-Up: New Scour Protection Solution That Has Potential to Cut Costs by 70 Pct Inspired by Turtles
At the beginning of May, Balmoral presented a scour protection solution that could replace rock dumping and is set to potentially cut costs by up to 70 per cent when compared to this conventional method. In an interview with offshoreWIND.biz, the company revealed that the initial concept behind its new HexDefence system was aimed at a solution for the oil and gas industry but was further developed with the offshore wind industry in mind and that its design was inspired by – turtles.
As reported last month, the Scotland-based engineering company introduced HexDefence saying the solution could drastically reduce scour phenomena around fixed offshore wind turbines that cause seabed erosion and a reduction in foundation strength and stiffness.
The structure provides a non-invasive approach to protecting the monopile and the immediate surrounding area and eliminates the need for rock installation which can cost up to 70 per cent more when compared to this new solution, according to Balmoral.
So, where do the cost savings come from? Besides not using rock installation vessels, HexDefence allows for cost reduction that reaches far into a project’s lifespan, the company says.
“The savings also come through operational cases such as allowing, for instance, CPS systems to become much shorter because scours become shorter, which enables faster burial and thus having less cable exposed in a highly dynamic environment. These are all going to make cables last longer and, in terms of OpEx, will potentially reduce servicing and lead to less downtime”, said Dr Aneel Gill, Product R&D Manager at Balmoral.
The OpEx savings are at the front and centre of the structure’s application on existing offshore wind farms, where HexDefence is seen as a retrofit option in case the conventional solution that was already employed has been damaged or removed and there is excessive erosion that could be causing issues to the cable and the monopile.
The new scour protection structures can also be outfitted specifically to enable easier installation at existing offshore wind projects, including hinge designs, segmented sections, quick-connects and other features designed into the system which allow for an ROV-installable process.
Dr Gill pointed out that the system was also a more advanced end-of-life solution that can be easily decommissioned and removed.
“Once a project reaches the end-of-life stage, you have to decommission it and leave the site as you found it. With rock, this means complex and time-consuming operations but with things like HexDefence, we do not have to go in and disturb the seabed since only a traditional lifting operation is needed to take the system off”.
Furthermore, the structure can be produced by using environmentally friendly materials, if required. While this would increase the cost at this time, in the future, this version could be more aligned with environmental protection and sustainability requirements in project development tenders.
The company says that it approached the development of the system as it does with most of its products – getting input and feedback from project developers/owners on potential issues which they are looking to minimise or solve.
“We always start at the top, at the developer and the operator side, and the reason we do that is to get a glimpse into a lot of the issues that they see at their level, which is important for us as a product solutions provider. This then steers our product developments and highlights what we should be looking at”, Dr Gill said.
“HexDefence, in its inception, originated as an oil and gas solution to reduce vortex-induced vibration, or VIV, for drill stacks and we have done a lot of work in that area, long before moving onto the issues with scour protection. We have built further on that hydrodynamic shape and followed it through to where it is now, which is the point where it is showing some really strong figures in terms of reduction of scour compared to traditional protection methods”.
Gill also revealed that the HexDefence design was inspired by none other than turtles, more specifically, turtle shells.
This kind of design has steady flow separation points which is important with things like VIV in oil and gas, and preliminary work on the design showed it can reduce accelerated flow.
“We saw really good results in the reduction of accelerated flow, as well as a significant reduction in turbulent kinetic energy. At that point, we started further research into whether this has an effect on scour and we kept testing and developing the product. We did a lot of testing at the University of Newcastle and used this data to validate our CFD models.”, Dr Gill said.
In its press release last month, Balmoral said it was encouraged by the industry to bring the new scour protection solution to the market as soon as possible.
According to Balmoral’s Engineering and Projects Director, Fraser Milne, the company is seeing increased interest from the industry in its newly developed solution and is currently looking to find partners to deploy HexDefence in-field for a full-scale demonstrator.
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