We are very proud that our Swift Anchors technology has been selected as one of the ten promising innovations that can play a full part in the net zero revolution and create significant growth in the tidal industry:
INNOVATIVE ANCHORS FOR FLOATING DEVICES
BACKGROUND
Innovative anchoring solutions can take many forms. These solutions offer lower CAPEX, lower material usage, quicker installation time and lower OPEX throughout the lifetime of a floating TS project in comparison to gravity based and grouted anchors.
One example of an innovative anchoring solution is the use of self-drilling, grout free rock bolt anchors, that which is offered by Swift Anchors. In addition to their use in the TS sector, Swift Anchor’s solution has also been explored for operation in various other sectors including floating wind, floating solar and aquaculture, but demonstrations at scale will be required to prove their solutions are appropriate for use in each respective industry. Despite multiple innovative anchoring solutions being currently available for both the TS and FOW sectors, the focus here will primarily be on rock bolt anchor solutions due to the hard nature of seabed seen at most TS sites, with comparison being made to gravity based and grouted anchors.
Significant CAPEX costs could be avoided through the use of rock bolt anchors from the huge reduction in material required to support a given mooring load. For example, a one tonne grout free anchor can support a mooring load of around 200 tonnes while having far smaller mass and spatial requirements (i.e., a rock bolt anchor is typically several metres long which is mostly embedded within the rocky seabed, compared to a gravity based solution which requires many tonnes of ballast material while taking up tens of square meters in seabed area). These smaller spatial requirements bring about less environmental impact which can also play a role in streamlining the consenting process. Environmental impact is also reduced compared to grouted connections as these anchors are removable at the end of their life and leave no footprint after a TS project has been decommissioned.
Focusing again on anchor material and spatial requirements; calculating the interface friction between the clump and the seabed is hard to accurately predict on TS systems using gravity based anchors, with the implications of high flow introducing additional hydrodynamic loads which must be considered. This can therefore bring a degree of uncertainty, with there being many cases where additional material is used beyond the actual loading and hydrodynamic requirements, thus worsening the already excessive material usage in comparison to rock bolt anchors.
When considering mooring load management provided by grout free anchors, they have their pros and cons compared to grouted solutions. For example, with grouted solutions, inconsistencies can be experienced during the grout curing process which results in some grouted installations having lower than anticipated load capacities, compared with the same anchors which have cured fully during the installation process. On the other hand, despite grout free anchors being free of the uncertainty that is brought about by the curing process, like a grouted solution, they are also dependent on the strength of the rock in which they are installed, which can be difficult to ascertain across all anchor locations.
Sizable cost reductions may be achievable during the installation phase by using rock bolt anchors instead of gravity based ones, but this is yet to be demonstrated. Much of this would be down to the far quicker installation times and lower vessel charter costs. According to Swift Anchors, their solution can be installed in around 35 minutes over the course of a slack tide period. This gives them the opportunity to install several anchors a day off relatively small vessels, compared to the installation of gravity based foundations which require far larger, more expensive vessels. There have been cases where the cost of vessel hire for rock bolt anchors has been around a quarter that of gravity based solutions.
INNOVATION CHALLENGES AND LCOE REDUCTION POTENTIAL
At present there are a range of rock bolt anchors, both grounded and grout free, that could potentially offer a viable alternative to gravity based solutions, but these are yet to be demonstrated at full scale. Even once a rock bolt anchor has been proven at scale, the lack of standards for rock bolt anchors will remain an issue that requires resolution. A standardised set of anchor sizes which can satisfy a range of device scales across different seabed conditions will need to be agreed upon by the wider TS industry. According to Swift Anchors, this is an area which would enable the biggest cost reduction for their business through the ability to volume manufacture and reduce material usage in the production process. Swift Anchors estimated that such standardisation could reduce their manufacturing costs by 20-30%.
The way in which anchor standardisation is reached is hard to determine at this stage. Regardless, developers have an instrumental role to play in the cost reduction journey by engaging with their suppliers early in the project development phase. By working closely with anchor suppliers to determine aspects such as mooring loads and geometry in the design phase of the wider anchoring/mooring system; costs can be minimised by avoiding excess chain being purchased while maximising the mechanical performance of the system.
In terms of the final LCoE reductions that can be achieved through innovative anchoring solutions, it must be acknowledged that there will be a degree of variation from site to site. This will be influenced by factors such as the bathymetry and geology of the seabed (e.g., sandstone, granite), as well as overburden and the overall strength of the seabed in which anchors are being placed. For example, the strength of the seabed will influence the length of anchor used which will determine overall anchor CAPEX, with weaker seabed requiring longer anchors. However, through previous stakeholder engagement via the TIGER project and internal ORE Catapult modelling, an estimated LCoE reduction of 5-10% can be achieved by using innovative anchoring solutions. To maximise LCoE reductions even further in the future; anchoring/mooring systems should be optimised in shared configurations so that their enhanced efficiency and ease of installation allows for significant decreases in anchor CAPEX across a given project’s lifetime. However, shared anchors will only achieve substantial cost reductions once larger floating arrays are developed, whereby they become the cost-optimal solution.
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