Sustainable Installation & Maintenance Methods Keith McDermott Commercial Director for Tidal Energy Mike Wilson - Managing Director Mike Wilson Managing Director Ecosse Subsea Systems Ltd
Personnel ESS provide a specialist personnel and resourcing support business service across the full spectrum of offshore requirements. Today more than 350 million of subsea projects are managed by ESS personnel resource for and on behalf of our clients. Engineering Consultancy Ecosse offer bespoke engineering and design solutions with a team combining a vast experience curve, specialist subsea expertise, coupled with procurement, fabrication, and installation know-how. Pipeline Engineering ESS Technologies comprises of innovative patented offerings specifically developed over more than 25 years to address subsea operational challenges. These include trenching,cable/pipelay, and lifting applications. Ambient Lifting ESS s patented subsea lifting and positioning technologies Ambient lifting is a flexible mechanism using incompressible gas which facilitates control of the accent, decent and underwater positioning of offshore structures. Equipment Hire A wide range of equipment is available for hire to support and deliver subsea installation projects. Including 800-2000Te Carousel, 10Te Hydraullic Tensioners, SCAR Plough in its four configurations and PREP (Plastic Reeled Elastic Pipelay System).
High Energy Environment High energy can be defined in a number of different ways:- average wind speeds tidal ranges current flow sea state Very rarely is there only one source of high energy influencing the environmental conditions at a particular site. For example waters around the UK and Canada coasts are well documented and renowned for the challenging environmental and geological conditions they present in the near shore; this is consistent with coastal conditions surrounding many countries. These same challenging conditions, however, present the ideal, highenergy environments for the placement of Renewable Energy Generation devices. Thinking differently, Ecosse Subsea Systems (ESS) have developed installation solutions that are applicable to all variations of Offshore Renewable Generation.
Unconventional Cable Protection There are distinct cabling systems within any generation array: Export Cable and Inter Array Grid cabling. Traditionally, both sets of cables are buried throughout most of their length and are protected at entry into the generation device. In the case of a high energy environment, sediment or organic deposits are usually eroded away, exposing the underlying bedrock. The ability to protect the cable in such an environment through burial therefore becomes increasingly unpredictable and hence an almost limitlessly expensive option. ESS have developed a methodology that uses off-the-shelf products that are available in abundance to protect both Export and Array cables for their entire life cycle
Unconventional Cable Protection using line pipe as steel ducting Utilising ESS patented Olympic Spoolbase technology, the installation contractor has the ability to prepare onshore the entire field array cabling and export lines, off the critical path, prior to installation, and the cables can be towed out, in bundles or individually to site as required. By carrying out a detailed pre-engineering campaign, the most effective pipeline characteristics can be selected from a vast range of standard inner diameters, outer diameters and wall thickness, to provide the necessary on bottom stability for the specific site conditions. This system is suitable for protecting from not only all environmental hazards but also from anthropogenic hazards present in coastal waters.
Economic Benefits of Olympic Spoolbase cable in line pipe compared to conventional armoured cable COST:- heavy armoured power cables can be six times more expensive than conventional land power cable. RISK:- Installation risks are massive and costs are excruciatingly expensive On bottom life time cable risks in high energy environments are currently unknown but our FO experience is horrendous AVAILABILITY:- Armoured cable lead times are long and project cash flow busting CAPEX is required By comparison COST:- Conventional cable and steel pipe is relatively cheap RISK:- Pipe is robust, highly reliable and is a known quantity, cable is readily available Pipe is quick and low risk to install and replace by towing to and from site. AVAILABILITY:- Local companies can make and install your cables.
Cable Shore Landings in Challenging Terrain When landing a cable in a high energy environment, the transition through the intertidal zone can be one of the most challenging installation risks to manage. High current flow found in these areas is caused by a tidal range of several meters difference. ESS method of cable-within-pipe protection can be extended to include the shore landing by utilising further lengths of more robust pipe of a larger diameter than the carrier pipe and installing this as a caisson. This pipe can be deformed plastically off critical path prior to pull in to follow almost any route required. The pull through of product through the carrier pipe being performed from shore with a suitably installed winch, greatly reducing the costs and risks associated with current methods of installation in hard, rocky geology.
Difficult cable protection using caissons
Subsea Lifting Without Cranes using Ambient Lifting Typically, syntactic foam or air-filled bags/buoys would be used to provide the buoyancy required to perform the float out. This method, though perfectly adequate and providing buoyancy, carries with it a number of hazards such as; Cost Time taken to install Introduction of point loads in the system Dependence on a crane system to control the decent ESS have developed, using their experience and simplistic ideology, a complete installation solution: a way of providing a constant and uniformly distributed buoyancy force that is also a method of introducing a finely controllable ballasting element to facilitate installation through the water column
Ambient Lifting Ambient Lifting is another ESS patented technology, developed wholly internally, which uses the principle of incompressible gas to deliver a constant buoyancy force down to sea depth to allow controlled lifting operations to take place subsea. This allows the product to be lowered to the seabed in the correct position. The water/gas ratio will be carefully monitored to ensure the descent is controlled. The ability to redistribute this ratio with fine control gives the installer the ability to pause and even reverse this lowering, if required. This system also has applications for the installation of Gravity Base structures.
Technical and Commercial Features Technical: Safe, simple & robust Tubular buoyancy and ballast pressure containing system Fully scalable Can lift <1Te to >1000Te Suited for confined operating spaces All testing/commissioning done on land Controlled decent & accent for underwater ROV or diver positioning Low sensitivity to surface weather conditions for installation Recovery process is reverse installation process Commercial: Low cost materials Off-the-shelf components Can be built by local contractors Rapid fabrication, sized to suit application Re-usable Installed by small vessels Negates the need for expensive heavy lift vessels Air and Water Tight Receptacle for Floatation and Ballast Medium (Typical example HDPE Gas Pipeline)
Mooring & Foundation Alternatives Adapting Ambient Lifting, a way of providing a complete installation solution has been devised by replacing the ballast element with a pumpable, Ballasting fluid. Once the Array or Export cable has been sunk to position, the water in the piggyback line and in the cable/pipe annulus would be replaced with a gel of SG 3.0, greatly increasing the mass on the seabed, further increasing the on-bottom stability of the product. The cost and time efficiencies in this system are far reaching and the potential benefits to schedule and risk reduction are game-changing in this emerging market.
Managing Risk; Improving Safety ESS ethos is to provide robust, inherently safe, risk reducing and efficiency improving products, systems and methodologies to the subsea market. The equipment provided is designed to broaden the ability of the local contractor to work in these high energy environments by reducing the number of moving parts, limiting the possible failure modes and thus broadening the operating environmental limits. Besides the above illustrated cable protection where there are little or no sediment, Ecosse is advocating SCAR pre-cut trenching in difficult and challenging seabed sedimentary conditions. If the product is not present during the most risky phase the risks that are associated with simultaneous and post lay burial options are completely mitigated as they simply do not exist.
SCAR Boulder Clearance
Conclusion Renewable energy generation devices are installed with a limited consenting period and so any methodology which can consolidate and improve efficiency of the installation sequence will have the effect of keeping installation costs down, increasing the productivity and operating lifetime of the array and ultimately reducing the cost of energy to the customer. Olympic Spoolbase:- cable lay. Ambient Lifting:- structure and device installation/removal and ballasting/deballasting SCAR ploughs:- pre-cut trenching and backfill in difficult soils
Keith McDermott Commercial Director Mike Wilson - Managing Director Thank you for listening! mike@ecosse-subsea.com