The existing transmission grid was designed to take power from coal fields and export it to London and Birmingham.
The grid is weak —it has a limited capacity— in many of the peripheral areas where there are significant renewable resources. This is especially true of Scottish islands where submarine cables are used. Weak, lower voltage cables lose more energy than stronger, higher voltage, cables. This is why 400 kV cables are preferred for long distance transmission. Currently, North of the central belt (with the exception of the Beauly-Denny link) 275 kV or 132 kV cables are used. National Grid’s Electricity Ten Year Statement (ETYS) 2020 reports that “Scotland is experiencing large growth in renewable generation capacity, often in areas where the electricity network is limited”. The rapid growth in renewables requires network reinforcement in many areas.
The 2017 ClimateXchange report Meeting Scotland’s peak demand for electricity finds that although Scotland has historically been a net exporter of electricity even at times of peak demand, “recent closure of fossil fuel generation and the expected closure of nuclear stations over the coming 15 years will lead to a need for greater transmission import capability combined with adequacy generation capacity across GB to secure Scotland’s own peak demand”.
Traditionally decisions on network capacity have been driven by peak power flows. An alternative to this approach is to encourage consumer behaviour that reduces peak loads. This is not a new approach; the Economy 7 seeks to do this. Smart meters, smart tariffs and flexible demand (combined with localised storage and the exploitation of EV batteries) have the potential to reduce peak demand. Savelli and Morstyn discuss the importance of incorporating the operation of local flexibility into distribution network investment decisions and show how this impacts network charges. They conclude that moving consumers with significant flexibility onto locational prices benefits all consumers by reducing the network charges needed to recover investment costs.
Network reinforcement is a complex, expensive and time-consuming process. SSEN report that the upgrade of the Beauly-Denny line to 400 kV (from 220 kV) supported more than 2000 jobs over a 7-year period. In addition to installing over 600 new steel towers new substations were required, these require a large amount of civil works ahead of the construction and delivery of equipment that can weigh up to 180 tonnes. This is complex, skilled work, which requires specialists engineering designers, project managers and technicians, often working alongside environmental consultants. Subsea cable projects also need specialist installation vessels.
Lead times for the manufacture of subsea cables are increasing as worldwide demand grows and their installation can be problematic. A 2018 ORECatapult report states “Subsea power cable failure is frequently reported as an issue for offshore wind farm operators. Such failures are reported to account for 75-80% of the total cost of offshore wind insurance claims – in comparison, cabling makes up only around 9% of the overall cost of an offshore wind farm”. The report goes on to state that 88% of these failures occur in the high voltage export cables and that installation and manufacturing faults are the most common cause.
Without reinforcement it can be difficult or impossible for a renewable energy project to gain consent for a grid connection. Even with a connection, production may be curtailed due to insufficient grid capacity. Where new lines are needed, to connect to the national transmission grid at an appropriate substation, an application must be made to the Scottish Ministers for consent under section 37 of the Electricity Act 1989 and deemed planning permission under section 57 of the Town and Country Planning (Scotland) Act 1997. Such consent can be refused even when the development of the wind farm has been granted.
One particular area of difficulty has been the reinforcement of the grid connection to Orkney. The islands are currently connected to the SSEN grid by a distribution network operating at 33kV. The two submarine cables were installed in 1982 and 1998, crossing the Pentland Firth between Thurso and Hoy. These cables have a capacity of 40MW and were designed to export power to Orkney from the Scottish Grid. This is insufficient capacity to enable the on and offshore wind and tidal energy potential of the islands to be exploited and is low enough that many exiting generators must be curtailed (i.e. switched off) when they could be operating at maximum efficiency. Given that many of these grids connected turbines are community owned this has an unacceptable impact on communities who rely on electricity and fuel oil for heating. Even with these constraints Orkney consistently generates more electricity than it uses.
Since the establishment of EMEC in 2003 it has been recognised that both the 40MW export cable and the inter-island distribution grid and no-longer fit for purpose. After years of argument in 2019 Ofgem finally gave conditional approval to the SWW Final Needs for the Orkney electricity transmission project. This will see a 220MW transmission link between mainland GB and Orkney. Ofgem state that they must be satisfied by December 2021 that generation projects totalling 135MW must either have been awarded a Contract for Difference (CfD) or are likely to proceed despite not being awarded a CfD. Projects without a CfD must demonstrate (to external audit) that they are financially viable, have a grid connection agreement and have been granted planning permission. These conditions are extremely onerous and are based on a need to ensure “GB consumers were appropriately protected from the risks and costs associated with building an underutilised transmission link to Orkney”
I believe it is unreasonable for ofgem to have refused to consider:
Onshore wind technology is well established with large scale projects such as the Whitelee Windfarm providing generating capacities of over 500MW with 239 turbines. Onshore turbines are typically rated at 2 to 3 MW with turbines a tip height of around 120m. Larger turbines are seen as key to achieving a low enough strikeprice for onshore wind to make progress in Contract for Difference (CfD) auctions. The transport of the very long blades needed by Road is challenging and will limit the deployment of large machines on land.
Offshore turbines continue to grow in size GE have announced the Haliade-X 14MW turbine with a rotor diameter of 220m (the blades are 107m long). This complements the 12MW and 13MW versions of the Haliade-X turbine. The 12MW turbine weights almost 700 tonnes and the 14MW version at over 800 tonnes. These substantial weights must be installed on the tops of very tall turbine towers and require specialist lifting vessels.
These very large turbines have yet to be used in anger. Total Energies and SSE Renewables are installing 9MW turbines at Seagreen offshore wind farm site off Montrose (typical of the current generation of marine projects).
Deeper water projects, such as the Beatrice—comprising of 84 7MW turbines—and Seagreen offshore wind farms, use jacket structure rather than monopiles to support the turbine tower.
These lattice towers that were adopted from the offshore oil industry are effective in depths of up to 50 metres and use about 50% less steel than a monopile. As well as supporting turbines, Jackets are commonly used to support offshore electricity substations. As projects move further offshore, they can also be used to support maintenance facilities and offshore crew accommodation as is often done in the North Sea oil and gas fields.
Floating offshore wind
In water deeper than 60m or 70m jacket structures cannot be used and turbines must float. Several options are being considered to achieve this. The spar type, requiring water deeper than 100m, has been used for the Hywind Scotland project. Whilst a semi-submersibles design has been used for Kinkardine offshore wind farm.
Tension Leg Platforms (TLPs) and Tension Leg Buoys (TLBs) are widely used in the offshore oil and gas sector and are being developed by companies like AXIS Energy Projects to support wind turbines, they are able to operate in shallower water than spar type foundations but require complex installation processes.
Semi-submersibles and barges use traditional moorings and a floating platform to support the turbine. Current designs such as the IDEOL barge, Principle Power’s Wind Float and the EnerOcean W2Power platform (which carries two wind turbines on a single foundation) have all been demonstrated at sea.
Well-designed floating systems can be easily assembled in port and towed to site, reduce maintenance costs by permitting easy access and minimise the platform mass per MW. Much of the technology to build, assemble and install such platforms can be drawn directly from the Oil and Gas sector providing new sources of revenue and employment as North sea production ramps down.
Power from the turbines is aggregated together using field cables, before being exported using the main wind far export cable(s). These export cables transmit power to the onshore substation where the farm is connected into the grid. Over longer distances high voltage DC cables are preferred to high voltage AC as this reduces losses, though the cost of the on- and off-shore substations and the cables themselves is higher. Cables are a perennial problem for wind farm operators. The ORE-Catapult report that
Subsea power cable failure is frequently reported as an issue for offshore wind farm operators. Such failures are reported to account for 75-80% of the total cost of offshore wind insurance claims – in comparison, cabling makes up only around 9% of the overall cost of an offshore wind farm.
The majority of these failures (88%) affect the export cables with 37% of failures caused by installation or manufacturing and 47% by electrical faults. The Catapult also comment that “The cost of a cable failure can be considerable, taking into account repair costs and generation revenue loss. From 2014 until the end of 2017, recorded cable failures at UK projects have led to a cumulative generation loss of approx. 1.97TWh, equating to approx. £227M”.
The situation with cables will be more complex when floating systems are deployed as dynamic—rather than static—electricity cables will be required for the inter-array connections to the offshore substation.
Many of the larger wind turbines are supplied by their manufacturer with a “digital twin” computer model which is continuously updated by sensors on the turbine allowing predictive maintenance operations to be undertaken. A report from Windpower Engineering & Development says
For the wind industry, the true value of digital twins lies in its ability to monitor the condition of an entire fleet of turbines, regardless of location. This has innumerable benefits, but in particular it allows wind farm operators to proactively plan maintenance visits, reduce labor costs, limit down time and identify inefficiencies.
The Edinburgh Centre for Robotics has been leading the EPSRC ORCA (Offshore Robotics for Certification of Assets) Hub which brings together internationally leading experts with over 30 industry partners to revolutionise Asset Integrity Management for the offshore energy sector. The development of Industry 4.0 coupled with rapid growth in offshore wind have the potential to make this a high value growth area.
In the tidal sector technologies are converging onto two- or three-bladed horizontal axis tidal turbines. The larger devices—from Orbital, SIMEC Atlantis and Hammerfest-Strøm—have a rotor diameter of typically 15 to 20m and a rated power of between 1 and 1.5MW for each rotor. The SIMEC Atlantis and Hammerfest turbines have been installed as part of the Meygen project in the Pentland Firth’s Inner Sound. Orbital’s O2 is a twin rotor device —rated at over 2MW—and installed at the EMEC test site in Orkney. Four of NOVA Innovation’s smaller 100 kW turbines are installed in Bluemull Sound, Shetland—with a further two installations planned this summer.
The rotor blades are generally manufactured from composite materials—similar to wind turbines—but need much greater strength to resist the very large forces created by tidal currents. For a wind turbine to experience similar forces it would need to be strapped onto the front of a shinkansen train!
The generators, power conversion equipment and array cables are very similar to those used in offshore wind farms—though at a lower rated capability—and need similar maintenance operations. Seabed mounted turbines, like those at Meygen and in Shetland, are less exposed to wave forces but need to be lifted out of the sea for maintenance. Floating machines, like the O2, are much simpler to maintain, but must be designed to withstand wave loadings.
Like their larger cousins these machines now tend to operate with a parallel digital model and specialist sensors to allow predictive maintenance operations to be undertaken.
Wave energy devices are much more diverse in design. Following the collapse of Pelamis Wave Power, Highlands and Islands Enterprise established Wave Energy Scotland (WES) to fund the development of new, and robust, wave power machines. WES have used a structured innovation approach and, through a competitive procurement programme, has support a range of projects focused on the key systems and sub-systems of Wave Energy Converters. Two devices—the Mocean Energy’s BlueX and AWS Ocean Energy’s Advanced Archimides Waveswing—are currently in stage 3 development. The BlueX has recently been deployed at the EMEC scale testing site in Orkney.
Building on the success of their approach Wave Energy Scotland are now helping to run the European EuropeWave—an innovative R&D programme for wave energy technology—that will provide over €22.5m of national, regional and EU funding to drive a competitive Pre-Commercial Procurement (PCP) programme for wave energy. Their stagegate model crates a funnel where developers who have responded to an open call are progressively winnowed down until the best performing concepts are selected for deployment in Orkney and the Basque country.
The Wave Energy Scotland programme has focused not only on devices but on the separate development of power take offs (PTO), control algorithms, quick connectors and structural materials. This allows straight forward technology transfer to other projects. For example, the C-Gen permanent magnet generator developed in Project Neptune has been used in the Mocean BlueX machine.
Whilst the cost of fixed offshore wind has fallen dramatically in recent years, the costs of floating offshore wind, tidal and wave power have remained comparatively high.
The cost reductions in wind are directly attributable to “learning by doing” – simply put the more devices we install the better we get at making, installing and maintaining them, and the lower the overall cost will be. Lecca et al reported in 2017 that the planned 600% increase in offshore wind deployment was unlikely to produce the 30% drop in the levelised cost of energy desired by the UK Government. They also found that certainty over the timing and size of CfD auctions was critical to achieving success, stating that “Continuing delay and lack of clarity over the timing and budgets for the next CfD allocation may compromise the UK targets on low-carbon electricity generation.”
They report that given a deployment rate of 100 MW per year from 2021/22, the tidal stream market would be worth £1.4bn to the UK economy by 2030, creating 4,000 jobs. The find also find that by installing 100MW (the equivalent of 50 Orbital O2 turbines) the levelised cost of energy would be reduced to £150 per MWh. Once 2GW has been installed (the equivalent of a nuclear power station) they expect the cost of energy to be around £80 per MWh. They note that “Significant cost reductions are expected in the near-term as the industry takes the step from pre-commercial arrays to commercial projects”.
Similar reductions are reported for the floating offshore wind sector. The Catapult reports that costs will fall to around £55 per MWh by 2032 if innovation is supported and between 8GW and 16GW of floating offshore wind capacity is installed.
At the early-stage innovation must be supported in the floating wind, tidal stream and wave energy sectors. This support enables learning by doing and drives down costs. The structured innovation model used by Wave Energy Scotland provides one route as did the enhanced Renewable Obligations Certificates (ROCs) scheme until it closed. The high costs of novel technologies needs to be supported and the CfD scheme (which always seeks the lowest price) is unable to do this. Many of the devices tested at EMEC benefitted from the ROCs scheme and since it’s closure developers such as Sustainable Marine Energy and Nova Innovation have begun to develop machines in Canada.
The introduction of Innovation Power Purchase Agreements (IPPAs) would incentivise developers to continue to develop their technologies in Scotland ensuring not only that we make the most of our abundant marine energy resource, but that we maintain our place as world leaders in the tidal energy sector.
The supply chain for onshore wind is well established and has demonstrated an ability to deliver cost effective and reliable projects.
As part of the Offshore Wind Sector Deal the Scottish Government, working with the sector established the Scottish Offshore Wind Energy Council (SOWEC) in 2019. A key goal of which is to:
Work to increase local content in line with the ambitions set out in the UK Sector Deal, developing a sustainable, world-class supply chain in Scotland. The number of offshore wind jobs in Scotland will increase to more than 6,000; an increase of 75% on 2019 figures.
The Scottish Industries Directory for Offshore Wind identifies:
Key barriers identified by a workshop held in February 2021 by the Scottish Council for Development and Industry (SCDI) identified a number of barriers and strengths in the Scottish offshore wind energy pipeline and supply chain.
One of the key points raised is that the current scale of ambition is problematic. The “overambitious” targets for local content in the offshore wind sector deal are unlikely to be met without a stronger focus on identifying expectations of local communities. Considerable investment is required to develop specialist infrastructure, and this cannot be dependent on a single project.
An example of this is the announcement in May 2021 by Forth Ports on an investment to develop a renewable energy hub in the Port of Leith. The £40 million private investment will see the creation of a bespoke, riverside marine berth capable of accommodating the world’s largest offshore wind installation vessels. The facility will feature a heavy lift capability of up to 100 tonnes per square metre, backed up by 35 acres of adjacent land for logistics and marshalling. This will be supplemented by the upgrading of a 140-acre cargo handling site to accommodate lay down; assembly; supply chain and manufacturing opportunities.
Given towage distances—especially on the west coast—further investments will be needed to build installation and maintenance port capacity.
The development of the supply chain can be limited by a lack of long-term perspective. SCDI state:
This is not just about 8-10 years development or a 25-year operation but the technologies that will come downstream from that. Developers and government have the potential to create a programme which benefits from a long-term vision and stable partners who work together for the duration”.
Ben Wray’s article on the Bifab failure reports that EDFs Neart naGoaithe (NnG) offshore windfarm placed contracts for eight out of 53 sleeves with Bifab, the rest coming from Indonesia. The Seagreen windfarm is using jacket structures built in China and the United Arab Emirates. In the end Bifab was unable to supply even one. Unite’s General Secretary said “Two projects worth a total of £5 billion, requiring 168 turbine jackets to power our future, and not even one will be built in Scotland”.
It seems that Carbon accounting is not used as a criteria for designing the supply chain and that cost is an overriding factor. Lack of skills and a sufficiently large, qualified, and competent workforce is also a factor. It has been widely reported that Allan MacAskill—boss of Kincardine Offshore Wind Limited—said that firms are being forced to give work to overseas companies because Scottish yards don’t have the capacity to cope with major offshore wind developments. He said the nature of the design meant they had to recruit overseas companies to develop the six-turbine 50 megawatt (MW) project because the facilities weren’t available in Scotland.
The floating wind foundations and jacket structures needed for deeper offshore wind projects are very large. Yards also need deeper water to enable key operations to be undertaken. Investment is needed to create fabrication and assembly facilities, as was done at Rosyth for the Aircraft Carrier project. Allan MacAskill said “Making yards competitive should not be the developers job, that’s the job of the supply chain and that takes investment”. Such changes also take time.
The ORE Catapult, the Carbon Trust, Highlands and Islands Enterprise and the Scottish Government have been working to develop the supply chain. The ORE Catapult has set up a Floating Offshore Wind Centre of Excellence. This seeks to accelerate the build-out of floating farms, create opportunities for the UK supply chain, and drive innovations in manufacturing, installation and Operations & Maintenance. It is a collaborative programme with industry, academic and stakeholder partners.
The Carbon Trusts Offshore Wind Accelerator (OWA) is a flagship collaborative research, design and development programme, set up in 2008. It aims to reduce the cost of offshore wind, overcome market barriers, develop industry best practice and trigger the development of new industry standards.
The current phase involves participation and funding from nine international energy companies: EnBW, Equinor, Ørsted, RWE Renewables, ScottishPower Renewables, Shell, SSE Renewables, and Vattenfall, who collectively represent 75% of Europe’s installed offshore wind capacity. It is currently looking at Cables, Electrical Systems, Foundations, Logistics, Operations and Maintenance.
The Carbon trust also run a Floating Wind Joint Industry Project with 15 leading international offshore wind developers and support from the Scottish Government. Their July 2020 report looked into turbine requirements and foundation scaling; heavy lifting operations; dynamic export cables; and, monitoring and inspection.
A key finding of the Carbon Trust report is that the Supply Chain needs greater clarity on future turbine sizes and when they will come to market. They also comment that Turbine suppliers should work more closely with the supply chain, working to make the next generation of turbines more installation friendly.
The supply chain for tidal energy projects is emerging with use being made of both oil and gas installation techniques and equipment and fabrication yards. A clear pathway to building out larger projects with more devices is needed to enable sustained development of the supply chain rather than a “boom and bust” situation.
Many of the companies developing new offshore renewable energy technologies (particularly in the emerging areas of tidal current, floating offshore wind and wave energy) are SMEs with limited resources. These companies have been supported to access test facilities to boost their competitiveness and drive technologies to higher Technology Readiness Levels (TRLs) by the European MARINET and MARINET-2 programmes and through Intereg actions such as the Marine Energy Alliance (MEA). Both these programmes provide consultancy services and access to world leading test facilities to SMEs through a competitive application process. In both cases the clients are guided to the facilities and services which are best suited to their needs.
Whilst the MARINET-2 programme primarily exists to provide trans-national access to facilities (i.e. A Scottish developer must apply to use facilities outwidth the United Kingdom). It has also included collaboration between facilities to improve testing and develop standardised procedures and practices.
The FloWave Ocean Energy Research Facility, hosted by the University of Edinburgh, is a unique 25m diameter, 2m deep, circular basin able to recreate realistic, combined, wave and tide conditions like those found at EMEC and around the UK. Testing at FloWave has enabled device developers including Sustainable Marine Energy, Orbital Energy, MOcean Energy, Axis Energy Projects and EnerOcean to test large scale tidal, wave and floating wind models respectively. FloWave was built using funding from the EPSRC, Scottish Enterprise and the University of Edinburgh and was opened by Rt Hon Amber Rudd in 2013. Approximately 50% of its work relates to academic research projects and 50% to industrial projects. Over the last 8 years it has provided an important steppingstone for developers wishing to de-risk deployment at EMEC.
FloWave recreating the EMEC wave site (top left), O2 model being craned in (top right), MOcean device mark 2 under test for Wave Energy Scotland (bottom left) and an array of three electrically connected tidal turbines ready for testing (bottom right).
Recently Innovate UK has run a similar programme. The A4I program provides access to National Laboratories (National Engineering Laboratory, National Physical Laboratory, and Facilities run by the Science and Technology Facilities Council). It supported companies to “Gain access to world-leading experts and cutting-edge facilities, techniques and technologies to solve an existing analysis or measurement problem facing their business.”
If we are to continue to be at the forefront of renewable energy development and deployment, there is a need to support companies developing technologies (in particular SMEs) to test and analyse their innovations and gain experience. Schemes like A4I that provide access to large scale facilities like the FloWave Ocean Energy Research Facility, EMEC’s ¼ scale tests sites and component test facilities (for turbine blades, electrical cables, and power trains) operated by the ORE Catapult and University groups is critical to accelerating development.
Once developers are ready to deploy large scale, grid connected, prototype machines they must be supported until sufficient learning has been done to make the technology competitive in CfD auctions. A paper setting out the role the UK Marine Energy Industry can play in our energy system and our economy has been published by Scottish Renewables. They propose the establishment of three interlinked support mechanisms that bring developers from early-stage devices though to machines which are competitive with fixed offshore wind technologies.
The Innovation Power Purchase agreement would support deployment of prototype machines at locations like EMEC, whilst protecting consumers from costs by providing off-takers a tax rebate when buying marine energy. It is effectively a replacement for the ROCs scheme which was very successful in brining machines to EMEC for testing. The absence of such agreements/tariffs means developers are moving to Canada where such support is available.
The Innovation Contract for Difference (iCfD) is a bridging mechanism that enables developers to scale up to utility scale projects able to compete in the current CfD mechanism. Essentially providing a new “pot” in the auction rounds into which emerging technologies can bid for projects of up to 100 MW, delivering the learning needed to make technologies market competitive.
Work by the ORE Catapult and Scottish Renewables has suggested that IPPA support is needed for the first 120MW of deployment (with funding for single machines and small arrays of around 5 MW), with an iCfD mechanism supporting 800MW of deployment.
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