Government support for renewable energy has taken a hit in recent years, with subsidies cut and funding competitions prematurely closed. This has seen some promising companies developing wave and tidal technology go under, including marine energy companies Pelamis and Aquamarine. However, two tenacious companies, Atlantis and Nova Innovation, have weathered the financial storms and are making waves with their first major commercial tidal energy projects.
Nova Innovation has recently deployed the world’s first fully-operational, commercial, grid-connected offshore tidal array off Shetland. The second in a series of three Nova M-100 100kW turbines was deployed alongside the first turbine in August.
The Scottish tidal energy specialist installed the first Nova M-100 turbine in the Bluemull Sound, Shetland, last March. The company says the device has been generating to full power across all tidal conditions.
Nova partnered with Belgian renewable energy company ELSA on the array. Nova became the first company in the UK to have raised enough money to launch a commercial tidal array. Simon Forrest, managing director of Nova Innovation, says that as a company that has “blazed a trail” in the tidal energy sector there have been challenges in just about every facet of the business, from developing the technology to raising finance. However, he stresses that the main stakeholders in the project, including the Scottish government, the Shetland Islands Council, Marine Scotland and the Crown Estate, have been “very enabling” and helped Nova to overcome a lot of business hurdles, freeing the company to focus on the technology.
Cost-effective target
The Nova M-100 is a two-bladed turbine with a horizontal axis. The blades have a diameter of 9.5m and the turbines are seabed gravity mounted, weighing 140 tonnes each, including ballast. The systems are connected to the grid by a 1.2km subsea cable to shore.
Forrest says: “One of the big things we still face as an industry is that, while we have shown that it can be done, we now need to move beyond the R&D phase and show that it can be done reliably and cost-effectively.”
Having installed its first grid-connected device in 2014, Nova had already learned a great deal about setting up and operating a device in what can be a very harsh environment. The difficult installation conditions led to a major turbine design change. “We have gone from three blades to two,” explains Forrest. “That has been informed in learning by doing, and two blades is much easier to handle, particularly on a boat.” Thanks to its two years’ experience working in the field, the Nova team can carry out operations and maintenance in both summer and winter, something that Forrest says was a first for the industry.
Deployment and maintenance have also become more streamlined. The team was able to remove the first turbine, carry out maintenance work and put it back in the water, and install the second turbine within a 24-hour period.
“That is a huge step-change in bringing down costs and improving reliability at the site,” says Forrest. “It bodes really well for the future.”
Deborah Greaves, professor of ocean engineering at Plymouth University and director of the Coast Lab, hopes that the industry will benefit from such trailblazing stories and will push forward progress. However, she explains that such projects are still very much a testbed for new technology.
“We lack the experience of real deployments at sea so we don’t know what the effects are,” she says. “We can do some modelling and try to predict what they might be but until we get some more experience in the field it is all a bit hypothetical.”
Forrest says that, while there have been no maintenance issues so far, there will be challenges ahead for the industry, such as how the materials of the turbines react to the sea over the next 20 years.
The Nova M-100 turbines are made from steel, and the company has drawn on experience from the oil and gas industry local to the area in Scotland to ensure that they are as robust as possible. Forrest says that Scottish Enterprise put the firm in touch with oil and gas companies and the sector’s supply chain to find help with steelwork, as well as painting, coatings and protection.
“We have also been working very closely with local company Shetland Composites for our blades over the last 5-10 years to understand how the material best performs in the marine environment. It has been essential to making it work so well,” he says.
Forrest says that operation and maintenance account for half of the estimated costs for the lifetime of the project. The firm will be investing in condition monitoring to drive down those costs.
Storage options
The company will also look to improve how it provides power to the grid as well as exploring energy storage. So far the company has used supercapacitors and capacitors but it will consider other storage solutions to “improve the quality of the energy it is sending to the grid”.
Commercial tidal projects do not seem set on one particular turbine, cable connection or foundation technology, and continue to refine and test as they expand. This is no truer than with MeyGen, the world’s largest free-stream tidal power project, run by tidal turbine company Atlantis.
The first of four 1.5MW turbines that make up phase 1A of the project was unveiled in September. The turbines stand 15m tall, with blades of 18m in diameter, and weigh almost 200 tonnes each. Three of the units were built by Andritz Hydro Hammerfest and the fourth is an AR1500 Atlantis turbine. All four units will be deployed to the MeyGen site in the Pentland Firth.
Phase 1B of the project, which is due for financial close at the end of this year, should see another four turbines deployed in 2018, while phase 1C will see a further 53 installed.
Drew Blaxland, director of turbines and engineering services at Atlantis, says: “There will be more than one turbine design installed. There has to be for the industry. The next phase 1B turbines will be a SeaGen 20 1.5MW by Atlantis-owned Marine Current Turbines.”
The SeaGen will have a different rotor, be slightly bigger to more efficiently capture energy, and will have a different pitching system.
Design optimisation
Blaxland says that when operating with different turbine designs you can take what works best from each to further optimise the next that will be installed. He expects that turbines in phase 1C and phase 3 will most likely be a combination of all the subsea designs currently installed. “That is the beauty of an industry that is reverting to type,” he says. “If you go back 5-10 years, everybody’s turbine was wacky and different. Now they generally have three blades and are of a very similar design.”
Blaxland says that, to retain its competitive edge in the market, Atlantis has had to become more than just a turbine supplier, but also a service provider, understanding the installation and maintenance issues too.
This has seen the company take key decisions about the technology used for the installation process. One will be a change in the foundation designs. Atlantis currently uses gravity base foundations made up of three legs, each of which has 400 tonnes of ballast on it. While practical for low-volume installations, gravity foundations are not suited to a jagged seabed and take time and money to manufacture. In a bid to lower costs, Atlantis will most likely use drilled pile foundations for phase 1B.
The cable management system is a key differentiator between the two different turbine designs so far installed. The three Andritz turbines have a dry mate cable connector – a type of connection that can only be made in dry conditions either onshore or on board a vessel – that typically takes 24 hours to install. The Atlantis unit is pioneering a wet mate connection – an easier “plug in” connector that can be installed subsea much quicker, saving time and money.
Tim Cornelius, chief executive of Atlantis, says that the company successfully carried out a turbine installation using the wet mate connector in less than 40 minutes, which “back in prototyping days would have been a month of fiddling around”.
Cornelius hopes that the wet mate technology will become an industry standard and has plans to commercialise it and sell it to other turbine manufacturers.
Looking at these two fledgling commercial tidal energy projects, it is clear that there is a lot of innovation, skill and experience being built up which will benefit the sector as a whole. However, what is not so clear is the future of government support for the industry, particularly in the form of contracts for difference (CfD).
Greaves says: “With Brexit we don’t know exactly what is going to happen. The EU have been very good at supporting marine energy. Our government energy policy is not so clear, so we could be losing a very important source of support.”
Paul Wheelhouse, the Scottish minister for business, innovation and energy, is in firm support of the fledgling tidal energy industry in Scotland. However, there is concern over inaction at Westminster. He says that his department is yet to receive a reply from the new cabinet to a letter sent to former prime minister David Cameron questioning whether the UK government will continue to support tidal energy.
“I think it’s a huge opportunity not just for Scotland but the UK as well and we want to work with business and energy secretary Greg Clark to see if we can unlock the potential,” says Wheelhouse. “CfD for 100MW have been promised for the main energy sector. It’s about honouring a promise that was given to the industry.”
Cornelius echoes this sentiment, and says the sector, and Atlantis, are keen for the announcement to be made so “we can get on with doing”.
Price fears
The government initially promised a CfD strike price of £305/MWh, but there are concerns that this could be reduced to £200/MWh when projects reach an installed capacity of 200MW.
Cornelius says: “Tell me any industry in the world – solar or wind – that would be able to achieve that. We want £305/MWh because that’s the commitment made in 2014 and we brought £60 million worth of project finance in predicated on that. The business case is built around that.”
So there is good progress being made with the technology for the UK’s commercial tidal energy sector. However, for it to truly flourish and reach economies of scale it is up to the government to confirm its support and allow these projects to continue and thrive.
If not, the UK could risk losing out not only on all the benefits that this renewable energy source brings but also on valuable skills and expertise in the sector