Blue Energy: The marine renewables sector starts to show promise

Tidal and wave power have received millions in both private and public investment. While the industry still has a long way to go before it becomes commercially viable, a few experiments are demonstrating how the sea might be used to power our future

Ashley Coates
Wednesday 11 October 2017 16:16 BST
A Scotrenewables vessel harvests tidal power with currents of seven knots that can last for six hours in the same direction
A Scotrenewables vessel harvests tidal power with currents of seven knots that can last for six hours in the same direction

Three hundred miles north of Edinburgh, and located in some of Britain’s most turbulent seas, the people of the Orkney Islands have been tested by the region’s weather for centuries.

A remote archipelago of 20 inhabited and 50 uninhabited islands, Orkney is exposed to the full force of the both the Atlantic and the North Sea’s climate, with around 52 hours of gales recorded every winter.

Today the islands’ windiness has been put to good use – 120 per cent of the Scottish county’s electricity demand in 2016 was supplied by renewable energy sources, mostly through wind turbines. The seas around Orkney also make it a prime location for advanced experiments in marine renewable technology.

These islands are also home to the world’s leading centre for the testing of marine renewable energy devices at sea. There are two dominant strands to these trials, with tidal energy typically harnessed through huge underwater turbines, often more than 150 tonnes per turbine, and wave power which can be extracted through a range of prototype technologies.

Orkney has some of the strongest tidal currents in the world, moving as fast as four metres per second at the European Marine Energy Centre (Emec)’s tidal test site. At its wave test site off the west coast of Orkney, EMEC have recorded waves of over 18m, 2km from the shore. Having both these conditions in one place makes this possibly the best location in the world for the early days of marine energy.

Waves power MayGen’s 200-tonne 1.5 megawatt turbine

Back in 2011, the Carbon Trust 2011 estimated as much as 20 per cent of the UK’s total energy supply could come from wave and tidal power.

Recognising the potential of Orkney for marine energy research, the European centre was established there in 2003 with funding from the Scottish and UK governments and the EU. Emec provides infrastructure and research support to businesses looking to test their equipment in the sea. Companies pay Emec for the use of their grid-connected test berths, which connect the prototype technologies to the national grid via underwater cables and allow for their technologies to be professionally monitored and accredited.

Having received £36m in public money to launch Emec, the organisation has been self-sufficient since 2011, with companies paying to use their facilities.

These firms are investing in extensive research and development programmes with the hope of perfecting commercially viable marine technology that can be sold around the world and compete with solar and wind power for a slice of the energy mix. In contrast to wind and solar, tidal power holds the promise of being highly predictable (it can be predicted years in advance), making it particularly valuable to grid “balancing” operators. Wave energy, while less predictable, has tremendous potential as a massive untapped source of energy.

The test beds off the Orkney Islands have been witness to a number of world firsts. In 2004, a large “red sea snake” known as the Pelamis Wave Energy Converter became the first device to supply electricity to the national grid with energy derived directly from the movement of waves. In 2008, OpenHydro became the first company to generate tidal energy into the UK grid.

The Orkneys are not short of rapidly flowing waters

Last month, a community initiative successfully generated hydrogen from the action of tidal energy for the first time. (Known as the Surf 'n' Turf, the project was lead by Community Energy Scotland, working with Emec, Orkney Islands Council, Eday Renewable Energy, and ITM Power.)

“Tidal energy is further advanced than wave energy at the moment,” says Emec’s Lisa MacKenzie.

“They’ve taken a lot of learning from the wind energy industry with many – not all – tidal technologies looking similar to the three-bladed horizontal access turbines you see in the wind industry.”

“When it comes to wave, there isn’t an analogous form of energy generation to take inspiration from. Instead there are a whole range of really interesting designs being developed.”

August world-record setting month for Scotland and energy derived from tidal power. The MeyGen project, which utilises the rapidly flowing waters of the Pentland Firth to operate three 200-tonne 1.5 megawatt turbines, generated 700 megawatt hours of (MWh) over the course of the month.

David Taaffe, the project delivery director said: “August proved to be a world record month, providing enough energy to power 2,000 Scottish homes from just two turbines.

The world’s most powerful tidal turbine, the SR2000 

With yet another successful installation campaign expertly completed by the Atlantis [owners of MeyGen] operations team, we expect to continue to break records throughout the rest of the year, generating both predictable power and revenue.”

The project generated 700 MWh over the course of the month.

Separating the coast of Caithness with the Orkney Islands, the Pentland Firth is a strait with some of the fastest-flowing tides in the world. Parts of the strait experience a phenomenon known as “tidal races”, where large volumes of water surge through narrow outlets as the tide rises and falls.

The locals have given these races names, such as “The Merry Men of Mey”, a section of tidal current that can be as fast as 11mph. The area has also been dubbed “the Saudi Arabia of tidal power” by Scotland’s former First Minister, Alex Salmond, whose government set ambitious targets for the future use of renewables in Scotland.

The machines being deployed around Orkney and in the Pentland Firth have to be able to withstand the effects of storms, strong tides and saltwater corrosion.

“You can go from having currents of seven knots in one direction for the best part of six hours, and then you get 20 minutes of breathing space before it starts going in the other direction,” says Scotrenewables Tidal Power chief executive, Andrew Scott.

Andrew’s company is developing a novel floating tidal technology which has raised hopes for the whole sector.

The company’s first commercial scale machine and the world’s most powerful tidal turbine, the SR2000 2MW, is undergoing a grid-connected test programme at Emec. While still a prototype this single turbine has exported electricity equivalent to 7 per cent of Orkney’s electricity needs while generating, about 800 households.

“We are tremendously pleased with these latest results from the test programme” says Andrew Scott, chief executive of Scotrenewables.

“The SR2000 has met, and in many instances exceeded expectations, and combined with the fact this is the world’s most powerful operating tidal turbine, it means we’re making a material contribution to the generation mix in Orkney with just this single unit”.

Key to the early success of the SR2000 has been thinking about tidal power in an entirely new way, according to Scott. The “first generation” attempts at harnessing tidal energy have been based on lifting a lot of technology and principles straight from the wind industry.

In contrast the SR2000 mounts turbines on a towable, floating platform, rather than planting them on the seafloor – so more analogous to a ship than a wind turbine. All turbine components are therefore situated above or close to the surface for ease of access for maintenance.

“We carry out all installation and maintenance operations with low cost, locally based work boats making our cost and risk profile must much analogous with offshore wind than other tidal technologies.” An

A sea installation operated by OpenHydro, the first company to generate tidal energy into the UK grid

Offshore wind-powered turbines require regular servicing, as much as 20 visits to a single turbine every year. But technology that sits on the seabed cannot be serviced with the same regularity as the conditions required for a safe dive to the seabed off the coast of Orkney can be hard to come by.

But for all the excitement around these recent developments, we are yet to see the creation of a tidal or wave device that has been used on the same scale as today’s solar or wind plants.

The renewables landscape has also changed dramatically in the years since momentum first built up around wave and tidal energy.

“Onshore wind has become a huge success and reduced its costs over the 15 years since major investments started in wave and tidal sectors,” says Scott.

Also, in that time, offshore wind has appeared, and at scale, and reduced its costs. Solar emerged as well and has recently reduced its costs astronomically. For the energy pioneers that have invested their time in these projects, the investment is worth it.

“We’ve got all the world-leading supply chain capabilities and know-how here; they are part of the UK maritime heritage established over 100’s of years in industries like offshore oil and gas,” says Andrew Scott.

And if wind technologies can get their costs down, you have to apply the logic that we can get our costs down too, and we believe our innovative approach can start that trajectory from an unprecedentedly low point.”

“We’re a little bit later coming to the renewables party, and we recognise that there has been a lot of expectations built up here, but we believe we’ve got a disruptive technology with clear ability to create a new low-cost form of sustainable power generation in parallel with delivering significant industrial opportunities”.

For Scott, and other innovators in this sector, there is a worry that public sector support of marine energy might be coming to an end in the UK. The guaranteed market price to buy energy from marine renewables was recently ended, removing a crucial form of support which has motivated the significant private sector investments made to date, estimated to be well in excess of £500m.

“For the first time in well over a decade, the UK doesn’t have a targeted market support for marine renewables. With UK PLC having done 90 per cent of the hard work to get us to this point, we might be about to walk away when the industrial opportunities start to spawn”.

Caroline Bragg, a policy manager at RenewableUK, says: “The wave and tidal sectors are working hard to reduce costs with Atlantis announcing recently that it expected its next phase to cut costs by two thirds”.

To cut costs further, we want to work with policymakers to find innovative ways of making sure the UK captures these sectors’ benefits for our coastal communities without creating additional cost for consumers – including through the corporate PPA market”.

As with many technologies at the early stages of development, both public and private sector investment will be needed to make marine renewables a significant part of the energy mix.

While the sector still has a long way to go, the successes of projects over the summer has given renewed optimism to the people who have dedicated much of their working lives to developing these complex devices and testing them off a remote corner of Scotland.

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