Isle of Wight

Tidal energy has taken a backseat in the renewable energy market, despite being one of the most reliable forms of generating power. Tides go in and out every day, regardless of the weather, so there is no risk of it being undependable. Still, tidal hasn’t been a huge contender in the UK.

The development on the Perpetuus Tidal Energy Centre (PTEC) could help change this. In April, government body the Marine Management Organisation (MMO) granted PTEC the green light to build the largest tidal stream energy project in all of England and Wales.

The 30MW project will consist of 60 seabed turbines just off St Catherine’s Point on the Isle of Wight, which the developers say could power a quarter of all the homes on the island.

“We feel it will play an important role in the future energy mix of the UK, alongside offshore wind, other renewables and also nuclear,” says PTEC project leader Mark Francis. “This is especially important because of all the decommissioning of coal power stations that are taking place. And also because we cannot be reliant on future imports of gas and electricity.”

Tidal power: reliable and predictable  

The PTEC team has looked at various sites across the UK which have the potential to produce tidal power from motion currents, and from there develop the sites, secure the consents, get all the relevant commercial and technical agreements in place and ultimately choose the turbine manufacturers and technologies to actually produce the power.

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Francis believes that tidal energy is going to have a reversal of fortunes, despite being between ten to 20 years behind the offshore wind technology market. While the market may be immature, there has been a lot of development over the past decade, which means the team at PTEC and all the turbine manufacturing companies are now at a high level of technical and commercial readiness.

“Effectively we've had less than 10MW installed across the UK since the beginning of tidal stream energy, which is nothing,” Francis says. “But over the next decade we could quite easily see that increase to 200+MW.”  

"The beauty of tidal power is it is completely and utterly predictable."

Renewable energy can have a bad reputation for being unreliable, and people in the UK do not want uncertainty over whether their lights will switch on or not. The intermittency of sun and wind can be a problem for investment, but this isn’t a problem for tidal power. 

“The beauty of tidal power is it is completely and utterly predictable,” says Francis. “So we could tell you what the power output would be in one years’ time, ten years’ time, or 15 years’ time.”

“Because of that predictability, and the fact it is not dependent on the weather, such as sun and wind, it can actually be managed and integrated with the grid system a lot easier.”

A good deal for investors and locals

The PTEC team is confident that this project will accelerate the growth of the industry and are keen to bring long-term investment to the local area, as well as create jobs.

“One of the key benefits of our project is that we believe that it will lower the costs and risks of future tidal projects,” says Francis. “This is because of our unique project structure and, by bringing together a number of different turbine manufacturers onto the same site to use the same infrastructure and share the same consents, we will ultimately reduce the costs and accelerate the industry.”

The turbines being used for the project are second-generation, which means they are different to the huge underwater wind turbines used before.

The machinery will be very close to the surface, as energy yield is maximised by having the turbines as high up the water column as possible. This positioning also makes it cheaper to install and recover these turbines than the huge conventional units that lie deep below the surface.

The new turbines are also a lot smaller, so in terms of financially viable manufacturing strategies, they will be cheaper to make and easier to set up.

The key goals for PTEC are to reduce the cost and risk facing tidal projects. Francis says the team achieves this by gaining experience of using multiple different turbines on the site.

“It improves reliability, it improves designs, but also ultimately reduces costs,” he says. “If we can combine the unique elements of those turbines that have been designed to reduce costs, this is completely across the lifecycle, then we can open up a much bigger market.”

Something that makes the PTEC project influential is that it is situated off the Isle of Wight, where currents are a lot slower than places like Orkney and the Bay of Fundy in Canada, which host two large-scale tidal ventures.

“Our site actually represents the majority of the exploitable tidal sites in the world,” says Francis. “So if we can make PTEC work, we can make a huge number of sites across the UK and further afield work as well.”

Facing opposition and challenges

Like any large project there are challenges and one that comes with PTEC is that the whole development is in a completely new area that no company has attempted before.

The fundability of the project was paramount as the team had to create a structure which aligned to the revenue subsidy framework that would satisfy investors. PTEC also had to consider any risks and environmental constraints.

“Every day we face challenges,” Francis says. “What we wanted to do and we successfully achieved was get a broad consent envelope for the site because at the time of writing the environmental impact assessment and performing the front end engineering design, we didn't actually know which turbine technologies we would select.”

"The whole development is in a completely new area that no company has attempted before."

PTEC has now chosen three turbine manufacturing companies, which it will announce at the end of the year, but it was beneficial to have a thorough, albeit lengthy, consent process to ensure that the technologies chosen wouldn’t be rejected.

There has been concern from locals and fishermen in the area about noise, what the project would look like, and potential negative impacts on shellfish beds. Two thousand islanders signed a petition against PTEC when it came before the Isle of Wight council, and permission was granted on the conditions that the visual impact and noise generated by the energy centre and control room were reduced.

Soothing fears: the environmental report

An environmental impact assessment was carried out by the independent specialist Royal HaskoningDHV, a leading expert in wave and tidal.

The thorough assessment involved speaking to every fisherman in the area, considering the impact of PTEC on boats and yachts, and environmental matters such as the migratory routes of crabs.

“The findings from our environmental impact assessment stated that the impact with some mitigating actions should be minor,” Francis says. “We're obviously very interested about what the fishermen have to say and we want to make sure we try and mitigate any potential impacts as much as possible.”

Ultimately, the MMO accepted the consent application, and conversations have been had with Natural England and SeaFast, so Francis says that there shouldn’t be a major impact at all.

PTEC hopes the project will start construction in 2017 and potentially start generating electricity from late 2018, also that it will cost around £150m to install; working out at about £5m per megawatt. Francis sees this as a bargain though, considering PTEC will likely produce enough electricity to power 18,000 homes on the Isle of Wight.

“That sounds like a lot when compare to solar and wind farms, but it is actually cheaper than the current costs of energy for tidal power, and with PTEC we can drive down the future costs and risks of tidal projects,” he says. “We think it's a winner.”