We are in fascinating times for the clean power sector and for none more so than tidal energy. Of all the potential sources of renewable energy, tidal power has long been a cherished dream of many looking for clean, sustainable forms of electricity generation on a large scale.
After all, if it can be made to work at scale and cost-effectively the predictability of tidal power gives it a significant advantage over wind and solar PV technologies where output is variable. For those managing a country's electricity grid the ability to know exactly when and how much electricity will be generated by a power station on any day and at any specific time is invaluable. And that makes tidal projects an enticing possibility.
Two types of tidal technologies - tidal stream and tidal lagoons/barrage - are seen as most promising. Leading the way in taking these technologies forward is the UK. The country is "now synonymous with tidal power in the same way tech is with Silicon Valley", says Tim Cornelius, Chief Executive Officer of Atlantis Resources. While the UK has just announced an independent review into the potential for tidal lagoons (see below), tidal stream projects are moving forward. While estimates of global potential may vary, it is widely believed that tidal stream energy capacity could exceed 120GW globally. The UK has one of the largest marine energy resources in the world, estimated to be more than 10GW, representing about 50% of Europe’s tidal energy capacity (Scotland alone is reported to have 25% of Europe's tidal energy potential).
Tidal stream turbines use the kinetic power of tidal currents in the same way that wind turbines use the movement of air. This type of generation has lower capital cost and minimal environmental and visual impact when compared to other types of marine energy systems. Atlantis explains that sea water is 832 times denser than air, giving ocean currents an extremely high energy density, which means that tidal turbines have a smaller rotor size than an offshore wind turbine of equivalent power rating. As a result, tidal turbines require less seabed for an equivalent amount of installed generation capacity when compared to wind power, because tidal turbines can be installed closer together within each array. In addition, tidal stream does not require significant alternation of the natural environment, unlike traditional hydro power or tidal barrage schemes, while it has the advantage of minimal visual pollution when compared to offshore wind.
"Tidal energy’s greatest advantage over other alternative energy sources is that it is almost entirely independent of the weather and hence, although it is variable, it is also predictable," the company adds.
Atlantis is the majority shareholder in the 398MW Meygen tidal stream project, located at Inner Sound in the Pentland Firth, Scotland. As the largest fully consented tidal stream project in Europe, it is widely acknowledged as a flagship project for the industry. Construction works began in January 2015, with delivery of the first 6MW due this year. This will comprise of four 1.5MW turbines - three Andritz Hammerfest Hydro HS1500 turbines and an AR1500 machine designed by Lockheed Martin. The next 6MW stage after that is expected to start construction next year and will comprise of next-generation Seagen U tidal turbines developed by Marine Current Turbines (MCT), which is now owned by Atlantis.
Completion of the full 398MW is expected around 2020. Meantime, a deal (announced in December) saw it acquire ScottishPower Renewables two-project portfolio of tidal projects and means Atlantis will install a total of 640MW tidal capacity (including Meygen) in Scotland by 2022.
The two ScottishPower Renewables projects comprise 10MW at the Sound of Islay in western Scotland and a 100MW development at the Ness of Duncansby at Scotland’s north eastern tip. The project assets include lease agreements with The Crown Estate for both sites, and the Sound of Islay site also has a grid connection offer and construction consents from the Scottish Ministers. The Sound of Islay project has also been awarded €20.7 million of grant funding from the European Commission’s NER300 fund by way of capital and revenue support. With consents, grid connection and grants secured, this project is the most advanced commercial scale project in the UK after MeyGen. It is expected to achieve financial close in 2016.
Following completion of the acquisition of Marine Current Turbines Limited from Siemens AG in an all share deal earlier in 2015, the Atlantis group has agreements for lease for two further Scottish tidal sites, at the Mull of Galloway in south-west Scotland and Brough Ness, to the north of the MeyGen and Ness of Duncansby sites in the Pentland Firth. The company is in the process of adding these two projects, with a combined capacity of 130MW, to its Scottish portfolio, which is being delivered by a dedicated project development vehicle, Tidal Power Scotland Limited.
The rest of Europe
Elsewhere in Europe, work on a planned 100MW tidal energy plant near Ballycastle, off the north Antrim coast could start in 2018. The £400 million Fair Head Tidal project is a joint venture between DP Energy (based in Cork) and Bluepower NV (a company established by DEME Blue Energy and Nuhma, both Belgian companies). A marine licence application for the first 10MW phase is now expected to be submitted this summer and if all goes to plan the full 100MW project will generate the equivalent electricity to power an estimated 70,000 Northern Irish homes by 2020. The project developer is working with a number of tidal technology OEMs and is taking a “technology neutral” approach to consenting the site.
The Fair Head project is adjacent to a second 100MW project being developed at Torr Head by Tidal Ventures Limited (TVL), which is a joint venture between OpenHydro and Brookfield Renewable Energy Group. The project will use 50-100 tidal turbines - OpenHydro has been testing its Open-Centre Turbine at the European Marine Energy Centre (EMEC) in Orkney since 2006. To date, no marine life incidents have been recorded. The turbine has a simple design with four key components: a horizontal axis rotor, a magnet generator, a hydrodynamic duct and a subsea gravity base foundation. The turbine base sits directly on the seabed floor, out of the way of ships, and without drilling. TVL hopes to have consents in place o enable the first 30MW phase of the project to start constuction next year, with the 70MW second phase completed by 2020.
Tidal stream projects are also being developed in France. Two 16m OpenHydro tidal turbines, realised on behalf of EDF, will be installed in Paimpol-Bréhat and will produce their first kW/h this year. Meantime, seven OpenHydro turbines will also be installed for the 14MW Normandie Hydro project, also being developed in partnership with EDF, in the Raz Blanchard (the French side of the Alderney Race). The turbines will be deployed in 2018 and will generate enough electricity to supply 13,000 local residents.
A joint venture between GDF Suez (now known as ENGIE) and Alstom (now owned by GE) was also given the green light for a tidal project in the Raz Blanchard in December 2014. The 5.6MW project will use four of Oceade 18 1.4 MW tidal turbines, which will be able to supply power to 5000 homes. The project is slated to begin in 2017 and is expected to operate for a period of 20 years.
Looking even further into the future, OpenHydro is working with Alderney Renewable Energy (ARE) to develop a 300 MW tidal array in Alderney waters. The joint venture company, named Race Tidal Ltd (RTL), says the array will be located 55 miles from the south coast of Britain and 8 miles from France. It expects to submit planning consent applications next year, with the array deployment expected to take place from 2020. It will connect into the planned FABLink interconnector between France, Alderney and the UK.
Canada is recognised as being the UK's main competitor in the race to get tidal stream development moving. The Bay of Fundy between New Brunswick and Nova Scotia is the most promising location in North America for tidal energy and could potentially produce as much as 30,000 MW of energy. Several leading companies, including Atlantis and OpenHydro, are actively testing their technologies at the Fundy Ocean Research Center for Energy (FORCE) and investing in demonstration projects there.
OpenHydro's turbine, for example, will be used for the 300MW Cape Sharp Tidal project it is developing with Emera in Nova Scotia. The partners hope to deploy a fully grid-connected 4MW tidal array in the Bay of Fundy in the coming months. "This project has potential to be one of the world's first multi-megawatt arrays of interconnected tidal turbines, providing energy to more than 1000 customers in Nova Scotia," the company says. "Cape Sharp Tidal is seeking to use the initial 4MW farm as the first phase of a commercial-scale project which, subject to regulatory approvals, will see the development grow to an output of 16MW in 2017, 50MW in 2019, and up to 300MW of energy in the 2020s, generating power for nearly 75,000 customers."
ABOUT THE AUTHOR
Gail Rajgor is a freelance journalist, editor and photographer.