Difficulty: Introductory | Prerequisites: None
This topic sits at the intersection of renewable energy engineering and emerging marine technology. Magallanes Renovables is a case study in how tidal stream energy devices move from concept through prototype testing to commercial deployment. Even if you have no background in marine engineering, the material is accessible, covering device design principles, testing methodology, and the regulatory pathway (Contracts for Difference) that supports commercial-scale ocean energy in the UK. If you missed earlier lectures on renewable energy sources, start here.
Magallanes Renovables is a Spanish company that builds floating platforms with underwater turbines to generate electricity from tidal currents. Their main device, the ATIR, uses two counter-rotating turbines mounted beneath a ship-like hull, and has been tested at full scale in Orkney, Scotland since 2019. The company has now secured UK government contracts (Contracts for Difference) to supply tidal power commercially at sites in Wales and Scotland.
Tidal stream energy
Electricity generated by capturing the kinetic energy of moving water in tidal currents, using submerged turbines. Think of it as underwater wind power, except the "wind" is water driven by the gravitational pull of the moon and sun, making it far more predictable than actual wind.
ATIR (Magallanes device)
The name of Magallanes Renovables' floating tidal energy platform. A ship-like hull moored in place with underwater turbines hanging beneath it. In simple terms, it is a floating barge with two propellers underneath that spin as the tide flows past, generating electricity.
Counter-rotating turbines
A pair of turbines mounted on the same driveshaft that spin in opposite directions. The aft (rear) turbine recovers additional energy from the slipstream of the forward turbine, and the opposing rotation balances the torque reaction on the platform. Think of it as two fans facing the same airflow but spinning opposite ways, so neither one tries to twist the whole structure sideways.
Variable pitch (rotor blades)
Rotor blades whose angle of attack can be adjusted while in operation. This allows the device to capture energy from tidal flow in both directions (ebb and flood) without needing to be physically repositioned.
EMEC (European Marine Energy Centre)
A purpose-built testing facility in Orkney, Scotland, where wave and tidal energy devices are deployed and evaluated at real-sea conditions. In simple terms, it is the proving ground where marine energy prototypes go to show they can survive and perform in open water.
Contracts for Difference (CfD)
A UK government mechanism that guarantees renewable energy generators a fixed price (the "strike price") for the electricity they produce. If the market price falls below the strike price, the government pays the difference; if it rises above, the generator pays back. Think of it as a price guarantee that de-risks investment in new renewable technologies.
Mooring (bow and stern lines)
The anchoring system that holds a floating device in position. The ATIR is moored at both ends, allowing it to remain stationary while tidal currents flow past its turbines.
Bureau Veritas (Basic Design Assessment)
An international certification body. Their Basic Design Assessment for the ATIR 2.0 confirms that the engineering design meets recognised standards for structural integrity and safety. In simple terms, it is an independent stamp of approval that the design is sound.
Magallanes Renovables, S.L. is a Spanish developer of floating tidal stream energy devices, founded in 2009 by Alejandro Marques de Magallanes.
Head office: Redondela, Galicia, Spain.
UK subsidiary: Magallanes Tidal Energy Ltd., based in Kirkwall, Orkney.
Parent company: SAGRES SL, which coordinated early European funding.
The ATIR is a floating platform resembling a ship's hull, moored in place by lines at bow and stern.
Two three-bladed counter-rotating turbines are mounted approximately 15 metres (50 ft) below the hull, at either end of a common driveshaft.
The turbines capture kinetic energy from tidal currents flowing past, powering onboard generators.
The hull is symmetrical fore-aft, so the device does not need to be turned around when the tide reverses.
Both rotors are variable pitch, enabling energy capture from both ebb and flood tides without repositioning.
Modular construction: the platform is designed in modules to reduce manufacturing cost and simplify assembly.
Counter-rotating efficiency: the aft turbine recovers energy from the forward turbine's slipstream, and the opposing rotation balances torque so the platform stays stable.
In-situ maintenance: the design allows access to machinery during operation without disconnecting the turbine, a significant advantage for offshore devices.
Cross-sector engineering: the device draws on methodologies from naval architecture, offshore wind power, and the oil and gas industry.
ATIR 2.0: the second-generation design, whose engineering was completed in 2023, has received a Basic Design Assessment certification from Bureau Veritas.
2013 to 2014, small-scale prototype: a 1:10 scale model (6 m long, 2.3 m wide, trimaran hull) was tested at the EMEC nursery site in Shapinsay Sound, Orkney. Not grid-connected. Sea trials began 28 November 2013. Cost approximately US$1.2 million, funded by the Marinet project, Spanish government agencies, and private investors.
2017, tow testing in Spain: the full-scale 1.5 MW ATIR (45 m hull, two 19 m diameter rotors) was built in the Ria de Vigo and launched in 2017. Over 20 tests across seven towing operations, generating up to 450 kW (limited by tug power).
2018, transit to Orkney: the device was towed to Orkney in September 2018 and installed at the EMEC Fall of Warness test site near the island of Eday.
2019, grid connection: deployed in February 2019 and connected to the electricity grid in March 2019, generating power shortly after. This made it a full-scale, grid-connected tidal stream device.
2020 to 2021, maintenance: towed to Edinburgh for maintenance at the Imperial Dry Dock, Port of Leith (the device had to be tipped onto its side using buoys to enter the dock). Returned to site in April 2021.
Funding sources: European OCEAN_2G project, Interreg OceanDEMO, and MaRINET2 projects extended testing beyond the initial two-year programme.
Magallanes Tidal Energy has been awarded Contracts for Difference in UK Allocation Rounds AR4 to AR6 to supply subsidised electricity to the GB National Grid.
Planned deployments include a farm of six turbines at Morlais, North Wales, and three more at EMEC in Orkney, Scotland.
These projects will use the second-generation ATIR 2.0 device.
Magallanes aims to install devices at additional sites, including locations in Spain.
The Strait of Gibraltar has been identified as having significant tidal energy potential.
Tidal stream devices like the ATIR could supply predictable, baseload-like renewable electricity to coastal communities and island grids where wind and solar output fluctuate. The modular, floating design also means the platform can be towed to a conventional dry dock for maintenance, avoiding the expense of specialist offshore vessels, which is one of the biggest cost barriers in offshore wind and subsea tidal installations.
Students often assume tidal energy devices sit on the seabed. The ATIR is a floating platform with turbines suspended beneath it, not a seabed-mounted structure.
Students sometimes confuse tidal stream energy with tidal barrage (dam) systems. Tidal stream devices capture kinetic energy from moving water in open channels. Tidal barrages impound water behind a dam and release it through turbines. They are fundamentally different approaches.
It is a common mistake to think the device must rotate 180 degrees when the tide changes direction. The ATIR's symmetrical hull and variable-pitch blades let it harvest energy from both ebb and flood tides without repositioning.
Students occasionally believe counter-rotating turbines are less efficient because they "interfere" with each other. In fact, the aft turbine recovers energy from the forward turbine's wake, and the opposing torques stabilise the platform.
Know the key specifications: 1.5 MW rated capacity, two 19 m rotors, 45 m hull, turbines mounted 15 m below the waterline.
Be able to explain why counter-rotating turbines improve efficiency and platform stability (energy recovery from slipstream, torque balancing).
Understand the role of variable pitch blades in bidirectional energy capture without device repositioning.
Know the testing progression: 1:10 scale prototype (2013 to 2014) to full-scale grid-connected deployment (2019).
Be prepared to explain what a Contract for Difference (CfD) is and why it matters for emerging renewable technologies.
Remember that the ATIR can be towed to a standard dry dock for maintenance, a design advantage over seabed-mounted tidal devices.
True or False: The ATIR device is mounted on the seabed. (False, it is a floating platform.)
Fill in the blank: The ATIR's two turbines are mounted approximately ______ metres below the hull. (15 metres.)
True or False: The ATIR must be physically turned around when the tide reverses. (False, its symmetrical hull and variable-pitch blades handle both directions.)
Fill in the blank: The UK government mechanism that guarantees a fixed price for renewable electricity is called a ______. (Contract for Difference, or CfD.)
True or False: The full-scale ATIR was first connected to the electricity grid in 2019. (True.)
Q: Describe the ATIR device concept and explain how it captures energy from tidal currents.
A: The ATIR is a floating platform shaped like a ship's hull, moored at bow and stern. Two three-bladed counter-rotating turbines are suspended about 15 m below the hull on a common driveshaft. As tidal currents flow past, the turbines spin and drive onboard generators. The hull is symmetrical fore-aft, and the rotors are variable pitch, so the device captures energy from both ebb and flood tides without needing to be repositioned.
Q: What advantages does a counter-rotating turbine configuration provide over a single-turbine design?
A: Two advantages. First, the aft turbine recovers additional energy from the slipstream of the forward turbine, increasing overall efficiency. Second, the opposing rotation of the two turbines balances the torque reaction, keeping the platform stable and reducing stress on the mooring system.
Q: Explain what a Contract for Difference (CfD) is and why it is important for tidal stream energy developers like Magallanes.
A: A CfD is a UK government mechanism that guarantees a renewable energy generator a fixed "strike price" for each unit of electricity produced. If the market price falls below the strike price, the government pays the shortfall; if it exceeds it, the generator pays back the difference. For emerging technologies like tidal stream, the guaranteed revenue makes projects bankable and attracts the investment needed to scale from prototypes to commercial farms.
Q: Outline the testing progression of the ATIR device from prototype to commercial readiness.
A: A 1:10 scale prototype was tested at the EMEC nursery site in Orkney in 2013 to 2014, without grid connection. The full-scale 1.5 MW device was built in Vigo, Spain, tow-tested in 2017, towed to Orkney in 2018, and connected to the grid at EMEC in March 2019. After maintenance in Edinburgh (2020 to 2021), the company secured CfD contracts for commercial farms using the next-generation ATIR 2.0.
Q: What design feature allows the ATIR to be maintained without specialist offshore vessels?
A: The floating design means the ATIR can be unmoored and towed to a conventional dry dock for maintenance, avoiding the need for expensive specialist offshore service vessels. During its 2020 maintenance period, it was towed to the Imperial Dry Dock at the Port of Leith in Edinburgh.
This material connects to broader energy systems coursework: understanding how intermittent versus predictable renewable sources (wind, solar, tidal) complement each other in grid planning. The CfD mechanism ties into energy policy and market design topics, where you will see the same instrument applied to offshore wind and other low-carbon technologies. The engineering discussion of counter-rotating turbines and variable-pitch blades links to fluid dynamics and turbomachinery principles covered in mechanical engineering modules.
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