The Renewable That Runs to a Timetable
Tidal stream energy occupies a unique position in the renewable energy landscape because its output is predictable with a precision that no other renewable technology can match. The gravitational interaction between the earth, moon, and sun that drives tidal cycles is understood with sufficient accuracy to predict tidal stream velocities at specific locations decades in advance. A tidal stream turbine installed in a high-velocity tidal channel will generate power according to a schedule that grid operators can plan around with the confidence that weather-dependent renewable technologies cannot provide. This predictability is the fundamental commercial differentiator that tidal stream energy offers relative to wind and solar, and it is the characteristic that makes tidal stream a complementary rather than competing technology in the portfolio of low-carbon generation that electricity systems require to manage the variability of dominant renewables at high penetration levels. The commercial challenge of tidal stream energy is not its predictability value but its cost, which remains substantially above that of offshore wind and far above onshore wind and solar, limiting its deployment to the early commercial phase in which capital costs are being reduced through accumulated installation experience and manufacturing scale.
The engineering challenges of tidal stream turbine development were genuinely formidable and have been substantially resolved by the commercial developers who have survived the attrition of the sector's development phase. Operating a turbine in a high-velocity tidal stream imposes loading conditions on the rotor, nacelle, and support structure that combine the cyclic fatigue of wind turbine operation with the higher density of water that creates forces approximately eight hundred times greater per unit of swept area than air at equivalent velocity. The biofouling of submerged structures by marine organisms, the corrosion of metallic components in saltwater, and the maintenance access challenges of servicing equipment installed in locations characterised by the fast currents and associated sea states that made them energetically attractive are all engineering problems whose solutions the leading tidal stream developers have demonstrated through operational experience in the most demanding tidal channels in the world.
Orbital Marine and the Floating Turbine Approach
Orbital Marine Power's O2 tidal turbine, deployed in the Orkney islands of Scotland, is the world's most powerful tidal stream turbine and the commercial demonstration whose operational performance has most directly influenced the investment community's assessment of tidal stream's commercial viability. The O2 is a floating tidal stream turbine whose two rotor assemblies are mounted on a floating pontoon that is moored to the seabed rather than fixed to it, allowing the turbine rotors to be raised to the surface for maintenance without requiring the heavy lift vessel operations that seabed-fixed turbine maintenance requires. The floating approach also allows the turbine to be deployed in deeper water than seabed-fixed monopile or gravity-base structures, expanding the geographical range of sites where the technology can be deployed beyond the shallow water sites that fixed foundation approaches address. The O2's two megawatt rated capacity and its operational track record generating electricity to the Orkney grid have provided the performance data that project developers and investors use to assess the generation economics of floating tidal stream turbines at commercial array scale.
The cost reduction pathway for tidal stream energy follows the same logic that has driven cost reduction in offshore wind: manufacturing scale, installation experience, and supply chain development reduce the per-unit capital cost as the number of devices deployed increases. The challenge for tidal stream is that the volume of devices deployed to date is far smaller than the early offshore wind deployment that allowed offshore wind costs to begin their dramatic reduction trajectory. The number of tidal stream turbines in operation globally is measured in tens rather than the thousands of turbines that created the manufacturing scale and installation efficiency that drove offshore wind cost reduction. The commercially demonstrated tidal stream projects whose expanded deployment would create the volume effects that cost reduction requires are concentrated in a small number of high-resource locations in Scotland, France, Canada, and South Korea whose combined addressable capacity, while commercially significant, does not create the global market scale that has driven renewable energy cost reduction in the technologies that have preceded tidal stream.
Tidal Arrays and the Commercial Project Pipeline
The transition from demonstration devices to commercial arrays is the development stage that the tidal stream industry needs to complete to access the cost reduction that scale provides. MeyGen in the Pentland Firth, the highest-tidal-resource site in the UK and one of the strongest tidal resources globally, is the commercial tidal stream project furthest advanced in array development, with four turbines installed and generating and a planning framework for significant additional capacity. The Raz Blanchard tidal stream project off the Normandy coast of France, where the tidal resource is among the strongest in continental Europe, is the commercial project around which the French tidal stream industry led by HydroQuest and Sabella has been developing. Fundy Tidal in the Bay of Fundy, whose extreme tidal range creates the strongest tidal stream resources in the world at specific sites, is the Canadian commercial frontier whose development has been more constrained by the engineering demands of its extreme tidal environment than by the resource quality that makes it globally unique.
Top 10 Companies in Tidal Stream Energy Globally
- Orbital Marine Power: Developer of the O2 floating tidal stream turbine whose 2 MW Orkney deployment is the most powerful operating tidal turbine and the commercial demonstration most closely watched by project developers and investors assessing floating tidal stream viability at array scale.
- SIMEC Atlantis Energy: Developer of the MeyGen tidal array in the Pentland Firth, the world's largest operating tidal stream array, and the AR2000 turbine whose seabed-fixed monopile design is the reference installation approach for high-resource shallow water tidal sites.
- HydroQuest: French tidal stream turbine developer with a vertical axis turbine design for the Raz Blanchard French tidal project; its participation in the French tidal energy development programme and its vertical axis rotor concept create the commercial differentiation from the horizontal axis designs that dominate the UK and international tidal markets.
- Sabella: French tidal turbine company operating the D10 turbine off Ouessant Island; its remote island power supply application demonstrates tidal stream energy's ability to provide reliable baseload power to isolated communities whose grid connection costs make local generation commercially compelling regardless of levelised cost comparisons with mainland grid power.
- ANDRITZ Hydro Hammerfest: Norwegian tidal stream company whose HS1000 turbine has operational experience in Norwegian tidal resources; its ANDRITZ parent company's hydraulic turbine manufacturing expertise creates the engineering credibility and manufacturing infrastructure that independent tidal stream startups cannot access.
- Sulnova: UK tidal energy developer focused on optimising tidal stream turbine arrays for maximum energy yield from constrained tidal channels; its computational fluid dynamics modelling of tidal channel flow and turbine wake interactions addresses the array optimisation challenge that distinguishes multi-device commercial arrays from single demonstration turbines.
- Nova Innovation: Edinburgh-based tidal turbine company with the world's first offshore tidal array providing power to the Shetland grid; its modular turbine design and its direct power purchase agreement with the local grid create the commercial model for small-island tidal stream deployment that is most immediately replicable without the project scale that mainland grid connection requires.
- Sustainable Marine Energy: Developer of the PLAT-I floating tidal energy platform with deployments in Canada and Scotland; its platform approach carrying multiple turbine units on a single moored structure creates the capital efficiency that single-turbine floating installations cannot achieve at the array scale that commercial energy production requires.
- Tocardo: Dutch tidal turbine company whose turbines are deployed in the Eastern Scheldt tidal barrier in the Netherlands; its installation in an existing tidal barrier structure demonstrates the co-location of tidal stream generation with existing marine infrastructure that reduces installation cost relative to open-water deployment.
- EMEC (European Marine Energy Centre): Orkney-based marine energy test facility providing the grid-connected test berths where tidal and wave energy developers validate their devices before commercial deployment; its test infrastructure and its accumulated operational data from decades of marine energy device testing make it the commercial proving ground whose approval is the de facto qualification requirement for devices targeting the UK and European tidal stream market.