The power of tidal energy

Green marine energy

Andrew Scott, CEO of Orbital Marine Power, describes the exciting progress made in tidal power generation

In 2021 Orbital Marine Power emerged as a leader and demonstrated its leading position in the emerging tidal energy market with the launch of its futuristic O2 2 MW turbine – the likes of which had never been seen before – proudly designed, developed, tested, refined, fabricated, and now generating power in and for the UK.

The Orbital story

Orbital is a Scottish renewable energy company focused on the development and global deployment of its pioneering floating turbine technology. The company is on a mission to unlock a new source of clean, predictable power for millions of people, homes and businesses around the world.

Beneath this mission there is a complex tapestry of interacting dynamics that stand as important drivers for the Orbital business. Essential elements include the creation of sustainable, green jobs and growing these in a manufacturing industry and coastal communities where businesses and workers already exist and are motivated to work in the effort of decarbonising society.

The early years

O2 arriving in Orkney. Photo: Orbital Marine Power

The Orbital technology has been under continuous engineering development, including rigorous testing of scaled systems in both tank conditions and open ocean environments, since the company was founded in Orkney in 2002.

In 2011 Orbital was the first company in the world to successfully grid-connect a floating tidal turbine with its SR250 (a 250kW unit). Then, in 2016 the company launched the (2 MW) SR2000 from the historic Belfast shipyard of Harland & Wolff, which became the world’s most powerful tidal stream turbine. The SR2000 produced in excess of 3GWh of electricity over its initial 12-month continuous test programme connected to the UK grid at the European Marine Energy Centre (EMEC) in Orkney. At the time, this represented more power from a single turbine than had been generated cumulatively by the wave and tidal sector in Scotland over the 12 years prior to the launch of the SR2000. Clocking up 12,000 operational hours, the SR2000 maintained continuous power generation in heavy North Atlantic storms, which saw wave heights of over 7 metres.

Taking tidal to the next level: the O2

Manufacture of the O2, Orbital’s first commercial turbine, began in 2019, and, despite a global shutdown due to the Covid-19 pandemic, it was successfully launched in 2021 – the first vessel launched from a Dundee shipyard in 40 years.

The O2 incorporates key innovations and lessons from the SR2000 and reflects Orbital’s commercial demonstration unit. It was installed on its moorings at EMEC in June 2021, exporting its first power shortly afterwards; the O2 had become the most powerful operational tidal turbine in the world.

Exceptional innovation matched the bold scale of the O2 which, at over 650 tonnes, has similar dimensions to a 747 jumbo jet. The 74-metre-long turbine is expected to operate in the fast-flowing waters off Orkney for the next 15 to 20 years with the capacity to meet the annual electricity demand of around 2,000 UK homes with clean, predictable power, while offsetting approximately 2,200 tonnes of CO2 production per year. In 90 seconds of generation O2 can generate enough low-carbon electricity to meet the demand of the average UK home for a week.

The O2 floats on the surface and is held on station with a four-point mooring system; each mooring chain has the capacity to lift over 50 double-decker buses. It has hinged wing structures which are attached on their inboard end to the main buoyancy hull and are mounted on their outboard end to the power-generating nacelles and rotors. The hinged wings are actuated via a hydraulically driven linkage system that in the down position holds and locks the nacelles in the fastest flowing regions of the currents near the surface. A gull-wing motion brings the wings up to a point where nacelles and pitching hubs breach the surface of the water and can be readily accessed for inspection, service and repair.

On a like-for-like basis, Orbital optimised the O2 to enable a 35 per cent improvement in yield over the SR2000 by including rotor diameters of 20 metres. This provides a 600 square metre rotor area, the largest ever on a single tidal generating platform to date; when the blades rotate, they cover the same area as three whole tennis courts. In a little over two turns of O2’s rotors, it can generate enough electricity to meet the demand of the average UK home for a day.

There is also 360-degree blade-pitching control, for safe, dynamic control of the O2’s rotors, enabling power to be captured from both tidal directions without needing to yaw the entire platform.

A green agenda

O2 with the rotors fitted, wings raised in the position for maintenance access. Photo: Orbital Marine Power

By building in the UK, the company has enabled UK suppliers to commit their fantastic capabilities to deliver a vision and uphold Orbital’s standards and principles. With a supply chain that spans the length and breadth of the country from Orkney to Gosport, Anglesey to Scunthorpe, the story behind the build of the O2 is a prime example of how new green industries can play a significant role in helping the UK economy to build back better, build back greener and help the levelling-up agenda.

The manufacture alone of O2’s 2 MW tidal turbine is estimated to have created around 80FTE jobs in the UK. That’s just one turbine – and Orbital is in a position to multiply that statistic many, many times over by building a new industry for the future that delivers predictable green power and sustainable UK jobs, and grows UK exports.

Furthermore, the company is committed to minimising its carbon footprint in order to maximise the net overall reduction in carbon emissions from the grid mix. The carbon footprint of Orbital’s generating technology is already low due to the relatively competitive material content, particularly fabricated steel, and the engineering team’s use of small, locally based workboats for installation and maintenance.

After the build of the O2 began, the company quantified the carbon emissions from the entire project lifecycle – from manufacturing the tidal turbine to transporting it to the site, including the installation, operation and decommissioning, including all vessel activities associated with these phases. The assessment concluded that while the project can run for 20 years, it can offset from the UK grid mix the carbon emitted by the project within just one year and four months of operation, or 11 months if it is assumed that the electricity being generated is offsetting gas power generation, which is often the case in the UK.

An exciting future: UK government endorsement provides a cost reduction pathway

In the 2022 UK Allocation Round 4 (AR4) process, Orbital was awarded two contracts for difference (CfDs) – a historic move by the UK government, as these energy policy auctions are so important, and never before has funding gone to a tidal energy project. Orbital now has a tangible policy and market engagement in the UK to facilitate our technology’s journey down the cost curve.

As with all clean energy and heavy manufacturing industries, the costs for deploying a first-of-kind technology are disproportionately high and will naturally reduce over time due to the economies of scale, so Orbital is currently progressing with a detailed innovation programme to reduce the cost of energy, which includes key incremental innovation in the areas of blade design and nacelle size.

A significant milestone in the company’s growth, these CfDs underpin the delivery of a multi-turbine project in Eday, Orkney, capable of delivering 7.2 MW of predictable clean energy to the grid, to power up to 7,200 homes. Orbital’s legacy of being truly ground-breaking will be proven once again, as this project will include integration with a hydrogen production facility and battery storage at EMEC in Orkney, and the development of a multi-vector energy system for the future.

Construction is expected to begin in 2023, and the company is committed to using a strong UK supply chain that spans the length and breadth of the country. Orbital also has an established global portfolio of further multi-MW tidal stream projects, focused initially within UK waters, including sites in Anglesey, Wales and the Isle of Wight.

Andrew Scott joined Orbital as CEO in 2015. In 2019, he was awarded the Lennard-Senior prize for outstanding achievement in the field of marine energy. For more information, visit