Expanding the scope and power of tidal stream energy   

Tidal Stream Energy

When we think about renewable energy, often what comes to mind is the turbine that generates energy from the wind, or a photovoltaic panel designed to capture energy from the sun. Despite the fact that they cover 71 per cent of the Earth’s surface, the ability to generate energy from our rivers, lakes and oceans often seems to go overlooked. But that may be about to change. 

New technologies that take advantage of tidal streams and river currents have some significant advantages over other renewable energy sources, particularly due to the fact that they do not suffer from any concerns over intermittency. The ability to generate energy from wind and solar is affected by weather conditions, and an irregular energy supply can lead to severe consequences, as we have seen over the last year with a lack of wind leading to energy supply shortages and rapid cost increases in the UK and Europe. In contrast, tidal streams and river currents are a reliable constant that allows for the generation of predictable amounts of energy throughout the day. 

At present, water-based energy generation technology is not on track to grow at the rate required to meet the International Energy Agency’s (IEAs) Net-Zero by 2050 Scenario, which projects the need for an average growth rate of 33 per cent between 2020 and 2030. Despite this, there is relative optimism among the community of businesses developing water-based renewable energy solutions. 

Supporting R&D initiatives 

Pepi Maksimovic, director of application engineering at Ansys, says that tidal stream power generation is still an emerging renewable technology, primarily because it involves complex engineering challenges. These problems need to be addressed successfully before tidal power can be captured on the massive scale needed to support aggressive renewable energy targets.  

Research and development are crucial factors in putting tidal energy on the renewables map. In Orkney, Scotland, tidal energy company Orbital Marine Power was established in 2002 to bring together the engineering expertise to develop the advanced technologies needed to commercialise and install powerful tidal turbines around the world.  

To realise this ambition, their flagship project, O2, was positioned in a powerful tidal stream in the Fall of Warness, where its large one-megawatt (MW) twin underwater rotors could capture energy. The rotors’ ten-metre blades provide more than 600 square metres of area to capture flowing tidal energy. Electricity is transferred from the turbine to the seabed via a dynamic cable, while a static cable running along the seabed carries the energy to an onshore distribution facility. 

The O2 was designed by Orbital to address many of the historic obstacles to commercialising tidal turbines. Unlike seabed-mounted underwater turbines, its rotors are attached to legs that can be lifted to the water surface for maintenance and repair. This is a critical design feature, as oceanic conditions are harsh – and the difficulty and high costs of equipment maintenance have historically been viewed as significant obstacles to the broad commercialisation of tidal turbines. 

With its thoughtful design, the O2 is expected to have significantly lower production and maintenance costs than existing tidal turbine designs, and Orbital hopes that it will prove to be a key enabler in the widespread adoption of tidal-based energy generation.  

Progress on the O2 might not have been possible without the support of Ansys Mechanical, who were able to provide advanced technical solutions to aid in the simulation of structural and environmental loadings on the entire turbine design. From rotors to anchors and chains, to offshore test and demonstration programmes, each element was examined to ensure that it would successfully withstand the harsh oceanic conditions, including extreme weather events. 

“Mechanical has enabled the Orbital development team to study fatigue, vibration, stiffness, bending, and other issues both at the system level and the component level – including rigorous analysis of the hundreds of individual connection points across the O2 design,” says Maksimovic. “Mechanical integrates seamlessly with other engineering tools used by Orbital’s engineers, making it easy to collaborate and hand off design tasks. 

“By applying Mechanical to quickly model and verify its designs in a low-cost, risk-free virtual environment ahead of offshore testing, Orbital has been able to accelerate the initial design of the O2, cutting years from the development cycle. The next task is to explore performance and cost improvements such as mass and weight reduction, improved manufacturability, and the use of alternative materials.” 

With the ability to produce enough power for 2000 homes – offsetting approximately 2000 tonnes of CO2 production – and the prospect of providing power for the European Marine Energy Centre’s onshore electrolyser for green hydrogen production, O2 highlights the potential that tidal stream energy has in accelerating the energy transition. 

A bright future for tidal energy 

The future market for tidal stream power in the UK is high. UK Tidal Energy, a tidal stream advocacy group, estimates that the UK is perfectly placed to benefit from a market that could reach upwards of £76 billion worldwide by 2050, with the UK potentially able to have more than £1 billion market share as early as 2030. This is supported by the fact that the UK holds 50 per cent of Europe’s capacity for tidal stream energy. 

Rob Hunt, energy account executive at Aspectus Group, highlights the fact that several UK companies are already currently operating to introduce tidal energy infrastructure. SIMEC Atlantis Energy, for example, has already secured several sites across the UK, including around the island of Islay and Strangford Narrows, as well as on mainland Europe and across Indo-China and North America. Ventures like those of Simec Atlantis, he says, should also take heart from data from the UK Government which suggests that over 20 per cent of the UK’s energy needs could be met by tidal energy if the sector was fully exploited. 

“Given that the geopolitical intricacies of the UK’s gas supply seem unlikely to be resolved in the near future, and that wind and solar power have been worryingly unreliable in recent months, there has never been a more appropriate time to consider tidal energy,” concludes Hunt. “It is now clearer than ever that the UK should go with the flow and harness the power of the tide.” 

 

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