Study highlights complex ocean conditions facing world’s most powerful tidal turbine
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The O2 floating tidal turbine, operated by Orbital Marine Power, sited in the heart of the Orkney Islands with survey boat Green Quest in the background
view moreCredit: University of Plymouth
The number of tidal power and other offshore renewable energy installations is set to grow significantly around the UK coastline over the coming decades.
However, launching state-of-the-art devices into often turbulent ocean flows has the potential to pose a range of challenges for the tidal energy industry, including uncertainty around how they may interact with the environment.
To address that, a team of scientists used a combination of aerial drone technology and boat-based surveys to map out the complex tidal flows encountered by the world’s most powerful tidal turbine – Orbital Marine Power’s O2, sited in the heart of the Orkney Islands, Scotland.
Unlike conventional tidal stream turbines, the O2 floats on the sea surface, anchored by mooring lines to the seabed. The platform is over 70 meters long and is connected to the grid at the European Marine Energy Centre (EMEC), with estimates that it could power 2,000 UK homes per year.
The study included highlighting how changing tidal flows, that exceed 8 knots, could impact the device and its performance, but also how the O2’s wake downstream could impact the placing of other turbines as well as marine habitats.
Through this, the scientists provide new insights around the optimal placement of tidal stream turbines, while emphasising the importance of site-specific assessments at potential turbine sites to help bridge the gap between real-world measurements and computer simulations.
They also hope their approach can be used to address uncertainties surrounding interactions with the natural environment and marine habitats.
A previous study by the lead authors found that a turbine wake generated a predictable foraging hotspot for nearby breeding seabirds, however if the turbine arrays are too tightly packed it could restrict the movement of some marine fauna.
In addition to seabirds, the authors encountered orcas travelling past the turbine during one of their drone surveys, demonstrating the importance of addressing this.
The study, published in Nature Communications, was conducted by researchers from the Marine Biological Association (MBA), the University of Plymouth, and the University of the Highlands and Islands (UHI) Shetland.
Dr Lilian Lieber, Research Fellow at the MBA and the University of Plymouth, is the study’s lead author. She said: “Conducting oceanographic surveys in one of the world’s most powerful tidal streams, where currents can exceed 8 knots, is both exhilarating and challenging. Yet collecting data in these turbulent environments is crucial for addressing some of the complexities the tidal energy industry faces today. The optimal placement of these turbines in narrow channels fringed by islands is a complex endeavour, but our novel methods provided robust insights into these turbulent flows and wake signatures.”
Tidal power is seen as one of the more reliable sources of clean energy, with the tides – unlike wind and waves – being both regular and predictable.
The turbines, designed to harness tidal power near the sea surface, work much like windmills underwater and convert the kinetic energy of moving water into electricity. But with water being over 800 times denser than air, they generate more energy than wind turbines of the same size.
In future, it is envisaged there could be more installations around the UK, with previous research by those involved in the current study suggesting tidal stream energy could meet up to 11% of the UK’s annual electricity demands.
Shaun Fraser, Senior Scientist and Fisheries Lead from UHI Shetland, added “This study showcases the benefits of combining scientific expertise and deploying new technologies so that significant progress can be made in understanding dynamic tidal environments. With further development of marine renewable energy infrastructure in the Highlands and Islands region likely in the near future, this work is more relevant than ever to local industries and communities.”
Despite the promise of tidal energy, the sector still faces substantial challenges, including the costs of scaling up the technology, grid connection capacity, and ensuring turbines can continue to function in extremely turbulent currents.
The new study aimed to address some of those challenges by advancing field measurement techniques necessary to inform the long-term reliability and sustainable development of tidal technologies.
Alex Nimmo-Smith, Professor of Marine Science and Technology at the University of Plymouth and the study’s senior author, said: “Whether it is floating offshore wind farms in the Celtic Sea or tidal turbines off the coast of Scotland, we are going to see more offshore renewable energy platforms being installed all around the UK coastline over the coming decades. However, the natural conditions in the waters around the UK are incredibly varied and complex, something that it is impossible to fully replicate in controlled laboratory experiments or computer simulations. This study demonstrates a cost-effective means of countering that, and if we are to get the greatest benefits from the clean energy revolution, assessments that factor in real-world environmental conditions will be of critical importance.”
Journal
Nature Communications
Method of Research
Survey
Subject of Research
Not applicable
Article Title
Sheared turbulent flows and wake dynamics of an idled floating tidal turbine
Article Publication Date
27-Sep-2024
Untapped potential: Study shows how water systems can help accelerate renewable energy adoption
New Stanford-led research reveals how water systems, from desalination plants to wastewater treatment facilities, could help make renewable energy more affordable and dependable. The study, published Sept. 27 in Nature Water, presents a framework to measure how water systems can adjust their energy use to help balance power grid supply and demand.
“If we’re going to reach net zero, we need demand-side energy solutions, and water systems represent a largely untapped resource,” said study lead author Akshay Rao, an environmental engineering PhD student in the Stanford School of Engineering. “Our method helps water operators and energy managers make better decisions about how to coordinate these infrastructure systems to simultaneously meet our decarbonization and water reliability goals.”
As grids rely more on renewable energy sources like wind and solar, balancing energy supply and demand becomes more challenging. Typically, energy storage technologies like batteries help with this, but batteries are expensive. An alternative is to promote demand-side flexibility from large-load consumers like water conveyance and treatment providers. Water systems – which use up to 5% of the nation’s electricity – could offer similar benefits to batteries by adjusting their operations to align with real-time energy needs, according to Rao and his co-authors.
A framework for flexibility
To help realize this potential, the researchers developed a framework that assesses the value of energy flexibility from water systems from the perspectives of electric power grid operators and water system operators. The framework compares these values to other grid-scale energy storage solutions, such as lithium-ion batteries that store electricity during periods of low energy demand and release it during peak demand periods. The framework also takes into account a range of factors, such as reliability risks, compliance risks, and capital upgrade costs associated with delivering energy flexibility using critical infrastructure systems.
Researchers tested their method on a seawater desalination plant, a water distribution system, and a wastewater treatment plant. They also explored the effect of different tariff structures and electricity rates from utilities in California, Texas, Florida, and New York.
They found that these systems could shift up to 30% of their energy use during peak demand times, leading to significant cost savings and easing pressure on the grid. Desalination plants showed the greatest potential for this kind of energy flexibility by tweaking how much water they recover or shutting down specific operations when electricity prices are high.
The framework could help electricity grid operators evaluate energy flexibility resources across a range of water systems, compare them with other energy flexibility and energy storage options, and modify or price energy, according to the researchers. The approach could also help water utility operators make more informed financial decisions about how they design and run their plants in an era of rapidly changing electricity grids.
The study also highlights how important energy pricing is for making the most of this flexibility. Water systems that pay different rates for energy at different times of the day could see the biggest benefits. Facilities might even be able to make extra money by reducing energy use when the grid is stressed, as part of energy-saving programs offered by utilities.
“Our study gives water and energy managers a tool to make smarter choices,” said Rao. “With the right investments and policies, water systems can play a key role in making the transition to renewable energy smoother and more affordable.”
Meagan Mauter, associate professor in the Photon Science Directorate at SLAC National Accelerator Laboratory, is senior author of this paper. She is also a senior fellow at the Stanford Woods Institute for the Environment and the Precourt Institute for Energy, and an associate professor, by courtesy, of chemical engineering.
Co-authors of the study also include Jose Bolorinos and Erin Musabandesu, postdoctoral scholars in civil and environmental engineering; and Fletcher Chapin, a PhD student in environmental engineering while doing the research.
The research was supported by the National Alliance for Water Innovation and the U.S. Department of Energy.
Journal
Nature Water
Article Title
Valuing Energy Flexibility from Water Systems
Article Publication Date
27-Sep-2024
