The Eᶜ simulator – A tool for helping us make sustainable investments in Floating Offshore Wind Farms (FLOW)

Authors – Justin Olosunde (Project Lead) and Professor Lars Johanning (the Deputy Head of Engineering and Co-Director Centre for Doctoral Training in Offshore Renewable Energy at the University of Exeter)

The Cornwall and Isles of Scilly Local Enterprise Partnership (CIOS LEP) have identified the Cornwall and Scillies region as the birthplace of commercial wind generation in the UK. It has one of the best wind climates in Europe and has committed to the UK Government agenda as one of only two places in the UK singled out by the Government’s Net Zero Strategy for large-scale FLOW deployment. Some 300MW of projects are already moving forward, with a 30–40MW demonstrator expected to be on-site by 2025.

“The LEP has set a target of 3GW of installed capacity, which could support more than 11,000 jobs and generate £900 million of net additional gross value added.”

~ Mark Duddridge, Chair of The Cornwall and Isles of Scilly Local Enterprise Partnership, 2021

Celtic Sea Power is leading the Cornwall Floating Offshore Wind Accelerator, a part European Regional Development Funded project, which will develop tools, knowledge, and data to accelerate the Celtic Sea FLOW opportunity. They hope to lay the significant groundwork to develop a pipeline at both a FLOW project and supply chain level. The University of Exeter, University of Plymouth, and the Offshore Renewable Energy Catapult have partnered to achieve this. Here at the University of Exeter, we are working toward designing, developing, and building a floating offshore wind simulator as a vehicle to help provide research-led expertise to reduce carbon footprints and underpin the FLOW service.

Partnerships created between the University of Exeter and external partners are contributing toward the development of tools, knowledge, and data that accelerate the Celtic Sea FLOW opportunity. These partnerships are laying significant groundwork, with respect to developing a pipeline at both a FLOW project and supply chain level.

A team within the University of Exeter are undertaking research on Floating Offshore Wind via the Cornwall FLOW accelerator, which is a part of The European Regional Development Fund (ERDF) programme. The programme is led by Celtic Sea Power, a wholly owned subsidiary of Cornwall Council. Justin Olosunde, The Impact and Partnership Development Manager for Cornwall FLOW Accelerator and Lars Johanning, the Deputy Head of Engineering and Co-Director Centre for Doctoral Training in Offshore Renewable Energy at the University of Exeter, are part of the Exeter team leading on the design of the tool, to develop a floating offshore wind simulator as a vehicle.

¹ Team photo for the Exeter floating offshore wind simulator team. Left to right: Jessye Boulton, me, Dr Hailun Xie, Dr Barton Chen, Professor Lars Johanning, Dr Mi Tian, Dr Kanchan Joshi and Dr Shuya Zhong.

² Floating offshore wind turbines identified for Hexicon Celtic Sea development site (RenewablesNow

The Eᶜ simulator is a software tool, used to assess economic values and the environmental impacts of floating offshore wind farms. The assessment is based on life cycle analyses, which include five development stages: pre-development, manufacturing, assembly and installation, operations and maintenance, and decommissioning.

This tool is designed to help stakeholders such as wind farm developers and policymakers in decision-making processes in FLOW development. The aim is to enable the effective optimization of the maximum energy yield from any proposed development locations, while minimising the carbon intensity, associated net environmental impact and cost of electricity generation.

A holistic model has been established to encapsulate the whole procedure in assembly and installation of FLOW, including the transport of major FLOW components (tower, blades, nacelle, mooring system, cables, and floating platforms) from manufacturing port to assembly port. This involves the assembly

of wind turbine generators at assembly port, the transit from assembly port to installation port, and the installation at the farm site.

The installation tasks are classified into four categories, i.e., assembly at the port, offshore installation, installation on the seabed, and onshore installation. Three assembly activities at ports or shipyards are considered, including wind turbine assembly, storage of mooring chains, and storage of anchors. The offshore installation includes the transport activities from manufacturing to assembly port, transport activities between installation port and to farm site, as well as offshore operations for installing wind turbines and the mooring system. Installation on the seabed considers the installation of inter-array and export cables, being the cables connecting the wind turbines to one another.

Lastly, onshore installation is dedicated to the installation of onshore substations and export cables. Various types of vessels are employed for the installation of components, such as tugboats, cargo vessels and crane vessels, dependent on specific tasks. The impact of weather conditions on maritime operations is considered by simulating the vessel transit and operation time for wind farm installation, maintenance, and end-of-life decommissioning operations. Additionally, the fuel consumption rates of each vessel for vessel transit and operation are considered separately. A similar environmentally conscious approach is deployed for the analysis of FLOW decommissioning, where the research team considers the recycling and recovery of materials at end of life.

During the maintenance life of the floating offshore wind farms (approximately 25 years), approaches are being taken to account for uncertainties in the failure of them operating effectively. Statistical techniques are being used to determine any uncertainties in the development of the models. The team is currently exploring surrogate-based methods and representative learning approaches to achieve an effective trade-off between computational cost and model fidelity. The hope is to ensure the simulator can be used commercially and by policymakers, to inform investment decisions and future offshore industrialisation, both with confidence and within reasonable timeframes. The impacts of metocean conditions at various locations on vessel accessibility and transit time are determined for all of the offshore operations. This is to ensure the generation of real-world results in terms of both economic costs and carbon emissions. Only by adopting the “cradle to the grave” approach outlined can stakeholders be assured that the major impacts are being captured for any individual wind farm development or series of developments.

3 Cradle to grave life cycle model (University of Exeter, 2022)

Once fully developed and implemented, this tool will allow the optimisation of wind farm design and the planning of multiple windfarms at regional spatial levels. Consideration will be taken into the potential impact of installation, decommissioning, and marine maintenance operations on marine-based flora and fauna. Additionally, solid metrics will be determined on the lifetime costs of energy production, the lifetime carbon costs, and the total energy returned as a ratio to the total energy invested at an individual farm level.

There is a proposed extension of the tool, to further support the modelling of seabird habitat use and how they interact with wind farms. The aim is to use the existing tool to test a series of different wind farm configurations (orientation, spacing of turbines, etc), to provide guidance on those designs that give economic yields, while at the same time minimising their impact on seabirds. Investigations could be taken to discover how to mitigate against the potential losses of birds to wind farm installations by compensation mechanisms, such as the creation of new breeding areas, bycatch reductions methods, or invasive species eradications. The final tool output can inform the creation of a UK-wide risk map that highlights areas around the UK where wind and seabird interests align, to inform wind-farm planning and development policy at a national level.

Having a tool that allows developers and policyholders to virtually explore the interactions between one or more farms at a sea-scape level, enables us to plan wildlife corridors within a farm or between farms, enabling populations to flourish. The approach can inform where and where not to develop and evaluate the associated impact on the cost of generation and energy yield. Generally, this tool will provide valuable information to further inform policy decisions and potentially drive investment in the local supply chains. Multiple scenarios can be evaluated within the simulator, enabling the alignment of low carbon power generation, with the development of local content manufacturing, assembly, and marine operations supply bases. This tool has great potential to help guide environmental impact assessments, whilst also providing a source of energy across the region.

Many thanks to the floating offshore wind simulator team at the University of Exeter for contributing this research to and the Cornwall FLOW Accelerator for leading this project.

References:

1. Team photo for the Exeter floating offshore wind simulator team Image taken at the University of Exeter, Penryn, Cornwall, 2022

2. Sweden’s Hexicon buys consented Celtic Sea site for floating wind demo. Renewablesnow.com. 2022. Available from: https://renewablesnow.com/news/swedens-hexicon-buys-consented-celtic-sea-site-for-floating-wind-demo-749519/

3. Cradle to grave diagram, created by the University of Exeter, 2022.

Developing a New Floating Wind Turbine

Model Tests with a Novel Floating Wind Turbine Concept

Dr Ed Mackay & Prof. Lars Johanning, Offshore Renewable Energy Group

Dr Ed Mackay (Left) and Prof Lars Johanning (Right)

Floating offshore wind energy has been identified as being able to provide a significant contribution to meeting future renewable energy generation targets. Compared to traditional offshore wind turbines, which are fixed to the seabed, floating turbines can access deeper waters and areas with a higher wind resource. Current floating wind turbines are at the pre-commercial stage, with small arrays of up to five turbines being demonstrated. The cost of floating offshore wind turbines is currently significantly higher than fixed offshore wind. One of the main areas identified for reducing the cost of the structure is in the design of the platform. The platform must be designed to withstand large wave loads and keep the wind turbine as stable as possible. Large platform motions lead to reduced energy yield and increased loads on the wind turbine and drive train.

As part of the EPSRC funded RESIN project, the University of Exeter has been working with Dalian University of Technology (DUT) in China to investigate the use of porous materials in the floating platform for an offshore wind turbine, as a passive means of reducing platform motions. Porous materials are commonly used in offshore and coastal structures such as breakwaters or offshore oil platforms. As a wave passes through the porous material, energy is dissipated, reducing the wave height and wave-induced forces. The question posed by the RESIN project is: can porous materials be beneficial for floating offshore wind?

Examples of porous structures used in coastal and offshore engineering

The project has investigated this question using a combination of physical and numerical modelling. A range of analytical and numerical models have been developed [1-3] and validated against scale model tests in wave tanks. Two tests campaigns were conducted at the large wave flume at DUT in the summers of 2018 and 2019. The initial tests last year considered simple cases with flat porous plates with various porosities and hole sizes [4] and tests with fixed porous cylinders. These tests were used to validate the numerical predictions in a range of simple scenarios and gain an understanding of the effect of the porosity on the wave-induced loads.

 

A wave interacting with a fixed porous cylinder

Following the successful validation of the numerical models with simple fixed structures, a design was developed for a 1:50 scale model of a floating turbine, which could be tested with and without external porous columns. The model was tested at DUT this summer and further tests were conducted in the FlowWave tank at the University of Edinburgh this autumn. The test results showed that the motion response could be reduced by up to 40% in some sea states by adding a porous outer column to the platform. Work is ongoing to analyse the test results and optimise the design a platform using porous materials. However, initial results indicate that using porous materials in floating offshore wind turbines offers potential for reducing the loading on the turbine and mooring lines and improving energy capture.

1:50 scale model of a floating platform for an offshore wind turbine in various configurations. Left: inner column only. Middle: medium porous outer column. Right: Large porous outer column. The turbine rotor and nacelle are modelled as a lumped mass at the top of the tower.
The scale model installed at the FloWave tank at the Univeristy of Edinburgh

Thanks Ed!

To keep up to date with the Renewable Energy team, give them a follow on Twitter @Renewables_UoE 

For information on the Offshore Renewable Energy research group, check out their webpages.

References

  • Mackay EBL, Feichtner A, Smith R, Thies P, Johanning L. (2018) Verification of a Boundary Element Model for Wave Forces on Structures with Porous Elements, RENEW 2018, 3rd International Conference on Renewable Energies Offshore, Lisbon, Portugal, 8th – 10th Oct 2018.
  • Feichtner A, Mackay EBL, Tabor G, Thies P, Johanning L. (2019) Modelling Wave Interaction with Thin Porous Structures using OpenFOAM, 13th European Wave and Tidal Energy Conference, Napoli, Italy, 1st – 6th Sep 2019.
  • Mackay E, Johanning L, (2019). Comparison of Analytical and Numerical Solutions for Wave Interaction with a Vertical Porous Barrier. Ocean Engineering (submitted)
  • Mackay E, Johanning L, Ning D, Qiao D (2019). Numerical and experimental modelling of wave loads on thin porous sheets. Proc. ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering OMAE2019, 2019, pp. 1-10.

#ExeterMarine is an interdisciplinary group of marine related researchers with capabilities across the scientific, biological,  medical, engineering, humanities and social science fields.

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If you are interested in working with our researchers or students, contact Emily Easman or visit our website!

 

My #ExeterMarine Expedition: updates from the Indian Ocean

This is a series of updates from #ExeterMarine researcher, Dr Ines Lange, who is on a research expedition in the British Indian Ocean Territory with Professor Chris Perry, the Bertarelli Foundation and ZSL.

Hard at work in the Indian Ocean

03/05/2018 Somewhere in the Indian Ocean

We are in the Central Indian Ocean, sailing south on the “Grampian Frontier”. Prof. Chris Perry and myself, Dr. Ines Lange, from the Geography department are on a research cruise to study the coral reef ecosystems of the British Indian Ocean Territory (BIOT). The project is part of a large expedition funded by the Bertarelli Foundation and on board are twelve scientist, working on six different projects.
Chris and I are studying the carbonate budgets of coral reefs around islands of the Chagos archipelago. The “ReefBudget” method we use was developed by Chris and calculates how much carbonate is produced by corals and calcifying algae, and how much is eroded by grazing sea urchins and fish, as well as by internal bioeroders such as boring worms and microorganisms. The results provide a metric of reef “health” in terms of whether it is growing or eroding. On this trip we have two main goals:

1) To revisit sites that were surveyed in 2015, before the severe bleaching event that hit the Central Indian Ocean in 2016. We expect to see dramatically reduced rates of carbonate production due to low coral cover.
2) To investigate local rates of coral and calcifying algal growth as well as internal erosion rates by deploying experimental substrates.

On the two-day transit from the Maldives down to Chagos we are busy preparing material for the deployment of experimental substrates and discussing calculations for the model. Of course we also have to include a few safety exercises; it is very hot here so I would not mind going for a swim, but we ended up not abandoning the ship…

Stay tuned for our upcoming adventures underwater.

Survivors in the reef

News from the “Reef team” in the Indian Ocean. The sites in the Salomon and Peros Banhos Atolls we visited so far show a dramatically reduced coral cover due to the severe bleaching event in 2016, causing carbonate production rates to drop to about a third of the values in 2015. On the upside, there are many Porites and also some Acropora colonies that apparently survived the bleaching, and large numbers of small recruits of different genera. Especially in the understory of the reef structure we find many live encrusting corals. Also, the substrate is quite clean of macroalgae, thanks to the high abundance of grazing herbivorous fish. Calcareous algae covering the dead coral substrate continue to produce substantial amounts of carbonate which help “glue” the existing structure together and offer a great substrate for further coral recruitment. We therefore hope we can see a fast recovery of the once glorious reefs over the next years.

To investigate local bioerosion rates in the reefs we had a “fun” day sawing 1000s of blocks from dead Porites skeleton (well, it certainly felt like that, on my last count it was actually 28). Today we successfully deployed the substrates in the reef, where they will be settled by encrusting and bioeroding organisms (or eaten by parrotfish? Hope not …). The work days are long and it’s actually not always as sunny as you would imagine (see how we enjoy our surface interval in the rain?!). But the company is great, and encounters with curious turtles, dancing eagle rays and confused birds trying to land on our heads make every day a great adventure…

#ExeterMarine is an interdisciplinary group of marine related researchers with capabilities across the scientific, medical, engineering, humanities and social science fields. If you are interested in working with our researchers or students, contact Michael Hanley or visit our website!

Life on a Russian Icebreaker: ACE Maritime University

Author – Jen Lewis, PhD researcher

This blog originally featured on fabiogeography.com.

Before departure in Bremerhaven Germany

Last year (I can’t believe it’s been a whole year!) I was lucky enough to be awarded a scholarship to attend a one off opportunity, the ACE Maritime University. The scene for this month long ‘floating university’ was the Eastern Atlantic Ocean, aboard the Russian Polar Research Vessel Akademik Treshnikov.

On the 19th of November 2016, 49 students and 16 scientists from 20 different nationalities joined the ship in Bremerhaven, Germany for Leg 0 of the Antarctic Circumnavigation Expedition. Over 27 days we sailed down across the equator, to Cape Town, South Africa. ACE was a

privately funded expedition, that went on to circumnavigate the continent of Antarctica last summer, visiting the islands, measuring things like marine mammal populations, ocean acidification, carbon dioxide dynamics and marine plastic distribution. There were 22 different research projects, and if you want to read more about them then check out the ACE expedition website and blog.

The aim of the course was to bring together a global group of young researchers and introduce marine science as a cross-disciplinary field. Days were full of lectures on various principles of oceanography, or how to use different type of ocean monitoring instrumentation.

Releasing a radiosonde balloon to take atmospheric measurement

 

Deploying the CTD and water sampler

 

 

 

 

 

 

 

 

 

 

We even had homework every other day! We also took part in daily deck work with the different projects that were setting up for the Antarctic legs. This included things like assisting with the CTD deployment, processing data, collecting water samples and filtering them. Highlights included working with Florian and Yajuan to make a film about their research  investigating microbial and plankton communities that have big influences on primary production and the carbon cycle, seeing the different layers of biomass on the echosounder display, and also setting up and deploying a radiosonde balloon that measures the atmosphere.

Dolphins riding the bow waves

 

CTD profile from cruise data. Each graph shows information about temperature, salinity or oxygen from the surface down to 1000m depth. Samples start from near the Mediterranean (CTD001), over the equator (CTD10) and further south towards the African coast. You can see things like the high salinity Mediterranean outflow at the start, and oxygen minimum zones either side of the equator.

As part of a personal project, I was also filtering seawater samples from different depths from the CTD casts every day. These samples are being used to look at the difference in species diversity through the North to the South Atlantic, by looking for traces of DNA that has been left in the water by different species that are in the area at different depths – so watch this space!

#Research: Testing new mooring systems for #MarineRenewableEnergy

Author – Dr Tessa Gordelier

A new paper has been published by #ExeterMarine academics Prof. Lars Johanning, Dr Tessa Gordelier and Dr Philipp Thies in collaboration with the French research institute IFREMER (@Ifremer_en).

The mooring systems were put through their paces at the University of Exeter’s DMaC facility

Assessing the performance durability of elastomeric moorings: Assembly investigations enhanced by sub-component tests”  investigating novel mooring tether performance for offshore renewable applications.

The growing marine renewable energy sector is placing new demands on mooring systems; not only are they required to hold devices on station they must also provide the compliance required to harvest energy from the marine environment.  In response to this, several innovative mooring tethers have been proposed, with increased compliance and a degree of customisation of the stiffness profile.  Many of these novel systems utilise materials in a unique application within the challenging marine environment and their long term durability remains to be proven.

The novel mooring system underwent 6 months of sea trials on a mooring limb of the South West Mooring Test Facility

In response to this challenge, the work presented in this paper summarises a multifaceted investigation into the durability of a novel mooring tether with an elastomeric core.  Tether assembly testing is conducted before and after a 6 month sea deployment in addition to detailed laboratory investigations.  At a sub-component level, to represent the operational demands of the tether on the elastomer core, detailed material investigations review the effect of both marine exposure and repeated compression loading on key material properties. This work is the first of this type to be published and will be of interest to anyone utilising this material in other relevant applications.

Overall the results indicate an increase in both material and tether stiffness profile with use; this will affect both system dynamics and mooring loads.  If we are to realise the benefits of these novel mooring systems, this characterisation is crucial to ensure reliable and effective integration into offshore engineering projects.

#ExeterMarine is a interdisciplinary group of marine related researchers with capabilities across the scientific, medical, engineering, humanities and social science fields. If you are interested in working with our researchers or students, contact Michael Hanley or visit our website!