waves; waves;

Convex, UK

Convex: reducing the costs of wave energy production

Wave energy has the potential to form a critical part of the future energy mix. However, the cost of harnessing wave energy today is much higher than using other forms of renewable energy.  

As we seek to transition to low carbon energy systems to support our net-zero targets, it’s essential to ensure these solutions are financially feasible and accessible.

Our client, Wave Energy Scotland (WES), set out to discover how alternative materials could reduce the cost of wave energy converters (WECs) to ensure the wider wave energy sector could adopt modern innovations. Arup was appointed to respond to this challenge and unlock opportunities that could drive down the cost of WECs by researching, designing, modelling and testing the use of new structural materials.

Arup’s specialist material and structural experts concluded that replacing steel with concrete could significantly reduce the levelised cost of floating WECs by up to 20%. Concrete also benefits from being more durable than conventional materials, including steel, and with an existing local supply chain in Scotland, its use would boost local value. Additionally, the use of concrete would typically result in a lower rate of embodied carbon compared to steel based on the level of recycled content.

To promote a greater understanding of the potential of concrete, Arup went a step beyond the project scope to create a digital decision-making tool, named Convex, helping wave energy device developers to assess the feasibility of incorporating concrete, for lower cost, more resilient, and more sustainable designs.   

Project Summary

20% whole life cost reduction compared to steel

40%reduction in structural CAPEX

2xthe design life of the structure

Enabling cost reductions

Throughout the project, we conducted a sector-wide review of leading steel device designs to demonstrate the potential for cost reduction. Working closely with two device developers, Carnegie Clean Energy and AWS Ocean Energy, we developed structural designs for their floating WECs using concrete. This required us to understand the details, constraints, and opportunities associated with their existing steel designs to design for manufacture and drive down costs through new efficient and innovative construction techniques. 

We carried out full-scale physical testing to demonstrate the performance of our design, which incorporated a novel concrete connection detail that we developed. To ensure design for manufacture, we also engaged with BAM, an experienced offshore contractor. In addition to providing valuable insights into state-of-the-art concrete construction techniques and opportunities for efficiency gains, BAM provided independent cost calculations which validated our findings. Our designs of the two devices proved that concrete was a viable alternative, demonstrating cost reductions of up to 20%.

Building a stronger business case

We endeavoured to make our findings more accessible so developers could make a more robust business case for concrete WECs. Our team of user experience designers, software developers and engineers undertook a series of eight interviews with wave energy developers, including AWS Ocean Energy, Carnegie Clean Energy and Bombora, to shape the tool’s content. Findings in this phase helped establish the user types and user needs with user-testing crucial to validate design assumptions and shape the tool further during development.

The development of Arup’s Convex tool will allow wave energy device developers to easily explore the potential benefits of incorporating concrete as a structural material in their design solutions. The tool provides access to a wealth of knowledge about designing with concrete through an attractive interface and the GIS-based supply chain map identifies the manufacturing potential. ” Tim Hurst Managing Director of Wave Energy Scotland

Convex: facilitating decision-making

Convex brings together the knowledge gained throughout the project and makes it readily available to the wave energy sector. The digital tool allows developers to use the data we gathered and explore how using concrete in their designs compares to steel solutions. Its value is in its flexibility, delivering tailored results around feasibility, cost, carbon impact, and construction, based on a range of variables that a developer can input about its proposed concrete device, such as its mass, submerged volume, and target buoyancy. 

Carbon impact 

It is a common belief that using concrete could have a detrimental effect on the embodied carbon of a wave energy device. For our two designs, this is not the case. After three years or in as little as six months, concrete wave energy devices can become carbon negative despite having a predicted lifetime of 25 years. 

Our team of circular economy specialists helped develop guidance for lifecycle assessments in the context of wave energy devices for use in Convex. The guidance includes high-level calculations of the relative carbon impact between concrete and steel devices, demonstrating that concrete can have less impact than steel. This critical functionality allows us to support device developers to make informed decisions for more sustainable WEC designs.

Convex is a great tool for wave energy technology developers wanting to quickly assess the feasibility of a design using concrete for their WEC. The tool is intuitive and provides outputs that are easy to comprehend. Concrete design can deliver significant reduction in LCOE for WECs and this tool will facilitate this transition. ” Alexandre Pichard CTO at Carnegie Clean Energy

Supply chain mapping  

Steel devices are often manufactured and assembled off-site and shipped to the deployment site. This is not practical for concrete devices, which will require setting up dedicated construction sites at suitable port locations. Convex includes an interactive supply chain map to facilitate the assessment of Scottish port locations where concrete WECs can be manufactured and the capacity of the concrete supply chain to enable serial production in Scotland.

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