Making waves: Renishaw & Biome Renewables discuss the additive manufacture of ocean turbines

Biome Renewables is a technology development firm based in Toronto, Canada that specialises in designing aerodynamic improvement technologies for wind turbines. Founded in 2015, the firm has sought to advance renewable energy using biomimicry, the practice of solving human design challenges by observing strategies found in nature.

The company designed the PowerCone, a retrofit component for wind turbines that allows the turbine to produce 10 to 13% more power at lower wind speeds, while reducing turbulence on the rotor and minimising noise. The team based the design on the falling path of a maple seed, made unique by its geometry and ability to efficiently use wind. The start-up is at the forefront of its field, pioneering new equations to develop its nature inspired products.

Biome approached Nova Scotia Community College (NSCC) to expand its offering in tidal wave energy generation because of the college’s specialism in the field. However, NSCC primarily develops plastic solutions which would be inappropriate for hostile tidal environments. The turbines would have to withstand corrosion, debris impact and cope with the strong tidal forces acting upon them. Biome had to completely reimagine the product to work in a new environment.

The new PowerCone would also need to withstand incredible loads. Failing to obtain the appropriate level of robustness in the product could result in the prototype failing and being lost in the ocean, pushing the project significantly back and polluting the testing site. Building a PowerCone out of stainless steel would improve its robustness. Further, by using innovative geometries and non-traditional designs, the PowerCone had the potential to avoid cavitation; damage to turbines caused by rapid changes of pressure in a liquid, which is common in marine applications.

We saw an opportunity to adapt our technology to a market ripe for innovation.

For these reasons, NSCC approached the Canadian subsidiary of global AM leader Renishaw for technical assistance. Rapid testing and revising of prototypes is particularly easy with AM technology, as designers can digitally edit and build using one machine and a variety of metal powders, instead of using multiple processes. This technique also allows engineers to build more complex geometrical shapes with ease, enabling Biome Renewables to push the biomimetic application one step further.

“From a technical standpoint, Renishaw’s team synched really well with ours,” explained Ryan Church, Founder and CEO at Biome Renewables. “We did not have a big skillset in AM, so they were the missing piece to the puzzle and together we had all the components for a successful project.”

When contacted by NSCC, Renishaw recognised the technical challenges of the project and offered to help. The team decided to use an off-the-shelf turbine that they could retrofit with an AM built PowerCone. NSCC used its Renishaw RenAM 250 system to manufacture the parts which, when originally installed, was one of the first AM machines used in Canada.

The project moved forward with daily collaboration via phone and video conferencing between the three parties and several Renishaw AM specialists in the UK. The build itself was divided in two between NSCC and Renishaw, taking one month in total to produce all parts. Biome Renewables worked on updating its designs to account for the PowerCone moving in water and for the new manufacturing process.

Given Biome Renewable’s requirements, the blades had to be light to tolerate the marine environment but could not be hollow as it would make them weaker and susceptible to debris impact. Engineers used an internal lattice structure to reduce weight while preserving the robustness of the turbine, and to also significantly reduce build time. Surface finishing made the blades more hydrodynamic, minimising potential roughness.

“The project was a great opportunity for us to adapt our expertise,” continued Church. “AM seemed an obvious choice because we could prototype complex designs with ease. The biggest challenge we faced was adapting our CAD designs to both a new environment and manufacturing method in an efficient way. Getting the meshing and lattice right took some work but rapid prototyping helped us make the final product seamless.”

The project required the machine to operate for long periods of time, with the longest build lasting 150 hours. The PowerCone was larger than the space available within the AM250, so each blade was printed in separate parts and then welded.

“I have worked on several hundred builds and manufacturing the PowerCone was one of the more challenging ones,” explained Mark Kirby, Additive Manufacturing Business Manager at Renishaw Canada. “I often get questions from clients asking if AM parts can be welded together and this project proves that it can certainly be done without negatively impacting the product’s efficiency.”

NSCC, Biome Renewables and Renishaw successfully built a prototype and spent the second month of the project in testing. The build was sent to the UK, where it was tested in Strangford Loch, Northern Ireland. Ocean testing was completed on October 1st, 2019, and confirmed Biome Renewable’s hypothesis – the modification on the turbine produced significant levels of power over a wide range of tidal velocities.

“As a business with extensive experience in wind energy, we saw an opportunity to adapt our technology to a market ripe for innovation, such as tidal energy,” continued Church. “The potential has always been there but there is a lack of products that can extract power in any long term and practical fashion. Creating internal structures in the blade as load-bearing elements using composite manufacturing would have taken more work, money and time than it did with AM. We saved months of time and reduced costs by around 80% with this method.”

The European Commission reports that companies have designed around 170 types of wave energy converter, yet less than 20% make it to full-scale prototyping. AM offers quicker prototyping and a more cost-effective manufacturing process, which gives the tidal PowerCone an edge over competitors.

“Speed was the most impressive aspect of this project, Biome Renewables managed to go from their first design to a successful prototype in a time that would be hard to replicate without AM” continued Kirby. “Effective collaboration and a balance of expertise made the project an absolute pleasure to work on. It led to an intense four weeks but its success is a testament to good communication and competence.”

“In the future we plan to develop a large-scale PowerCone to function as a full rotor. This makes the most sense as fewer components mean less load, production time and cost,” explained Church. “We would welcome another collaboration with Renishaw in the future.”

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