Scientists at SBM Offshore are drawing on their expertise in floating oil and gas systems to develop an unusual and innovative renewable energy technology that uses the power of ocean waves and flexible materials to generate electricity.
The S3 wave energy converter differs from many wave energy concepts in that it lacks the mechanical parts that have made earlier efforts to harness the power of ocean waves unreliable and maintenance-intensive, SBM says.
The Netherlands-based company has installed equipment to assemble the multi-layer rubber tubes that form the heart of the system at its research and development centre in Carros, France, north of Nice.
The tube is filled with seawater and embedded with an electroactive material that generates electricity as waves “squeeze” and push the liquid along the length of the tube, causing it to bulge and contract.
Artificial muscles
The technology was inspired — and enabled — by advances in artificial muscles, says Ambroise Wattez, SBM Offshore business development manager for renewables and offshore energy systems.
“Muscles are an incredible way to convert chemical energy into movement,” says Wattez, who came to SBM in 2009 with a background in materials engineering.
“At the time, there was a lot of research in artificial muscles — how to convert electricity to movement. We decided to use it the other way around and convert movement that is given by this bulging tube to electricity,” he says.
“The beauty of that is that it is done directly — there is no intermediate medium to transfer the energy. It goes directly from the wave to electricity.”
The company had been working on what Wattez calls “a more conventional approach” to wave energy as early as 2006, putting its oil and gas competency to work on a steel structure with hydraulics.
“In 2009, we realised it was going nowhere — there’s no way we could build the structure cheap enough and light enough to make it viable at large scale.
“We had to completely re-think the approach to wave energy,” he says.
Wattez credits the engineers who worked on the programme in its early stages with “bio-inspiration”, looking to nature for a way to harness the power of the ocean.
“They really saw the trend of the global energy transition at that time, particularly pushing towards the offshore world, with more and more push to use the vast space and forces available offshore,” he says.
The S3 has a precedent in the Anaconda concept, which proposed a similar bulging tube technology but with a mechanical power take-off, which SBM engineers decided for their purposes would require too much maintenance to make the technology viable, he says.
“We thought, this is not going to work. We have to go one step further, and the one step further was inspired from artificial muscles.”
Electroactive polymers had been developed for robotics applications but did not meet the performance requirements of the S3.
“We conducted a lot of research to increase performance and we continue to do that,” Wattez says.
Antenna
Embedded with layers of film made with the electroactive material, the tube acts as a sort of antenna that collects the energy in waves and amplifies it as the polymers expand, converting motion into electricity.
One of the biggest challenges, Wattez says, has been putting together the supply chain needed to take the manufacturing processes involved to an industrial scale.
SBM will assemble the prototype tubes in the Carros facility but various components of the system, including the electroactive polymer materials, will come from a carefully selected group of suppliers.
The company plans to test a prototype of the S3 tube offshore Monaco in 2021.
“For this demonstrator project we are doing now, we already need to involve quantities of this (electroactive polymer) material that are representative of industrial-scale manufacturing,” he says.
A subsequent phase could involve a pre-commercial pilot with an array of three to six seabed-moored devices with capacity of around 1 megawatt each.
The company envisions commercial-scale wave energy farms at some point but has not set a specific timeline or determined precisely how much capacity each S3 unit will have at that point.
To serve the utility market, the device will need to have a rated generating capacity of at least 6MW, Wattez says.
“Yet there are other markets that are much smaller — the off-grid market, the remote-communities market — where you might not need that much power. So, we think there will probably be two branches of this project, one for utility-scale, large-scale machines, and one for off-grid applications.”
The latter could include power supply for a floating production, storage and offloading unit or another oil and gas project, he adds. “Clearly, there is an interest from oil and gas operators to offset emissions and decarbonise.”
Untapped resource
Wave energy is a relatively untapped renewable resource compared with wind and solar but its backers say it could provide an important complement to those energy sources and is less susceptible to intermittency of supply.
“Experts and scientists say wind and solar will not be enough for the energy transition — we will need other forms of energy with a very low carbon content. There’s a consensus around that,” Wattez says.
“In the long term, we will need other sources of energy that complement wind and solar, and here is where we think the ocean can provide sources of energy that correspond to that. We think our approach to wave energy is the way to get to this price and availability level.”
