The sea is the final frontier of renewable energy. Both waves and tides could in principle provide reliable baseload electricity, crucial in balancing the intermittency of wind and solar power and allowing us to move away from our continued reliance on fossil fuel energy.
To support the full decarbonisation of our electricity supply, we need to exploit multiple renewable energy sources including the high energy content of waves and tides. The large-scale commercial application of these free and abundant energy sources have so far eluded us.
The reason is not hard to grasp. Technologies for extracting energy from the wind and the sun had already been developed when interest turned to them as alternatives to oil and coal in the 1970s, it just needed a few steps to convert them into commercially viable electricity generators.
Wave and tidal power presented a whole set of new challenges that are only now being overcome. Chief among these is the need to place wave energy converters (WECs) in the challenging ocean environment, where they need to be robust enough to withstand all the sea can throw at them while still able to produce cost effective electricity.
Many promising wave energy converters have been developed, only to fail when the challenges proved too great. Now a new product called mWaveTM, developed by Bombora, is set to break this cycle.
Bombora mWave in the water
Western Australia
Bombora has its origins in Western Australia, where two engineer brothers Glen and Shawn Ryan who grew up on a large wheat farm came up with the idea of an underwater solution that would capture wave energy using the pressure of the waves passing overhead.
They first tested their concept in their farm shed in 2009, using a tractor to create the waves in a tank the size of a swimming pool.
Rigorous testing
The Ryan brothers patented their wave energy converter three years later and that same year set up Bombora Wave Power. By 2014 seed capital had been raised and a 1:15 scale WEC was ready for testing at the Australian Maritime College (AMC) in Tasmania. Data from these tests was used to validate modelling software.
In 2015 Bombora was awarded an Australian Renewable Energy Agency (ARENA) grant to carry out further feasibility studies. Bombora received a further grant from the Australian Government to help with commercialisation. In 2016 a larger, 1:7 scale WEC was tested in Western Australia and gathered data for over two years.
In 2016 Bombora completed a feasibility study for a 60MW wave farm, which concluded that the levelised cost of electricity from wave power generated by mWave could quickly become competitive with wind and solar power.
mWave testing at Australian Maritime College, Tasmania
Fast track development
During 2017 the company identified Europe as the best place to further the commercialisation of mWave and relocated its operations to Pembroke Dock in West Wales. At the same time global energy and utility consultancy Enzen came on board as a strategic investor.
In early 2018 Bombora was awarded £10.3 million in funding from the European Regional Development Fund (ERDF) through the Welsh Government to support its Pembrokeshire Project. This project will culminate with the commissioning of a 1.5MW mWave off the west coast of Wales.
During 2019 a purpose-built test tank was set-up at Pembroke Dock to conduct rigorous testing of the cell module and membrane ahead of the offshore deployment.
Fabrication of the main structure of the 1.5MW mWave wave energy converter is now nearing completion. The final assembly phase of mWave is now underway in preparation for deployment and commissioning in the waters off East Pickard Bay later this year.
Cell module performance testing at Bombora test tank in Pembroke Dock, Wales
Recipe for success
What differentiates mWave from other wave energy converters is the idea of placing it well beneath the ocean’s surface and of using the pressure generated under the waves. mWave can be either fixed to the seabed with piles (nearshore) or integrated into a floating structures (offshore) with the mWave cell modules located around 10m below the waves.
Most wave energy converters so far tested have floated on the surface where they have been exposed to the full force of the waves and of storms. This has required heavy engineering to withstand the extreme storm loads and significantly challenged their cost effectiveness.
Importantly 80% of a wave’s energy is available to be captured by the mWave when located beneath the ocean’s surface.
The 75m long by 17.5m wide wave energy converter uses a series of air-filled cell modules covered by a rubber membrane and fixed in a concrete structure placed at an angle to the oncoming waves.
As a wave passes overhead, the pressure pushes in the membrane, forcing the air into a duct where it is channelled through a turbine to generate electricity. The air then passes through a return duct to refill the cell modules ready for the next wave. The electricity generated by the turbine is transferred to the shore in a subsea cable.
Besides its cost-effectiveness, mWave has many other advantages. With the structure fully underwater there is no visual impact on coastal landscapes, and the depth at which it is placed allows recreational vessels to pass over it.
The mWave product has no exposed moving parts, reducing complexity and maintenance requirements. mWave’s modular design also allows for easy servicing reducing both maintenance costs and downtime.
The modular design also facilitates the rapid scaling of mWave, a critical factor in reducing the cost of energy.
Trial Assembly at Mainstay Marine Workshop
Clear commercialisation pathway
Following the Pembrokeshire Project, Bombora plans to install a grid connected wave park off the coast of Lanzarote in the Spanish Canary Islands, where the community is dependent on diesel for power generation. The first phase, a 2MW wave park, will be installed by 2022.
Beyond that, there are coastal regions in many parts of the world where the wave resource is high enough to make wave power a very attractive proposition. The International Energy Agency predicts that waves could provide 10% of the world’s energy by 2050. Bombora’s initial test sites are located close inshore but mWave has the potential to capitalise on both nearshore and floating offshore opportunities, as well as integrated wind and wave platforms.
Bombora’s managing director Sam Leighton thinks the time is right for a practical and cost-effective wave power product.
“Five to 10 years ago there was this early hype about wave power, but unfortunately a lot of those projects didn’t work. Now the outlook is more realistic and there are some sound solutions coming forward. We believe mWave delivers a robust, scalable approach that will once and for all address the survivability and cost efficiency challenge of harnessing wave power,” he said.
