We were standing in the pouring rain at Sabang Port, waiting for our turn to board a bangka (a traditional Filipino boat) that would take us to the entrance of the Puerto Princesa Underground River, which runs beneath a cave in Palawan, an island province on the western part of the Philippines. At last our bangka arrived, a trimaran with bamboo outriggers either side of its main hull.
The trimaran is a common sight on Philippine waters. The country pioneered this design in its early warships, then adopted it for its traditional sailboats and fishing boats. As an island nation, the Philippines relies on watercraft – boats, ferries and cargo ships – to transport people and goods across its more than 7,000 islands. But its fleet of cargo and passenger ships are one of the biggest contributors to the country’s greenhouse gas emissions. In 2012, transportation accounted for the second largest source of greenhouse gas emissions in the country’s energy sector, after heating and electricity.
Globally, 9% of all transport emissions came from international and coastal shipping in 2010. That’s a small figure next to the 72% that came from road transport, but it puts shipping on a similar level to aviation, which made up 10.6% of transport emissions. And with the volume of world sea trade projected to grow at a rate of 3.8% a year to 2023, emissions from the shipping industry are likely to increase too, unless the growth in sea traffic can be uncoupled from emissions.
The traditional bangka is an iconic part of life in the Philippines, evolving from its early role as a warship (Credit: Getty Images)
A new design of ship in the Philippines is hoping to pose a low-carbon alternative to the country’s usual bangka, by working with the power of waves rather than against them. The ship is a hybrid model, using multiple internal combustion engines for initial propulsion but switching to wave energy while cruising in open waters.
Sea power
This seacraft is the brainchild of Jonathan Salvador – a marine engineer and owner of shipbuilding company Metallica Marine Consultancy, Fabrication and Services – who was inspired by the conventional bangka’s design.
The outrigger constantly reacts to the upward and downward movement of the wave. What if we can convert this reaction into electrical energy? – Jonathan Salvador
“The outrigger’s job is to provide stability so the bangka doesn’t tip sideways,” Salvador says. “But I also noticed that each time a wave hits the outrigger, the outrigger constantly reacts to the upward and downward movement of the wave. What if we can convert this reaction – this kinetic energy – into electrical energy?”
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The way wave energy works will be familiar to anyone who has waded in sea waters. At times, the waves are strong enough to push you back to shore or tall enough to push you over. “Waves have a lot of momentum, and it’s that momentum you feel when you’re out in the water,” says Bryony DuPont, professor of mechanical engineering at Oregon State University. “Wave energy uses that momentum, sometimes as-is and you just need the motion of the waves, and sometimes we capture that momentum and force it through machinery that generates electricity.”
The hybrid trimaran has this machinery – a wave energy converter – in the form of hydraulic pumps integrated into its outriggers. As the pumps move through the waves, they harvest the momentum of these waves, converting their kinetic energy into electrical energy, which will then be fed into a generator that will supply electricity to the ship. The electricity then provides propulsion via a motor. The more waves the trimaran encounters, the more power it can produce from those waves.
Construction of the hybrid trimaran started in 2018 and was set for completion by early 2020, in a collaborative effort between the Metallica shipbuilding company and the Aklan State University. But a typhoon in 2019 delayed the project and community quarantines enforced this year due to the Covid-19 pandemic resulted in a skeletal workforce at best and brought the project to a standstill at worst. Despite these difficulties, the team is aiming to finish building the ship by the end of 2020, with a three-month sea trial scheduled for the first quarter of 2021. The vessel is expected to be capable of carring 100 passengers, four vans and 15 motorcycles.
The prototype wave-powered boat is hoped to be the first in a series of increasingly ambitious designs moving away from fossil fuels (Credit: PCIEERD/Aklan State University)
The hybrid trimaran’s use of wave energy could be a significant step toward reducing the need for environmentally damaging fuels such as diesel in the Philippines. And with wave energy offsetting gasoline use, Salvador and his team aim to bring down the vessel’s carbon emissions by a third compared with the most modern large-scale shipping lines.
The wave energy converter would also benefit from the ship’s traditional trimaran design. “Wave energy requires motion of one part of the system relative to another,” says Rob Cavagnaro, a mechanical engineer at the Marine Sciences Laboratory of the Pacific Northwest National Laboratory in the US. “Having outriggers that can heave – or move up and down – relative to the central hull may be well-suited for this purpose.”
We envision the future of public sea transport in the Philippines to be safe and green with less emissions, and we see the trimaran bringing that vision to life – Rachel Habana
Moreover, waves are energy-dense; in other words, they can be ferociously powerful. At coastlines, waves can reach power densities of 60–70 kilowatts per metre in areas with deep waters. In the UK and the US, for example, the average wave power density is between 40 and 60 kW per metre. “If we can translate that energy into other useful forms, we can do a lot with very little,” DuPont says.
But converting the high-force, low-speed motion of waves in an efficient way can be a challenge. “There may be many sources of loss along the way, from friction in the hydraulic systems to heat in the electrical generator,” Cavagnaro says. The engineering challenge that remains is to minimise these losses.
Another hurdle would be designing a wave energy converter small enough for the ship’s dimensions. “Wave energy converters generally develop more power the larger they are, but if they’re so large that the waves can’t move them, then can’t effectively harvest momentum,” DuPont says.
Even so, a private company in Boracay, a popular tourist island in the country, has already expressed interest in operating the ship once it’s launched, says Rachel Habana, a senior scientist at the Philippine Council for Industry, Energy and Emerging Technology Research and Development, which oversaw the trimaran’s development. “We envision the future of public sea transport in the Philippines to be safe and green with less emissions, and we see the trimaran bringing that vision to life,” she says.
Rough seas
But as yet the hybrid trimaran is still a prototype. “Because we have new technology for the vessel, we need a technology verification step before we can go for full-scale commercialisation,” says Yasmin Tirol, project leader and campus director of Aklan State University’s College of Fisheries and Marine Sciences. “We already conducted some test modelling for the wave energy converter, but we have to look into its actual performance and optimise it.”
Anyone who has surfed or swam in the ocean or been on a rocking boat has contemplated the immense power of ocean waves – Bryony DuPont
Cost is another issue. Funding for the project is at 76 million Philippine pesos (£1.2m; $1.5m), but Salvador estimates commercial-level costs to reach 250 million Philippine pesos (£4m; $5m) or more per ship. To keep expenses low, at least 80% of the trimaran’s parts are sourced locally, while the entire manufacturing and assembly process is done within the country. Staying local also opens up opportunities for improving the skills of the shipbuilding and ship engineering workforce in the Philippines, and allows smaller shipbuilders and the country’s large workforce of seafarers to participate.
The abundance of wave energy at sea could revolutionise travel in boat-dependent nations like the Philippines (Credit: PCIEERD/Aklan State University)
Salvador refers to the current trimaran as a “series one” prototype, with plans for more ambitious series two and three versions that will use wave energy to help the engine create more power, or even fuel the vessel entirely. But this might be a difficult feat given the considerable power demands of large modern ships. “The power available in waves interacting with the ship may not be enough to meet the full energy needed for propulsion,” says Cavagnaro. “It would also depend on how large and long the waves are – the highest-energy waves are ones that would not be comfortable to move through.”
Wave energy powered vessels are a nascent technology, and it’s still to be seen which is the best way to draw power from the sea. For instance, the Autonaut, an unmanned surface vessel, uses foils to harvest wave energy for propulsion. Meanwhile, the most common design concept for wave-powered boats uses fins that move like dolphin kicks or a whale’s tail to propel the boat forward. All these have yet to go mainstream or be applied to larger seacraft.
But for any boat navigating the choppy waters between the islands of the Philippines, it is a tantalising prospect to turn that churning energy into forward motion. The hope is that this abundant, clean resource will become as widely used at sea as its more mature renewable energy counterpart: the wind.
“I think anyone who has surfed or swam in the ocean or been on a rocking boat has contemplated the immense power of ocean waves,” DuPont says. “It’s thrilling to see brilliant ideas stem from that spark of inspiration – from being connected to the ocean.”
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