Wave energy has long struggled to find its feet in the clean energy transition but the tide could be turning for this clean energy technology that is already cheap enough to replace diesel generation on remote islands.
Off King Island, an island between Tasmania and Victoria in the Bass Strait, a catamaran-shaped structure has been generating energy from waves for the island community.
The UniWave200 prototype plant, which has been backed by the Australian Renewable Energy Agency, is the work of Australian company Wave Swell, which has spent many years trying to crack the code on wave energy that has so far struggled to compete with other forms of renewable energy.
Wave Swell Energy executive chair Dr Tom Denniss says the team had something akin to a lightbulb moment in 2016 that would solve some of the key issues with a subset of wave energy generation devices called oscillating water column (OWC) technologies.
These contraptions generate energy by mimicking naturally occurring blow holes. In an OWC system, as waves rise, the water displaces the air above it and causes it to rush out the opening above – just like a blow hole in a rock face. In a conventional system, this fast-moving air has been used to spin a turbine to create electricity during both the upward movement of air as well as when it’s sucked back down again as the wave recedes.
Denniss says his company’s technology, which was tested at the Australian Maritime College, is different because the turbine only spins one way – during the down cycle. It may sound counterintuitive, but even though the system misses out on a second opportunity to generate energy, Denniss says the adapted system is actually 15 per cent more efficient than a conventional OWC. There are a few reasons for this, namely that more water can get in the chamber, building more air pressure, and that unilateral turbines are more robust and simpler to build.
It also helps that the water has fewer opportunities to avoid the generating cavity – it can’t go over the top and, because the system is support by a water column seated on the ocean floor, the water also can’t go under.
“The net result is we get a lot more power and lower cost of generation compared to previous attempts to develop OWCs.”
Efficiency has long been a problem for wave energy but Denniss says it’s not the only barrier the technology has faced.
Survivability and accessibility are two other persistent concerns. Denniss says many systems struggle to withstand wild weather but thanks to the system’s firm foundations on the sea floor, it’s so far survived some major storm events at King Island.
The other problem is accessibility, with minor maintenance tasks to underwater equipment requiring divers in full scuba kits. As such, the team kept all moving parts above water so that any maintenance can be conducted in open air.
Denniss, who has a PhD in maths and oceanography, comes from a technical background and has had to adapt to the practicalities of running a business. While the small team of five have developed King Island demonstration project, he stresses his company is a technology development company and that it will be looking to partner with a larger company with the grunt to commercialise the technology at scale. The company is currently raising capital to continue its work.
A clean alternative to diesel generators on remote islands
Denniss is honest about the high cost of generation of wave energy compared to other renewables but has reason to believe it will drop.
According to a report by CSIRO commissioned by the company to assess the expected costs of wave energy technology in general, the technology is already competitive with diesel generation in remote areas. For island communities reliant on diesel generations – such as Hawaii, which relies on 70 per cent diesel generation – this could be a valid clean alternative.
The report also shows that wave energy technology is likely to reach price parity with offshore wind by the time between 25 and 45 megawatts of capacity are installed. Looking longer term, the prediction is that the technology will reach cost parity with onshore wind and solar by the time 2500 megawatts of global capacity is installed. By way of comparison, it’s noted that it’s taken wind and solar energy more than 700,000 MW each to get to the global cost point they are at now.
“The implication is that eventually it will be the lowest cost form of generation in locations with good waves,” Denniss says.
For wave energy, the CSIRO sees a 1.3 per cent share of the global electricity market, around 170,000 MW installed capacity, by 2050 if it continues to develop at the current pace. This is greater than the total projected contribution of biomass and geothermal generation combined.
Like any renewable energy, Denniss adds that its local suitability will come down to environmental factors and good waves.
Interestingly, the company also says the tech can double as seawalls to provide protection for coastlines vulnerable to sea level rise and extreme storm events. By generating green electricity, the company imagines these structures would pay for themselves and generate new streams of revenue.
Fish can swim worry-free
So what about its impact on marine life? Denniss says there’s “pretty solid evidence” that the impact on underwater animals is benign. Unlike tidal energy, which has spinning turbines underwater that may harm fish and other creatures, there’s nothing that can injure animals as they are passing by with wave energy.
Another general advantage of wave energy is that compared to wind and sun, Denniss says it’s much easier to predict what waves are doing in advance.
“Surfers rely on these predictions to see where the waves will be days ahead.”
And, once the waves come rolling in, they don’t suddenly stop. This is different from solar energy, which can plummet rapidly when a cloud passes by.
“But obviously, using all three together is the way to go as they all help fill the gaps when one is not generating. Having a third major renewable energy source into a grid helps to stabilise that grid even further.”
He also says wave energy has a smaller footprint than other renewables. This may make the technology attractive for communities concerned about the aesthetics of other forms of renewable energy. Denniss also says they won’t ruin popular surf breaks as they work best with unbroken swell.
Despite resting on a concrete surface, the systems aren’t permanent – they have buoyant pontoons that deflate to allow the kit to anchor on the floor but can then be reinflated to be repositioned as needed.
He hopes the flexibility of these systems will help keep permitting swift and pain free.
By Poppy Johnston