Drew Rooke
On January 10, 2021, a strange structure appeared in the shallow waters off Grassy Harbour on the south-eastern coast of King Island in Bass Strait. Roughly the size of a two-storey house and comprised of thick, angular concrete with steel flotation pontoons, it resembled a large brutalist sculpture. But it wasn’t an artwork; in fact, it was a power generator.
Developed by Melbourne company Wave Swell Energy, the UniWave200 was being trialled to see if it was able to generate power from the waves that had been whipped up by the howling winds over the Southern Ocean. Its technology was based on the concept of an oscillating water column which essentially mimics a naturally-formed blowhole: as waves enter the open chamber beneath the waterline, they force air upwards to the turbine at the top, which then generates power.
Six months after it was installed, the $12 million UniWave200 did indeed start generating electricity, which was delivered to the local Hydro Tasmania grid via a subsea cable. It continued doing so until the trial concluded in August 2022. Six months later, the unit was decommissioned.
According to Dr Jana Orszaghova, Senior Lecturer at University of Western Australia focusing on ocean renewable energy and Deputy Program Leader of Offshore Renewable Energy Systems at the Blue Economy Cooperative Research Centre, this trial was “a huge milestone” for the ocean energy industry in Australia.
“It was a full-scale device deployed in the ocean and grid-connected.”
Stephanie Thornton, General Manager of the industry-led Ocean Energy Group, agrees. “[The UnieWave200 trial] was very significant. It was the first demonstration of the commercial potential of ocean energy technology in Australia.”
Humans have dreamt of using the clean, predictable and enormous energy of the ocean for our own electricity needs since at least 1799, when a French engineer and inventor named Pierre-Simon Girard filed a patent for a machine which would use wave power to pump water for irrigation. But recent technological advancements have helped this dream move one step closer to becoming a reality.
Concrete steps are also already being taken to harness the energy of the ocean’s other powerful processes
In fact, according to a November 2023 report by Ocean Energy Systems, an intergovernmental collaboration established by the International Energy Agency, 300GW of energy could be generated by the ocean’s waves, currents and tides by 2050 – enough to power roughly 225 million homes.
The Australian Renewable Energy Agency has taken some steps to help make this happen: since 2012, it has funded thirteen ocean energy projects, including the UniWave200 trial. But Australia – which “has arguably the largest wave resource of any country in the world”, according to the final report of the CSIRO-led Australian Wave Energy Atlas, and in September will host the 2024 International Conference on Ocean Energy – is just one country where there is a rising tide of enthusiasm for ocean-based energy production.
In March 2023, nearby Tonga – which currently uses imported diesel fuels for power generation and has some of the highest electricity prices in the world – signed a memorandum of understanding with an Irish-based wave energy company to develop a 10MW wave power park off the main island of Tongatapu.
Other jurisdictions are seeking to go even further. In November 2020, the European Union published its strategy on offshore renewable energy, which included a target of 1GW of ocean energy by 2030 – and 4GW by 2050. To help achieve this, it is supporting EuropeWave – a $20 million research and development program developed by Wave Energy Scotland, Ocean Energy Europe and the Basque Energy Agency and designed to help wave energy technology advance to the commercial stage.
In September 2023, this program awarded Western-Australia-based company Carnegie Clean Energy $6.3 million to develop and operate a roughly 400KW version of its “CETO” wave energy converter off the coast of Spain by 2025. Named after a Greek sea goddess, CETO looks like a mechanical jellyfish; known as a ‘point absorber type wave energy technology’, it uses a submerged buoy moored to the seafloor which oscillates with the waves and converts their energy into electricity.
Concrete steps are also already being taken to harness the energy of the ocean’s other powerful processes.
In 2022, Japanese engineering company IHI completed a 3.5 year-long test of a 330-tonne, 100KW subsea generator known as Kairyu which is expected to be operational by the 2030s. Resembling a giant aeroplane, it will be anchored to the seafloor at a depth of thirty to fifty metres in the Kuroshio current – one of the most powerful ocean currents in the world, flowing at a rate of 2.5 metres per second – which will spin its two turbine fans to generate electricity.
Given that it is still an emerging technology, it is expensive which makes it difficult for wave energy to compete with incumbent and low-cost renewables such as wind and solar.
Dr Jenny Hayward, CSIRO Energy
Neighbouring South Korea is also home to the world’s largest tidal power project. Completed in 2011, the 254MW Sihwa Lake Tidal Power Station on the country’s western coast, where there are some of the highest tides in the world, uses a system of ten tidal turbines which are driven by the vast natural movement of water to generate enough power for 200,000 homes.
Similar projects have also been proposed for the Mersey Estuary in Liverpool and in waters of the Welsh city of Swansea. If completed, the former would rival the Sihwa Lake Tidal Power Station: it would produce between 1 and 1.5TWh electricity per year – roughly two thirds of Liverpool’s 2017 energy requirements – by exploiting the United Kingdom’s second highest tidal range.
But even though it is reliable, renewable and clean, ocean-based energy is, of course, only suitable for certain locations – namely, those cities and countries which are not only close to the ocean, but to very specific parts of it where there are strong waves, currents or tides. It is also poses some risks to the marine environment.
For example, the final report of the Australian Wave Energy Atlas project found there was “a small but statistically significant wave energy loss at discreet frequencies” attributable to the presence of wave energy converters.” In the case of tidal power projects, the U.S Energy Information Administration says they “can change the tidal level in the basin and increase turbidity” which can, in turn, disrupt the behaviour and distribution of local animal and plant species.
Orszaghova acknowledges this but says ocean energy devices have a “relatively small impact” – especially compared to more conventional forms of power production. “If the alternative is a power station, then perhaps visually the damage isn’t as immediately obvious, but we are all aware of the adverse long-term consequences of greenhouse gas emissions.”
A far more pressing problem, according to Orszaghova, is the current high costs associated with ocean-based electricity generation. Indeed, according to a 2019 report by the U.S Department of Energy, the cost of wave energy and tidal energy at a commercial scale would be US$120‒470/MWh and US$130‒280/MWh, respectively. For comparison, wind energy can now cost as little as US$20/MWh.
“Doing anything in the ocean is difficult,” Orszaghova says. “It’s a harsh, energetic, corrosive environment, so you need to design structures that can withstand that environment for their entire lifespan – say, twenty, thirty years. And that costs a lot of money, especially given that we need many individual units.”
Even though she thinks focusing purely on the financial cost of power generation is “narrow visioned”, Orszaghova says that it is ultimately the primary reason why ocean-based forms of energy generation aren’t more widely used at present. Dr Jenny Hayward, a principal research scientist in CSIRO Energy, agrees.
“Given that it is still an emerging technology, it is expensive which makes it difficult for wave energy to compete with incumbent and low-cost renewables such as wind and solar.”
In the near future, Orszaghova expects that the high cost of ocean energy will start to drop as the industry continues to innovate and mature. She hopes this will lead to widespread growth in the industry – something that modelling of the global electricity system indicates needs to happen in order to reach net zero emissions by 2050.
“Whether that’s by powering large cities or by powering island and remote communities and offshore operations, such as hydrogen production, is hard to predict,” Orszaghova says. “But ideally, it will do both.”