Industry leaders in ocean energy, experts in harnessing energy from waves, tidal changes and currents, reviewed the current state of their sector and what is needed for oceanic power to reach the scale necessary to contribute towards net zero emissions targets in a serious way.

Several of the panellists referred to tidal as the largest untapped renewable energy source on the planet, with some 500 GW of unharnessed generating potential worldwide. Some estimates for the theoretical resource potential of all marine energy are as high as 20,000–80,000 TWh/y in electricity generation, equivalent to 100–400% of today’s global demand for electricity.

Nevertheless, as Martin Carruth from Marine Power Systems, commented: ‘It’s not just about more energy capacity; it’s about providing energy when the wind doesn’t blow or the sun doesn’t shine.’ Orbital Marine Power’s Chris Milne agreed: ‘The current bankable renewable technologies are seasonal and/or weather dependent so there’s a huge need for ocean power to work in tandem with them.’

Indeed, marine power, unlike wind and solar, is highly predictable with accurate tidal forecasting stretching decades into the future. This suggests that working in tandem with intermittent renewable sources, the ocean could provide electricity grids with much-needed baseload power. It is this utility as much as anything else that could make it such a valuable addition to the world’s electricity grids.

Completing the jigsaw
The session was titled ‘Marine energy: The energy jigsaw – does marine energy fit?’ and the speakers were emphatic that marine power must provide some portion of the world’s energy needs. Milne maintained that battery storage technologies will help established renewable energy sources to overcome their intermittency problem, but we need multiple solutions. ‘There is no silver bullet to solving the energy transition challenge,’ he said, ‘we need to throw everything at this problem and now.’

Likewise, Dr Cameron McNatt from Mocean Energy emphasised that ‘energy storage is never going to fill the intermittency gap for wind and solar over seasonal time frames’.

Anders Jansson from CorPower Ocean affirmed that we need as many solutions as possible because we have a lot of different sectors to decarbonise. ‘Hydrogen has great potential for decarbonising the steel industry, but we need it for producing the world’s fertiliser too. Wave power can also help to produce more green hydrogen.’ In other words, marine power is just another part of the complicated and multifaceted jigsaw that we need to reach net zero and it can even support the decarbonisation of hard-to-abate sectors.

No country can rely too heavily on a single energy source; the dangers of doing this have been exposed most recently by Russia’s invasion of Ukraine with the resulting energy crises rippling across Europe and around the world. On the contrary, just as biodiversity increases the resilience of ecosystems to change, a diversified energy mix that includes marine power raises a country’s energy security.

What technologies are currently available?
Various technologies to capture oceanic energy are already available. Some exploit current technologies, such as Marine Power System’s PelaFlex floating wind turbine platform, which combines with its PelaGen wave energy converter to harness both wind and wave energy. Carruth discussed how this model increases the energy yield per km² of ocean and improves the consistency of the energy supply.

Other existing solutions are standalone energy generators from ocean power. Milne proudly presented a video of Orbital Marine Power’s O2, the most powerful tidal turbine in the world and the second 2 MW unit the company has made. The O2 is connected to the onshore grid at the European Marine Energy Centre (EMEC) in Orkney via a subsea cable and, according to Milne, ‘delivered more power to the [UK] grid in 12 months than the entire sector had in 12 years’.

Likewise, McNatt’s company Mocean Energy has successfully tested Blue X, a 20-metre long, 38-tonne wave machine at EMEC’s Scapa Flow test site in Orkney. In 154 days at sea, the device delivered steady outputs of up to 5 kW and peaks of 30 kW in seas with up to 2.3 metres maximum wave height.

But commenting on their accomplishments, Milne said he felt it was ‘too little too late’ and McNatt similarly acknowledged that Blue X was small scale. Both their companies and Carruth’s have longer term aims to improve their products and scale them up to make as much impact as possible.

For example, last year Marine Power System signed an agreement with EMEC to deploy two multi-megawatt WaveSub energy converters. It will be the company’s first deployment of a commercial-scale, multi-megawatt project and potentially the world’s only working example of large-scale combined floating wind and wave energy generation technology.

Meanwhile, Mocean Energy’s Blue X testing device is merely a prototype for building a mid-scale device that will produce hundreds of kW. That design, in turn, will then serve as a precursor for grid-scale technology producing MW, potentially in combination with floating wind technologies.

Similarly, Orbital Marine Power has already secured funding for its next model, the O2-X turbine. With the intention to launch in 2024, it will improve on the O2’s design and be much larger with the capacity to generate even more power.

Turning the tide on oceanic power
Scaling up these technologies as soon as possible is absolutely crucial for marine power to fulfil its essential role in the renewable energy jigsaw. After all, ocean power has a place in most net zero road maps. The International Energy Agency (IEA) estimates that we need 27 TWh of electricity generation from this source by 2030.

Meanwhile, the EU’s Strategy on Offshore Renewable Energy has a target of deploying 100 MW of ocean power by 2025 and 40 GW of installed capacity for ocean energy and other emerging technologies like floating wind and solar by 2050.

The real challenge now is how to scale the existing technology to reach these targets. It might seem like an impossible target to reach given the current capacity of the sector. For instance, in its Net Zero Emissions by 2050 Scenario, the IEA estimates that ocean power generation would need to grow by an average of 33% every year until 2030 to reach target. That’s equivalent to around 1 GW of capacity added annually.

According to the International Renewable Energy Agency (IRENA), the cumulative global installed capacity of ocean energy in 2021 was 535 MW, a drop in the ocean compared to the total global installed capacity of renewable energy at around 2,600 GW. Moreover, the majority of this, 520 MW, consisted of tidal barrages, with just three large projects in Canada, France and the Republic of Korea dominating its generation. The remaining 13 MW was produced by a mix of tidal stream, wave energy, ocean thermal energy conversion and salinity gradient.

However, as McNatt pointed out, ‘Floating wind was a fringe technology just five years ago. Now it is a serious and well-funded energy sector.’ The aim of all the organisations represented by the panellists was to create a bankable product that can attract the investment needed to scale up ocean power to become a significant contender with fossil fuels as an energy source. Many had created working products; it’s getting to commercial scale that is proving difficult.

Public funding and interest
The panellists predictably looked at the examples set by wind and solar to guide their vision for the future of ocean power. But there was divergence over the best way to scale their sector. Jansson pointed to the need for more national targets on ocean energy in order to reach commercial scale. In his opinion, this would help the private sector to engage with this currently nascent power source.

However, there was some frustration over the lack of public sector investment from the UK government.

For example, Carruth disagreed with Jansson, saying: ‘We need to look for markets for this technology instead of waiting for investment from governments.’ He castigated the UK’s policies that do not allow dual integrated wind and wave systems to be installed offshore and criticised the country’s inadequate testing facilities that forced Marine Power System to deploy its technology in Spain instead of in the UK.

He further predicted that the UK will be left behind Australia, Canada and the US, which are expanding and developing their own marine power technologies.

McNatt also suggested that collaborations with fossil fuel companies may benefit the industry. The oil supermajors are increasingly investing in alternative energy sources and could provide some much-needed stimulus to the industry.

Standardisation for production or divergence for adaptation?
Another point of contention was whether models for capturing and converting oceanic energy should be standardised in the same way that wind turbines have been, or whether the sector needs to continue developing new designs.

Proponents of the former said that standardising the design would reduce supply chain costs and enable production en masse, resulting in a rapid scaling up of the industry.

However, Sue John, Chair of the Society for Underwater Technology, argued instead that the different environments involved with tidal and wave energy generation mean that different technologies will be needed. Picking up on this, McNatt said: ‘There’s not necessarily too many designs for tidal – the standardisation of wind turbines was almost accidental. It’s not a one-size-fits-all scenario and this kind of thinking is holding the industry back.’

Milne explained that the ultimate goal of the technology is to ‘produce as many electrons as cheaply as possible’. He added: ‘Driving divergence on this is a critical aim. However, the market itself will drive convergence as it seeks maximum generation for the minimum cost. This does not necessarily mean there can be only one design – different sites may need different designs. But the commercial market will thin out the number of products.’

Oceanic power generation cannot remain in the research and development stage forever; it needs to become a market player. The varied conditions at sea will likely mean that multiple technologies will be needed for optimum power generation. However, it seems highly likely that market conditions will thin their ranks in the search for cheap and efficient designs.

Ultimately, we need as many solutions to decarbonising our energy generation as possible and the technologies available are beginning to demonstrate ocean power’s enormous potential. The most important next steps for the industry are happening right now. They involve scaling up these existing designs, producing them as cheaply and quickly as possible, and connecting them to national grids to supplement wind and solar power generation.

It is therefore important to include marine power in plans for future energy systems as we need to take advantage of every tool at our disposal on the road to net zero.