In the space of just a few days, two separate projects have brought the promise of offshore floating solar a step closer to commercial reality.

First, the oil and gas major Equinor announced its involvement in an offshore floating solar trial with Moss Maritime off the Norwegian island of Frøya. Then, last week, fellow Norwegian firm Ocean Sun revealed it had secured European Union funding for a 250-kilowatt trial of its innovative floating PV system in the Atlantic off the coast of the Gran Canaria, in partnership with the offshore wind specialist Fred Olsen.

These trials bring new momentum to a subset of the floating solar concept that is as yet almost entirely untapped, despite the potentially limitless deployment opportunities it opens up. While floating solar on inland water bodies is currently experiencing something of a boom worldwide, the obvious challenges of building and operating PV systems at sea mean that offshore solar has so far remained an experimental rather than commercially practicable prospect. But that could be set to change.

Speaking to GTM, Ocean Sun CEO Børge Bjørneklett said the aim of the Canary Islands project is partly a research and development effort to test its technology in tough marine conditions, but it is geared to pave the way for commercial rollout.

Fred Olsen has “great plans” for commercialization, he said, and offers the opportunity to deploy offshore floating solar at the sort of scale needed to make it competitive. 

“There are some huge projects now and…Ocean Sun is not large enough to take these on,” he said. “Looking at a project with several hundred megawatts [and] hundreds of millions [in] costs of building these things, we need to team up with the more established players.”

Ocean surface cooling boosts solar yield

Ocean Sun has developed a proprietary floating technology that is particularly suited to deployment at sea, where storms and high waves present significant challenges to any human-made structure, let alone one that must operate profitably over a prolonged period.

At the heart of the design is a flexible pad or membrane on which the PV modules sit and that is able to ride the swell and dampen the impact of any particularly large waves. An added advantage is that by reducing the air gap between the modules and water level, a cooling effect increases yield by around 5 percent compared to systems where modules sit higher above the water.

Major utility Statkraft purchased four 500-kilowatt systems from Ocean Sun in March 2019. Once complete, they will operate as a demonstration project on a reservoir in Albania. The company is one of the largest hydropower operators in Europe.

Bjørneklett claimed the Ocean Sun’s unique design makes it more robust than other floating solar systems currently in circulation, many of which are based on a pontoon-type construction that is not well equipped to withstand wind and rough conditions. This assertion will certainly be put to the test in the company’s upcoming Gran Canaria trial, where the Ocean Sun system will face Atlantic waves up to 10 meters high.

Assuming this and the other trials of offshore floating solar technologies underway prove successful, the potential applications are numerous.

No rush for offshore wind hybrids

Although there has been much discussion about maximizing the value of offshore wind sites by combining turbines with floating PV, Bjørneklett is skeptical that such hybridization will be all that common, pointing out that the number of offshore wind sites that also offer good solar irradiance is comparatively small.

Instead, he said the greatest potential would be for near-shore applications, where relatively close proximity to land would reduce connection costs and where solar would be preferable to offshore wind because it is less visually intrusive.

As an example, Bjørneklett pointed to archipelagos such as the Maldives. Here, power consumption is high due to the tourism industry, but also costly and polluting due to a reliance on dated diesel generators. “Those places are ideal for floating solar power because they have very good irradiation,” he said. “And this is where we can make a big impact on the CO2 emission reductions because those [current] power sources are among the least efficient, and you have to ship the fuel way out in the Indian Ocean.”

Rolf Benjamin Johansen, director of floating solar at Fred Olsen Renewables, said offshore solar makes sense anywhere in the world where land is scarce, seawater is plentiful and the solar resources are suitable. “That’s a pretty big potential,” he said.

Even appropriate freshwater bodies, currently the main focus for floating PV deployments, are a relatively scarce resource in many countries, Johansen said, making near-shore sites a “natural next step” for floating technology. “And there are so many places in the world where you can do that,” he said, adding that Asia and Southern Europe are among the first places the company is considering for commercial deployment.

Green hydrogen presents another route to market

Looking farther out to sea, Johansen said he could also foresee a possible role for floating solar to directly power offshore clean fuel electrolyzers. The main consideration — and cost — of more remote offshore systems is the cabling to get the power to land, but Johansen said that could be overcome by removing the need for a cable at all. “If you look ahead, you could imagine that you could have other carriers of energy than a cable — for example, ammonia or hydrogen,” he said.

Such a proposition would certainly be in line with current thinking about how ambitious targets for green hydrogen production in regions such as the European Union will be met, with a number of significant proposals emerging in recent months for offshore green hydrogen plants powered by wind.

Johansen said that in parallel with trials of the Ocean Sun and other floating technologies, Fred Olsen Renewables is beginning the process of identifying possible locations for its first commercial deployments and seeking out local partners to work with.

“Because we will first start with offshore floating solar in Southern Europe and Asia, that means we have to set up operations in countries where we don’t have operations today. And in order to do that, we are going to work with local partners, so we are looking for strong local power producers that we can partner up with,” he said.

After that, projects will be subject to the usual planning, permitting and environmental impact processes typical of any solar development. Johansen said he hopes to be underway with the initial stages of the company’s first commercial offshore solar projects within the next year or two.