The long read: A seaborne alternative to burnt cash

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From pv magazine 02/2020

Small island nations have been playing a leading role in advocating for more ambitious national targets for carbon emission reductions – the Indian Ocean archipelago nation of Maldives chief among them. And with the existential threat posed by a hotter global climate – including more severe sea surges, the salination of freshwater sources, and damage to scarce land available for plant-based food production – there are good reasons for them to do so.

Somewhat ironically, the Maldives and other island nations remain heavily dependent on polluting diesel fuels for energy, including electricity production – and even subsidize its use in some cases. And with many islands lacking the space needed for ground-mounted solar, rooftop PV arrays cannot supply the energy required.

This dilemma was one encountered by solar developer Martin Putschek, the founder and managing director of Vienna-based Swimsol. And while practicing his violin one day early last decade, a vision for a solution crystallized in his mind’s eye. “An image popped up in my head,” says Putschek, “of a plastic box with a solar panel on it. And I thought, why is no one doing that?” He worked from this basic concept to develop and prototype a robust floating structure that is suitable for ocean environments.

Since 2014, Swimsol has installed 500 kWp of its ocean-floating PV platforms, coupled with an additional 5 MWp of rooftop arrays, almost exclusively in the Maldives. With around 200 Maldivian islands, the location of high-end resorts and their requisite high electricity demand, the company’s technology and business model is scaling fast. Swimsol expects to install another 1 MW of floating PV and 9 MW of rooftop PV in 2020.

Next step

The rapid pace at which floating solar has progressed from an unlikely idea to commercial projects has taken many PV industry observers by surprise. While there are numerous technical challenges to both the development and ongoing operation of floating arrays (see pp. 36, 37), the rate of innovation in the segment has been impressive.

In “Where the Sun Meets the Water: Floating Solar Market Report,” the Solar Energy Research Institute of Singapore (SERIS) noted that in 2018, 786 MW of floating PV was installed globally – representing more than half of the cumulative floating capacity to date. Thomas Reindl, deputy CEO of SERIS, said that the institute’s work on the subject looks to engage both public and private stakeholders, “while minimizing possible negative environmental and social impacts” of floating PV development.

Alongside the scaling of floating PV as an application, the development of supporting technologies is particularly encouraging. Floating solar arrays with tracking capability are currently being deployed at megawatt-scale in the Netherlands. The 25 MW of “floating PV islands” sit atop reservoirs operated by water utility PWN, and power treatment facilities. The project was slated for completion in November 2019. Floating Solar B.V. developed the technology being deployed and has since signed cooperation agreements with other Dutch water utilities.

The circular solar islands track the sun by rotating over the course of the day – an approach that can be utilized in adverse weather conditions. Floating Solar claims that its arrays can be rotated to reduce the impact of waves – reporting that its system can withstand waves up to 1.5 meters in height.

Facing waves

Weather mitigation strategies will also be required if floating PV is to be successfully deployed beyond lakes, dams, and inland reservoirs. Independent solar engineer Nicolas Chouleur, from Everoze, describes ocean-floating PV as presenting “virtually no limit” to development opportunities – if, that is, the technical challenges to deployment can be overcome. Given the progress made in the offshore wind sector, which has overcome anchoring and mooring challenges while becoming cost-competitive, there are reasons to be optimistic.

Swimsol’s strategy for dealing with waves is by floating its platforms, with capacities between 20 and 30 kWp, between 1 and 1.5 meters above the water’s surface. The more likely the site is to encounter waves, the bigger the platform. The platform itself is composed of an aluminum and steel structure, with buoyancy provided by a combination of Styrofoam and plastic. “It’s important to note that they are all corrosion-resistant components,” notes Swimsol’s Putschek.

The PV modules themselves also have to be resistant to the corrosive effects of saltwater. Swimsol uses dual-glass modules that come with a special rubber seal, preventing water ingress. Relatively constant high humidity in the Maldives prevents the use of glass-backsheet modules, as there are so few opportunities for water that may permeate a backsheet to escape later. Putschek says that the introduction of dual-glass modules utilizing polyolefin (POE) as an encapsulant will increase the number of potential suppliers to Swimsol’s projects – potentially improving the economics of individual projects.

While generating electricity from diesel remains expensive, its supply from the Gulf Region to the Maldives is largely reliable and comes at a cost of $0.50-$0.70/liter. It incurs no import duties. This presents challenges when demonstrating the economic benefits of a solar-diesel hybrid solution to resort operators, or the wider Maldivian community.

To meet this challenge Swimsol currently supplies its systems on the basis of a solar lease. It signs a 20-year PPA with resort operators and can supply clean solar electricity for a price below the cost of diesel generation, with the system ownership transferring to the offtaker on its termination.

“We don’t want to take all the risk all the time but to introduce the product onto the market we have to do that because it’s new,” says Putschek. “And we do everything for the customer – provide clean energy and you pay per kWh, rather than burn the money, which is literally what they are doing with diesel.”