Solar-based generating capacity is expanding worldwide, and while most of this development is occurring on land, floating solar systems are beginning to show potential for contributing to renewable energy supplies. Growing levels of government support and investor appetite will help drive almost 10 GW of new floating solar generating capacity by 2025, either co-located with hydropower systems or riding the ocean waves.

Why bring solar power systems into the aquatic/marine realm? A significant benefit of floating solar is that terrestrial resources are not consumed for power plant placement. Land can be preserved for agricultural, forestry or other uses when solar farms float on reservoirs, which exert a cooling effect on photovoltaic panels, potentially increasing power conversion efficiencies by up to 10%. The shade provided by these panels also reduces evaporation, an important consideration in arid areas, and limits the growth of algal blooms.

The floatovoltaic-hydro combo

Pairing floating solar photovoltaic (FPV), or floatovoltaic, systems with hydroelectric power stations could boost global power generation capacity by up to 7.6 TW from the solar energy contribution alone. An assessment conducted by U.S. National Renewable Energy Laboratory (NREL) researchers indicates that almost 380,000 freshwater hydropower reservoirs worldwide could accommodate, combining FPV sites with existing hydropower capacity.

Combining hydropower generation with floating solar panels can yield promising results, as demonstrated by the first floating solar/hydro system constructed. Operational in Portugal since 2016, the 220 kW solar system includes 840 solar modules and occupies an area of about 2500 m2 of a hydropower reservoir. The power system was projected to produce of 332 MWh of electricity in its first year and delivered 160 MWh to the grid in its first seven months of operation.

The contribution of hydroelectric power to electricity supply in Africa is declining in the face of increasingly frequent and severe droughts. An analysis of the FPV potential at 146 of Africa's largest operational hydropower plants as of 2016 concludes that with solar coverage of less than 1%, the installed capacity of existing hydropower plants could be more than doubled to produce an additional 46 TWh annually.

Floatovoltaics at sea

Sometimes offshore is the only place to go. Without available space for such a project, densely populated Singapore is nearing completion of a 5 MW peak offshore floating solar farm in the Straits of Johor, between Singapore and Malaysia. Installation of one of the world’s largest floating solar farms on seawater by solar energy provider Sunseap involved a total of 13,312 panels, 40 inverters and more than 30,000 floats. When operational, the system showcased in this video is expected to produce an estimated 6,022,500 kWh annually, potentially offsetting an estimated 4,258 tons of carbon dioxide.

An artist’s rendition of the North Sea pilot plant. Source: Moss MaritimeAn artist’s rendition of the North Sea pilot plant. Source: Moss Maritime

Norwegian offshore oil and gas giant Equinor is moving ahead with plans to test an open-sea floating solar technology developed by Moss Maritime at a site off the island of Frøya in the Norwegian North Sea. The 1 MW pilot installation, which will measure 80 m2, will be installed this summer and trialed for one year at the site, which lies off Trondheim, west of the Nordic country. The pilot program is intended to gauge the impacts of harsh weather conditions on the solar power plant in addition to monitoring system output and reliability.

Challenges and conclusions

Despite its potential, floating solar represents less than 0.5% of total solar photovoltaic installations globally. Its benefits must be weighed against a 20% to 25% increase in system costs incurred by floating structures, anchoring and mooring systems, which also pose installation challenges related to water level variations, the reservoir bed type and depth, and extreme weather situations. Safety issues are a concern as more consideration must be given to cable management and insulation testing than on land, especially when cables are in contact with water.

Fortunately, a guide to reducing risks for developers and increasing investor confidence in the construction of floating solar power plants has been issued by Norway-based energy consultancy DVN. The recommended practices offer insight into the technical complexity of designing, building and operating on and in water, especially in terms of electrical safety, anchoring and mooring issues, operation and maintenance, and designing floating plants that can withstand site-specific environmental conditions.

Generating renewable energy through floating solar farms is likely to grow as an important part of efforts to address climate change. As the technology develops, the costs and technical challenges are expected to fall as demand for floating solar power increases in response to global population growth and urbanization.

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