Floating solar takes on high seas

Offshore solar energy systems are an emerging application in which photovoltaic (PV) systems are installed directly over bodies of water.

Floating solar photovoltaic is a subset of that technology in which PV panels are mounted on buoyant substructures.

PV panel technology is similar to traditional ground-mounted PV, except the panels rest on a platform usually of plastic and stainless steel designed to float on water.

Floating PV platforms are linked together in arrays with designated walkways and are anchored to the shore or bottom.

The main electrical conversion equipment resides on the shore where electricity is transmitted from the floating PV system to the grid or load via underwater cables.

Recent studies show that ocean-based solar has an enormous gross resource potential, but is severely constrained by extreme wave conditions on the ocean surface that would likely damage conventional photovoltaic systems and support structures.

However, National Renewable Energy Laboratory (NREL) study also tells that US waters in the Gulf of Mexico have sheltered bays and water bodies closer to urban load centers that could better take advantage of solar resources and may present a future opportunity, especially if new technology concepts for floating solar are developed.

To date, floating solar has been installed predominantly on human-made bodies of water such as wastewater storage ponds, reservoirs, remediation and tailing ponds, and agricultural irrigation or retention ponds.

Systems must be designed to withstand fluctuating water levels, wind and wave loads, and other extreme weather conditions.

Saltwater applications pose additional challenges due to corrosion and extreme wave conditions, with the latter exceeding practical design limits in most cases.

However, because the floating solar industry is still in its infancy it is expected that siting will gradually expand to locations with more challenging physical conditions as industry experience grows.

In 2017, six Dutch companies and research organizations including TNO, MARIN, ONE-Dyas and Oceans of Energy started with the development, construction, testing, and operation of the first offshore floating solar utility at open sea in the world.

The first 17 kW of the modular system has been installed in the North Sea, and this should be expanded in the coming months towards a 50 kW pilot that will be operational during a testing period of a year.

The Oceans of Energy offshore solar system is designed and tested to withstand 13 meters high waves.

Since November 2019, the system is in operation and has already survived several winter storms.

Italian contractor Saipem and Norwegian energy giant Equinor have recently signed a cooperation agreement to develop a floating solar panel park solution for near coastal and offshore applications.

The partners will combine their experiences and know-how to further develop the concept into a competitive and cost-effective solution that should meet the increasing demand of renewable energy solutions.

The technology will be based on the in-house developed concept by Moss Maritime, part of Saipem’s XSIGHT division.

According to Moss Maritime, the solar park will have a modular design that eases construction and repair. It will be customized to fit various locations and power demands and should be able to operate in waves without damage to solar panels.

DNV GL’s Energy Transition Outlook reveals that society will need to grow solar power by more than ten times to 5TW in order to close the emissions gap, the difference between the forecasted rate at which our energy system is decarbonizing and the pace we need to reach, to limit global warming to well below 2°C as set out by the Paris Agreement.

According to a recent report from the World Bank, the global potential of floating solar, even under moderate assumptions, is 2000 Gigawatt-peak on man-made reservoirs alone. When adding coastal waters the potential becomes enormous.

To remind, DNV GL has also recently awarded a conformity statement to Norwegian solar energy company Ocean Sun for its floating solar design methodology.

The conformity statement is the first of its kind and was issued following a verification process which sets the standard for the expansion of floating solar globally and opens opportunities to scale up solar energy production around the world.

The deployment of floating solar systems in the open ocean is a significantly more challenging technology step.

An offshore solar array must be designed to withstand the extreme weather events and resulting loads where it is deployed as the possibility of furling the panels under extreme conditions is limited.

Designing solar support-structures to survive extreme wind and wave events could drive system cost up rapidly and may prove to be cost prohibitive in some areas.

Generally, there are no insurmountable technological barriers to the advancement of floating solar technologies into deeper water with larger wave extremes.

However, it is yet unknown how the system cost and reliability would be impacted for designs capable of surviving larger wave and wind events.

Pioneering projects mentioned above could eventually deliver the much-needed industry experience on how to tap into this marine energy source.