Four floating solar platforms have been installed within the lagoon of Tumaraa by the energy providers of French Polynesia in order to conduct experiments for the generation of electricity using offshore renewable resources.
These floating panels are situated right above the sensitive community present at the bottom of the shallow lagoon.
Monitoring carried out for one year showed that although the floating panels were casting dense shade and reducing the amount of light reaching the bottom of the sea, the temperature of water beneath them was unaffected.
Blocking solar radiation with offshore floating platforms
French startup Solar in Blue placed four floating modular systems in the marine waters of Ra‘iātea to test the effectiveness of tropical offshore solar power.
The heavy sea anchors hold down the buoyant modules on the top of the live ecosystem, enabling the modules to remain atop the wave crests.
The mounted photovoltaic panels produce about 57 MWh/year and do so in a small area within the lagoon.
Solid pontoon decks prevent sunlight from getting into the thin water column below the array.
Submerged optical sensors recorded a significant decrease in photosynthetically active radiation on the coral reef floor below.
Diluting thermal impacts in a dynamic tropical lagoon
Scientists first predicted that shielding the lagoon from the harsh rays of the tropical sun would cool the water column below the platforms.
The temperature readings from sensors placed throughout the water column showed no statistically significant temperature variations.
Tidal currents and waves from the wind ensure that there is constant mixing of the shallow waters in the lagoon of Tumaraa.
Great amounts of water from the oceans move quickly enough through the barrier reef so as to prevent any formation of microclimates around the four platforms.
The thermal mass of the open lagoon ensures rapid distribution of heat variations.
Balancing light deprivation against heat stress on corals
In the first place, marine biologists are investigating whether utilizing artificial shading on the platforms could be a way to protect the corals from extreme heat waves.
The corals require small algae that live inside them as a source of food to help them survive.
Artificial shading could possibly lead to starvation of the zooxanthellae algae and might lead to some metabolic disorders in the future.
Excessive shading may alleviate the solar radiation stress but increase the nutrient stress, but this needs further investigation.
Testing modular energy generation on isolated island grids
Scarce land areas in mountainous South Pacific islands limit land-based utility solar systems.
Use of floating marine platforms allows avoiding territorial land restrictions by employing public space in the oceans within barrier reefs.
The pilot project provides energy directly to the power grid of Ra‘iātea using subsea cables, as reported by SolarinBlue.
Clean energy generation at sea minimizes the need of island economies for costly diesel fuel imports via long-distance sea shipping routes.
Modular floating platforms provide flexibility in the scale of projects for island countries seeking energy independence.
Installation of solar equipment in marine environments helps overcome land limitations but creates new challenges for marine engineering.
Tracking long-term ecological risks before expanding offshore
Preliminary findings have shown that four floating structures are able to provide consistent power generation while enduring tropical oceanic environments.
Monitoring the environment within the Tumaraa Lagoon will continue until the end of 2027 to examine trends in coral life over several years.
At the moment, researchers are unable to determine whether long-term absence of light leads to the death of corals in multi-year periods.
Smaller demonstrator projects provide vital information prior to implementation of commercial projects with increased floating solar capacity.
Floating solar provides energy autonomy for islands, but the further expansion into sensitive lagoons should prove that corals can tolerate constant shade.
The full study can be read here: Adgé, M., Hédouin, L., Drahi, E., & Planes, S. (2026). The Effect of Shading by Floating PV on Light and Temperature in a Tropical Lagoon. Journal of Marine Science and Engineering, 14(17), 1605. https://doi.org/10.3390/jmse14171605
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