Expanding renewable energy infrastructure to supply island communities in the South Pacific is complicated. The main reason is a shortage of land. Lagoons sheltered from rough offshore conditions are a potential alternative for localized offshore floating solar arrays. But there are environmental concerns. The hardware would have to be installed over sensitive marine ecosystems.
A one-year-long French Polynesian field experiment focused on the effects of floating solar arrays on underwater light levels and water temperature in shallow coral reef environments.
How floating solar arrays were tested in a tropical lagoon
In order to study the impact of offshore solar power generation on the environment, four offshore solar power plants have been built within the tropical lagoon located near French Polynesia. The project was called “Solar in Blue Coral” and involved installation of solar arrays above the shallow benthic ecosystems.
The floating modules were fixed by mooring lines capable of resisting the waves of the sea. The platform created a barrier between the sun and the underwater world.
For twelve consecutive months, the sensors automatically measured the environmental parameters under the floating solar arrays and also in the nearby open waters.
The research team also tracked the solar radiation that reached the seafloor and the fluctuating water temperatures at various depths within the strata. Data collection continued during the varying weather seasons. Scientists were able to develop an accurate baseline of how the physical solar system affects microclimate in coral lagoons.
Quantifying light reduction and water thermal stability
The data collected for the entire year showed that there was a drastic reduction in the amount of light under the solar pontoons. The physical effect of the four pontoons significantly reduced the photosynthetic active radiation levels at the bottom of the sea compared to the controls. It was a constant barrier that resulted in a unique low-light microhabitat within the reef bed beneath the solar pontoons.
However, surprisingly, the water temperature beneath the floating structures stayed practically equal to those of the adjacent open water regardless of the significant shading effect caused by the structures.
Water under the platforms was subject to constant hydrodynamic circulation due to tides occurring in the lagoon. As a consequence, there were no thermal stratifications nor any artificial heating within the shaded area during the entire course of monitoring.
Balancing clean energy goals with tropical marine conservation
The results show that it is possible to create a sustainable model of offshore energy production and bring some environmental advantages to the island regions, according to SolarinBlue.
With coral reef species relying on photosynthetic zooxanthellae for energy, the possibility of long-term impact on benthic condition, growth rates of corals, and community dynamics cannot be ruled out due to decreased light availability underneath such solar arrays.
However, lack of local warming is good news for coastal management authorities, as warm waters are one of the leading causes of mass coral bleaching all over the world. The non-heating aspect of floating solar panels helps in ensuring that no extra thermal stress is imposed on marine life. Moreover, strategic shading during intense summers can even help protect sensitive corals from light-related thermal stress.
Insights for coastal energy planning
With increasing use of floating photovoltaics as small island nations strive towards their ambitious clean energy goals, knowledge about microclimate effects becomes important from the perspective of coastal management in the future. Proper configuration of arrays can be achieved by keeping the required light reaching the water for photosynthesis.
Finally, this pioneering year-long study has shown that floating solar farms may change benthic lighting dynamics without affecting heat balance, providing possibilities for peaceful coexistence with fragile tropical marine ecosystems.
The full study can be found 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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