The fisrst reason is a land scarcity avoiding. Traditionally solar panels occupy a lot of valuable land space.
The second reason is higher solar panel efficiency due to water cooling effect. Solar cell performance decreases with increasing temperature. The operating temperature plays a key role in the photovoltaic conversion process. Both the electrical efficiency and the power output of a solar panel depend linearly on the operating temperature.
Some studies show that the relative annual average output energy is about 12.96% higher at sea compared with land.
However, in some months, this relative output energy increases up to 18% higher energy yield at seaevision (source).
Typically, floating solar power plants are 30-50% more expansive than ground-based. In some cases, customers do not have available land space for solar panels, but they have access to the water, near-shore locaitons and to be able to generate a clean energy, more expensive solution can be the option.
The floating solar power plant is not dangerouse for fish, recent research was performed by Buro Bakker/ATKB. However, multi-year research is required to establish clear results (source).
HelioRec is installing floating solar power plants on unused or shallow water and it does not disturb maritime activities.
The floating solar market is growing exponentially (installed in 2004 - 10MWp and in 2021 – 1.6GWp) and it opens enormous market opportunities and advantages for the environment and society. It is one of the fastest growing sector with CAGR (compound annual growth rate) of 33.7% (source and source).