courtesy  :  wikipedia

Floating solar

Floating solar or floating photovoltaics (FPV), sometimes called floatovoltaics, is solar panels mounted on a structure that floats on a body of water, typically a reservoir or a lake.

The market for this renewable energy technology has grown rapidly since 2016. The first 20 plants with capacities of a few dozen kWp were built between 2007 and 2013.^[1] Installed power reached 3 GW in 2020, with 10 GW predicted by 2025.^[2]

The costs for a floating system are 20-25% higher than for ground-mounted systems.^[3]

Challenges[edit]

Floating solar presents several challenges to designers:^[16][17]

1. Electrical safety and long-term reliability of system components: Operating on water over its entire service life, the system is required to have significantly increased corrosion resistance, particularly when installed over salt water.
2. Waves: The floating PV system needs to be able to withstand wind and heavy waves, particularly in off-shore or near-shore installations.
3. Maintenance complexity: Operation and maintenance activities are as a general rule more difficult to perform on water than on land.

History[edit]

Installed capacity worldwide in MW^[18]

American, Danish, French, Italian and Japanese nationals were the first to register patents for floating solar. In Italy the first registered patent regarding PV modules on water goes back to February 2008.^[19]

The MIRARCO (Mining Innovation Rehabilitation and Applied Research Corporation Ontario, CANADA) research group quotes several solutions that were put forward in 2008-2011 and 2012-2014.^[1] Most of the installations can be classified into three categories:

• PV plants constituted by modules mounted on pontoons
• PV modules mounted on rafts built in plastic and galvanized steel
• PV modules mounted on rafts, fully in plastic.

A 45 MW combined solar and hydropower plant was installed in Thailand in 2021.^[20] A 320 MW facility opened in China in 2022.^[21]

There are several reasons for this development:

1. No land occupancy: the main advantage of floating PV plants is that they do not take up any land, except the limited surfaces necessary for electric cabinet and grid connections. Their price is comparable with land based plants, but they provide a good way to avoid land consumption.^[4]
2. Installation and decommissioning: floating PV plants are more compact than land-based plants, their management is simpler and their construction and decommissioning straightforward. The main point is that no fixed structures exist like the foundations used for a land-based plant so their installation can be totally reversible.
3. Water saving and water quality: the partial coverage of basins can reduce the water evaporation. This result depends on climate conditions and on the percentage of the covered surface. In arid climates such as parts of India this is an important advantage since about 30% of the evaporation of the covered surface is saved.^[5] This may be greater in Australia, and is a very useful feature if the basin is used for irrigation purposes.^[6][7]
4. Cooling: cooling the floating structure is simple. Natural cooling can be increased by a water layer on the PV modules or by submerging them, the so-called SP2 (Submerged Photovoltaic Solar Panel).^[8] In these cases the global PV modules efficiency rises thanks to the absence of thermal drift,^{[clarification needed]} with a gain in energy harvesting up to 8-10%.
5. Tracking: a large floating platform can be easily turned and can perform a vertical tracking:^{[clarification needed]} this can be done without wasting energy and without the need for a complex mechanical apparatus as in land-based PV plants. Equipping a floating PV plant with a tracking system costs little extra while the energy gain can range from 15 to 25%.^[9]
6. Storage opportunity: the presence of water naturally suggests using gravity energy storage mainly in the coupling with hydroelectric basins. However other possibilities have been explored and in particular compressed-air energy storage systems have been suggested.^[10]
7. Environment control: algal blooms, a serious problem in industrialized countries, may be reduced. The partial coverage of the basins and the reduction of light on biological fouling just below the surface, together with active systems can solve this problem. This is only a part of the more general problem of managing a water basin generated by industrial activities or polluted by them.^[11]
8. Efficiency improvement: Many studies claim that solar panels over water are more efficient. The energy gain reported range from 5 to 15%.^[12][13][14]