Floating Solar as the third pillar 

This uptake in recent years is fuelled by the many advantages floating solar offers over more traditional ground-based or roof-mounted solar farms. Chief among them is the fact that they do not require land, apart from the small amounts needed for electric cabinetry and grid connections. Since the space required has no great commercial value, unlike many land sites, there can be significant cost benefits in a floating solution. If, as happens in many cases, the panels are located on an existing hydro project, the solar installation can enjoy further advantages by using existing distribution infrastructure. 

Secondly, floating solar panels can offer an increase in operating efficiency of up to 15% due to the cooling effect of the water close to the photovoltaic panels. This can help offset the additional construction cost associated with a floating installation, estimated at between 10% and 25% above the cost of a land-based solution. The extra costs are due in part to floating solar being a relatively new technology, needing specialised equipment and different installation expertise. Solid anchoring is a critical factor, and comprehensive wind and tide analyses are needed for near-shore and onshore installations to ensure the safety of the solar park.

Savings can be made in the pre-construction phase, as there are no ground features to be factored in, or even moved. Many on-land sites require extensive preparation, including the removal of existing trees and vegetation.

Another, perhaps surprising, benefit is water conservation.  Scientists from the University of Ponta Grossa in Brazil and the University of Louisiana investigated the impact of floating solar on the water evaporation rate on the Passaúna reservoir in the Brazilian state of Paraná. The reservoir spans 8.5 square kilometres, has an average depth of 6.5 metres and a total volume of 69.3 cubic hectometres. They found that 4.47 million cubic metres of water evaporated from the reservoir in the space of a year, equivalent to 10.4% of the water volume consumed annually by the local population. The team calculated that the floating solar system reduced water evaporation by 60%, which is an important consideration in water-scarce areas. The researchers shared their results in a paper that was recently published in Energies. Similar research conducted with floating solar panels on a reservoir in Jordan in 2021 found that evaporation was reduced by 42%.

An associated environmental benefit is that the presence of floating panels provides shade for the water surface, preventing the growth of toxic blooms of blue-green algae, which causes health hazards. That same shade may cause problems for aquatic life, however, so some experts prefer to see floating solar installed on bodies of water without an abundance of wildlife.

Furthermore, large floating platforms can be rotated easily horizontally and vertically to enable sun-tracking using mechanical, geospatial and light sensors to follow the sun's path without the need the complex mechanical apparatus required for land-based PV installations; this can deliver an energy gain of up to 25%.

Safety is a key consideration, given the incompatibility of water and electricity, so more attention must be paid to cable management and insulation testing than on land, especially where cables will be in contact with water. Other challenges include taking account of the hydrodynamic loads on the structure, and the need for significantly greater corrosion resistance, particularly when installed on salt water.

However, with solar power becoming the lowest-cost option for new electricity generation in most of the world, according to the International Energy Agency, floating solar has an increasing role to play. The IEA says there needs to be more than a threefold increase in annual solar capacity deployment until 2030, “requiring much greater policy ambition and more effort from both public and private stakeholders”. We can expect increased interest and investment in floating solar projects in the years to come as the ‘third pillar’ alongside ground-based and rooftop installations.