Solar photovoltaic energy is already well established in the collective imagination: everyone has seen a photovoltaic park while driving down the road, read about a company that has “switched to photovoltaic self-consumption” or has an acquaintance who has had installed solar panels on the roof of his or her house. It is very clear to us that PV panels can be installed on the ground, or on the roofs of buildings, and we have even heard of “integrated PV”, on windows or on the walls of modern buildings. However, solar energy can also be generated from the surface of bodies of water.
In this article we talk about what is known as floating photovoltaics.
What is floating photovoltaics
Floating PV installations are those in which the PV modules are supported on structures that float on the surface of a body of water. These surfaces are typically irrigation ponds, reservoirs or wetlands, although their application in other elements, such as the sea, is also being studied.
From a technical point of view, floating photovoltaic systems consist of 4 main components: the photovoltaic panels, the floating support elements, the anchoring systems and the cabling and other electrical and electronic elements. Each of these components faces its own technological and economic challenges:
The classic photovoltaic solar panel, which is already able to withstand wet environments without degrading, now faces the challenge of withstanding other environments generated by liquid bodies where floating photovoltaics are being tested.
Floating systems should have a design that is both lightweight and robust and that allows for ease of assembly, installation in the water body and maintenance.
Anchoring systems must be adapted to each type of installation: the shape of the body of water, its depth, the material of which its walls and shores are made, the wind speed of the location, etc.
The wiring and electrical system elements must, like the panels, withstand the humidity and environmental characteristics of the location where they are placed.
Diagram of the components of a floating photovoltaic system unit. Source: own elaboration based on Isifloating system schematic by Isigenere (www.isigenere.com)
Despite these challenges, floating PV has advantages that make it the third pillar of solar energy, after ground and rooftop. The main advantages of this type of installation include the following:
The location of energy production systems on water bodies allows the land to be used for other productive uses, such as cultivation.
In addition, placing the panels in the water body usually avoids shadows, as there are no obstacles, such as trees on the ground, or architectural elements in building locations.
Partially covering the surface of the water body with flotation elements and photovoltaic panels decreases evapotranspiration, which can be beneficial in agricultural applications, reservoirs, or other applications where water level control is required.
It also improves water quality by helping to reduce algae blooms.
Floating systems allow for a better performance of PV panels, as they are bottom-cooled (water heats up slower than the ground or building roofing materials).
Main applications and potential market
This type of photovoltaic installation can be used both for grid-selling applications, in its widest version (for example, using the surface area of reservoirs and wetlands), and for self-consumption applications. Logically, the latter will make sense as long as there is a body of water close to the consumption to be covered.
On the one hand, the “dual use” of reservoirs presents a great potential for the installation of floating photovoltaics, together with hydroelectric power plants, so that both the potential and kinetic energy of the water is used, as well as the space that a reservoir already occupies for the production of photovoltaic energy. It should be borne in mind that Spain is the European Union country with the largest number of large reservoirs, so the potential for this application is high. On the other hand, in self-consumption applications for industrial use, this can mean an important logistical advantage, as it allows the production of energy using already existing areas of water necessary for industrial processes, thus giving them a double productive use.
Examples of sectors for which floating PV is of particular interest are wine, agriculture and livestock, aquaculture, mining, water treatment plants and water bottling.
The wine industry in particular should be mentioned as one of the sectors with the greatest potential to benefit from floating photovoltaic energy, as it is a very powerful economic activity that is highly affected by global warming, but at the same time presents great opportunities for the penetration of renewable energies. Vineyards often have water ponds for irrigation and water purification for the winery. These ponds can easily be used for the installation of floating photovoltaic systems, thus making use of the land and making vine and wine production more sustainable.
Floating photovoltaic system on the Viñas del Vero water treatment pond, installed as a demonstration pilot for the LIFE REWIND project. The two photographs above show the finished system, while the photograph below shows the process of installing the system on the pond.
It is no wonder that the first floating photovoltaic solar energy projects were developed in the wine sector in California. Here in Spain we have the example of the European LIFE REWIND project, which developed a demonstration installation at the Viñas del Vero winery to demonstrate the integration of various renewable technologies for self-consumption, including a floating photovoltaic system. This system, with 44kWp of power, is installed on the water surface of the winery’s purification pond, and is the first commercial floating photovoltaic system.
Another possibility for floating photovoltaics is their use in underdeveloped or developing regions where there are extreme difficulties in accessing water and energy. Here, this technology can be an effective and cost-efficient solution, both from the point of view of stable and sustainable electricity generation, and from the point of view of minimising water evapotranspiration, thus preventing water depletion in certain reservoirs.
Moreover, as already mentioned, floating PV installations are not limited to freshwater bodies: there are several projects at sea, close to the coast, where installations face the challenge of adequately withstanding saline environments and the onslaught of waves. For the time being, this application is still in the research phase.
But salt water is not the only medium other than fresh water where this technology is being tested: Intergia is currently working on a research project to apply floating photovoltaics to slurry ponds in the Spanish livestock sector (“Alternativas en el aprovechamiento y control del potencial de las balsas de purines”, within the call for subsidies to support collaborative actions of agents in the agricultural sector 2020 (Aragon Rural Development Programme 2014-2020)).
While floating PV requires a higher investment than ground- or roof-mounted PV, it also presents a great opportunity for cost-effectiveness in applications where there is a body of water that can be used for energy in addition to its normal use.
On the other hand, the need to deploy renewable energies brings with it the demographic challenge of dedicating land space to them, which is no longer available for other productive applications, such as agriculture. In particular, the energy density of photovoltaic installations is not very high, i.e. a larger amount of land is needed to produce the same amount of energy than with other technologies. In this respect, floating photovoltaics offer a solution to alleviate this problem, allowing photovoltaic production to be moved to areas that have hitherto been “unoccupied”, thus reducing the impact on the land and generating added value.
For these reasons, the enormous potential and scope of this technology in Spain and Europe makes it one of the most promising renewable energy technologies for the near future to accelerate the energy transition.
For the time being, while research into its application to different liquid bodies and uses continues, floating photovoltaics is today an excellent solution for self-consumption in various production sectors, where it is already advantageous, profitable and sustainable.