Floating solar plants: An alternative for generating renewable energy

Floating solar plants are an innovative model within the renewable generation. We will tell you how they work and what their advantages and challenges are.

The sun is our main source of energy, it is renewable and inexhaustible. It is also abundant: If we only managed to collect 6% of solar energy, we could meet the energy requirements for the whole of humanity. That is why there is exponential growth of solar power plants around the world: Global installed capacity has doubled in the last three years and reached 1 TW in April 2022.

One of the main advantages of photovoltaic technology is that its installations are very adaptable. They range from huge solar plants on the ground to smaller panels on the roofs of homes.

The least known modality is floating solar plants, which are located on water surfaces and appear as a major alternative to boost solar energy in countries where there is a shortage of available land.

This type of photovoltaic panels can be installed on any water surface, from the sea to lakes, drinking water tanks, dams and irrigation channels, but they are ideally installed on calm waters, where there is little variation in level, and a short distance from the shore or bank.

What does a floating solar plant consist of?

Floating solar plants are not exactly the same as those on land, although they have a very similar system. They usually consist of a fixed structure with an inclination of between 5 and 15º and they usually face south or east-west to try to capture the entire path of the sun. They are composed of four basic parts:

Floating system or pontoon

Structure that supports the solar panel. It is composed of a structure and a float that keeps the installation suspended above the water.

Mooring system

It anchors the structure to the bottom and helps adjust to fluctuations in water level.

Photovoltaic system

This is the photovoltaic generation equipment. The most used are crystalline lenses.

Wiring system

Underwater wiring transports the energy generated to the electricity substation.

Making use of the land, cleaner and more efficient

The first advantage of floating plants is that they are a good option for generating solar energy in places where there is no availability of land.

In these installations the ratio of hectares per megawatt is 1:1. "In cases such as Portugal, where the state tenders the use of the water surface, the need to search for and rent land is eliminated," explained Miguel González, Manager of Renewable Business Development at Enel Green Power for Portugal.

Another advantage, compared to terrestrial systems, is that floating photovoltaic panels do not get so dirty. As they are not on land, they do not collect as much dust. Although the maintenance system is similar and is always undertaken by specialised personnel.

However, "the main advantage of floating photovoltaic panels compared to those on land is their greater cooling which improves their performance," said MiguelAs they are close to the water, the panels cool very well compared to terrestrial photovoltaic panels, which do not perform as well with the heat. The hotter the material, the less electricity is produced with the same amount of sunlight. 

“The main advantage of floating vs. terrestrial photovoltaic panels is that they stay cooler and so perform better”.

– Miguel González, Manager of Renewable Business Development at Enel Green Power for Portugal.

But as they are fixed panels, they produce energy for fewer hours than a panel on the ground, which has the possibility of following the sunlight. Floating systems and moorings are also expensive compared to those installed on land.

From the environmental point of view, these installations appear to have certain benefits by preventing the evaporation of water and also the proliferation of algae and mosses.


Floating solar plants in the Iberian Peninsula

The floating photovoltaic plants currently installed in Spain are located in reservoirs or artificial rafts and most are intended for self-consumption to power irrigation systems in the agricultural sector.

Outside Spain, the capacity of floating photovoltaic plants has been increasing over the last ten years. According to the World Bank, in 2018 the cumulative installed capacity of floating solar energy was approaching 1.1 GWp, the same milestone that onshore photovoltaics reached in 2000.

Currently, most of the world's installed capacity is in Asia, which is leading in the installation of floating solar power. However, as Miguel González stated, "although there are large-scale installations in China, Korea and Japan, new plants have recently been created in France, Switzerland and, now also in Portugal, where we have won the first auction for a floating solar installation in reservoirs in the Iberian Peninsula". 

“New plants are being created in France, Switzerland and, now, in Portugal, where we have won the first auction for a floating solar installation in reservoirs in the Iberian Peninsula”.

– Miguel González, Manager of Renewable Business Development at Enel Green Power Spain.

Our project in Portugal, where we were assigned the connection rights for 42 MVA, will enable us to install a floating solar power plant in the Portuguese reservoir of Alto do Rabagão.

In the short term our aim is to continue developing renewable energy in the neighbouring country. Rafael González, Endesa's General Manager for Generation, assures us that "after the winning project for the Fair Transition Contest in Pego, we will invest in this innovative renewable production project for floating solar power". Alto do Rabagão will be a hybrid installation that will combine photovoltaic and wind power generation. 

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