Switzerland is at a historic crossroads in its energy transition. With the acceptance of the 2050 Energy Strategy and the imperative need to move away from dependence on fossil fuels and to compensate for the gradual closure of nuclear power plants, the country must massively increase its production of electricity from renewable sources. The major challenge? Lack of space.
In a country characterized by steep mountainous topography, densely populated valleys, protected forest areas and untouchable agricultural land, finding areas to install gigantic terrestrial solar farms is a political and spatial obstacle course. It is in this context of extreme land constraints that a disruptive technological innovation emerges as a miracle solution: floating solar, or Floatovoltaics in international jargon.
Rather than artificializing the soil or limiting itself to the roofs of buildings, Swiss engineering is turning to an abundant resource already exploited for energy: artificial reservoirs. The pioneering project of Romande Energie on Lac des Toules has proven to the world that the installation of floating solar parks at high altitudes is not only a technical feat, but a strategic necessity offering spectacular yields (up to 15% higher than terrestrial installations).
In this ultra-detailed file, developed by experts from Solar Panel Swiss, we offer you an exhaustive dive into floating solar technology in Switzerland. We will analyze the thermodynamics of water cooling, environmental impact studies (EIA), virtuous synergies with hydroelectricity, and investment prospects for the decades to come.
1. The Genesis of Floating Solar: What is “Floatovoltaics”?
The term “Floatovoltaics” is a portmanteau born from the contraction of “floating” and “photovoltaics”. It designates large-scale solar power plants installed on bodies of water: natural lakes, artificial reservoirs, water treatment basins, or hydroelectric dam lakes.
1.1 Global developments vs. the Swiss context
Globally, floating solar has exploded in Asia (notably China, Singapore and Japan) on lowland lakes or flooded former coal mines, with the main aim of preserving agricultural land. In Switzerland, the philosophy is different. The challenge is not to float on calm ponds at low altitude, but to tackle alpine reservoirs, located at altitudes ranging from 1'500 to more than 2'000 meters. This involves colossal engineering constraints: tidal range of more than 40 meters, extreme snow loads and the formation of thick ice.
1.2 Why target artificial and unnatural lakes?
The Federal Office of Energy (FOEN) and environmental protection associations (such as Pro Natura) agree that natural lakes (such as Lake Geneva or Lake Neuchâtel) must be preserved for their ecosystems, tourism and the landscape. The artificial accumulation lakes are industrial infrastructures already modified by man. Their biodiversity is low due to variations in water height, making them the ideal target for maximizing clean production without degrading wilderness.
2. The Space Paradox in Switzerland: Water as a New Frontier
The densification of the Swiss territory jealously protects crop rotation areas (SDA). If we explore solutions such as agri-photovoltaism, floor space remains limited. Furthermore, although the potential of Swiss roofs is great (estimated at 50 TWh/year), the rate of residential installation remains insufficient to cover the industrial energy transition. The accumulation reservoirs represent thousands of hectares of space already anthropized. Equip only 1% to 2% of the surface of these lakes would make it possible to generate several Terawatt hours of essential winter electricity.
3. The Thermodynamics of Yield: The Technological Gain of 15%
Placing the panels on the water allows a major thermodynamic gain. Silicon solar cells lose efficiency under the effect of heat (the temperature coefficient reduces efficiency by 0.35% per degree above 25°C). On dark roofs, panels can reach 65°C, losing almost 14% of their rated power.
The cold water of Alpine lakes acts as a temperature regulator. Continued evaporation and heat dissipation by cool lake air cools the panels. On average, floating panels operate at a temperature lower than 10°C to 15°C compared to terrestrial ground installations, which generates a net gain in yield of 10% to 15% over the year.
4. The Pioneer Case: The Exploit of Lac des Toules (Romande Energie)
The pilot project of Lac des Toules in Valais, located at 1'810 meters above sea level, is a world first launched by Romande Energie. It was necessary to design articulated aluminum rafts capable of withstanding a 60 cm layer of ice, winds of 120 km/h, and a tidal range of 40 meters. The structures descend gently in winter as the lake level drops, and rise again in spring.
The plant uses bifacial panels inclined to slide the snow. The rear side additionally captures the strong light reflection (albedo) from the surrounding water, ice and snow. The yield of this park is thus higher by 50 % to that of an equivalent solar power plant in the plain.
5. The Ultimate Synergy: Floating Solar and Hydroelectricity
The combination of floating solar and storage dams offers exceptional synergies:
- Shared infrastructure: The floating power plant uses the dam's existing access roads, transformers and high voltage lines, drastically reducing the grid connection investment cost.
- Pumping-storage (hydraulic battery): Excess solar electricity produced during the day can power the pumps to raise water in the storage dams. This stored energy is then turbined in the evening during peak consumption.
- Reduction of evaporation: Partial coverage reduces water loss through evaporation due to wind and direct sunlight, maximizing turbine volumes.
6. The Alpine Asset: Fighting the winter electricity deficit
Alpine floating solar directly responds to the challenge of winter deficit (Stromlücke). At high altitudes, UV is more intense due to a thinner atmosphere. In addition, from November to February, while the Swiss Plateau is often covered in fog (stratus), the Alpine lakes benefit from maximum sunshine above the sea of clouds. Combined with the albedo effect of snow, floating solar produces highly strategic winter electricity for the Swissgrid national network.
7. Environmental impact assessment
In accordance with the requirements of the Environmental Protection Act (LPE), projects are subject to rigorous impact studies. On natural lakes, shading disrupts plankton and ecosystems. On the other hand, deep alpine reservoirs have low biodiversity and have not revealed a negative impact during scientific monitoring. Visually, the dark colored floats fit into these already modified industrial spaces. In terms of recycling, the aluminum, the HDPE of the floats and the silicon of the panels are entirely recycled at the end of their life (SENS eRecycling).
Conclusion: Water and Sun serving the network of tomorrow
Floating solar or Floatovoltaics transforms Alpine dams into powerful hybrid hydro-solar power plants. It is an effective, ecological and technological response to the space challenge and the Swiss winter deficit. While the solar offensive (Solarexpress) facilitates the development of these large-scale projects, floating solar asserts itself as a pillar of the future for Switzerland's sovereignty and energy independence.