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"The Case For Floating Solar"

image credit: Floatovoltaic installation
Ron Miller's picture
Principal Reliant Energy Solutions LLC

Ron Miller is an energy industry expert creating value by analyzing assets, markets, and power usage to identify, monetize, and implement profitable energy and emission reduction projects. He is...

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  • Jun 18, 2021

Restrictions on land use for greenfield solar projects, roof orientation, and inherent technical advantages, may prove floating solar, or floatovoltaic to be a viable energy alternative.

When it comes to large-scale solar projects, the most common alternatives to rooftop solar panel systems include ground mounts or solar canopies. There’s a newer alternative that’s making quite the splash in the solar industry: floating solar.

What is floatovoltaic?

Floatovoltaic is defined as solar panels arrayed to float on the top of a lake or reservoir, placed on a buoyant sub-structure, and anchored with a measure of flexible movement. The technology is relatively-new starting in 2008 with China, Japan, and the U.K. as the early adopters.

Floatovoltaics installation growth

Floatovoltaics are projected to growth substantially in the future as key advantages will spark early adoption and installation as shown in Graph 1.


Graph 1 – Floatovoltaic Growth in MW

Source: "Where Sun Meets Water: Floating Solar Market Report," World Bank Group and SERIS, Singapore, 2018.

Floatovoltaics advantages

  • No loss of valuable land space that could be used for food production.
  • Greater utilization of relatively-little used water surfaces of man-made lakes, reservoirs, and wastewater treatment ponds.
  • No surface preparation required to remove trees or vegetation.
  • Water temperatures moderate the ambient temperatures that the solar panels operate within (cooler), thus increasing the efficiency, yielding greater energy production.
  • Floatovoltaics reduce evaporative water losses from lakes/reservoirs as it reduces contact of water surface with direct sunlight. For industrial operations that require water, this advantage reduces the water drawn from local aquifers that are shared with local communities, and/or reduce the cost of purchasing make up water. This advantage is especially important in arid climates as 80% of the water evaporation can be eliminated.
  • Shade from floatovoltaics reduces the activity of algae blooms in bodies of fresh water, which can cause problems for water used for drinking.
  • Source of renewable electricity.
  • Requires no fixed structures, i.e. foundations used for a land-based plant so their installation can be totally reversible.
  • Floatovoltaic installations can track the sun’s movement providing additional 15-25% increased energy production vs. fixed PV.

Disadvantages of floatovoltaics

  • Floatovoltaics have a higher capital cost due to early stage of its adoption and the buoyancy requirements for its sub-structure. These current costs will eventually follow solar and wind, and decline.

Key technologies to be paired

Floatovoltaics can be even more valuable when paired with a hydropower generation facility for a number of reasons. Portugal saw the first combination of floatovoltaics and a hydroelectric generation plant in 2017 installed by EDP.

One of the detractors for solar is its intermittent nature, i.e. it only produces energy when the sun is shining. One of the detractors of hydro is that once water goes through the turbines, its energy production is spent. Combining the two, increases energy reliability.

By combining solar and hydro, energy from the sun saves the potential energy of falling water for a later time for which solar cannot be the energy solution. Since hydro generation is very reliable and the stored water is extremely dispatchable, solar increases hydro’s importance by holding more water during the day for translation into energy overnight. The combination increases the grid stabilization and reliability

High-altitude floatovoltaics

Use of the man-made Lac des Toules at high altitude in Switzerland near the Swiss-Italian border for solar offers key advantages to extend the benefits described above combining solar and hydro.

The floatovoltaics project combines 2,240 square metres of solar panels to produce 50% more energy than one on lower-lying land because of: 1)  the colder temperatures (which increase panel efficiency), 2) stronger UV rays (high altitude, less fog), and 3) light reflected from the surrounding snow (taking advantage of bifacial panels) as shown in Figure 1. This is the world's first high-altitude (1,810 meters above sea level) floatovoltaic farm near the Swiss village of Bourg-Saint-Pierre. The facility was installed in December of 2019 by Romande Energie.


Figure 1 – High Altitude Floatovoltaics In Switzerland


The use of two-sided solar modules is key in that when snow lands on a panel, the light reflected from one side heats up the other side by generating energy, causing the snow to slide off and for the panels to continue energy production.

Installations around the globe

There are several floatovoltaic installations around the world, with increasing adoption due to the advantages mentioned above.

The largest installation in the world is 40 megawatts (MW) in Anhui province, China, built by Sungrow Power Supply. Its 166,000 panels powers over 15,000 homes in China as shown in Figure 2.


Figure 2 – China Anhui Installation

The first public floating solar system in America is located in Kelseyville County, California, USA, built by Ciel & Terre and is 252 kilowatts. It has 720 solar panels and floats on a man-made wastewater treatment pond as shown in Figure 3.


Figure 3 – California Installation

The largest floatovoltaic installation in Japan is 13.7 MW built by Kyocera and is located in Chiba Prefecture. The installation uses 44 acres of space and generates power for Tokyo Electric Power Company as shown in Figure 4.

Figure 4 – Japan Chiba Prefecture Installation

The largest floatovoltaic installation in the U.S. is at a water treatment plant Floating PV plant at a Healdsburg, California built by White Pine Renewables and co-developed with Noria Energy with a 4.8 MW capacity as shown in Figure 5.


Figure 5 – Largest Floatovoltaic Installation In U.S.


As opportunities to combine solar and hydro open ways to increase renewable reliability, and floatovoltaic costs decline, we could see increased use of this technology, especially in arid climates where water is a prized commodity.

Copyright © Jun 2021 Ronald L. Miller All Rights Reserved

#solar #floatingsolar #floatovoltaic #reservoir

Matt Chester's picture
Matt Chester on Jun 18, 2021

Obviously not all bodies of water are created equal when it comes to siting something like this-- wildlife, geography, access to transmission, etc. Is there an 'ideal' land portfolio that should be looked at for floatovoltaics?

Ron Miller's picture
Ron Miller on Jun 19, 2021

Key concerns would be wind/hurricane forces, gradual slope from the reservoir limits to and height of nearby trees to reduce any shading, rapid rise and fall of reservoir levels such as those used for hydro pumped storage, larger area reservoirs to mitigate water level rapid changes.

Ron Miller's picture
Thank Ron for the Post!
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