Floating solar — also known as floatovoltaics — is a small but growing segment in the solar energy industry.
More than 1,600 megawatts of solar projects were reported to be floating in waters around the world as of 2019, less than 1% of total global solar installations. Before 2014, only three floating solar installations were reported to have been installed worldwide, each with an output under one megawatt. At the end of 2014, global installed capacity had increased to 10 megawatts. The most significant leap in growth to date was between 2016 and 2017, when installed capacity of floating solar increased by 676% on a year-over-year basis.
A 2019 report by Wood Mackenzie forecasts demand for floating solar to grow by an average of 22% year-over-year from 2019 through 2024.
Floating solar has the greatest appeal in areas where land is scarce. Locating a solar installation on water can save on real estate costs, while leaving valuable real estate available for agriculture, residential, industrial or other purposes. Floating solar can also increase megawatts installed closer to electricity consumers. This could be particularly relevant in countries where the alternative might be to put ground-mounted solar projects in less populated areas that have high insolation but that lack adequate transmission infrastructure.
Floating solar may have additional operational benefits. While studies to-date are not conclusive, floating solar installations have documented increased efficiency and energy yield when compared to ground-mount or rooftop solar. The efficiency and energy production benefits are linked to a decrease in the temperature of panels, which results from the ambient water temperature contributing to more effective panel cooling. Whether or not this outcome is achieved depends in part on each project's design, as well as environmental factors at the project site.
Environmental benefits of floating solar have also caught attention. By covering a body of water, a floating solar installation can help reduce evaporation, limiting the effect of oxygen loss in the water during hot seasons. The reduction in evaporation is particularly relevant for floating solar installations on reservoirs. Reports indicate that floating solar installations may have positive effects for fauna and can slow the growth of algae by limiting the amount of light that reaches below the water's surface. As with efficiency, these potential benefits will vary based on site-specific factors and will form part of the analysis of any potential floating solar project site at the early development stage.
Diligence on any project must take into account not only traditional insolation data, but also data about the body of water, including depth measurements, evaluation of the bottom surface and high and low water levels throughout the year, the impact of wind on the water surface, flora and fauna within the body of water, and other environmental metrics and impacts. Many bodies of water have varying points of depth, and water depths may also vary over the course of the year. Reservoirs, in particular, may periodically dry up.
There is great variety in anchoring technologies and floating structures. The nature of the body of water and the percentage of the water surface to be covered may require different approaches to anchoring and floating. Three main structures are most widely used for flotation — pontoons, single floats (one float per module) and multi-floats (an array of modules per float). Innovation continues; new technologies are steadily being introduced, and what is in use and under development today may change over time.
Capital expenses for installation tend to be higher than for ground-mounted or rooftop installations. There are additional electronic and structural balance-of-system costs and higher labor costs than for projects on land.
Floating solar arrays are usually mounted on the floating structure on land and then dragged into the body of water.
Comparisons of operation and maintenance expenses between floating and ground-mounted or rooftop solar are not yet conclusive. When it comes to cleaning, floating solar may have an advantage over ground-mounted systems with less dust and dirt accumulation, although bird droppings may be a bigger issue in some areas. Inland floating solar installations can also use the body of water on which they are installed as a source of water for panel cleaning.
A majority of floating solar development has been on artificial bodies of water such as reservoirs, dams, irrigation and storage ponds. Floating solar can be co-located with existing hydroelectric projects or installed on bodies of water that have gathered in waste areas from prior industrial activities. Most of these artificial bodies of water are already close to roads and transmission lines. Inland natural bodies of water, such as ponds, can also be used.
Offshore development is currently only a small segment of the growing floating solar industry, despite the potential. There are examples of offshore floating solar development in Belgium, the Maldives, the Netherlands, Singapore and the United Arab Emirates, but the offshore installations have generally been much smaller than their inland floating counterparts. Offshore floating solar brings additional challenges, including the potential for saltwater corrosion, greater wear-and-tear from regular wave movement and a need for stronger anchoring. Sheltered seawater locations may mitigate some of these additional challenges, which will be greatest in open-sea locations.
In June 2020, DNV GL launched a joint industry project with 14 industry participants, primarily based in Europe and the United States, to develop a set of recommended practices for floating solar projects.
This joint industry project will focus on five key topics: site-condition assessments, energy-yield forecasts, mooring-and-anchoring systems, floating structures, and permitting and environmental impacts. The goal is to come up with guidelines that can be applied to all floating solar projects regardless of technology and design. A draft document is expected at the end of 2020, with publication of the verified recommended practices currently scheduled for the first quarter of 2021.
No single technology or design is the clear market leader today. The technologies and designs will have to reach scale before the cost can decline.
China has more than 100 cities with populations of more than one million inhabitants. Not surprisingly, China is currently the country with the largest floating solar installations.
China has set ambitious renewable energy targets. As of 2019, 38.3% of the country's electricity came from renewables. Cumulative solar installed capacity was 208,000 megawatts at the start of 2020. Floating solar accounted for less than 1% of the total.
Of the top 20 reported operating floating solar projects in the world by size at the end of 2019, 12 were in China with four of those installations 100 megawatts or larger. Of the remaining eight top-20 floating solar projects, the largest was 47.5 megawatts (Vietnam) while the other seven ranged from 17 megawatts to 7.55 megawatts (in France, Japan, Netherlands, Taiwan and Thailand).
A majority of the floating solar projects in China are on collapsed coal mines where water has pooled in highly toxic unusable lakes.
Land is at least as scarce in Japan as in China, if not more so. Japanese multinational electronics manufacturer Kyocera started developing floating solar projects in 2014.
One of the largest Japanese floating solar power plants is on the Yamakura Dam reservoir in Ichihara, Chiba prefecture. The Yamakura Dam project opened in March 2018 and has an installed capacity of 13.744 megawatts. Kyocera developed and built the plant. The project is owned by the Chiba Prefecture Public Business Agency. All of the energy generated is sold to local electric utility, the Tokyo Electric Power Company.
The South Korean Ministry of Commerce, Industry and Energy announced plans in 2019 to build the world's largest floating solar power plant on Lake Saemangeum, on the west coast of Korea. At the time of the announcement the project was expected to require $3.9 billion of private capital. Original plans were for the 2,100 megawatts project to start construction in the second half of 2020 following regulatory review processes, including an environmental impact evaluation.
In Taiwan, Google became one of the first companies to enter into a power purchase agreement under the 2017 Taiwan Electricity Act, which allows non-utility companies to purchase renewable energy directly. Until 2017, only utilities could buy renewable energy directly. The 10-megawatt project in Tainan City that will supply power to Google will be installed by Taiwanese energy developer New Green Power on fishing ponds. This project will experiment with a new floating solar design using panels that are hoisted just above the surface, increasing fishing yields for fishermen in the area. When completed, the project will be connected to the regional power grid. Taiwan is also home to a 7.674-megawatt floating solar project that started operating in 2018.
India issued several tenders in the past two years for solar electricity from floating projects. In 2018, the Solar Energy Corporation of India (SECI), a government agency, invited expressions of interest to build 10,000 megawatts of floating solar over a three-year period. The specific project tenders issued by SECI to date all appear to be below 20 megawatts.
The United Arab Emirates has set a goal of turning Dubai into a global green energy center by 2050. In 2019, the Dubai Municipality and Dubai Electricity and Water Authority issued a request for proposals from consultants to study, develop and construct floating solar installations in the Arabian Gulf. Dubai wants 75% of its electricity to come from clean energy by 2050. To support that target, the government plans to build a large "solar lake" in the emirate. The first floating solar project began energy production in early 2020 in Abu Dhabi as an open-sea installation of 80 kilowatts off the small resort island of Nurai. The UAE has a significant number of artificial islands where land is at a particularly high premium. The higher costs of open-sea floating solar may be easier to justify in this region than in other parts of the world. The Nurai project is expected to be studied closely as a test for other open-sea installations.
Floating solar in Europe is being built on a much smaller scale than in Asia. France and the Netherlands have recently made small-utility scale installations.
France had the largest floating solar project in Europe — a 17-megawatt floating solar project in Piolenc, France — when the project went into service in October 2019. A 30-megawatt floating solar project planned for Lac de la Madone, on two bodies of water at a former gravel pit, recently received local approvals to move forward after a 230-kilowatt test project was previously installed.
In the Netherlands, BayWa r.e., together with its Dutch partner GroenLeven, successfully built its third floating solar park in a record time of just six weeks. The Sekdoorn project in the Netherlands, near the town of Zwolle, has a total capacity of 14.5 megawatts. That was topped by what is currently reported to be the largest floating solar project in Europe, the 27-megawatt Bomhofsplas project on a sandpit lake in Zwolle, which started construction in February 2020 and was built by BayWa r.e. in seven weeks. A sale of the Bomhofsplas project to a Dutch consortium was reported in July 2020. Prior to the Bomhofsplas project coming on line, the Netherlands had already added 25 megawatts of installed floating solar capacity in less than one year.
The Netherlands also has a pilot offshore floating solar installation. At initial installation in 2019, the pilot project was 8.5 kilowatts. In January 2020, it doubled to 17 kilowatts. More modules are expected to be added in 2020. Oceans of Energy, the developer, hopes to install floating offshore solar in tandem with offshore wind in the Netherlands.
Floating solar has not gotten the same traction to date in the United States as in Asia and Europe. Land is not as scarce near population centers and transmission lines. As a result, greater concern is shown over the lack of long-term data to show how floating panels will perform and be maintained over the span of decades, or how arrays could affect water quality and the natural habitats where they are installed over extended periods of time.
In 2008, Far Niente, a California winery, installed a 477-kilowatt floating solar system in Napa Valley, an area where land is particularly expensive. The project is over a water containment area used for irrigation. Installing a solar array on water, Far Niente kept its land dedicated to growing vines, a more profitable use for the winery. The solar array is connected to the power grid.
More than 10 years after Far Niente, a 4.4-megawatt Hydrelio floating solar project was completed in Sayerville, New Jersey at the end of 2019. The project was developed by Ciel & Terre, one of the world's largest suppliers of floating solar energy systems, in collaboration with Solar Renewable Energy and RETTEW. It appears to be the largest floating solar project currently in North America.
A National Renewable Energy Laboratory report in December 2019 said that floating solar has the potential to supply up to 10% of electricity in the United States. The report estimated that there are 24,000 artificial lakes, ponds and reservoirs that could host floating solar panels throughout the continental United States. It found the greatest potential for floating solar installations in parts of the US where both solar energy and agriculture may be competing for the same land. NREL estimated approximately 2.1 million hectares of land could be saved for agricultural or other uses if solar panels were installed on water instead of on the ground. NREL reviewed land value, evaporation rates and insolation data to identify areas in the continental United States that could be prime locations for floating solar.
Floating solar development in the United States is hampered by the lack of established precedent for issuing permits for floating solar installations. This makes estimating development costs and timelines more difficult.