TODAY’S STUDY: Charting The Emergence Of Floating Solar
Where Sun Meets Water; Floating Solar Market Report
(Solar Energy Research Institute of Singapore)
Why floating solar?
Floating solar photovoltaic (PV) installations open up new opportunities for scaling up solar generating capacity, especially in countries with high population density and competing uses for available land. They have certain advantages over land-based systems, including utilization of existing electricity transmission infrastructure at hydropower sites, close proximity to demand centers (in the case of water supply reservoirs), and improved energy yield thanks to the cooling effects of water and the decreased presence of dust. The exact magnitude of these performance advantages has yet to be confirmed by larger installations, across multiple geographies, and over time, but in many cases they may outweigh any increase in capital cost.
The possibility of adding floating solar capacity to existing hydropower plants is of particular interest, especially in the case of large hydropower sites that can be flexibly operated. The solar capacity can be used to boost the energy yield of such assets and may also help to manage periods of low water availability by allowing the hydropower plant to operate in “peaking” rather than “baseload” mode. And the benefits go both ways: hydropower can smooth variable solar output by operating in a “load-following” mode. Floating solar may therefore be of particular interest where grids are weak, such as in Sub-Saharan Africa and parts of developing Asia.
Other potential advantages of floating solar include:
• Reduced evaporation from water reservoirs, as the solar panels provide shade and limit the evaporative effects of wind
• Improvements in water quality, through decreased algae growth
• Reduction or elimination of the shading of panels by their surroundings
• Elimination of the need for major site preparation, such as leveling or the laying of foundations, which must be done for land-based installations
• Easy installation and deployment in sites with low anchoring and mooring requirements, with a high degree of modularity, leading to faster installations.
An overview of floating solar technology
The general layout of a floating PV system is similar to that of a land-based PV system, other than the fact that the PV arrays and often the inverters are mounted on a floating platform (figure 1). The direct current (DC) electricity generated by PV modules is gathered by combiner boxes and converted to alternating current (AC) by inverters. For small-scale floating plants close to shore, it is possible to place the inverters on land— that is, just a short distance from the array. Otherwise, both central or string inverters on specially designed floats are typically used. The platform, together with its anchoring and mooring system, is an integral part of any floating PV installation.
Currently most large-scale floating PV plants are deployed using pontoon-type floats, with PV panels mounted at a fixed tilt angle. Typically, the floating structure can be made of so-called pure floats or floats that are combined with metal trusses (figure 2). A pure float configuration uses specially designed self-buoyant bodies to which PV panels can be directly affixed. This configuration is the most common. It is available from several suppliers and claims an installed capacity worldwide of several hundred megawatts. Another type of design uses metal structures to support PV panels in a manner similar to land-based systems. These structures are fixed to pontoons whose only function is to provide buoyancy. In this case, there is no need for specially designed floats. The floating platform is held in place by an anchoring and mooring system, the design of which depends on factors such as wind load, float type, water depth, and variability in the water level.
The floating platform can generally be anchored to a bank, to the bottom, to piles, or to a combination of the three. The developer selects a design suitable to the platform’s location, bathymetry (water profile and depth), soil conditions, and variation in water level. Bank anchoring is particularly suitable for small and shallow ponds, but most floating installations are anchored to the bottom. Regardless of the method, the anchor needs to be designed so as to keep the installation in place for 25 years or more. Mooring lines need to be properly selected to accommodate ambient stresses and variations in water level.
The current global market for floating solar
The first floating PV system was built in 2007 in Aichi, Japan, followed by several other countries, including France, Italy, the Republic of Korea, Spain, and the United States…Medium-to-large floating installations (larger than 1 MWp) began to emerge in 2013. After an initial wave of deployment concentrated in Japan, Korea, and the United States, the floating solar market spread to China (now the largest player), Australia, Brazil, Canada, France, India, Indonesia, Israel, Italy, Malaysia, Maldives, the Netherlands, Norway, Panama, Portugal, Singapore, Spain, Sweden, Sri Lanka, Switzerland, Taiwan, Thailand, Tunisia, Turkey, the United Kingdom, and Vietnam. Projects are under consideration or development in Afghanistan, Azerbaijan, Colombia, Ghana, and the Kyrgyz Republic, as well as other countries.
Recently, plants with capacity of tens and even hundreds of megawatts have been installed in China; more are planned in India and Southeast Asia. The first plant larger than 10 MWp was installed in 2016, and in 2018 the world saw the first several plants larger than 100 MWp, the largest of which is 150 MWp. Flooded mining sites in China support most of the largest installations (box 1). With the emergence of these new markets, cumulative installed floating solar capacity and annual new additions are growing exponentially (figure 3).
As of mid-2018, the cumulative installed capacity of floating solar was approaching 1.1 gigawatt-peak (GWp), the same milestone that ground-mounted PV reached in the year 2000. If the evolution of land-based PV is any indication, floating solar could advance at least as rapidly, profiting as it does from all the decreases in costs attained by land-based PV deployment. Most of the installations to-date are based on industrial basins, drinking water reservoirs, or irrigation ponds (figure 4), but the first combinations with hydropower reservoirs, which bring the added benefits of better utilization of the existing transmission infrastructure and the opportunity to manage the solar variability through combined power output, have started to appear (box 2). In these installations, special attention needs to be paid to possible effects on the downstream flow regime from the reservoir, which is typically subject to restrictions related to water management (in case of cascading dams), agriculture, biodiversity, navigation, and livelihood or recreational uses…Marine installations are also appearing…The biggest uncertainties are long-term reliability and cost…
Policy and regulatory considerations
Currently, even in countries with significant floating solar development there are no clear, specific regulations on permitting and licensing of plants. Processes for the moment are assumed to be the same as for ground-mounted PV, but legal interpretation is needed in each country. In some countries, drinking water reservoirs or hydropower reservoirs are considered national-security sites, making permitting more complex and potentially protracted.
As highlighted in this report, floating solar deployment is expected to be cost-competitive under many circumstances and therefore not to require financial support. Nevertheless, initial projects may require some form of support to overcome barriers associated with the industry’s relatively limited experience with this technology.
So far, a number of countries have taken different approaches to floating PV. Typical policies currently supporting floating solar installations can be grouped into two categories:
• Feed-in tariffs that are higher than those for groundmounted PV (as in Taiwan, China)
• Extra bonuses for renewable energy certificates (as in the Republic of Korea)
• A high feed-in tariff for solar PV generally (as in Japan)
• Extra “adder” value for floating solar generation under the compensation rates of state incentives program (as in the U.S. state of Massachusetts).
Supportive governmental policies:
• Ambitious renewable energy targets (as in Korea and Taiwan)
• Realization of demonstrator plants (as in the Indian state of Kerala)
• Dedicated tendering processes for floating solar (as in China, Taiwan, and the Indian state of Maharashtra)
• Openness on the part of the entities managing the water bodies, such as tenders for water-lease contracts (as in Korea).
However, for most countries hoping to develop a well-functioning floating solar segment of a wider solar PV market, the following policy and regulatory considerations need to be addressed:
• Unique aspects of permitting and licensing that necessitate interagency cooperation between energy and water authorities. This also includes environmental impact assessments for floating PV installations.
• Water rights and permits to install and operate a floating solar plant on the surface of a water body and anchor it in or next to the reservoir.
• Tariff setting for floating solar installations (which could be done as for land-based PV, for example, through feed-in tariffs for small installations and tenders or auctions for large ones).
• Access to existing transmission infrastructure: – How will this be managed? – Who will be responsible? – What permits/agreements will be required?
• Special considerations for hydro-connected plants:
– Whether the hydropower plant owner/operator is allowed to add a floating solar installation
– Whether the hydropower plant owner/operator is allowed to provide a concession to a third party to build, own, and operate a floating solar plant
– Management of risks and liabilities related to hydropower plant operation and weather events that can affect the solar or hydropower plants
– Rules of dispatch coordination of the solar and the hydropower plants’ outputs.
There are more than 400,000 square kilometers (km2 ) of man-made reservoirs in the world (Shiklomanov 1993), suggesting that floating solar has a theoretical potential on a terawatt scale, purely from the perspective of the available surface area. The most conservative estimate of floating solar’s overall global potential based on available man-made water surfaces exceeds 400 GWp, which is equal to the 2017 cumulative installed PV capacity globally…There are individual dams on each continent that could theoretically accommodate hundreds of megawatts or, in some cases, gigawatts of floating solar installations…
Costs of floating solar and project structuring… Capital costs…Levelized costs of electricity, including sensitivity analysis…Project structuring…Challenges…
Conclusions and next steps
The deployment of floating solar looks set to accelerate as the technologies mature, opening up a new frontier in the global expansion of renewable energy and bringing opportunities to a wide range of countries and markets. With a global potential of 400 GW under very conservative assumptions, floating solar could double the existing installed capacity of solar PV but without the land acquisition that is required for ground-mounted installations. At some large hydropower plants, covering just 3-4% of the reservoir with floating solar could double the installed capacity, potentially allowing water resources to be more strategically managed by utilizing the solar output during the day. Additionally, combining the dispatch of solar and hydropower could be used to smooth the variability of the solar output, while making better use of existing transmission assets, and this could be particularly beneficial in countries where grids are weak.
When combined with other demonstrated benefits such as higher energy yield, reduced evaporation, and improved water quality, floating solar is likely to be an attractive option for many countries. Although the market is still nascent, there are a sufficient number of experienced suppliers to structure a competitive tender and get a commercial project financed and constructed, and the additional costs appear to be low and are falling rapidly.
The priority over the next few years should be to carry out strategic deployments of floating solar at sites where it is already economic, while applying the “precautionary principle” when it comes to possible environmental or social impacts. This may include initial limits on the portion of the water surface that is covered and efforts to avoid installations in the littoral zone near shore, where plant and animal life may be more abundant. In addition, development of the constituent technologies and knowledge of positive and negative impacts will be greatly enhanced if early installations are diligently monitored, which will entail some public expenditure. The need for monitoring, added to the possible additional capital costs of floating solar over those of ground-mounted systems, makes early installations in developing countries a strong candidate for concessional climate financing.
To support market development, an active dialogue among all stakeholders, public and private, is required to further global understanding of floating solar technologies and to spread lessons learned from early projects across a wider area. Through this market report and an upcoming handbook for practitioners, the World Bank Group and SERIS hope to contribute to this goal, and we look forward to working with governments, developers, and the research community to expand the market for floating solar by bringing down costs, supporting grid integration, maximizing ancillary benefits, and minimizing negative environmental or social impacts.
In addition to the financing of public and private investments, the World Bank Group is committed to supporting the development of floating solar as well as hydro-connected solar by generating and disseminating knowledge. Publications and tools planned for the Where Sun Meets Water series are:
• A floating solar market report
• A floating solar handbook for practitioners
• Global mapping of floating solar potential (a geospatial tool)
• Proposed technical designs and project structuring for hydro-connected solar