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Golroodbari, Sara, Fthenakis, Vasilis and van Sark, Wilfried G.J.H.M. (2022) Floating Photovoltaic Systems. In:
Letcher, Trevor M. (eds.) Comprehensive Renewable Energy, 2
nd
edition, vol. 1, pp. 677–702. Oxford: Elsevier.
http://dx.doi.org/10.1016/B978-0-12-819727-1.00174-6
© 2022 Elsevier Ltd All rights reserved.
1.32 Floating Photovoltaic Systems
Sara Golroodbari
a
, Vasilis Fthenakis
b
, and Wilfried GJHM van Sark
a
,
a
Copernicus Institute of Sustainable Development, Utrecht
University, Utrecht, The Netherlands and
b
Utrecht University, Utrecht, The Netherlands and Columbia University, New York, NY,
United States
r2022 Elsevier Ltd. All rights reserved.
1.32.1 Introduction 677
1.32.2 Global potential, market and economics 679
1.32.2.1 Potential 679
1.32.2.2 Economics 680
1.32.2.2.1 Market analysis 680
1.32.2.2.2 Cost analysis 681
1.32.3 System design 682
1.32.3.1 Technical designs 682
1.32.3.2 Rafts built of plastic and galvanized steel 683
1.32.3.3 Rafts build exclusively of plastic 683
1.32.3.4 Pontoons 685
1.32.3.5 Other components 685
1.32.4 Performance 685
1.32.4.1 Cooling 685
1.32.4.1.1 Immersion cooling 686
1.32.4.1.2 Forced water circulation 686
1.32.4.1.3 Water spraying 686
1.32.4.2 Overview of floating PV performance 686
1.32.4.2.1 Example: Korea water resources corporation 687
1.32.4.2.2 Example: Floating, tracking, cooling, concentrating system 687
1.32.5 Modeling offshore photovoltaics 688
1.32.5.1 Irradiation over tilted surface 688
1.32.5.2 Wave model 689
1.32.5.3 Heat transfer and equilibrium temperature 693
1.32.5.4 Cooling effect and apparent temperature 693
1.32.5.5 Performance differences 694
1.32.5.6 Including dynamic albedo 695
1.32.6 Environmental impacts 698
1.32.6.1 Land, flora & fauna impact 698
1.32.6.2 Construction phase 698
1.32.6.3 Operation stage and decommissioning 698
1.32.6.4 Waste management 698
1.32.6.5 Positive impact 698
1.32.7 The future of FPV 699
1.32.7.1 Hybrid power plants 699
1.32.8 Conclusions 700
Acknowledgments 700
References 700
1.32.1 Introduction
To combat global warming and meet the targets set by the 2015 Paris Agreement, the world will have to rely increasingly on
renewable energy sources. Electricity generation is one sector in which the move towards non-polluting sources can be highly
effective. In the recent World Energy Outlook 2020 of the International Energy Agency (IEA) states that solar photovoltaics (PV) is
the “new king of electricity supply”, in their Net Zero Emissions by 2050 (NZE2050) scenario, which assumes additions of PV to
reach 500 GWp annually by 2030 (International Energy Agency, 2020).
Global energy related CO
2
emissions have been reported to be around 33 Gt in 2019, flattening after 2 years of increase and the
record value of 2018. Renewable energy, mainly wind and PV, will play an important role in decreasing the CO
2
emissions from
Comprehensive Renewable Energy, Second Edition, Volume 1 doi:10.1016/B978-0-12-819727-1.00174-6 677
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the power sector in advanced economies, also in IEA's NZE2050 scenario. The total emissions of the power sector have reached
close to 13 Gt of CO
2
in 2019, a slightly lower level compared to 2018 (1.2% lower) (International Energy Agency (IEA), 2020).
Immediate action is required to reduce to net zero emissions by 2050.
PV presently accounts for about 23% of the total of 2.54 TW globally installed renewable energy technologies (International
Renewable Energy Agency (IRENA), 2020), as a result of fast technological growth and increased investor confidence in PV
installations (International Energy Agency (IEA), 2020), (Choudhary and Srivastava, 2019). As evidenced in other chapters, soon
PV cumulative installed capacity will pass the terawatt mark, continuing the 15–20% annual market growth rate.
Besides deployment of PV modules on and/or in roofs and façades, PV has also reached utility-scale sizes, for which massive
tracks of land are used. While much roof area is not utilized yet, further development of large ‘solar parks’may be hampered by
limited land availability mostly due to land costs. Especially development of large utility-scale PV system installations is limited
due to (i) the cost and availability of land, (ii) decrease of efficiency at high operating PV cell temperatures, and (iii) potential
environmental impact including biodiversity (International Energy Agency (IEA), 2021), (Sahu et al., 2016), (Cazzaniga et al.,
2018), (Ranjbaran et al., 2019). This has prompted the development of floating PV systems (FPV), both on-shore, on inland
bodies of water, and off-shore (Trapani and Millar, 2013;Kougias et al., 2016;Rosa-Clot and Tina, 2018,2020;World Bank
Group, 2019a).
Installation of FPV systems on water firstly saves land which may be otherwise implemented for agricultural use, and secondly the
natural cooling potential of the water body may enhance PV performance. Additional benefits include less shading loss and less dust
compared to land-based PV systems. There are many places around the world that do not have enough land for PV installations, such
as Japan, Singapore, Korea, Philippines, island states such as the Maldives, and demand for FPV is growing at those locations (World
Bank Group, 2019b). Floating solar systems can be installed at water bodies like oceans, lakes, lagoons, reservoir, irrigation ponds,
wastewater treatment plants, wineries, fish farms, dams and canals, also showing the potential for dual use of water bodies.
Moreover, due to the fact that more than 50% of the entire world population lives within 100 km of an oceanic coast an off-shore
FPV system installed at sea can be conveniently located to supply energy to these regions (Wang et al., 2019).
FPV systems are using the same technology as land-based PV, but they differ as they float over water bodies. The design of FPV
support systems is similar to designs used for land-based systems, as these inland water bodies are relatively quiet in terms of wind
and waves. For applications offshore other designs are required. One major efficiency deficit for traditional PV systems is open
circuit voltage loss due to increase in cell temperature. As solar cells “bake”in the sunlight, the cells heat up to a temperature
greater than the surrounding ambient temperature. Solar cells are ‘rated’at 25 1C, and efficiency can typically decrease 0.25–0.5%
for every degree higher than the rated temperature, depending on the used PV technology (Dupré et al., 2017). Thin film
technology has typically lower temperature coefficients than wafer-based silicon technology (Verma et al., 2021). Realistically, in a
relatively hot climate this can equate to 10–25% reduction in power output for silicon-based modules. FPV systems can alleviate
this efficiency loss by operating at cooler temperatures. Although the modules themselves typically do not float on the water
directly, the water is relatively close to the bottom of the modules, and this creates an environment with cooler ambient
temperature. Lower ambient temperature yields lower cell temperature, thus decreasing efficiency loss.
FPV systems are not only beneficial in terms of power output but can also have a positive impact on the environment.
Modules shading the water have proven to decrease algae growth, which may be beneficial for certain water bodies such as
water treatment facilities and irrigation canals (Ranjbaran et al., 2019), (Santafé et al., 2014). The shading aspect of these
systems also limits water evaporation, which is especially beneficial for FPV systems on reservoirs for drinking water or
irrigation systems.
FPV systems can be categorized in three main groups with respect to their supportive structures (Pringle et al., 2017) (1)
submerged: with or without pontoon, including special low weight thin film modules (Trapani and Millar, 2013) and (2) surface
mounted tilted arrays: needs rigid pontoons. Many examples are described in Rosa-Clot and Tina (2018) and Rosa-Clot and Tina
(2020). Performance of systems built between 2007 and 2013 has been reviewed (Trapani, 2014), (Trapani and Redón Santafé,
2015). An overview of these systems is shown in Fig. 1. The common benefits from these installations were identified as (i)
reducing water evaporation from the reservoir/pond on which these systems are located, and (ii) decreased algae growth. It should
be taken into consideration that none of the reviewed research projects was installed at sea or ocean. The following factors may
indicate if an FPV system is designed optimally: modularity, flexibility, robustness, safety, optimum supportive structure size,
simplicity of installation, and minimizing the final costs (Rosa-Clot and Tina, 2018).
The first FPV system was built in 2007, and up until 2018 there were only about 100 notably sized FPV systems in the world.
Spencer et al. (2019) assessed the potential of implementing FPV systems on suitable water bodies in the United States. According
to their criteria, covering 50% of all feasible water bodies in the US with FPV systems would produce about 20% of the country's
electricity demand. The criteria for feasibility takes into consideration ownership (private or public), water depth (5–15 m) and
water bed area (40.25 km
2
). This figure just gives a glimpse into the future growth of FPV implementation.
An in-depth review of the complete FPV sector has been prepared recently (World Bank Group, 2019a), (World Bank Group,
2019b). Finally, FPV installation has been growing very fast, from 2 MWp installed in 2011 to an estimated 2 GWp at the end of
2019 (Rosa-Clot and Tina, 2018), and this fast growth of the sector is expected to continue.
The combination of FPV with hydropower plants has been proposed to be able to provide constant power to the grid (Haas
et al., 2020). It has been reported that hydropower energy production may be increased by 65% when FPV plants are installed on a
mere 10% of the area of 20 largest hydropower reservoirs (Cazzaniga et al., 2019). Such hybrid power plants are also possible in
combination with offshore wind parks (Golroodbari et al., 2021).
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1.32.2 Global potential, market and economics
1.32.2.1 Potential
Rosa-Clot and Tina (2018) have estimated a global potential of FPV systems assuming covering only 1% of global freshwater
surfaces. Total technical potential is very large at 5.5 TWp and could cover about one-quarter of the global electricity demand, see
Table 1. It was noted that many of these surfaces are close to populated areas and consist of lakes, basins for drinking water or
irrigation, wastewater treatment, hydropower basins. Another analysis shows similar potential (World Bank Group, 2019b). Their
analysis of man-made reservoirs and dams only led to total water surface of 404,454 km
2
, or about 10% lower than the analysis in
Table 1 (Rosa-Clot and Tina, 2018). With 10% FPV coverage technical potential is estimated at 4044 GWp. Economical potential is
typically smaller.
When offshore FPV is considered as well, the potential even is much larger. The length of the global coastline is 1.16 million
km, while total ocean surface is 361 million km
2
(CIA, 2021). Assuming a 50 km wide off-shore FPV system, and using 1% of that
coastline, technical potential of off-shore FPV systems could be some 700 GWp, using the same density of 122 MWp/km
2
as used
Fig. 1 Floating PV projects timeline, from 2007 to 2014 (Trapani and Redón Santafé, 2015).
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by Rosa-Clot and Tina (2018). Using only 0.01% of the global ocean surface, FPV potential would be about 44 TWp, which would
generate nearly 50,000 TWh.
As an example of this enormous potential, the Netherlands recently realized that on-shore as well as offshore FPV (and wind)
could play a very important role in supplying renewable power in support of their climate ambitions. A roadmap analysis showed
that off-shore FPV potential would be about 45 GWp, and 24 GWp for in-land floating systems (Folkerts et al., 2021), (Quax et al.,
2021). Total potential is estimated at 237 GWp, including land-based and roof-mounted systems. Floating PV thus would
contribute some 30% to total energy generation in the country.
1.32.2.2 Economics
1.32.2.2.1 Market analysis
Since the first floating photovoltaics system was built in 2007 in Japan, the research and development of those systems has
increased, and as a consequence the market size of FPV systems has dramatically increased. Since the first mid-size (1 MW) FPV
installation in 2013 the market of FPV has boomed. In 2016 the first 10 MW was installed and in 2018 the largest system of
150 MW was installed (see Fig. 2). The cumulative capacity of floating photovoltaics hit 1.1 GWp in 2018 (World Bank Group,
2019b) and is estimated at about 2 GWp at the end of 2020 (Grand View Research, 2019). Fig. 3 shows the growth in cumulative
and annually added FPV capacity up to 2019, as well as the projected ones up to 2027 (World Bank Group, 2019b), (Grand View
Research, 2019). The projections are based on a recent report that estimated the market in 2019 to be 615 MW and expected a
compound annual growth rate of 28.9% between 2020 and 2027 (Grand View Research, 2019).
The initial market was Japan, Korea, and United States. However, the market has expanded to countries such as China
(currently the biggest), Australia, Brazil, Canada, France and India. China has currently installed FPV systems up to hundreds of
MW (World Bank Group, 2019b). Fig. 4 provides information about FPV at the end of December 2018, illustrating that large-size
Fig. 2 Photo of the first 150 MW system in China installed in 2018 by the Three Gorges New Energy Corporation. Total investment was $151
million (Yu, 2017).
Table 1 Global FPV power and energy potential (Rosa-Clot and Tina,
2018).
Climate zones Total water surface Technical potential
km
2
GWp TWh
Tropical 1,254,831 1528 1851
Temperate 1,506,256 1832 2064
Cold 1,789,819 2176 2155
Total 4,550,906 5536 6070
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installations are dominating the total market size, and that 3/4 of the installations are in China, followed by Japan and Korea
(World Bank Group, 2019b).
1.32.2.2.2 Cost analysis
Floating PV is expected to be cost competitive, however initial deployment was very difficult due to the high initial capital
expenditure needed. Many countries have created policies and regulations in order to accelerate the deployment of FPV. These
comprised of feed-in tariffs (China, Taiwan), extra bonuses (Korea), compensation rates of state incentives programs (e.g.,
Massachusetts), renewable energy targets (Korea), subsidies (the Netherlands). The cost of FPV installations are higher than regular
PV ones since typically balance of system (BOS) costs are higher. Total expenditure for FPV systems range from $0.8–1.2 per Wp.
The major differences in the cost analysis of FPV systems compared to land-based PV systems can be split into four categories:
Fig. 3 FPV annual and cumulative installations (GWp) from 2010 to 2027. Data sources: 2010–18 World Bank Group (2019b) ESMAP, SERIS,
Where Sun Meets Water: Floating Solar Market Report. Washington, DC: World Bank, https://openknowledge.worldbank.org/bitstream/handle/
10986/31880/Floating-Solar-Market-Report.pdf (accessed 29 August, 2021); 2019–27 Grand View Research (2019) Floating Solar Panels Market
Size, Share
&
Trends Analysis Report By Product (Tracking Floating Solar Panels, Stationary Floating Solar Panels), By Region, And Segment
Forecasts, 2020–2027, https://www.grandviewresearch.com/industry-analysis/floating-solar-panels-market (Accessed 29 August, 2021).
Fig. 4 Distribution of FPV plants according to their size and country, as of December 2018 (World Bank Group, 2019b).
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1) Surveys: An important factor previous of installing the FPV systems is to conduct the appropriate measurements. Such are:
irradiation measurements, bathymetry, wind and wave intensity, grid connectivity, and naval traffic surveys. These type of
measurements and surveys can range to a cumulative expenditure of $20,000–70,000 per survey.
2) BOS cost: Another important difference is the cost of the balance of systems. The most important addition to the expenditure
are the floating components of the system. According to a major installer of FPV systems, Ciel et Terre, costs vary depending on
the environmental conditions. For standard conditions the cost is $100 per panel while for rigid structures this price goes up to
$200 per panel. For semi-submerged panels the cost is around $50 per panel, while for thin-film panels its under $20 panel.
Moreover, another important factor is the cabling of the systems. The cabling must be water resistant since it will be exposed to
water. Not only are the water-resistant cables more costly, but underwater installation uses expensive equipment.
3) Mooring system: The mooring system is made up from components such as anchors and connectors and is used to keep the
system rigid and at the same location during all-weather conditions. The cost of the mooring systems is about $60 per panel.
4) Installation: The installation of a FPV system is more expensive than that of a terrestrial system. The system in the beginning is
assembled on the ground and then it is moved into the water. For this, special vehicles are used such as ROV's (remotely
operated vehicles) that check the cables locations and the mooring system on the bottom of the water surface. The price of
those vehicles can reach up to $120,000 each.
Comparing a large terrestrial PV system with a FPV system result in 4% increase in the expenditure cost due to the floating
mechanisms. Furthermore, maintenance is very important in FPV systems. Since both terrestrial and floating PV systems require
special types of vehicles for maintenance, the overall operational cost for small systems is the same. However, the bigger FPV
systems are relatively more expensive to maintain (Barbuscia, 2017). As example, the reported costs of an FPV system in Taiwan in
2016 amount to $1269 per kWp (Dizier, 2018)(Table 2).
1.32.3 System design
1.32.3.1 Technical designs
One cannot just take a traditional solar panel and place it on a body of water. There are a few main criteria to take into
consideration when designing and implementing a floating photovoltaic plant. These parameters allow the FPV system to be easily
assembled, maintained, and optimized while reducing its impact on the environment it is implemented (Rosa-Clot and Tina,
2018).
1) Modularity: This relates to the ease of assembling a large FPV plant on land in order to directly launch into water (see Fig. 5)
(Beshilas, 2021). This includes most of the electrical connections being made ready.
2) Flexibility: The FPV should be flexible and open to modifications for optimization of the system. These could include incor-
porating a cooling system, tracking apparatus, etc.
3) Robustness: It is essential for a floating photovoltaics system to withstand the environment where it is implemented. This
includes wind and potential waves, as even small forces could have a large impact on the photovoltaic modules. These stresses
can lead to the formation of cell crack formation, due to rigid PV module inflexibility.
4) Safety: In order to maintain and repair the FPV system, workers must be able to move about the platform to reach all
components while the system is on water. Safety is also a concern in relation to the environmental impact of the system on the
ecosystem around it. The environmental impact of these systems are further explored in a later section.
Table 2 Price breakdown for a 1.1 MWp FPV system in Taiwan, based on internal Ciel & Terre documents.
Category Equipment Cost ($/kWp)
PV modules Modules 600
Balance of system Inverters 200
Floating structures 300
Anchoring 36
Other electrical 100
Installation and labor 150
Transport 20
Cooling system Pump 10
Filter 4
Pipes 6
Sprinklers 5
Monitoring sensors and automation 35
Support and fixation 3
The total price is reported to be $1269 per kWp (Dizier, 2018). We however note that summing of cost for all individual components
leads to $1469 per kWp.
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5) Optimal raft size: Transportation and assembly come into consideration, while also taking into account the ideal module
number and thus, the size of the plant for power output required.
6) Minimum cost: This parameter is key when considering the wide-scale implementation of FPV systems. It is important to take
into account the price of electricity and optimize the system to minimize the cost.
Essentially, the components of a floating photovoltaics system are the same as a conventional land-based systems: PV modules,
cables, electrical connections, and inverters. The main differences are in the floating mechanisms to hold the modules and BOS
must be prepared for exposure to water, see also Fig. 6, and the criteria above. This includes the implementation of a buoyant
platform to support the system, such as a pontoon or floats, as well as mooring systems and anchoring. Three main types of
floating supports are being implemented in many plants today. These include PV modules mounted on: rafts built of plastic and
galvanized steel, rafts built of exclusively plastics, and pontoons. Examples are shown in Fig. 7 and are further discussed below.
1.32.3.2 Rafts built of plastic and galvanized steel
First, PV modules mounted on plastic and steel rafts are discussed. Systems utilizing polyethylene and galvanized steel rafts have
been implemented in plants such as the Suverto plant (200 kWp) and the Colignola (Pisa) plant (30 kWp) for investigating
optimization of FPV designs (Cazzaniga et al., 2018). These systems are particularly successful due to their durability and
flexibility. In 2011 the Colignola plant was created to support three modules and has since been adjusted to implement minor
material modifications to add HDPE (high-density polyethylene) and PVC (polyvinyl chloride) components. The Suverto plant
was connected to the grid in 2011 and was modified in 2014 to improve efficiency by adding a tracking system which allows
rotation of the complete system around a vertical axis (Cazzaniga et al., 2012a).
1.32.3.3 Rafts build exclusively of plastic
This system has further evolved to using rafts exclusively produced using plastics. In 2012, the company Ciel & Terre had created
and implemented an entirely HDPE system of mono-panel, modular rafts. The design had proved to be a large step in the right
direction for FPV systems. This system significantly reduces cost through ease of production and transportation. Installation costs
are also greatly reduced as the modules can be attached at the point of deployment and connected to create a system of any desired
size (Rosa-Clot and Tina, 2018). Since its success, the concept has been widely commercialized, and tens of megawatts have been
installed including competitors modular rafts. However, the overall PV plant faces issues when undergoing various stresses from
wind/waves and the flexibility of retrofitting optimizations are extremely difficult. The robustness of this system falls significantly
behind the plastic/steel raft structure. Also, pontoons are a rather expensive option, and they are mainly used for small and
medium size systems.
Fig. 5 FPV installation in Walden, Colorado. Photo by Dennis Schroeder, NREL, 2019 Beshilas L (2021) Floating Solar Photovoltaics Could Make
a Big Splash in the USA, NREL Blog.https://www.nrel.gov/state-local-tribal/blog/posts/floating-solar-photovoltaics-could-make-a-big-splash-in-the-
usa.html#:B:text=A%20floating%20solar%20photovoltaic%20%28FPV%29%20system%20is%20an,opposed%20to%20on%20land%20or%20on
%20building%20rooftops (Accessed 30 August, 2021).
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1.32.3.4 Pontoons
Lastly, pontoon systems are also utilized. These systems are normally small to medium sized plants, with special attention to
robustness. Due to the multipurpose use of pontoons, the support system is not specifically optimized for supporting FPV. Thus,
this option has fallen behind due to the promising nature of raft systems. Beyond systems being currently implemented, there are
many innovative solutions arriving in the field. One of the promising ideas include linking modular rafts to create a strong but
flexible system using recycled tires, with one pipe supporting the PV modules along its length. This support also attempts to tackle
an immense waste issue that our world faces and reusing it as a very cheap and effective alternative. The absence of a rigid structure
allows the plant to experience less stress when facing wind and waves due to flexibility. Off-shore implementation of these systems
is extremely promising for the future of FPV.
1.32.3.5 Other components
In addition to the raft systems employed, multiple plastic hollow floats are needed which guarantee the buoyancy and stability of
the FPV system. They are either made from MDPE (medium density polyethylene) or HDPE, which is known for its tensile
strength, maintenance free, and UV and corrosion resistance. Glass fiber reinforced plastic (GRP) can also be used for construction
of floating platforms (Sahu et al., 2016), (Santafé et al., 2014).
A mooring system is needed that can adjust to water level fluctuations while maintaining its position in a southward direction
(Sahu et al., 2016), (Choi, 2014a). In the case of a floating solar system, the mooring system keeps the panels in the same position
and prevents them from turning or floating away (Sahu et al., 2016), (Sharma et al., 2015). The mooring system can be done with
nylon wire rope slings which can be tied to bollards on banks and lashed at each corner (Sahu et al., 2016), (Santafé et al., 2014).
An anchoring system holds the floating system in place and transmits horizontal forces to the sides of the reservoir.
While typically crystalline silicon solar PV modules are used (Sahu et al., 2016)asflat and rigid modules (Cazzaniga et al.,
2017), (Cazzaniga et al., 2012b), also thin film flexible modules can be used (Trapani et al., 2013), (Trapani and Millar, 2014). For
offshore deployment, new designs should be considered to address metal corrosion especially over salty water.
Cables, MPPT converters, and other electronics needed in an FPV system need to be protected from humidity and water. For
devices in an FPV system it should always be taken into consideration that the ingress protection (IP) code should be high enough.
In (Sahu et al., 2016) IP67 is recommended. Note that the first digit in the IP code refers to protection against solid particles, and
the second one refers to protection against water and humidity. For instance in case of IP67, this means the device is both dust
tight and can be immersed in water up to 1 m depth. For IP68 other than being dust tight the device can be immersed deeper than
1 m. In many FPV systems, cabling is implemented above water (Sahu et al., 2016). However, with an appropriate design the
system could have cables under water.
Finally, especially in regions with high penetration of distributed generation, energy storage may be required to reduce
inadvertent stress on the grid and provide an additional service for the regional grid (Cazzaniga et al., 2017), (Bussar et al., 2016).
Although the main storage system for FPV is a battery pack, there are some other methods introduced, such as water/seawater
pumped storage (Manfrida and Secchi, 2014) and Compressed Air Energy Storage (Cazzaniga et al., 2017). These non-battery
storage systems could be also effective in decreasing the load on the transmission grid.
1.32.4 Performance
1.32.4.1 Cooling
Another unique and promising aspect of floating PV systems is the ease of implementation of water cooling technologies. Solar
cells in PV module face a decrease in efficiency when exposed to higher temperatures due to higher intrinsic recombination losses
at increased temperatures (Dupré et al., 2017). Small cell material specific variations exist, but the overall maximum power of a
module is linearly related to the temperature and irradiance (Verma et al., 2021). Active cooling has been studied in the past using
water in order to decrease the temperature that the panel experiences. For example, Prudhuvi and Sai showed an increase of
module energy generation by 7.75% when the module was covered with a thin layer of water over the solar panel front (Prudhvi
and Sai, 2012). These cooling techniques could be more easily implemented as the panel is already surrounded by water. The
following equation can be used to model the usual hourly energy (E
usual
) in watt-hours generated by a panel,
Eusual ¼Pref Ehourly
Eref
1þbTpanel Tref
tð1Þ
where P
ref
is the reference wattage of the panel in watts. The reference power is scaled with the current irradiance, E
hourly
, and the
reference irradiance, E
ref
, with units of watts per meter squared. The temperature adjustment is calculated using the panel
temperature, T
panel
, and the reference temperature, T
ref
. The temperature coefficient, b, depending on the type of panel utilized for
the system based on findings from Skoplaki and Palyvos, with mono-crystalline silicon being between 0.3%/K and 0.5%/K,
and polycrystalline to be about 0.4%/K (Skoplaki and Palyvos, 2009). Sample time tis set at 1 h. It can be seen that as the panel
temperature is decreased, the output energy of the panel is increased. By replacing the temperature of the panel with the
temperature of a cooled panel, T
cooled
, the energy output, E
cooled
, of that panel can be calculated, in watt-hours. To reach these cooler
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temperatures, there has been a lot of current research in the field of active water cooling technologies. The main contenders include
immersion cooling, forced water circulation, and water spraying (Dwivedi et al., 2020).
1.32.4.1.1 Immersion cooling
This involves the immersion of solar panels in a small depth of water. High efficiency improvements can be achieved using this
approach. Results have shown an increase of 17.8% of electrical efficiency when incorporating water with a depth of 1 cm
(Mehrotra et al., 2014). This technique has a low environmental impact, however, it has been proven extremely difficult to
implement it into floating PV systems due to the requirement of waterproofing the entire system. Nevertheless, Reduction in
temperatures have been seen up to 40 1C, depending on water depth (Dizier, 2018).
1.32.4.1.2 Forced water circulation
This technique involves the implementation of coolant thermal pipes mounted on the back of a solar panel. The overall efficiency
of this system is dependent on the pipe material heat transfer properties (Wu et al., 2011). The main disadvantage of this system is
the high installation and material costs, thus making them non-ideal for large floating PV plants. Reduction in temperature is
usually around 20–30 1C.
1.32.4.1.3 Water spraying
Using a pump sprinkler system, water is sprayed onto the front of the PV modules. Several studies mention the success of this
technique showing an electrical efficiency of up to 15% in high solar irradiance locations (over 1000 W/m
2
)(Salih et al., 2014). As
this may be difficult for a land-based system to pump water over a distance to reach the panels, a floating PV system is in the
perfect spot for this implementation. This reduces cost associated with the transport of water to almost zero and could be an easy
modification for existing systems. Maximum reduction in temperature is about 30 1Cor221C depending if it is sprayed on both
sides or just the front, respectively (Dizier, 2018).
1.32.4.2 Overview of floating PV performance
As FPV is a relatively new branch in PV technology, high quality performance data is scarce. Results presented here are taken from
Ref. (International Energy Agency (IEA), 2021). An early overview of FPV designs provided estimates of B10% larger energy yields
compared to similar installations on land (Trapani and Redón Santafé, 2015), which is explained by the cooling effect of the
underlying water body leading to lower PV module temperatures. Also, it was reported that the average efficiency of an FPV system
in Korea is 11% larger compared to a land-based PV system (Choi, 2014a).
As one of the first attempts to provide detailed performance data the Singapore Tengeh Reservoir test-bed has been developed
(Liu et al., 2018). In this test-bed, eight different commercial FPV technologies have been installed, and rigorous monitoring has
been performed to study the potential cooling effect depending on the specific technology. Also, environmental impact studies
have been performed, i.e., water evaporation and biodiversity. Fig. 8 shows an aerial photograph of the test-bed. A reference system
was installed on land. Main findings are that ambient temperatures over water typically are 2–31C lower than on land, while wind
speed on water is generally higher (Liu et al., 2018), (Reindl, 2018a). Also, humidity above water is higher, and albedo on water is
Fig. 8 Aerial photograph of the Singapore Tengeh Reservoir test-bed with different FPV technologies (Reindl, 2018b).
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considerably lower (0.05–0.07) than on land (0.10–0.14). This leads to module temperatures that are about 5 1C–10 1C lower
than similar modules mounted on rooftops. As a result, annual performance ratios are found to be 10–15% larger than typical PR
(75–80%) of rooftop systems in Singapore.
Fig. 9 shows PR for the nine systems, from April 2017 to March 2018 (Reindl, 2018a). Differences are mostly due to differences
in cooling which depends on floating structure, location within the platform, and weather conditions. PR of system A is low due to
excessive bird droppings and system B suffered from inverter downtime. The very high PR of the reference system is caused by the
installed bi-facial modules which were also well ventilated. Two FPV systems consisted of bi-facial modules, but no clear
advantage is seen, due to the much lower albedo on water than on land.
Recent reports on FPV at the west coast of Norway shows similar energy yield advantages of 5–10% larger yield for an FPV
system in direct contact with water compared to an comparable air-cooled FPV system (Seij et al., 2019)(Kjeldstad et al., 2021). A
theoretical study for an FPV system with horizontally placed modules on the North Sea shows B4% larger annual PR compared to
a land-based system, where it is noted that this is due to cooling of the modules, and the effect of waves is limited, although
weather and wind patterns have been considered (Golroodbari and van Sark, 2020); also see next section. Another theoretical
study shows that energy loss to moving modules due to waves can range from 3% for medium wave intensity up to 9% for extreme
wave intensity (Dörenkämper et al., 2019).
In summary, it can be concluded that FPV systems will show higher energy yields compared to similar systems on land, but this
depends on the type of modules and the specific FPV design. Obviously, more measurements combined with modeling are
needed. Even small-sized experiments can be useful in this respect (Kumar and Kumar, 2019). Of special interest will be the effect
of (salty) water on long-term reliability.
1.32.4.2.1 Example: Korea water resources corporation
Two research FPV systems have been installed on the Hapcheon dam water reservoir by Korea Water Resources Corporation
starting already in 2011. The 100 kWp system was the first FPV demo system on a dam reservoir in the world. Both systems are
built up using 240 Wp c-Si modules and these are tilted by 33 degrees; actual installed capacity is 99.36 kWp and 496.8 kWp. The
performance has been compared to a 1 MWp land-based PV system on a location 60 km southeast from Hapcheon, with similar
irradiance and temperature. The land-based system comprises 250 Wp modules, tilted by 30 degrees (Trapani and Redón Santafé,
2015), (Choi, 2014a), (Suh et al., 2020).
Three years of monthly yield data are shown in Fig. 10 (Suh et al., 2020). The annual yields were 1297, 1364, and 1260 kWh/
kWp, for 2012, 2013, and 2015, respectively. The land-based system showed an annual yield of 1272 kWh/kWp (for 2012), which
would lead to a 2% benefit for the floating system. However, due to missing data, blackouts, maintenance and data errors, only
half of the days in 2012 were useful for comparison. As a conclusion, it was found that the FPV system has 13.5% higher yield than
the land-based system, which was attributed to the cooling effect of the water. This has been found to be more apparent in spring
and summer.
1.32.4.2.2 Example: Floating, tracking, cooling, concentrating system
A special type of FPV systems denoted as Floating, Tracking, Cooling, Concentrating (FTCC) systems have been developed and
deployed in Italy, a 30 kWp pilot system near Pisa and a 200 kWp grid-connected one in Livorno (Cazzaniga et al., 2012b). This
includes reflectors on horizontally placed modules on a platform that is supported by polyethylene tube, and also allows for
Fig. 9 Performance ratio of the FPV systems in the test-bed. Typical PR for rooftop systems in Singapore is indicated by the blue dashed line,
data from (Reindl, 2018a), (Reindl, 2018b).
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efficient tracking around a vertical axis (Koiné Multimedia, 2021)(Fig. 11). The system also includes a cooling system for modules,
which is reported to increase energy yield by 15%. The FTCC system performance is reported to be 30% larger than a similar land-
based PV system. A 30 kWp FTCC system was also installed in Cheongju-si, Korea (Kim et al., 2016).
1.32.5 Modeling offshore photovoltaics
Modeling the energy yields of an FPV system in essence is not different from that of land-based systems, however cooling effects
will be different. Also, the floating systems are prone to wave motion which may lead to dynamical tilt and azimuth changes. This
is especially the case for offshore systems where waves are much higher than on inland basins.
In the modeling example shown here, we assume the FPV system to be installed on a pontoon (as in Fig. 7B), therefore, both the
tilt angle and the azimuth may vary, albeit slightly. First, we will discuss the irradiation on the tilted surface. Instead of angular
reflection losses, we are going to model the system more precisely and calculate the tilt angle for each time interval, because the
angular reflection is a function of both latitude and tilt angle (Martin and Ruiz, 2005). Second, we need to model the wave motions
based on the wind characteristics. Here we assume that the FPV system is installed in a specific region at the North Sea, in front of the
Dutch coast. Third, heat transfer and the apparent temperature method are described,in which the effects of bothwind and humidity
on temperature change are considered. Finally, the effect of dynamic sea surface albedo s ¼is compared to constant albedo.
1.32.5.1 Irradiation over tilted surface
Global irradiation on a tilted surface (GTI) is calculated as follows:
GTI ¼DIRjþDIFjþRjð2Þ
where DIR
j
,DIF
j
, and R
j
are direct, diffuse, and reflective irradiance components, respectively, and j¼{b,g} with bis surface
tilt angle and gis azimuth angle. Direct tilted irradiance DIR
j
is calculated as follows:
DIRj¼Bhrbð3Þ
Fig. 10 Three years of monthly yield data for the 100 kWp FPV system at the Hapcheon dam water reservoir. Data from Suh J, Jang Y and Choi
Y (2020) Comparison of electric power output observed and estimated from floating photovoltaic systems: A case study on the hapcheon dam,
Korea. Sustainability 12: 276.
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where B
h
is direct normal irradiance (DNI), and r
b
is the direct irradiance conversion factor and calculated via
rb¼max 0;cos y
cos yz
ð4Þ
with
cos y¼cos yzcos bþsin yzsin bcos gsgðÞ ð5Þ
where y
z
and g
s
are solar zenith and azimuth angles.
Many models have been developed to calculate diffuse tilted irradiance DIF
j
. Their main difference is coming from the fact that
these consider the diffuse irradiance being isotropically distributed over the sky dome or not. In this study we assume the
anisotropic model called Klucher model (Klucher, 1979). DIF
j
in this model is estimated via the following equation:
DIFj¼DhRdif for Rdif 0ð6Þ
where D
h
is diffuse horizontal irradiance (DHI), and R
dif
is calculated via the following formula:
Rdif ¼Rd;L;J1þfKcos2ysin3yz
1þfKsin3b
2
ð7Þ
where R
d,L,J
and f
K
are the Liu-Jordan isotropic model diffuse irradiance transposition factor and and the Kluchers conversion
factor, defined in Eqs. (8) and (9), respectively:
Rd;L;J¼1
21þcos bðÞ ð8Þ
fK¼1Dh
Gh
2
ð9Þ
in which G
h
is GHI.
The classical approach to the modeling of the reflected irradiance R
j
assumes that reflected rays are diffuse and coefficients of
reflection of the direct and diffuse rays are identical (Gulin et al., 2013):
Rj¼rGhRhð10Þ
where ris the foreground albedo, which is taken as a constant and equals 0.06 for the sea surface (Payne, 1972) and
Rh¼1
21cos bðÞis the transposition factor for ground reflection.
1.32.5.2 Wave model
Each wave can be seen as a combination of many small waves with different characteristics. Thanks to Joseph Fourier (1768–1830)
for developing Fourier decomposition, all complex wave forms can be reproduced with an infinite sum, or series, of simpler
functions. Mathematically, the complex wave W(t) in the time domain can be described as:
WtðÞ¼ X
1
k¼1
Akcos oktþyk
ðÞ ð11Þ
Fig. 11 Floating, tracking, cooling, concentrating systems, (A) Colignola-Pisa, Italy (Cazzaniga et al., 2012b), (B) Cheongju-si, Korea (Koiné
Multimedia, 2021).
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where A
k
is amplitude (or Fourier coefficient), o
k
is angular frequency, and y
k
is phase angle. Fig. 11 shows a simple example
for wave decomposition; the wave in the bottom box, denoted by f(t) in the figure, is the final wave which results from the
summation of all single frequency waves (d
1
to d
8
) with characteristics shown in the above subplots, where it can be seen that the
wave frequencies are increasing from the first to the eight component. Note, A
k
values differ slightly from each other. It is quite
complicated to study the wave in the time domain, which is why in this study we discuss wave characteristics in the frequency
domain. This so-called wave spectrum will be discussed in the following (Fig. 12).
Wind is mainly responsible for wave generation at sea. A wave can be described using frequency f, wavelength l, Time Period T,
amplitude aand height H, which is double the amplitude. In this model we considered wave energy and its conversion to force.
The amount of force from a wave may move the pontoon and is responsible for the (dynamic) tilt angle of the panel surface.
The energy density and power density of a harmonic wave can be calculated from the following equations (Muetze and Vining,
2006):
Ehw ¼rwater gH2
8¼rwater ga2
2;Phw ¼Ehw
Tð12Þ
where gis gravitational constant (9.81 m/s
2
). According to linear wave theory, wave energy per unit crest width (J/m) for a specific
wave is calculated as follows:
E¼rgH2l
8ð13Þ
Maximum power (W/m) under ideal conditions is proportional with the calculated energy and per meter of the wave front and
is equal to:
Pideal ¼rg2H2T
32pð14Þ
However, obtaining these parameters for irregular waves or real waves should be calculated in a different way. To this end, the
wave characteristics at fully developed open seas are generated by the so-called Joint North Sea Wave Project (JONSWAP) spectrum
as shown in Eqs. (15)–(17) (Hasselmann et al., 1976), (Yu et al., 2017). This spectrum is a fetch-limited wind wave spectrum,
which was developed for the North Sea by the offshore industry and is used extensively. The elevation S(o) of (linear) fully
developed open seas is described as:
SoðÞ¼ag2
o2exp 5
4
op
o
4
gfð15Þ
with
Fig. 12 Wave decomposition. The wave in the bottom box is composed of the waves shown in the eight top boxes.
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r¼exp 1
2
oop
sop
ð16Þ
a¼5:061 op
2p
4Hs10:287log g½ ð17Þ
where o
p
is peak spectrum angular frequency, gis a peak enhancement factor, H
s
is significant wave frequency, and parameter
s¼0.07 for ooo
p
and s¼0.09 for oZo
p
.
For a real wave, which does not consist of only one sinusoidal wave with one frequency, the wave energy and maximum power,
per unit meter, respectively are:
E¼rgZ1
0
SoðÞdð18Þ
P¼rgZ1
0
vgSoðÞdð19Þ
where v
g
is group velocity. For deep water conditions v
g
¼g/2o(Ásgeirsson, 2013). Using this and knowing the weight and
dimensions of the pontoon the tilt angle of the pontoon as a function of time can be estimated. Let us assume that the energy from
wave is transferred to rotating kinetic energy E
R
which can rotate the pontoon e.g., about an axis in line with its length.
ER¼1
2Io2
rð20Þ
where Iis moment of inertia, and o
r
is angular velocity for the pontoon. Fig. 13A and B depict the rectangular pontoon with
length, width and height of a,b, and c, respectively. In the following, first we discuss how to calculate the moment of inertia and
then explain how to use it for calculating the tilt angle.
T
Fig. 13 Wave interaction with pontoon. (A) Pontoon dimensions, (B) Pontoon at sea level, (C) Torque ttouches the pontoon and tries to rotate
it around the shown axis, (D) Pontoon rotated by y, (E) Coordinates and the pontoon dimensions (Golroodbari and van Sark, 2020).
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The definition for moment of inertia is:
I¼Zm
0
r2dm ð21Þ
where mis mass of substance, and ris the radius from the axis. It is assumed that the pontoon is symmetrical regarding the z
axis shown in Fig. 13E. Now, let us assume that the coordinates are chosen such that the point z¼0 is at the middle of the
pontoon's height. A small rectangle inside the pontoon is considered while its normal vector is parallel with the yaxis (rotational
axis) and its radius from that axis is r. Based on these assumptions we have:
dm
dxdz ¼m
bc ð22Þ
Which is used to rewrite Eq. (21) to:
I¼2I1=2¼2Zb
0Zc
2
0
m
cb x2þz2
dzdx ð23Þ
By solving this, the moment of inertia for the described pontoon and the rotating yaxis is calculated as follows:
I¼1
3mb2þ1
12 mc2ð24Þ
The moment of inertia for the pontoon such that the rotating axis is assumed to be on the xaxis is:
I0¼1
3ma2þ1
12 mc2ð25Þ
For the assumed rectangular pontoon, we have:
a¼5b
&
acc
&
bcc)I0
C
5I ð26Þ
Therefore, comparing to rotation around the yaxis, rotation around the xaxis is negligible, for a cb. Thus, in this article, as
shown in Fig. 13C, we only consider 2D motion for the pontoon and once the wave crest touches the pontoon, a perpendicular
force makes a torque tas follows:
t¼F
!r1
!;r1¼bð27Þ
thus trying to rotate the pontoon clockwise, as shown in Fig. 13D, which shows a change in tilt of y.
Fig. 14 shows that the wave forces move while the wave is moving forward. Therefore, for simplicity we assume that lZb.
Thus, the sequence of variation of ycan be described as follows:
a) When the crest of the wave touches the pontoon as shown in Fig. 14A, torque is calculated using Eq. (27), which causes the
pontoon to rotate clockwise at an angle y.
b) The wave moves forward and touches the middle of the pontoon, this situation can be translated using linear algebra to the
following equation,
t¼F
!r1
!þr2
!
;r1¼r2¼b
2ð28Þ
c) Due to the symmetrical characteristics of the pontoon the vectors r1
!and r2
!are in opposite direction and have equal
magnitude so the total torque is equal to zero, which means that the normal vector for the pontoon at this scenario is p/2 and
the pontoon makes an angle of y¼0.
d) This situation is similar to (a), but r2
!is in the opposite direction which makes the pontoon to rotate anticlockwise at angle y.
In comparison with (a), the absolute value of the tilt angle is the same, but the orientation of the pontoon is different.
The approach described here has been applied on a pontoon (Fig. 7B) floating in the North Sea. Golroodbari and van Sark
(2020) showed that tilt angle variations are related to wind speed, as would be expected from the above, but they are restricted to a
maximum of 20 degrees. Fig. 15 shows tilt angle variations for 31 days in August 2016. For most of the days the sea is calm and tilt
Fig. 14 Force and radius vector in different positions when a wave crest touches for the first time (A) the left side (B) middle, and (C) right side,
of the pontoon (Golroodbari and van Sark, 2020).
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angles vary only slightly between 0 and 3 degrees. For some days tilt angles exceed 10 degrees, and only for 1 day they reach 20
degrees. This is highly correlated with wind speed variation.
1.32.5.3 Heat transfer and equilibrium temperature
In the FPV system the pontoon is constantly in contact with the sea water. Here we use steel as material for the pontoon. A land-
based PV (LBPV) system, which is assumed to be made exactly with the same material and of the same size is in contact with air.
The heat transfer in these two systems is discussed here.
We will use the concept of equilibrium temperature T
Eq
, which is the temperature after heat transfer from the PV side to the
fluid side, which might be either water or air. Calculating this value needs some consideration for the PV side temperature, which is
not measured, therefore, we estimate the operating temperature of a PV cell T
c
using the Servant correlation (Servant, 1986); it can
be written as:
Tc¼Taþa1þbTa
ðÞ1gvðÞGTI ð29Þ
where T
a
is ambient temperature, v is wind speed, and a,b, and gare constants that depend on the specific PV module structure.
We need to solve the thermal equilibrium problem between the pontoon/platform and the fluid around these. We first have:
mpcpDTp¼mfcfDTfð30Þ
where m
p,f
is mass of substance, c
p,f
is heat capacity and DT
p,f
is temperature difference. Indices p,fdenote pontoon/platform
and fluid, respectively. The formula can be rewritten as follows, with T
Eq
the equilibrium temperature:
mpcpTcTEq
¼mfcfTEq Tf
ð31Þ
It should be taken into consideration that the PV panels after heat transfer perform at the equilibrium temperature, obviously
in equilibrium T
Eq
¼T
c
¼T
f
. Note that due to the large heat conductivity of steel the heat transfer rate is large.
1.32.5.4 Cooling effect and apparent temperature
The recorded ambient temperature alone is not sufficient for performance analysis, as is evident from the Servant correlation
(Servant, 1986) that also takes into account the effect of other weather conditions, e.g., wind speed and humidity. For example, in
Huld and Gracia-Amillo (2015) the PV performance all over the world is studied considering the wind speed effect as well as
ambient temperature and local irradiation. However, in this article a more generic overview is needed which is why the effect of
humidity is also considered. We therefore use the so-called apparent temperature.
In Jacobs et al. (2013) the following equation is implemented to incorporate the effects of air temperature, humidity and wind
speed:
TA¼Tdb þ0:33pv0:7v 4ð32Þ
Fig. 15 Calculated tilt angle variation of the pontoon for all days in August 2016 [Gol].
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where T
A
is apparent temperature (1C), T
db
is dry bulb temperature (1C), v is the wind speed at 10 m height (m/s) and p
v
is the
vapour pressure of air (hPa) and can be computed from Steadman (1994):
pv¼exp 1:8096 þ17:69D
273:15 þD
ð33Þ
where D(1C) is dew point temperature computed from the simple approximation formula,
D¼T100 RH
5ð34Þ
where RH is the relative humidity, where it is assumed that RH is larger than 50% (Lawrence, 2005). In this work, the apparent
temperature is implemented as the effective temperature rather than to consider not only bulb dry temperature, but wind speed
and relative humidity as well.
In the study of Golroodbari and van Sark (2020) equilibrium and ambient temperatures for both the offshore FPV and land-
based PV systems have been calculated. Fig. 16 shows the monthly variations using box plots, also including sea surface tem-
perature. It is clear that all temperatures follow a similar trend during the year. However, the difference between the equilibrium
and ambient temperature for the offshore FPV system compared to the land-based PV system is significant. The figure shows that
the sea surface temperature is close to the FPV system equilibrium temperature, as can be expected on the basis of heat transfer
theory and the fact that the FPV system is in contact with the water body. On average, the land-based system temperature is found
to be nearly 30% larger than the FPV system temperature. Also, the variation of the equilibrium temperature for the FPV system is
much smaller than the variation for the LBPV system, which can be inferred from the narrower box plots.
1.32.5.5 Performance differences
To compare energy yield differences for the FPV and LBPV systems, GTI calculations are required. For the land-based system a
constant tilt of 0 degrees is used, while a varying tilt is used for the FPV system (example shown in Fig. 15). Golroodbari and van
Sark (2020) used the wave spectrum values for all days of the year 2016 for the North Sea, as well as irradiance and ambient
temperature of that year. Fig. 17 shows a bar chart of the output energy for the year 2016 on the left axis, and on the right axis the
relative difference between output energy thus comparing a land-based and a sea-based PV system. It illustrates that the FPV system
in all months performs better compared to the land-based system. The highest difference is seen for the month June where the
energy yield of the FPV system is 6% higher than the energy yield of the land system. In January both systems perform quite
similarly, and the relative difference is only almost 2%. The annual yield for the LBPV system is 1192 kWh/kWp, which is 12.96%
less than for the offshore FPV system which yields 1346 kWh/kWp in this year. However, it should be taken into consideration that
the GHI is not similar in both locations, in fact, GHI is about 8.54% higher at the offshore FPV location. Note further, that the year
2016 was an exceptional year with a 5% higher annual irradiance than the 30-year average. To account for differences in
Fig. 16 Equilibrium and ambient temperature for both the FPV and LBPV system, and sea surface temperature, for the year 2016 (Golroodbari
and van Sark, 2020).
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irradiation, we calculate the performance ratio, using the following equation:
PR ¼Yf
Yrð35Þ
where Y
f
is final system yield from PV panel and Y
r
is reference yield. It is found that the average PR for the LBPV during the year
2016 is 81.66%, while PR is 3.15% larger at 84.75%. or nearly 4% higher. For most months PR values differ, which clearly reflects
the temperature differences that occur in both systems.
1.32.5.6 Including dynamic albedo
The classical approach to the modeling of reflected irradiance R
f
assumes that reflected rays are diffuse and coefficients of
reflection of the direct and diffuse rays are identical (Golroodbari and van Sark, 2020), (Ineichen et al., 1988). Therefore, R
f
is
calculated as follows:
Rf¼aGhRhð36Þ
where aA[0,1] is the surface albedo, and R
h
¼0.5(1 cos b) is the transposition factor for ground reflection, with bthe
panel tilt angle (Ineichen et al., 1988). In most assessments of PV energy yield, albedo is kept constant, also in the analysis above.
However, here we aim to quantify the variation of the albedo for the ocean surface, which provides more accurate modeling of
energy yield of floating offshore PV systems (Golroodbari and van Sark, 2020).
Albedo is defined as a non-dimensional, unitless quantity that indicates how well a surface reflects solar energy. In the oceans,
the fraction of solar radiation penetrating the subsurface is controlled by the ocean surface albedo (OSA, a
OS
)(Séférian et al.,
2018). Despite its importance, OSA is a parameter that receives insufficient attention from both an observational and modeling
point of view and in most studies, it is assumed to be a constant (a
OS
C0.06 ) for the open ocean surface (Payne, 1972). It is
indicated that the solar zenith angle (SZA, ζ) is the most prominent driving parameter for OSA. Hourdin et al. (2013) developed
the following non-constant albedo model as part of an atmospheric general circulation model:
aOS ζðÞ¼ 0:058
cos ζþ0:30 ð37Þ
Hence, a
OS
varies between 0.0446 for a sun at zenith and 0.1933 for a sun at the horizon. However, other parameters such as
wavelength of ocean surface roughness, and atmospheric and oceanic properties also are of influence on a
OS
(Séférian et al., 2018),
(Jin et al., 2011).
Albedo commonly refers to the “whiteness”of a surface, with 0 meaning black and 1 meaning white. In the oceans, the fraction
of solar radiation penetrating the subsurface is controlled by the ocean surface albedo. We can separate the ocean surface albedo
into direct a
OS,DIR
and a
OS,DIF
contributions (Jin et al., 2011):
aOS ¼aOS;DIR þaOS;DIF ð38Þ
Given the wind speed, surface roughness and zenith angle a
OS,DIR
and a
OS,DIF
can be calculated explicitly. A mathematical
model developed by Cox and Munk (1954) is implemented here which estimates a function to parameterize the mean con-
tribution of multiple reflective facets at the ocean surface.
Fig. 17 Normalized energy yield in kWh/kWp for the offshore FPV and LBPV systems (right axis), and relative output difference (left axis)
(Golroodbari and van Sark, 2020).
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We will first describe the effect of wind speed on surface ocean albedo. Gordon and Jacobs (1977) separate the effect of wind
speed in two different and opposite effects: (i) the albedo of the surface decreases only slightly with increasing wind speed which
leads to increased roughness, and (ii) increasing the wind speed over the ocean results in another process which increases the
surface albedo: the formation of white caps. The effect of wind is not a simple linear effect.
The incident direct and diffuse solar radiation is first influenced by the presence of whitecaps, which have different reflective
properties than seawater. Second, the reflective properties of the uncapped fraction of the sea surface are determined separately for
direct and diffuse incident radiation (Séférian et al., 2018). At this point, we neglect the effect of the subsurface or the ocean
interior.
The fraction of whitecaps f
WC
can be calculated from the disturbance coming from the breaking of waves due to the wind. This
turbulence generates foam on the sea surface which can change the albedo considerably (Séférian et al., 2018), (Frouin et al.,
1996). Salisbury et al. (2014) have suggested the following equation for f
WC
as a function of wind speed vfor (vA[2,20] m/s) at a
height of 10 m above the sea surface:
fWC vðÞ¼3:97 102v1:59 ð39Þ
Whitlock et al. (1982) proposed a polynomial relationship for solar spectral dependence of the albedo as a function of the
fraction of whitecaps:
afWC lðÞ¼0:005 X
4
i¼0
ailn aWlðÞðÞ
Ið40Þ
with a
04
¼(60.063,–5.127,2.799,–0.713,0.044) and where a
W
is the absorption coefficient of clear water in m
1
. Values for
a
W
(l) are published for 400 olo2400 nm (Séférian et al., 2018), (Whitlock et al., 1982).
A calm sea surface reflects the sun like a mirror at the horizontal specular point. However, usually there are thousands of
“dancing”highlights. At each highlight there is a water facet, possibly quite small, which is inclined in such a way that it reflects an
incoming ray from the sun towards the observer (Cox and Munk, 1954). Sea surface roughness s
S
is estimated depending on wind
speed vas follows:
s2
S¼0:003 þ0:00512v ð41Þ
The major components of a
OS
are described by the Eqs. (42)–(44) below, and are the contribution of Fresnel reflection at the
ocean surface:
aOS;DIR l;ζ;oðÞ¼rFnlðÞ;mðÞ
rFnlðÞ;mðÞ
rFn0;mðÞ
fm;sðÞ ð42Þ
in which n(l) is the wavelength dependent refractive index of seawater, parameter m¼cos ζ,r
F
is the Fresnel reflectance for a
flat surface and f(m,s) is a function that accounts for the distribution of multiple reflective facets at the ocean surface estimated in
the visible spectrum (VIS). Values for variable n(l) are extracted from Séférian et al. (2018) and Jin et al. (2011). Also, it is assumed
that n
0
¼1.34 calculated from the refractive index of seawater averaged in the VIS.
The function f(m,s) is found from multiple regression by Jin et al. (2011) as follows:
fm;sðÞ¼0:015221:7873mþ6:8972m228:5778m3þ4:071s27:644ms
exp 0:164327:8409m23:5639m22:3588sþ10:0538ms
ð43Þ
A simple expression for the calculation of a
O,DIF
is implemented using only surface roughness and refractive index as variables
(Jin et al., 2011):
aOS;DIF l;sðÞ¼0:1479 þ0:1502n lðÞ0:0176n lðÞ ð44Þ
Combining the equations above to calculate a
OS
should be done using the ratio of direct and diffuse irradiation:
aOS ¼fDIRaOS;DIR þfDIF aOS;DIF ð45Þ
with f
DIR
and f
DIF
the direct and diffuse fractions in GTI, respectively, and are also wavelength dependent.
The effect of white caps is included as follows:
aOS;DIR l;ζ;vðÞ¼aOS;DIR 1fWC vðÞðÞþfWC vðÞafWC lðÞ ð46Þ
aOS;DIF l;ζ;vðÞ¼aOS;DIF 1fWC vðÞðÞþfWC vðÞafWC lðÞ ð47Þ
We note that the effect of whitecaps on the direct and diffuse albedo is formulated using (1 f
WC
(v)) as coefficient, which
means when f
WC
(v) is increasing the effect of whitecaps on albedo is becoming dominant.
Using the above, Fig. 18 shows scatter plots for daily averages of albedo and wind speed for all 12 months of the year 2016, as
well as sea surface roughness (Mirbagheri Golroodbari and van Sark, 2021). This figure shows that albedo is larger in winter
months compared to summer months and also that wind speed does not necessarily only increases the albedo value. Increasing
the wind speed leads to larger sea surface roughness and decreasing albedo, however, by exceeding a certain threshold value for the
wind speed the albedo starts increasing again. This is due to the formation of white caps on the sea surface which are more clearly
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visible during months with larger solar zenith angle. This threshold value can be easily found by solving (1 f
WC
(v)) ¼0
(referring to Eq. 39), which yields v¼7.61 m/s. This is shown by the dashed line in Fig. 18.
Using the albedo data presented here in the performance model simulation reported earlier (Golroodbari and van Sark, 2020)
results as depicted in Fig. 19 are obtained. It can be concluded that taking into account a varying albedo, the calculated PV system
performance is larger in all months throughout the year, with about 3.04% on average, without a clear seasonal effect, compared
to using a fixed value for sea surface albedo (of 0.06). Increased performance can be attributed to increased GTI.
Summing all months, annual GTI would be 46.5 kWh/m
2
higher using albedo variations as shown in Fig. 18, and as a result
the annual energy yield is 41 kWh/kWp higher than the reported 1346 kWh/kWp above, which is 3% higher. The rather small
increase in performance due to including dynamically varying albedo can be understood realizing that the floating PV system is
mounted horizontally in the water. The panel tilt is limited to 20 degrees and we have shown (Golroodbari and van Sark, 2020)
Fig. 19 Relative output energy difference in % between the system implementing a modeled albedo and a constant albedo for the location of the
FPV system (Mirbagheri Golroodbari and van Sark, 2021).
Fig. 18 Scatter plots of albedo and whitecap fraction as a function of wind speed for the year 2016. For the threshold wind speed value (dashed
line), see text (Mirbagheri Golroodbari and van Sark, 2021).
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that tilt angles are rarely above 10 degrees, only in case of high wind speeds. Additional reflected irradiation on horizontally
located PV panels thus is limited. It can be expected that floating PV systems that are installed having a permanent non-zero tilt,
will benefit more from including dynamically varying albedo.
1.32.6 Environmental impacts
1.32.6.1 Land, flora & fauna impact
FPV, unlike terrestrial PV, does not have any of the potentially negative impacts relating to deforestation, land allocation, loss of
habitat, flora and fauna. But the impact is not negligible, as there are some detrimental effects due to anchoring, trenching on soil
(on land) for connecting the FPV to the substation and cabling structure. Potential impacts from anchoring could be increase of
turbidity. Also, aquatic plants and animals can be affected due to accidental spills of lubricants, oil, and exhaust emissions from
machinery used during installation phase, and increment of suspended particles due to anchoring and mooring (Costa, 2017). We
should also consider the impacts caused due to the heavy machinery used during the transport of the FPV onto the water body,
such as dust generation, soil erosion and compacting (Pimentel Da Silva and Castelo Branco, 2018).
1.32.6.2 Construction phase
More trips are required for FPV to transport the buoyant structures onto the water bodies, but heavy machinery such as cranes and
tractors are not required. However, it also depends on the capacity of the project and the type of technology used for FPV. A
temporary negative impact during construction is noise and waste generation. Noise again depends on the type of machinery used
during installation. Various types of waste are also generated such as cardboard boxes, plastic materials, wooden pallets, metal
wastes and cables, office material and human sewage waste from toilets (Abbasi and Abbasi, 2000). So, there is a need to develop a
waste management plan to effectively dispose the waste generated during construction. Also, the plastic material used to wrap the
buoyant leads to waste even more than compared to conventional PV (Pimentel Da Silva and Castelo Branco, 2018).
1.32.6.3 Operation stage and decommissioning
Compared to conventional PV, the use of water for cleaning FPV systems is less (Cazzaniga et al., 2018) as they are kept far from
land and thereby away from the influence of dust carried by wind. But there is an indirect contamination such as from boats
required to access the FPV for maintenance. Also, there might be degradation of anti-corrosion paint (Costa, 2017) from the FPV
components itself. We know that covering the water bodies completely will have positive impacts such as reduction in eva-
poration, but this full coverage might have detrimental effects on natural lakes because it mitigates the production of oxygen and
thereby adversely affects the fish, algae and alters the microclimate. The impacts due to decommissioning are similar to ones
during installation, such as changes in geomorphology of the bottom of the lake, temporary impact on flora and fauna and due to
heavy machinery (Costa, 2017), (Pimentel Da Silva and Castelo Branco, 2018).
1.32.6.4 Waste management
For FPV there are components additional to conventional PV that must be disposed of, such as pontoons, floats and mooring system
(Choi, 2014b). The floating structures may contain galvanized iron, medium and high density polyethylene (the entire structure or just
the pipes), aluminium and steel frames, metal rods, polyester and nautical ropes, and an anchor structure (weights) that can be made
outofconcrete(Cazzaniga et al., 2018), (Santafé et al., 2014). Pultruded FRP (Fiber reinforced plastic polymer) can be used as an
alternative because of its superior mechanical properties and light weight. Corrosion resistance, the design, construction and installation
of FPV with pultruded FRP are presented in a research paper (Pimentel Da Silva and Castelo Branco, 2018), (Lee et al., 2014).
1.32.6.5 Positive impact
Generation of electricity without production of CO
2
and noise during operation phase. It is estimated that the FPV will generate
11% more electricity than terrestrial PV as there is cooling effect due to water evaporation (Choi, 2014a). There is also
employment generated during the installation, decommissioning and during operations and maintenance. However, the
employment created during the operation and maintenance phase is less compared to land PV as there is less necessity to clean the
panels: as the solar panels are located on the surface of the water, further away from sources of dust and dirt, the installation
reduces soiling. There is also less risk of overheating in FPV (Sahu et al., 2016). Other positive impacts include the reduction in
evaporation of water in agricultural lakes and irrigation ponds (Dupraz et al., 2011).
Also, loss of habitat can be minimized for birds which have been impacted by setting up nests around the floating panels. In water
bodies where water quality needs to be maintained, the installation of FPV can reduce the sunlight, which in turn reduces algae
growth (Choi, 2014b). If the shading of the water body is above 40% then we can mitigate the algae, but if this shading increases to
above 60% then it affects the aquatic ecosystem, So, the recommended shading in order to have a trade-off between cost and ecology
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is 40–60%. The above values were calculated in a study on the ecology of the Rapel reservoir located in Central Chile. Using dissolved
oxygen, nutrients, and total chlorophyll A as key indicators for water quality, and 3D-numerical-hydrodynamic water-quality models
(ELCOM, Estuary and Lake Computer Model) coupled with CAEDYM (Computational Aquatic Ecosystem Dynamics Model),
quantification was possible. However, these values seemed to be area specific and no generalization of any kind was mentioned in
the study (Haas et al., 2020), (Pimentel Da Silva and Castelo Branco, 2018). Regarding off-shore PV, one can learn from the studies
on in-land water bodies, but there will be obvious differences. A preliminary study though has shown that limited ecological effects
can be expected, while potentially new species could settle on the installation providing a starting point for artificial reefs thus
creating attractive environments for species such as crab, lobster, and fish (Hooper et al., 2021).
1.32.7 The future of FPV
The future of FPV can most reasonably be extrapolated when considering the number of available/feasible water bodies, economic
and technical benefits compared to mounted PV, and the growth of the photovoltaic industry as a whole. Since 1992, the
photovoltaic industry has been growing exponentially year-to-year, with continued double-digit rates of 20–30%. This trend is
expected to continue, due to the wide scale availability of earth abundant silicon, and the increasing demand for sustainable
energy sources. As FPV is a relatively newer technology, we can expect to see an even steeper increase in installations percentage-
wise in the coming years, compared to traditional PV. As discussed earlier, the number of feasible water bodies is plentiful in the
United States, and geographically speaking this holds true for most land masses worldwide.
One non-technological aspect to consider when it comes to constructing new power plants is sensitivity around land
ownership—as property may be owned by federal, state, local governments, corporations or individuals. However, per unit area,
water bodies are typically cheaper than land masses, independent of property ownership. For example, for the US, NREL filtered
out areas with ownership disputes and identified 24,400 reservoirs that have potential for FPV installation. If FPV systems were
to be installed on 25% of these identified water bodies, they would power 10% of the United States energy demand (Spencer
et al., 2019). We can conclude the potential for FPV energy supply globally is substantial when considering the fact that there are
over 500,000 reservoirs across the globe that are larger than 1 ha. Further, there is an enormous potential market for FPV
installations in India, where land scarcity is a prominent threat for development. In fact, in 2020 India is planning on building
the world's largest floating solar plant on the Indira Sagar Dam in Madhya Pradesh—with 1 GWp capacity (Institute for Energy
Economics and Financial Analysis (IEEFA), 2019). This power plant will occupy roughly 2000 ha, equivalent to 8% of the
reservoir's total surface area. This installation will exceed the 500 kWp Banasura Sagar power plant in Kerala; India's current
largest operating FPV system.
Current implementation of FPV is taking place most notably in China, Japan, South Korea, India, the United States, Italy, and
the Netherlands. These countries already have working systems, so they can learn from current power plants to continue to make
floating solar more efficient and scalable. In the near future, these countries are expected to experience the greatest growth of FPV
installations. Once solar power becomes even cheaper and current FPV systems prove effective, system prices will further decrease
and compete with current power generation technologies in other areas of the world.
It is also important to note what the water body is used for, as FPV systems can disrupt or benefit certain functions. FPV systems
are most beneficial when installed on reservoirs, dams, or irrigation canals—where limiting water evaporation and algae growth
helps preserve fresh water. Hence, FPV has the greatest potential impact in areas where there are mutual benefits of installing such
systems. South/Central Asia and Africa—specifically areas that lack stable energy supply and clean water—have the greatest need
for FPV installations. Modules floating on reservoirs, dams and irrigation canals limit water evaporation, thereby increasing the
amount of available clean water. These areas have a hotter climate as well, so FPV modules will operate at a substantially lower cell
temperature than ground mounted PV, thereby producing more power.
Another potential use of FPV is to install it on a water desalination plants, and have the power generated from the solar cells
directly supply power to the plant. This will again limit water loss due to evaporation, as well as provide a sustainable energy
resource to power the conversion of ‘dirty’to ‘clean’water.
The beauty of floating photovoltaics is that technology will continue to develop coincidently with standard PV technologies.
Next generation photovoltaics such as dye-sensitized cells and perovskites may prove to produce higher efficiencies than tradi-
tional technologies in the near future. If that is the case, these technologies can easily be converted to floating PV. As we transition
to a sustainable energy future, floating photovoltaics will play its part as one of the substantial contributors in energy production.
1.32.7.1 Hybrid power plants
In addition to the already huge potential of FPV systems, they may take advantage of operating in a hybrid power system as well.
For instance, hydro power, as mentioned above, or (floating) (offshore) wind energy systems could be very good options to
combine with FPV systems. Adding FPV to the systems in which the grid connectivity, i.e. transmission lines, transformers, etc. is
already present is more valuable.
In Farfan and Breyer (2018) the ability of a hydro power plant to act as a virtual battery for the FPV plant is studied. The hybrid
power system in this research is designed such that in periods with high irradiation the FPV system generates electricity and
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transmits that to the grid directly, while the hydro power plant is idle. During this time either the reservoir accumulates (when
there is an inflow stream) or just holds water that can be later used during times of low or absent solar irradiation. Thus, the
reservoir acts as a storage system, which in this research is called a virtual battery. The feasibility of hybrid power systems consisting
of hydro power and FPV, resulting from the high flexibility of hydro power plant operation, is demonstrated in many studies. The
focus on deploying FPV on hydro power reservoirs is due to the fact that they have lower potential cost integration, as grid
connectivity is already available (Farfan and Breyer, 2018), (Teixeira et al., 2015). However, the same argument is valid for other
floating power systems.
The deployment of offshore wind farms has been ongoing since the 1990s, and has experienced a considerable growth in the
last decade, especially in Europe (Esteban et al., 2011), (López et al., 2020). In (Esteban et al., 2011) a hybrid system consisting of
offshore wind and offshore floating PV is studied and the advantages of this combination are summed up as follows:
•The FPV system can fill up the required space between the turbine towers in the conventional off-shore wind farm. This
combination increases the capacity density of the whole system. It follows that a combined offshore wind–solar farm can
produce significantly more energy per surface unit area than an offshore wind farm. A recent study for the North Sea shows
economic advantages as well (Golroodbari et al., 2021), with the concept of cable pooling as key: making use of an existing
transmission cable that was designed for an offshore wind park only.
•In hybrid power systems with offshore wind and solar the intra-annual variation of the combined energy output reduces, thus
addressing one of the advantages in marine renewable energy (López et al., 2020), (Carballo et al., 2015). Since there is often
an anti-correlation between the solar and wind resource, it follows that hybrid systems combining FPV with offshore wind
produce a smoother power output than conventional systems with either stand-alone wind or FPV. This is also a significant
advantage in terms of power quality for the grid. However, in these studies the effect of partial shading due to dynamical rotor
and tower shading is not addressed and to this end, smart shade resilient modules (Golroodbari et al., 2019) have the potential
to (further) improve the FPV energy yield.
1.32.8 Conclusions
Photovoltaics are the most promising renewable energy source due to the enormous potential of solar irradiation. Floating
Photovoltaics have been developed and installed over the past decade in order to overcome some drawbacks of the conventional
terrestrial PVs—such as land sensitivity and efficiency loss from high cell temperature. As we reviewed and discussed in this paper,
FPVs have both positive and negative environmental impacts compared to conventional PVs. Performance typically is 5–10%
better compared to land-based systems. Moreover, we analyzed the economic feasibility and emerging markets deploying this
technology. Finally, we analyzed the potential future of FPVs. A detailed modeling example of off-shore FPV was provided, as off-
shore potential is very large.
FPV installations have increased very fast over the past years. Markets in Japan, Korea, and United States already have been
using this technology and countries such as China and India have been installing FPVs systems more recently. As the near future
demands transitioning from fossil fuels to clean energy sources, the photovoltaic industry, especially FPV on inland water bodies
but perhaps even more so on coastal areas, will have a crucial role in achieving this goal.
Acknowledgments
The authors acknowledge contributions to the background material presented in this manuscript by Christina Santa Lucia,
Jonathan Moallem, Sri Kapish Gollapalli and Antonios Pinotsis, as part of project “Floatovoltaics: Investigating Floating PV
systems”, in the course PV Systems Integration and Sustainability by prof. Fthenakis at Columbia University. The authors gratefully
acknowledge fruitful discussions with Brigitte Vlaswinkel and Allard van Hoeken (Oceans of Energy) and Anne de Waal (UU). This
work is partly financially supported by the Netherlands Enterprise Agency (RVO) within the framework of the Dutch Topsector
Energy (project Comparative assesement of PV at Sea versus PV on Land, CSEALAND).
References
Abbasi SA and Abbasi N (2000) The likely adverse environmental impacts of renewable energy sources. Applied Energy 65: 121–144.
Ásgeirsson GS (2013) Hydrodynamic Investigation of WavePower Buoys. Stockholm, Sweden: Master Thesis KTH.
Barbuscia M (2017) Economic Viability Assessment of Floating Photovoltaic Energy. Portugal: Instituto Superior Tecnico, Universidade de Lisboa.
Beshilas L (2021) Floating Solar Photovoltaics Could Make a Big Splash in the USA, NREL Blog. https://www.nrel.gov/state-local-tribal/blog/posts/floating-solar-photovoltaics-
could-make-a-big-splash-in-the-usa.html#:B:text=A%20floating%20solar%20photovoltaic%20%28FPV%29%20system%20is%20an,opposed%20to%20on%20land%20or%
20on%20building%20rooftops Accessed 30 August 2021.
Bussar C, Stöcker P, Cai Z, Moraes Jr. L, Magnor D, Wiernes P, van Bracht N, Moser A, and Sauer DU (2016) Large-scale integration of renewable energies and impact on
storage demand in a European renewable power system of 2050—Sensitivity study. Journal of Energy Storage 6: 1–10.
Carballo R, Sánchez M, Ramos V, Fraguela JA, and Iglesias G (2015) The intra-annual variability in the performance of wave energy converters: A comparative study in N
Galicia (Spain). Energy 82: 138–146.
700 Floating Photovoltaic Systems
Author's personal copy
Cazzaniga R, Rosa-Clot M and Rosa-Clot P (2012a) Apparatus and Method for Generating Electricity Using Photovoltaic Panels. Patent WO 2012/131543 A1, 4 October 2012.
Cazzaniga R, Rosa-Clot M, Rosa-Clot P, and Tina GM (2012b) Floating tracking cooling concentrating (FTCC) systems. In: 2012 38th IEEE Photovoltaic Specialists
Conference, pp. 514–519.
Cazzaniga R, Cicu M, Rosa-Clot M, Rosa-Clot P, Tina GM, and Ventura C (2017) Compressed air energy storage integrated with floating photovoltaic plant. Journal of Energy
Storage 13: 48–57.
Cazzaniga R, Cicu M, Rosa-Clot M, Rosa-Clot P, Tina GM, and Ventura C (2018) Floating photovoltaic plants: Performance analysis and design solutions. Renewable and
Sustainable Energy Reviews 81: 1730–1741.
Cazzaniga R, Rosa-Clot M, Rosa-Clot P, and Tina GM (2019) Integration of PV floating with hydroelectric power plants. Heliyon 5.e01918
Choi Y-K (2014a) A study on power generation analysis of floating PV system considering environmental impact. International Journal of Software Engineering and Its
Applications 8: 75–84.
Choi Y (2014b) A case study on suitable area and resource for development of floating photovoltaic system. International Journal of Electrical and Computer Engineering 8:
828–832.
Choudhary P and Srivastava RK (2019) Sustainability perspectives- a review for solar photovoltaic trends and growth opportunities. Journal of Cleaner Production 227:
589–612.
CIA (2021) The World Fact Book. https://www.cia.gov/the-world-factbook/. (accessed 27 August, 2021).
Costa SG (2017) Impactes Ambientais de Sistemas Fotovoltaicos Flutuantes. MSc thesis Lisboa: Universidade de Lisboa.
Cox C and Munk W (1954) Measurement of the roughness of the sea surface from photographs of the sun's glitter. Journal of the Optical Society of America 44: 838–850.
Dizier A (2018) Techno-Economic Analysis of Floating PV Solar Power Plants Using Active Cooling Technique. MSc Thesis Stockholm: Division of Heat and Power
Technology, KTH School of Industrial Engineering and Management.
Dörenkämper M, van der Werf D, Sinapis K, de Jong MM, and Folkerts W (2019) Influence of wave induced movements on the performance of floating PV systems. In:
Proceedings 36th European Photovoltaic Solar Energy Conference and Exhibition, Marseilles, France, pp. 1759–1762.
Dupraz C, Marrou H, Talbot G, Dufour L, Nogier A, and Ferard Y (2011) Combining solar photovoltaic panels and food crops for optimising land use: Towards new agrivoltaic
schemes. Renewable Energy 36: 2725–2732.
Dupré O, Vaillon R, and Green MA (2017) Thermal Behavior of Photovoltaic Devices. Cham, Switzerland: Springer.
Dwivedi P, Sudhakar K, Soni A, Solomin E, and Kirpichnikova I (2020) Advanced cooling techniques of PV modules: A state of the art. Case Studies in Thermal Engineering
21: 100674.
Esteban MD, Diez JJ, Lopez JS, and Negro V (2011) Why offshore wind energy? Renewable Energy 36(2): 444–450.
Farfan J and Breyer C (2018) Combining floating solar photovoltaic power plants and hydropower reservoirs: A virtual battery of great global potential. Energy Procedia 155:
403–411.
Folkerts W, van Sark, de Keizer C, van Hooff W, and van den Donker M (2021) Roadmap PV System en Toepassingen (in Dutch). https://www.uu.nl/sites/default/files/
roadmap-pv-systemen-en-toepassingen-final.pdf. (accessed 27 August, 2021).
Frouin R, Schwindling M, and Deschamps P-Y (1996) Spectral reflectance of sea foam in the visible and near-infrared: In situ measurements and remote sensing implications.
Journal of Geophysical Research, Oceans 101: 14361–14371.
Golroodbari SZ and van Sark W (2020) Simulation of performance differences between offshore and land-based photovoltaic systems. Progress in Photovoltaics: Research and
Applications 28: 873–886.
Golroodbari SZ, de Waal A, and Van Sark W (2019) Proof of concept for a novel and smart shade resilient photovoltaic module. IET Renewable Power Generation 13:
2184–2194.
Golroodbari SZM, Vaartjes DF, Meit JBL, van Hoeken AP, Eberveld M, Jonker H, and van Sark WGJHM (2021) Pooling the cable: A techno-economic feasibility study of
integrating offshore floating photovoltaic solar technology within an offshore wind park. Solar Energy 219: 65–74.
Gordon HR and Jacobs MM (1977) Albedo of the ocean-atmosphere system: Influence of sea foam. Applied Optics 16: 2257–2260.
Grand View Research (2019) Floating Solar Panels Market Size, Share & Trends Analysis Report By Product (Tracking Floating Solar Panels, Stationary Floating Solar Panels),
By Region, And Segment Forecasts, 2020–2027. https://www.grandviewresearch.com/industry-analysis/floating-solar-panels-market Accessed 29 August 2021.
Gulin M, Vašak M, and Baotic
´M (2013) Estimation of the global solar irradiance on tilted surfaces. In: Proceedings of the 17th International Conference on Electrical Drives
and Power Electronics, EDPE 2013, Dubrovnik, Hrvatska, pp. 334–339.
Haas J, Khalighia J, de la Fuente A, Gerbersdorf SU, Nowak W, and Chen P-J (2020) Floating photovoltaic plants: Ecological impacts versus hydropower operation flexibility.
Energy Conversion and Management 206: 112414.
Hasselmann K, Ross DB, Müller P, and Sell W (1976) A parametric wave prediction model. Journal of Physical Oceanography 6: 200–228.
Hooper T, Armstrong A, and Vlaswinkel B (2021) Environmental impacts and benefits of marine floating solar. Solar Energy 219: 11–14.
Hourdin F, Foujols M-A, Codron F, Guemas V, Dufresne J-L, Bony S, Denvil S, Guez L, Lott F, Ghattas J, Braconnot P, Marti O, Meurdesoif Y, and Bopp L (2013) Impact of
the LMDZ atmospheric grid configuration on the climate and sensitivity of the IPSL-CM5A coupled model. Climate Dynamics 40: 2167–2192.
Huld T and Gracia-Amillo AM (2015) Estimating PV module performance over large geographical regions: The role of irradiance, air temperature, wind speed and solar
spectrum. Energies 8: 5159–5181.
Ineichen P, Zelenka A, Guisan O, and Razafindraibe A (1988) Solar radiation transposition models applied to a plane tracking the sun. Solar Energy 41: 371–377.
Institute for Energy Economics and Financial Analysis (IEEFA) (2019) India planning 1GW floating solar project in Madhya Pradesh. https://ieefa.org/india-planning-1gw-
floating-solar-project-in-madhya-pradesh/ Accessed 30 August 2021.
International Energy Agency (2020) World Energy Outlook 2020. Paris, France: International Energy Agency.
International Energy Agency (IEA) (2020) Snapshot of Global Pv Markets 2020. Report IEA-PVPS T1-37: 2020 https://iea-pvps.org/wp-content/uploads/2020/04/
IEA_PVPS_Snapshot_2020.pdf Accessed 25 August 2021.
International Energy Agency (IEA) (2021) Performance of New Photovoltaic System Designs 2021. Report IEA-PVPS T13-15:2021 https://iea-pvps.org/wp-content/uploads/2021/
03/IEA-PVPS_Task-13_R15-Performance-of-New-PV-system-designs-report.pdf
International Renewable Energy Agency (IRENA) (2020) Renewable Capacity Statistics 2020, Abu Dhabi. https://irena.org/publications/2020/Mar/Renewable-Capacity-Statistics-
2020 Accessed 25 August 2021.
Jacobs SJ, Pezza AB, Barras V, Bye J, and Vihma T (2013) An analysis of the meteorological variables leading to apparent temperature in Australia: Present climate, trends,
and global warming simulations. Global and Planetary Change 107: 145–156.
Jin Z, Qiao Y, Wang Y, Fang Y, and Yi W (2011) A new parameterization of spectral and broadband ocean surface albedo. Optics Express 19: 26429–26443.
Kim SH, Yoon SJ, Choi W, and Choi KB (2016) Application of floating photovoltaic energy generation systems in South Korea. Sustainability 8: 1–9.
Kjeldstad T, Lindholm D, Marstein E, and Selj J (2021) Cooling of floating photovoltaics and the importance of water temperature. Solar Energy 218: 544–551.
Klucher TM (1979) Evaluation of models to predict insolation on tilted surfaces. Solar Energy 23: 111–114.
Koiné Multimedia (2021) http://www.koinemultimedia.eu/wp/sample-page/. (accessed 30 August, 2021).
Kougias I, Bódis K, Jäger-Waldau A, Moner-Girona M, Monforti-Ferrario F, Ossenbrink H, and Szabó S (2016) The potential of water infrastructure to accommodate solar PV
systems in Mediterranean islands. Solar Energy 136: 174–182.
Kumar M and Kumar A (2019) Experimental characterization of the performance of different photovoltaic technologies on water bodies. Progress in Photovoltaics: Research and
Applications 28: 25–48.
Floating Photovoltaic Systems 701
Author's personal copy
Lawrence MG (2005) The relationship between relative humidity and the dewpoint temperature in moist air: A simple conversion and applications. Bulletin of the American
Meteorological Society 86: 225–234.
Lee Y, Joo H, and Yoon S (2014) Design and installation of floating type photovoltaic energy generation system using FRP members. Solar Energy 108: 13–27.
Liu H, Krishna V, Lun Leung J, Reindl T, and Zhao L (2018) Field experience and performance analysis of floating PV technologies in the tropics. Progress in Photovoltaics:
Research and Applications 26: 957–967.
López M, Noel Rodríguez N, and Iglesias G (2020) Combined floating offshore wind and solar PV. Journal of Marine Science and Engineering 8: 576.
Manfrida G and Secchi R (2014) Seawater pumping as an electricity storage solution for photovoltaic energy systems. Energy 69: 470–484.
Martin N and Ruiz JM (2005) Annual angular reflection losses in PV modules. Progress in Photovoltaics: Research and Applications 13: 75–84.
Mehrotra S, Rawat P, Debbarma M, and Sudhakar K (2014) Performance of a solar panel with water immersion cooling technique. International Journal of Science,
Environment and Technology 3: 1161–1172.
Mirbagheri Golroodbari SZ and van Sark WGJHM (2021) Effect of dynamic albedo modeling on the performance of offshore floating photovoltaic systems. Solar Energy.
(submitted).
Muetze A and Vining JG (2006) Ocean wave energy conversion—A survey. In: Conference Record of the 2006 IEEE Industry Applications Conference, pp. 1410–14173, pp.
1410–1417 .
Payne RE (1972) Albedo of the sea surface. Journal of the Atmospheric Sciences 29: 959–970.
Pimentel Da Silva GD and Castelo Branco DA (2018) Is floating photovoltaic better than conventional photovoltaic? Assessing environmental impacts. Impact Assessment and
Project Appraisal 36: 390–400.
Pringle AM, Handler RM, and Pearce JM (2017) Aquavoltaics: Synergies for dual use of water area for solar photovoltaic electricity generation and aquaculture. Renewable and
Sustainable Energy Reviews 80: 572–584.
Prudhvi P and Sai PC (2012) Efficiency improvement of solar PV panels using active cooling. In: Proceedings 2012 11th International Conference on Environment and
Electrical Engineering, pp. 1093–1097.
Quax R, Londo M, van Hooff W, Kuijers T, Witte J, van Sark W, and Sinke W (2021) A tool for the assessment of spatial implications of photovoltaics deployment policies in
the Netherlands. Solar Energy. (submitted).
Ranjbaran P, YousefiH, Gharehpetian GB, and Astaraei FR (2019) A review on floating photovoltaic (FPV) power generation units. Renewable and Sustainable Energy Reviews
110: 332–347.
Reindl T (2018a) World's Largest Floating Solar Testbed—Overview and Findings. Singapore: ACEF Deep Dive Workshop on Floating Solar.
Reindl T (2018b) At the Heart of Floating Solar: Singapore. PV Tech Power, vol. 14, Buoyant Market, pp. 18–23.
Rosa-Clot M and Tina GM (2018) Submerged and Floating Photovoltaic Systems: Modelling, Design and Case Studies. Academic Press.
Rosa-Clot M and Tina GM (2020) Floating PV Plants. Academic Press.
Sahu A, Yadav N, and Sudhakar K (2016) Floating photovoltaic power plant: A review. Renewable and Sustainable Energy Reviews 66: 815–824.
Salih MS, Abd OI, and Abid KW (2014) Performance enhancement of PV array based on water spraying technique. International Journal of Sustainable and Green Energy 4:
8–13.
Salisbury DJ, Anguelova MD, and Brooks IM (2014) Global distribution and seasonal dependence of satellite-based whitecap fraction. Geophysical Research Letters 41:
1616–1623.
Santafé MR, Ferrer Gisbert PS, Sánchez Romero FJ, Torregrosa Soler JB, Ferrán Gozálvez JJ, and Ferrer Gisbert CM (2014) Implementation of a photovoltaic floating cover for
irrigation reservoirs. Journal of Cleaner Production 66: 568–570.
Séférian R, Baek S, Boucher O, Dufresne J-L, Decharme B, Saint-Martin D, and Roehrig R (2018) An interactive ocean surface albedo scheme (OSAv1.0): Formulation and
evaluation in ARPEGE-Climat (V6.1) and LMDZ (V5A). Geoscientific Model Development 11: 321–338.
Seij JH, Lereng IH, De Paoli P, Øgaard MB, Otnes G, Bragstad S, Bjørneklett B, and Marstein E (2019) The performance of a floating PV plant at the west coast of Norway.
In: Proceedings 36th European Photovoltaic Solar Energy Conference and Exhibition, Marseilles, France, pp. 1763–1767.
Servant J-M (1986) Calculation of the Cell Temperature for Photovoltaic Modules From Climatic Data, Intersol Eighty Five. In: Proceedings of the Ninth Biennial Congress of
the International Solar Energy Society, Pergamon, pp. 1640–1643.
Sharma P, Muni B, and Sen D (2015) Design parameters of 10 kW floating solar power plant. International Advanced Research Journal in Science, Engineering and
Technology 2: 85–89.
Skoplaki E and Palyvos JA (2009) On the temperature dependence of photovoltaic module electrical performance: A review of efficiency/power correlations. Solar Energy 83:
614–624.
Spencer RS, Macknick J, Aznar A, Warren A, and Reese MO (2019) Floating photovoltaic systems: Assessing the technical potential of photovoltaic systems on man-made
water bodies in the continental United States. Environmental Science
&
Technology 53: 1680–1689.
Steadman RG (1994) Norms of apparent temperature in Australia. Australian Meteorological Magazine 43: 1–16.
Suh J, Jang Y, and Choi Y (2020) Comparison of electric power output observed and estimated from floating photovoltaic systems: A case study on the hapcheon dam, Korea.
Sustainability 12: 276.
Teixeira LE, Caux J, Beluco A, Bertoldo I, Louzada JAS, and Eifler RC (2015) Feasibility study of a hydro PV hybrid system operating at a dam for water supply in southern
Brazil. Journal of Power and Energy Engineering 3: 70–83.
Trapani K (2014) Flexible Floating Thin Film Photovoltaic (PV) Array Concept for Marine and Lacustrine Environments. Laurentian University of Sudbury. pp. 1–217 PhD
Thesis.
Trapani K and Millar DL (2013) Proposing offshore photovoltaic (PV) technology to the energy mix of the Maltese islands. Energy Conversion and Management 67: 18–26.
Trapani K and Millar DL (2014) The thin film flexible floating PV (T3F-PV) array: The concept and development of the prototype. Renewable Energy 71: 43–50.
Trapani K and Redón Santafé M (2015) A review of floating photovoltaic installations: 2007–2013. Progress in Photovoltaics: Research and Applications 23: 524–532.
Trapani K, Millar DL, and Smith HCM (2013) Novel offshore application of photovoltaics in comparison to conventional marine renewable energy technologies. Renewable
Energy 50: 879–888.
Verma S, Mohapatra S, Chowdhury S, and Dwivedi G (2021) Cooling techniques of the PV module: A review. Materials Today: Proceedings 38: 253–258.
Wang Z, Carriveau R, Ting DS-K, Xiong W, and Wang Z (2019) A review of marine renewable energy storage. International Journal of Energy Research 43: 6108–6150.
Whitlock CH, Bartlett DS, and Gurganus EA (1982) Sea foam reflectance and influence on optimum wavelength for remote sensing of ocean aerosols. Geophysical Research
Letters 9: 719–722.
World Bank Group (2019a) ESMAP, SERIS, Where Sun Meets Water: Floating Solar Handbook for Practitioners. Washington, DC: World Bank, https://documents1.worldbank.
org/curated/en/418961572293438109/pdf/Where-Sun-Meets-Water-Floating-Solar-Handbook-for-Practitioners.pdf Accessed 29 August 2021.
World Bank Group (2019b) ESMAP, SERIS, Where Sun Meets Water: Floating Solar Market Report. Washington, DC: World Bank, https://openknowledge.worldbank.org/
bitstream/handle/10986/31880/Floating-Solar-Market-Report.pdf Accessed 29 August 2021.
Wu S-Y, Zhang Q-L, Xiao L, and Gui F-H (2011) A heat pipe photovoltaic/thermal (PV/T) hybrid system and its performance evaluation. Energy and Buildings 43: 3558–3567.
Yu X (2017) China to Create World's Largest Floating Solar Power Plant in Move to Clean Energy, 11 December, 2017. https://on.rt.com/8uhv Accessed 29 August 2021.
Yu Y, Pei H, and Xu C (2017) Parameter identification of JONSWAP spectrum acquired by airborne LIDAR. Journal of Ocean University of China 16: 998–1002.
702 Floating Photovoltaic Systems
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