Floating Solar: A Review on the Comparison of Efficiency, Issues, and Projections with Ground-Mounted Solar Photovoltaics

Floating solar has been an innovative technique for scaling solar PV project development. This research showcases the expected negative and positive ecological influences from photovoltaic frameworks with a specific interest in enormous scope ordinary and drifting photovoltaic. This research focuses on and thinks regarding the outcomes at all project execution stages; it includes arranging, development, activity, decommissioning, and zeroing in on encompassing situated in the jungles. The general effects related to project designation, like deforestation (for the undertaking execution and site getting to), bird deaths, disintegration, overflow, and climatic change, are expected to reach greater magnitudes during the execution of regular PV projects. The outcomes also feature the advantages of Floating PV over traditional PV during the functional and decommissioning stages [6].

The world is moving towards a net-zero emissions future, with solar energy being a key component. However, land use requirements for solar farms pose a challenge due to rising population density and land prices. Floating photovoltaics (FPV) addresses this by installing solar photovoltaics (PV) on water bodies. FPV is becoming a viable option for many countries, with a 1% coverage of global reservoirs generating 404GWp of benign power production. FPV offers numerous advantages over ground-mounted PV, but research on its impact on water quality and living organisms is still lacking. This review explores FPV's benefits, drawbacks, and future prospects, including its potential for integration with other technologies. A review of floating photovoltaic (FPV) systems found that while they offer numerous benefits, they also have known and unknown disadvantages. Advantages include cooling, no land use, reduced water evaporation, soiling, and algal blooms. Disadvantages include humidity effects on PV modules and unknown water quality effects. FPV is best suited for human-made water bodies like reservoirs, irrigation ponds, and industrial ponds. Hybrid systems with HPP reservoirs offer grid access and reduced water evaporation. Countries with high population densities are considering FPV as a renewable energy source [7].

Looking at the prospects of using new technology, the researchers study the performance compared to evaporation-based technology; in this study, they demonstrated that installing floating photovoltaics on US lakes would need a lot less space in terms of energy output than installing a potential evaporation-based solution. Floating PV systems may generate steady, round-the-clock electricity equal to 100% of US electrical demand if installed on the 128 greatest reservoirs in the US. If Floating PV were used on all lakes taken into consideration for the evaporation engine study, it would generate ten times as much energy. They also demonstrated and compared Floating PV systems connected to the hydroelectric power plants currently in service at the reservoirs beneath investigation; Floating PV is significantly more space-efficient. They can now generate an equivalent amount of electricity to hydropower by covering 1.2% of their surface with solar panels. This discovery may present significant opportunities for water managers. Managers might concentrate on achieving alternatives. Suppose hydroelectric production through turbines could be reduced or eliminated as a reservoir management aim by installing Floating PV on a very small percentage of the reservoir area. In that case, goals like flood control and adequate water supply may be achieved [8].

The energy-based parametric technique is employed in this research to comprehend the photovoltaic (PV) module's realistic performance and the energy conversion process in both water and land environments. Three amorphous silicon thin-film PV modules deployed using land PV, Floating PV, and submerged PV ways are being investigated to understand the energy performance further. The experimental findings demonstrate that each installation method has a different energy efficiency. The effectiveness of solar PV installation methods is shown should be accordingly 3.07 percent higher than that of Floating PV and 43.5 percent higher than that of land PV [9].

Floating solar arrays may be used in conjunction with other green technologies. and made a hybrid to expand the energy generation from a particular part of the area. Floating PV + hydrological systems, Floating PV + pumped hydrological, Floating PV + wave energy converter, Floating PV + tracking, Floating PV + conventional electricity, and Floating PV + hydrogen is some of the hybrid technologies considered. The review includes a list of the main advantages and disadvantages of hybrid floating solar PV operation. Hybrid Floating PV systems that combine hydropower and solar energy are among the most promising ones that have the potential to be employed for adequate power generation. The research highlights the potential of hybrid FPV systems to increase technological and economic competitiveness, offering an efficient alternative to traditional floating systems. The study also highlights the growth potential of hybrid FPV systems, particularly in hydro dams, and the potential for decarbonization. It emphasizes the need for more pilot studies and innovative approaches to achieve scale, cost reduction, energy yield, and high return on investment. The insights presented will support future research and pilot-scale deployment of hybrid FPV plants worldwide [10].

Looking at the Distributed Production of Flexible Floating Photovoltaic Modules for Aftermarket, a study suggests using extensive Flexible Floating PV systems are produced utilizing an open-source distributed manufacturing method. This study examines the three closed-cell foams that support the flexible thin-film solar PV's floating surface: neoprene, polyethylene, and minicell. The constructed Floating PV was tested indoors and outdoors for buoyancy, wave resistance, temperature, and resistance to algae build-up. While on comparison with land-based mounting, the average operating temperature for the Floating PV was reduced by 10 to 20 degrees Celsius, which indicates a significant increase in electricity output of about 2 to 4 percent for the amorphous Silicon used here and 5 to 10 percent for crystalline Silicon based PV when compared to the installation of any PV on the ground. It was also seen that foam-based Floating PV racking could drop prices to $0.37-0.61/W, which is much less expensive than raft-based Floating PV and traditional land-based racking [11].

There are many examples of floating solar PV projects successfully carried out. Still, as it is a new technology, many challenges and issues must be addressed to improve its efficiency and objectivity. The main aim related to review and study is to help and understand the:

(1) The benefits and drawbacks of installing Floating PV systems in aquatic bodies in comparison to land-based PV systems in terms of potential energy output and environmental issues.

(2) We are looking at the challenges the floating solar market faces regarding scalability.

PV, short for photovoltaic energy, is a Solar energy uses a photovoltaic effect-based technique to directly turn sunlight into electricity. A solar panel is made up of several photoelectric cells, each of which has a face that is exposed to sunlight. When sunlight strikes one of these faces, it creates an electric voltage difference between the two faces that causes electrons to flow from one to the other, creating an electric current [15].

Installing solar photovoltaic energy has various benefits, including lowering your carbon footprint and yearly electricity expenditures, lessening the impact of rising energy prices, and earning a tax-free income for the next 20 years. Additionally, Solar PV systems and panels are simple to install, maintenance-free, and guaranteed to last [16].

Solar panel technology, invented by Bell Labs over 60 years ago, has been used for centuries to harness the sun's energy. However, it has only gained significant popularity in the last decade as a renewable energy source. In 1954, Bell Labs invented the first silicon solar panel, which was about 6% efficient. Since then, solar PV technology has rapidly evolved, with prototypes over 30% efficient, producing 25% more electricity than lower-tier economy panels. Researchers have achieved 47.1% efficiency using advanced cell structures, but these super high-efficiency panels are typically made of expensive materials, making them not currently cost-effective [17].

Solar energy is booming, and PV applications are expanding to different horizons. Therefore, we try to classify the most used applications related to PV i.e., Land-based, Rooftop and Floating based PV systems.

Land-Based PV systems is a facility that generates electricity from the sun's energy using photovoltaic (PV) panels or concentrating solar power (CSP) systems. These systems are typically located on large plots of land, either on the ground or on top of structures, such as buildings or poles. The land-based solar power plants provide a clean, renewable, and sustainable source of energy that can reduce dependence on fossil fuels. Ground-mounted solar panels are lightweight, easy to install, and efficient in producing solar electricity. They require a separate structure for accurate tilt angle and easy maintenance. However, they may require higher initial investment and a longer installation process [18].

Rooftop PV system is a system of solar panels installed on the roof of a building to generate electricity. The solar panels convert sunlight into direct current (DC) electricity, which is then converted into alternating current (AC) electricity using an inverter. This AC electricity can then be used to power lights, appliances, and other devices in the building. Rooftop solar power plants offer many benefits, including reduced dependence on traditional energy sources, lower energy bills, and a smaller carbon footprint. Additionally, they can be a cost-effective option for building owners as the long-term savings from reduced energy costs can offset the initial investment. With technological advances, rooftop solar power plants are becoming more efficient and easier to install, making them a popular choice for homeowners and businesses. This system is cheaper than Off-Grid or hybrid systems due to its lack of battery banks and standalone components. It also allows net metering, allowing extra electricity to be sold back to the utility. However, it lacks a battery bank, cannot store electricity during grid outages, and requires monthly utility fees [19].

Floating solar PV systems are a relatively new technology that involves installing solar panels on floating platforms on bodies of water, such as lakes and reservoirs. These systems offer several advantages over traditional ground-mounted solar PV systems, including the ability to save valuable land resources, reduce evaporation and water loss, and increase the cooling of the solar panels. The panels are also less susceptible to shading and dust build-up, which can improve energy efficiency. The water stabilizes, making floating solar PV systems more resilient in harsh weather conditions. These systems are an innovative solution for countries and regions with limited land resources but ample bodies of water, offering a sustainable way to generate renewable energy [20].

Some of the components used in floating solar projects are [21]:

(1) PV Panels: PV Panels are photovoltaic cells that are used to convert sunlight into electricity. They are made of Silicon, gallium arsenide, and cadmium telluride. PV panels are an essential component of renewable energy systems and are becoming increasingly popular for their cost-effectiveness and environmental benefits.

(2) Floaters: Floaters are the main components used in floating solar systems. Floaters provide buoyancy and stability to the PV modules above the water surface. These structures are made of many materials, including plastic, rubber, and even steel. Depending on the design of the floater, it can also provide mounting points for the PV modules and other components. Some floaters also come with an anode system for corrosion protection. The design and shape of the floater will depend on the size, weight, and type of PV module used in the system.

(3) Combiner boxes: Combiner boxes are essential components in floating solar systems. They combine and protect multiple strings of solar modules and protect the system from overcurrent and short-circuiting. A Combiner box typically consists of a NEMA-type enclosure with junction boxes, DC circuit breakers, surge protection devices, lightning arrestors, and a ground lug. The combiner box typically has two inputs for each string of photovoltaic modules, which are then connected to one combiner box output and then to the power inverter for energy conversion. It also helps to protect the system from overcurrent, undercurrent, and other electrical hazards. The combiner box is essential in a floating solar system, as it ensures the system's safety and protects it against harsh UV rays and other environmental hazards.

(4) Mooring System: Mooring systems are an essential component of floating solar systems. The mooring system consists of mooring lines, an anchor system, and a buoyancy system. The mooring lines are typically composed of steel chains, wire ropes, or synthetic ropes and are connected to the anchor and buoyancy systems. The anchor system consists of anchors, weights, and lines, which are used to keep the structure securely in place. The buoyancy system is typically made of floats and provides the necessary buoyancy to the structure. The mooring system is designed to resist external factors like wind and waves and to provide the required tension to maintain the stability of the structure.

(5) Inverter: An inverter is a critical floating solar PV system component. It is responsible for converting the DC power generated by the solar array into AC power that can be used for the distribution network or fed into the grid. Inverters for floating solar PV systems are designed to handle the unique environmental conditions associated with these systems, such as high levels of moisture and salt. Depending on the system design, the inverter can be either a string inverter, a central inverter, or a microinverter. Inverters for floating solar PV systems also have protective features such as surge arresters, over-voltage and over-current protection, and temperature monitoring to ensure the system operates safely and efficiently.

(6) Transformer: A transformer is a critical component in a floating solar system. It converts solar PV system's electricity into power for the grid. The transformer is responsible for transforming the high-voltage electricity output from the solar panels into a usable form. It also helps to protect the system from power outages caused by grid disturbances. The transformer is typically an oil-filled, three-phase unit with a rating of up to 100MVA. The transformer is also designed to minimize energy losses during transmission and reduce energy production costs.

(7) Cable Network: A cable network is an integral component of a floating solar system. It connects solar panels to the control system and the energy storage device. In a floating solar system, cables are typically used for connecting solar panels to the power converter, the power converter to the charge controller, the energy storage device, and the charge controller's connection to the power distribution system.

(8) Transmission System: The transmission system is a critical component of a floating solar system, as it converts the generated energy into usable power. Typically, the floating solar system's energy is transformed into alternating current (AC) via a photovoltaic inverter, which is then transmitted over an AC transmission line to a nearby substation. The AC transmission line comprises an insulated copper cable, a grounding conductor, and a surge arrester. In order to ensure efficient energy transmission, it is crucial to select transmission lines suitable for the site's specific conditions.

(9) Floating Walkaways: Floating walkways are essential to the floating solar system. They provide a support structure for the solar panels and a pathway for personnel to access the panels for maintenance and repair. Floating walkways are usually constructed from heavy-duty aluminum or galvanized steel, which is highly resistant to corrosion and designed to hold up to the weight of the solar panels.

Looking at the cost breakup in Figure 1 of components for floating solar systems in India includes high cost related to Modules or solar panels as it is the most important components for the system and the cost is high due to taxes and transportation cost involved to it. Floating platforms are another major cost intensive components as it is not manufactured by many but by some of the companies so these components are majorly imported from other countries [22].

According to the Figure 2 we can see China has the highest number of solar PV installations done so far and Japan is second in the race till 2020. In 2007, Japan built the first Floating PV system. However, the initial applications of Floating PV systems were seen in the USA using the water reservoir after they were thought to be constructed for commercial use [23]. The first Floating PV system in the USA reportedly had an installed capacity of 175 kW. Kerala in India has established the greatest floating solar power facility in India, marking a significant development. The 500 KWp (Kilo Watt peak) power plant was inaugurated on December 4th, 2017 [24]. According to estimates, the facility would produce 7.5 lakh power units annually. Many of the big floating solar projects are coming up in India.

1.png

Figure 1. Cost breakup for installing floating solar [22]

2.png

Figure 2. The installed capacity of Solar PV systems at a global scale [25]

As we have seen in the above discussions, floating solar can have many positive effects and advantages, but to market and grow this technology, we need to mitigate certain challenges and improve the technology daily. Some of the major technological challenges are related to the mooring and anchoring layout, improved efficiency of solar panels, marine and logistics operations the material and components' durability [64]. The mooring systems usually ever hour experience clash with currents, waves and winds and help to keep the floating structure stationary. So, we need to innovate to come up with new and robust mooring components, which not only are less in price but maintenance is also less. We have encountered many applications of mooring systems in past when floating solar was not in the picture, like in offshore wind setups, oil and gas rigs/platforms, etc., but they all are costly affairs. Benassai et al. [65] discovered that by creating mooring patterns with a non-uniform angle distribution, mooring weight reduction can be accomplished for floating wind turbines in shallow water.

Benassai et al. [66] examined the motion control capabilities of tensioned line and catenary mooring systems for a Dutch tri-floater wind turbine at water depths between 50 m and 200 m, taking into account both operational and high load conditions. Benassai et al. [67] analysis was expanded to take into account line number, platform maximum acceptable offset, and mooring line pattern. Nine or twelve lines were suggested for mooring arrangements. The findings demonstrated that mooring line weight increases outside of this range, regardless of water depth, between 100 and 200 meters.

Brommundt et al. [68] created a numerical tool for catenary mooring system optimization, and a case study using a semi-submersible floating wind turbine with two different water depths was carried out [69].

The mooring system, which provides stability for vessels in deep water operations, is influenced by various types such as catenary, semi-taut, and taut. However, in harsh environments, these systems can experience instability due to extreme wave effects on the drillship and ship dynamics [70]. The mooring line dynamics become complicated in rough weather conditions, with large amplitude wave frequency motions and viscous flow-related hydrodynamic effects contributing to instability. The reliability of these systems is affected over time, as research shows that in large amplitude unstable sea states, the mooring system cannot keep the drillship on station [71, 72].

Now, taking up the issue of installing the structures in seas and rivers invites several complex activities like towing, positioning and maneuvering structures when and where required. The floating solar industry can take help and advantage of oil and gas companies working for many years related to the same. Another major challenge is the design of material/components used to sustain in a harsh oceanic environment where the material and components experience humidity, saltiness in water and stress; as we all know that saltiness in water compromises the materials and makes them corrosive, which can impact the increase of operation and maintenance costs and overall project costs and hamper the efficiency of the plant [22]. The tilt angle determination is another challenge faced in many projects, as the tilt is directly related to the site's latitude [73].

However, we see parameters like shading and soiling can influence it. If we increase the tilt angle, that would contribute to lower soiling but high self-shading. Certainly, a lower inclination will lower the wind effects and wind loads on the panels. Collecting data from surveys and studies such as geotechnical parameters, seasonal flow, bathymetry, water level variation, garbage quantity, and sediment movement is necessary. The industry does not have a standard approach to material life, testing, certification, and institutional process.

The supply chain is disjointed, and the suppliers' products differ. Floating solar panels require improved materials and coatings to withstand prolonged exposure to water, ensuring durability and corrosion resistance. Lighter panels and improved weight distribution mechanisms are crucial for stability and buoyancy. Improving solar panel efficiency is essential for both floating and ground-mounted installations.

Reducing heat sensitivity is also crucial for efficient solar panel use. Self-cleaning or low-maintenance solar panel coatings are beneficial for all solar installations, especially for floating solar. Minimizing the environmental impact of solar panel manufacturing and disposal is a global concern. Enhancing monitoring and control systems is essential for efficient power generation, distribution, and maintenance. Floating platform design needs continuous improvement to enhance stability, ease of installation, and resistance to extreme weather conditions. Water quality management is especially important for floating solar projects, as reduced circulation can lead to algae growth. Technologies for maintaining water quality and preventing ecological disruptions are specifically needed for floating solar projects.

Talking about commercial challenges faced by the floating solar business, especially in India, is because currently, in India, a handful of companies are present in the floating solar business. As we try to promote more floating solar businesses, more companies will come, and the knowledge pool will also increase, which can lead to lower costs by adapting certain innovative technologies and gradually decreasing the project cost [22]. However, the allocation and execution of projects are delayed by the lack of standard agreements for water rights and policies for using water bodies for floating solar. The lack of grids near solar power generating plants (FSPV) could be costly for developers and make the model inaccessible in hard-to-abate areas. Existing transmission lines near inland water bodies and the need for transmission infrastructure from water bodies to nearby sub-stations pose challenges.

The Maharashtra Bench of Authority for Advance Ruling and the Maharashtra Appellate Authority for Advance Ruling for Goods and Services Tax have determined that solar power generating plants are considered immovable property. However, with FSPV plants becoming mobile and floating over water bodies, legal determination or differentiation may be necessary [74].

Securing financing for floating solar projects can be challenging due to the relatively new and unique nature of the technology. However, promoting innovative financing mechanisms, such as green bonds, project financing, and risk-sharing models, can help attract investors. Collaboration with international funding agencies and banks can also provide access to low-cost capital. Encouraging private sector participation through public-private partnerships (PPPs) can also help attract investments. In addition, standard technical requirements for materials used in floats, mooring and anchoring, cables, solar panel technology, and balance of plant, among other things, are difficult to find but urgently needed.

4.png

Figure 4. Comparison of Capital cost for floating solar PV & land-based PV systems [75]

Note: Costs are based on a 10 MW system(assume). GST, 20% DC:AC overloading, and 25% safeguard duty on modules are all included in the price. In floating solar, testing and surveying expenses are higher because to hydrographic and bathymetric studies [75]

Talking about financial challenges in India, in Figure 4 we see how price comparison is done by Bridge to India for land based and floating solar PV components. We can see the structure cost is major actor for costly implementation of Floating PV projects. According to Charles Rajesh Kumar and Majid [76], the investment for installing the floating system in India is about 800 to 1200 USD per kW and for the land-based is about 600-650 USD per kW. The difference between the price for both systems is about 25 to 45%. Another thing is the supply of materials like floats and others, for which India must depend on other countries in Europe and China. Logistics is another challenge because the floats require a large space to be transported. For example, we say that to transport 20kW of floats, the space required is as big as required to transport 100kW of panels. The materials required to manufacture floats is HDPE, but import and transport become very expensive. So, in September 2018, an agreement was established between NTPC India and the Central Institute of Plastics Engineering and Technology (CIPET) to establish specific quality strategies, increase the number of suppliers, as well as floating industrial capacity. It is anticipated that increased volumes and a large local production capacity will reduce the 10% to 15% higher cost of floating solar plant.

Occupational health challenges also need to be considered while installing, operating, and maintaining floating solar systems. Solar PV projects in high-solar irradiation areas pose a risk to workers, with heat stress potentially causing a 2.2% global working hour loss by 2030. Acclimatized workers have higher work capacity, but heat-related conditions can affect productivity [77]. Solar radiation exposure can lead to skin cancer [78], and early interventions in the FSPV sector can help protect workers from these long-term health effects by providing shade, rest areas, sun-safety training, using sunglasses, headgear, sunscreens, and medical check-ups [79]. Bakhiyi et al. [80] highlight ergonomic risks in solar PV panel installation and maintenance, including electrocution, arc flash, wind speeds, fire, solar heating, and fall from elevated positions. Maintenance personnel should be aware of the PV system's inability to turn off and potential electrical leakage in highly humid environments, especially in cleaning and replacing panels [81]. FSPV workers face risks from microclimate, toxic chemicals, noise, and vibration. Prolonged wet-work during maintenance and repair of solar panels can lead to occupational skin disorders like Irritant Contact Dermatitis [12, 82]. During the installation of floating solar, the engineers and divers can experience cold and become hypothermic while underwater for the anchoring and mooring process, resulting in drowning underwater [76]. Employees may experience serious cuts and bruises while working in confined spaces. And also, the operator may experience a glare effect, which can have serious vision problems from solar panels and nearby water surfaces. If the floating solar is installed in high altitudes in lakes/rivers, the engineers and operators may also experience cold pressure. Also, if working in rivers and oceans, operators and engineers can experience natural calamities like hurricanes and tides, which can challenge operations and so cause serious life threats.

Certain challenges for land-based PV compared with Floating PV systems:

(1) Zoning and land-use restrictions: Local zoning laws and regulations can make it difficult to find suitable land for solar projects. Land availability can be limited, and conflicts may arise with agricultural or other land uses whereas floating solar systems utilize water bodies, which can reduce land use conflicts and free up land for other purposes.

(2) Interconnection and permitting: Connecting a solar power system to the grid can be complex and time-consuming, requiring various permits and approvals. Intermittent power generation and grid integration challenges affect both land based and Floating PV systems, necessitating solutions such as energy storage and advanced grid management needs to be arranged.

(3) Environmental impact: Some land-based solar projects may negatively affect local ecosystems, wildlife, and habitats. Careful planning and mitigation measures can help to minimize these impacts whereas Floating PV systems, when well-planned, can have a lower environmental impact and may even improve water quality in certain cases.

(4) Access to transmission lines: Solar installations are often located in regions with ample sunlight, which may be far from urban centers where electricity demand is high. Transmitting electricity over long distances can result in transmission losses and higher costs. Encouraging localized distribution of solar power by establishing microgrids or distributed energy resources can reduce the need for extensive long-distance transmission.

(5) Land ownership and leasing: In the case of land-based solar systems, securing land rights and easements for transmission lines from the solar site to substations or distribution points can be complex and may face resistance from landowners. Engaging with local communities and landowners to address concerns and provide incentives for allowing transmission lines to pass through their properties can help overcome land rights and easement challenges.

(6) Climate and weather: Land-based solar systems face climate and weather challenges like extreme temperatures, dust, and intermittent cloud cover. Solutions include robust panel materials, efficient dust control, weather forecasting technology, and solar tracking systems for improved performance. Floating solar systems can overcome climate and weather challenges by utilizing water's cooling effect, enhancing energy generation efficiency, reducing maintenance needs, and minimizing flood damage in flood-prone areas. This makes floating solar a resilient, climate-adaptive solution.

(7) High upfront costs: Both land-based PV and floating solar projects encounter the significant challenge of high upfront costs. In land-based PV installations, these costs include land acquisition, infrastructure development, and support structures. Similarly, floating solar systems require substantial investments for floating platforms, anchoring systems, and specialized components. The upfront cost challenge is common to both types of solar projects and underscores the importance of financial incentives, subsidies, and innovative financing models to reduce the economic burden on developers and promote the adoption of renewable energy solutions in India.