Floating Photovoltaics Solutions-the New Engine of Offshore Photovoltaics
With the in-depth promotion of the "dual carbon" goals, offshore photovoltaics has become an important field of global new energy development, leveraging its advantages such as not occupying arable land, superior lighting conditions, and high power generation efficiency. According to calculations by industry professional organizations, the potential installed capacity of global offshore photovoltaics is approximately 4 billion KW, and China's theoretical installed capacity of offshore photovoltaics exceeds 100 million KW, indicating a very promising development prospect.
With the continuous support of national and local policies, the development and construction of domestic offshore photovoltaic (PV) projects have entered the "accelerated implementation" phase. A series of landmark projects, such as the 2,000 MW mudflat PV demonstration project in Tianwan of China National Nuclear Corporation (CNNC), the 310 MW offshore PV pilot project in Changli of Hebei Huadian Power Generation Co., Ltd., the 400 MW PV project in Rudong invested by Guohua, and the 400 MW offshore PV project in Zhaoyuan of Yantai of China Guangdong Nuclear Power Group, have been implemented in a concentrated manner.
Meanwhile, coastal provinces such as Jiangsu, Zhejiang, Hebei, and Shanghai have successively completed the allocation of owners and confirmation of rights for offshore photovoltaic projects within their jurisdictions. According to statistics from Beiji Xing Solar Photovoltaic Network, the currently clearly planned offshore photovoltaic scale in China is close to 100 GW, and the offshore photovoltaic scene is steadily moving from the "pilot" stage to the "large-scale" stage.
However, it should be noted that currently, offshore photovoltaic projects in China mainly adopt the pile-based fixed technology in mudflats and intertidal zones. Although such technology is mature and reliable, it is highly dependent on nearshore shallow sea resources. As the exploitable areas in the nearshore become increasingly saturated, exploring deeper and more distant waters has become an inevitable choice, and the floating photovoltaic solution is the key direction for expanding the incremental space of offshore photovoltaics.
As we venture into the deep and vast ocean, the bottleneck of floating photovoltaic technology becomes increasingly prominent.
Although the floating photovoltaic solution is the core development direction for offshore photovoltaics in the future, its technological exploration is currently still in the "demonstration and verification stage", with multiple key technologies urgently needing breakthroughs.
On the one hand, floating photovoltaic solutions face harsh environments such as heavy waves, typhoons, sea ice, high salt spray, high humidity, and frequent temperature changes. Issues such as salt spray corrosion, seawater corrosion, and water vapor infiltration impose higher requirements on photovoltaic equipment. On the other hand, existing floating photovoltaic systems have obvious shortcomings. Some photovoltaic products, verified by multiple empirical projects in recent years, are still unable to fully meet the "large-scale, long-term stability" power generation needs in the deep and open sea.
Especially for the photovoltaic (PV) mounting system, which is the core of floating PV systems, the three mainstream structures currently available on the market - blow-molded floating body, thin-film, and high freeboard - all have certain "weaknesses".
Specifically, the blow-molded floating structure consists of a closed buoy made of polymer materials, which is then assembled into a floating PV mounting structure through clamps. Although it has advantages such as light weight, low processing cost, and convenient installation, its disadvantages are also prominent: weak wave resistance, poor fatigue resistance of connecting parts, and susceptibility to failure under long-term wave cyclic loading. The system's lifespan is usually less than 5 years, making it only suitable for enclosed waters with minimal wind and waves, and unable to meet the operational needs of open seas or semi-open waters. It is difficult to adapt to deep-sea scenarios.
Compared to the blow-molded buoy structure, the membrane structure has undergone optimization and upgrading in terms of wave resistance performance. It consists of photovoltaic modules, hydroelastic flexible membranes, buoyancy rings, and damping wires. The photovoltaic modules are attached and installed on the flexible membranes, which not only utilizes the water cooling effect to enhance power generation efficiency but also significantly improves wave resistance compared to the blow-molded buoy. In theory, it is more suitable for operation in deep and open seas. However, this technology has a core flaw: it relies on continuous water pumping to maintain system stability. If the water pump malfunctions, the entire system will lose balance, posing a risk of damage and serious reliability concerns, making it unable to ensure long-term stable operation.
Among the three mainstream structures, the high-freeboard structure is currently the most extensively explored direction for deep-sea environments. By raising the metal supports, it elevates the photovoltaic modules 7 to 10 meters above the water surface, and combines with a rigid framework to enhance wind and wave resistance. This design significantly improves the adaptability to harsh deep-sea environments, effectively addressing issues such as strong winds, waves, and deep water levels. However, this "strong adaptability" comes at a high cost, making it difficult to achieve large-scale promotion. This is contrary to the industry's development goal of "reducing costs and increasing efficiency," and it is currently unable to support the large-scale development of floating photovoltaics in deep seas.
These technical shortcomings were more intuitively exposed during practical project verification: The Hainan Wanning offshore floating test site, which adopted a blow-molded floating structure, was dismantled after just ten days of operation due to sea area approval issues, and test data showed that its maximum withstandable wave height was only 1.5 meters, indicating severe lack of wave resistance performance.
The Guoneng Dongtai 100kW offshore project, which employed a thin-film structure, suffered from reliability issues and became a core bottleneck for its promotion after two months of operation due to the absence of a water pump, resulting in damage to the thin film and photovoltaic panels and their sinking to the bottom. The Shandong Huaneng Huanghai No.1 project, which adopted a high freeboard structure, achieved technical breakthroughs in offshore distance of 30 kilometers, water depth of 30 meters, and extreme wave height of 10 meters, effectively avoiding wave impact on photovoltaic panels. However, due to the high cost of supports exceeding 10 yuan per watt, the economic shortcoming was difficult to overcome, making it impossible to achieve large-scale replication.
Balancing performance and cost, basalt scaffolding "breaks the mold"
When various technical approaches were caught in the dilemma of "either insufficient performance or excessively high cost", the emergence of basalt offshore floating supports provided a solution that balances performance and cost for offshore photovoltaic scenarios.
This floating photovoltaic (PV) bracket, specifically designed for marine environments, addresses core challenges faced by offshore PV systems, such as poor corrosion resistance, weak wind and wave resistance, and high operation and maintenance (O&M) costs, through targeted technological innovations, from material selection to structural design. It precisely compensates for the performance shortcomings of traditional floating PV brackets.
Specifically, regarding anti-corrosion and durability, the "primary challenge" of offshore photovoltaics, the core reason why traditional supports struggle to be used for long periods at sea lies in the vulnerability of floating bodies and metal materials to the impact of sea winds and waves, as well as erosion from marine microorganisms. Therefore, PE100 grade polyethylene round pipes are used for floating bodies. These materials have been verified through an 1,840kwh/㎡ ultraviolet radiation aging test, and meet standards for yellowing index and tensile strength, with a design lifespan of up to 25 years. For supports, basalt fiber composite profiles are employed, with a density only 25% of steel but a tensile strength four times that of ordinary steel. This not only reduces the structural self-weight but also avoids corrosion risks.
In terms of structural design, traditional supports often prioritize the stability of individual units, yet overlook the "systemic damage" caused by wave impact. To address this, a circular ring structure is formed as the floating body through hot-melt welding at both ends. The circular design serves a wave-dissipating function akin to a breakwater, reducing the direct impact of waves on the components. Moreover, with the concentric arrangement of multiple rings, peripheral loads (such as gravity, wind force, and pressure) can be evenly transferred to the rings, dispersing stress concentration and enhancing the overall structural resistance to deformation and load-bearing efficiency. Simultaneously, the spoke-like structure reduces unnecessary material usage through a design that "replaces compression with tension" and "supports more with less," significantly reducing self-weight while maintaining strength. The components are installed on basalt fiber composite purlins, minimizing the likelihood of direct wave impact on the components. The connection between the purlin and the floating body employs a pin design, allowing the purlin to rotate and swing within a certain angle, effectively dispersing stress concentration caused by wind and waves and preventing structural fracture.
The anchoring system serves as the foundation for offshore photovoltaic (PV) mounting structure. Traditional anchoring systems often exhibit poor adaptability and are prone to damage due to insufficient consideration of the variability of seabed environments. When designing anchoring systems for renewable energy, comprehensive consideration is given to environmental conditions such as wind, waves, and water levels under extreme conditions, providing users with solutions such as pile anchors and sinking anchors. The accompanying mooring lines adopt a three-segment structure: the upper part uses chains to avoid ultraviolet aging issues associated with plastic ropes; the middle part employs multi-layer woven polyester fiber ropes to reduce weight and prevent twisting; and the bottom part again uses chains to resist friction from seabed gravel. This layered design enables the anchoring system to adapt to changes in wind and waves while maintaining long-term stable operation.
The design for operational and maintenance convenience is quite outstanding. The circular floating body itself serves as a circumferential operational and maintenance channel. By replacing one of the photovoltaic panels with a grating panel in the radial direction, a radial channel is formed, allowing maintenance personnel to easily reach any position in the array. If a single spoke or photovoltaic panel is damaged, targeted replacement is sufficient without the need for overall disassembly. Dismantling the photovoltaic panel requires only simple ladder climbing tools, without the need for complex equipment.
In terms of key performance parameters, basalt scaffolding indeed demonstrates excellent performance: the maximum diameter of a single scaffolding ring is 100 meters. The power of a single component is 720Wp. The maximum number of components installed on a single scaffolding is 2000. The capacity of a single set of scaffolding is 1,440kw. The wind resistance is 50m/s, and the wave resistance is 4 meters high. All performance parameters are in the leading position in the industry.
