Key Points in the Construction of Floating Photovoltaic (PV) Systems
When designing floating photovoltaic systems, it is essential to consider the specific characteristics of the site. Climatic conditions such as wind load, snow load, and temperature must be taken into account, as well as environmental factors like sunlight, humidity, acid rain, and stress impacts. To ensure that arrays do not collide under extreme weather conditions, the transformer platforms should be staggered between two power generation units, sharing a single maintenance channel. This arrangement improves water surface utilization and reduces costs while ensuring normal access for maintenance. In terms of power unit layout, the use of DC cables should be minimized while ensuring maximum displacement of the units. Additionally, fatigue analysis should be conducted on the connection nodes of the floating pontoons under wind and wave conditions.
Floating PV systems are generally divided into five systems: the floating system, anchoring system, cabling system, grounding system, and substation with transmission lines.
The floating PV system includes the PV array floating system and the electrical equipment floating system. Material selection and installation methods should fully consider a 25-year lifespan and the convenience of maintenance. The anchoring system should use specialized anchors and incorporate measures to adapt to water level changes based on hydrological data and subsidence reports. The cabling system includes the laying of AC/DC cables and collector lines. DC and AC cables in the PV array area should be fixed to floating pontoons and laid using cable trays to facilitate maintenance. Collector lines should be laid on floating structures, ensuring ease of future maintenance. Cable design should account for water level fluctuations by providing sufficient cable length, and the cable sheath material should be selected based on the natural environment of the water body. The connection method between cable channels and transformer platforms should be clearly defined, as water level changes and strong winds significantly impact underwater collector lines, especially at cable joints. The grounding system should be determined based on factors such as water quality. Grounding leads for the floating parts should include measures to adapt to water level changes and provide redundancy. A unified grounding network should be established for protective grounding, operational grounding, and overvoltage protection grounding, with a grounding resistance of no more than 4Ω.
Among these five systems, the anchoring system is the most challenging aspect of designing a "floating power station" and is critical to the reliable operation of the floating, cabling, and grounding systems. During the design phase, calculations should include overall and local buoyancy of the floating structures, support system calculations, wind load, water flow force, wave force, local stress on floating structures, connection bolts and nodes, wire rope clamp tightening force, waterway design, and boat docking positions.
In terms of equipment selection, floating power stations often operate in high-temperature, high-humidity, and even salt-spray environments, leading to high failure rates of components. Equipment should minimize the use of vulnerable parts to reduce maintenance difficulties. The highest dust and water resistance ratings should be selected for equipment. To minimize the environmental impact of transformer oil leaks, dry-type transformers should be used. The numerous MC4 connectors between PV panels are prone to wear in high-humidity environments, complicating maintenance. During construction, environmental factors should be considered by elevating the panels above the water surface. Custom PV panels can have shorter positive leads and longer negative leads, with connectors placed below the panels and insulated to significantly reduce operational failures.
Preparation during the construction phase should be thorough. Design drawings and calculations should be detailed and comprehensive, providing sufficient information for contractors to develop installation plans. The construction team should be established according to contract requirements and bid commitments, with personnel arriving on-site as planned. Quality assurance, safety, and environmental protection systems should be improved, with corresponding management measures promptly issued. Transport and deployment vessels should be ready to meet schedule requirements, and rescue vessels should be on-site for emergencies. Other related equipment and instruments should arrive with personnel. Construction organization plans, emergency response plans, special measures (e.g., anchor block deployment, temporary assembly, transport, and special weather conditions), and project acceptance evaluation tables should be submitted and approved. Qualifications of personnel, equipment, and instruments should be reviewed and approved. Design drawings should be reviewed, and design briefings completed. Safety training for on-site personnel should also be finalized.
The anchoring system is critical to the safe and reliable operation of other systems, and the deployment of anchor blocks is a concealed project. The entire process, including the production and curing of anchor blocks, confirmation of underwater topography, connection of anchor wires to anchor blocks, determination of wire length, tightening and force testing of wire clamps, transport of anchor blocks, positioning and deployment of anchor blocks, and GPS positioning, should be monitored and promptly inspected. Temporary assembly of arrays should be based on the designed anchoring method, with temporary assembly areas sized accordingly and anchor blocks placed around the perimeter. Arrays should be anchored during the downtime to prevent wind-induced collisions. No mechanical equipment is needed for installation, but care must be taken to protect components and floating pontoons (wall thickness) during manual handling. During transport and deployment, arrays are vulnerable to wind-induced collisions, so weather conditions should be closely monitored to determine the optimal timing for transport, deployment, and anchoring. Arrays should be anchored immediately after deployment. Underwater collector lines should avoid water ingress at cable ends, and care should be taken to prevent damage to the outer sheath during towing. Flexible slings should be used for cable lifting, and cable heads should be designed with high waterproof ratings and rigid connections. Metal frames can be added to support cable heads and reduce stress. For the construction of electrical equipment floating platforms, the significant weight of the platforms and equipment require hoisting machinery with appropriate tonnage and lifting radius based on on-site conditions. Steel structures should be zinc-sprayed at the base, and care must be taken to avoid collisions and damage to the anti-corrosion layer during construction.
