Floating Photovoltaic (FPV) systems represent a rapidly growing segment of the solar energy market, offering a solution for land-constrained regions. However, the unique aquatic environment poses challenges not present in terrestrial installations. This study investigates a critical reliability and environmental issue: the potential submersion of photovoltaic cables. When cables are partially or fully submerged, the insulation material may degrade, leading to reduced electrical performance and the risk of contaminant release (e.g., copper, microplastics) into the water body. The research aims to quantify these effects under controlled freshwater and artificial seawater conditions, providing essential data for FPV system design, component selection, and environmental impact assessments.
The experimental design simulated real-world FPV cable exposure scenarios to evaluate material durability and environmental impact.
Two types of photovoltaic cables with different insulation sheaths were tested: one with a standard rubber-based insulation and another with a cross-linked polyethylene (XLPE) insulation. Cable samples were fully submerged in two separate tanks: one containing freshwater (simulating reservoir conditions) and another containing artificial seawater (prepared according to ASTM D1141 standard). The submersion period lasted for 12 weeks.
Water samples were collected weekly from each tank. Parameters monitored included:
Insulation resistance was measured weekly using a megohmmeter, applying a test voltage of 1000 V DC. The resistance ($R_{ins}$) was recorded in megaohms (MΩ). A significant drop in $R_{ins}$ indicates degradation of the insulating material's dielectric properties. The test followed the procedure outlined in IEC 60227.
The most significant finding was the accelerated degradation of the rubber-sheathed cable in artificial seawater. Its insulation resistance dropped by over 70% within the first 4 weeks, stabilizing at a critically low level. In contrast, the XLPE-sheathed cable showed a much slower decline, maintaining a resistance above the minimum acceptable threshold (typically >1 MΩ/km) for the entire test period. In freshwater, both cable types exhibited minimal degradation. This highlights the aggressive nature of saline environments on certain polymer matrices, likely due to chloride ion penetration and electrochemical reactions.
Chart Description (Imagined): A line chart would show "Insulation Resistance (MΩ)" on the Y-axis against "Time (Weeks)" on the X-axis. Two pairs of lines (one for each cable type in seawater and freshwater) would be plotted. The rubber-seawater line would show a steep, rapid decline. The XLPE-seawater line would show a gentle, shallow decline. Both freshwater lines would remain nearly flat and high.
Correlated with the insulation failure, a measurable increase in dissolved copper ions was detected in the seawater tank containing the degraded rubber-sheathed cable. Concentrations rose from below detection limits to approximately 15 µg/L by week 8, exceeding background levels and some environmental quality standards for aquatic life. No significant copper release was observed in the freshwater tanks or with the XLPE cable in seawater. This confirms that insulation failure is a direct pathway for heavy metal contamination from conductor corrosion.
FTIR analysis confirmed the presence of polymer particles in the water, identified as fragments of the cable sheath material. The quantity was higher in the seawater tanks, suggesting that mechanical abrasion combined with chemical degradation leads to the shedding of microplastics. This presents a secondary, long-term ecological concern for FPV deployments.
The insulation degradation can be modeled as a first-order kinetic process, where the rate of resistance loss is proportional to the concentration of aggressive ions (e.g., Cl⁻). The model can be expressed as:
$\frac{dR}{dt} = -k \cdot C_{ion} \cdot R$
Where $R$ is insulation resistance, $t$ is time, $k$ is a material-specific degradation rate constant, and $C_{ion}$ is the concentration of aggressive ions. Integrating this gives an exponential decay: $R(t) = R_0 \cdot e^{-k \cdot C_{ion} \cdot t}$, which fits the observed rapid decline in seawater for rubber.
An effective risk assessment for FPV cable deployment should follow this decision framework:
The findings directly inform the next generation of FPV technology:
Core Insight: This study isn't just about cable failure; it's a stark revelation that the current "land-PV-at-sea" approach is fundamentally flawed for large-scale, durable FPV deployment. The industry's blind spot has been assuming terrestrial components are fit-for-purpose in a highly corrosive, dynamic aquatic environment. The accelerated degradation of standard rubber insulation in seawater isn't an anomaly—it's the predictable outcome of using cost-optimized materials in an un-optimized context. The real cost isn't just cable replacement; it's systemic energy loss and latent environmental liability from copper and microplastic pollution, which could trigger stringent regulatory backlash, as seen in other marine industries.
Logical Flow & Strengths: The research methodology is robust, mirroring real-world stress factors (salinity, prolonged immersion) and employing a multi-pronged analytical approach (electrical, chemical, physical). The clear differentiation between material performances—rubber's catastrophic failure versus XLPE's resilience—provides an immediate, actionable guideline for developers. Linking insulation breakdown directly to measurable copper ion release is a powerful, evidence-based argument that moves the discussion from theoretical risk to quantified hazard.
Flaws & Omissions: While critical, the study's scope is a starting point. It lacks long-term data (>1 year) and doesn't account for real-world variables like UV exposure synergies, biofouling effects on degradation, or dynamic mechanical stresses from waves. The focus on complete submersion may overlook the more common and insidious risk of intermittent splashing and condensation in junction boxes. Furthermore, the economic analysis is absent. What is the levelized cost of energy (LCOE) impact when factoring in premature cable replacement or water treatment costs? Without this, the business case for premium marine-grade cables remains vague.
Actionable Insights: For project developers and investors, this study is a mandate for change. First, material specification must be paramount. RFPs should explicitly require cables certified for permanent immersion in the project's specific water chemistry (fresh, brackish, marine), referencing standards like IEC 60092 for shipboard cables. Second, design philosophy must evolve. Cables should be treated as critical, protected assets—routed in dedicated, sealed conduits or buoyant trays above the waterline where possible, not as afterthoughts trailing in the water. Third, embrace smart monitoring. As seen in offshore wind, integrating Distributed Acoustic Sensing (DAS) or time-domain reflectometry into cables can provide early failure detection, turning a reactive maintenance model into a predictive one. Finally, the industry must proactively collaborate with environmental agencies to establish science-based monitoring protocols and discharge limits, pre-empting restrictive regulations. The future of FPV isn't just about floating panels; it's about building intelligent, resilient, and ecologically integrated energy systems from the cable up.