Effects of Humidity and Salinity in Coastal PV Installations

Effects of Humidity and Salinity in Coastal PV Installations in India Effects of Humidity and Salinity in Coa...

Effects of Humidity and Salinity in Coastal PV Installations in India

Introduction

India's push towards renewable energy has resulted in rapid deployment of photovoltaic (PV) systems across diverse geographical terrains. Coastal regions, which receive high solar irradiance and have vast stretches of available land and rooftops, are attractive for solar investments. However, they are also prone to harsh environmental conditions such as elevated humidity and airborne salinity due to proximity to seawater. These factors can significantly deteriorate PV system performance and increase maintenance costs if not properly addressed.

This article delves deeply into how humidity and salinity affect PV installations in coastal India, with a focus on material degradation, system reliability, and long-term energy yield. We also include technical mitigation strategies, real-world case studies, and standardization practices that enhance system resilience in such challenging conditions.

1. Coastal Environmental Conditions in India

India's coastal belt spans over 7,500 km, covering states like Gujarat, Maharashtra, Goa, Karnataka, Kerala, Tamil Nadu, Andhra Pradesh, Odisha, and West Bengal. These regions are marked by unique climatic conditions that challenge solar PV infrastructure.

High Relative Humidity: Frequently ranges between 70% to 95%, especially during the monsoon season, affecting encapsulants and increasing moisture ingress risk.
Salt-laden Wind: Seawater aerosols carried by wind deposit chloride particles on surfaces, increasing corrosion risks and electrical faults.
Temperature Fluctuations: Diurnal temperature variation combined with humidity causes material expansion/contraction, aggravating mechanical stress.
High Rainfall and Flooding Risk: Coastal storms and cyclones can inundate ground-mounted systems, leading to insulation failures.

2. Impact of Humidity on PV Installations

a. Moisture Ingress and Encapsulant Degradation

Moisture ingress through the edges of PV modules accelerates encapsulant degradation. The commonly used Ethylene Vinyl Acetate (EVA) turns yellow and brittle over time, reducing light transmission and causing power loss.

Leads to delamination of module layers.
Reduces the structural integrity and electrical isolation of the cells.
Moisture-induced corrosion of interconnect ribbons causes electrical disconnection.

b. Reduced Electrical Insulation and Leakage Currents

High humidity lowers surface insulation resistance, especially in connectors, junction boxes, and inverters. This can cause:

Leakage currents and ground faults.
Risk of arc faults leading to fire hazards.
Loss in inverter efficiency and early component failure.

3. Impact of Salinity on PV Installations

a. Corrosion of Metallic Structures

Salt-laden air initiates electrochemical corrosion on all metallic surfaces. Chloride ions particularly accelerate pitting and galvanic corrosion, especially at junctions of dissimilar metals.

Frame corrosion may lead to water ingress and delamination.
Rusting of mounting structures compromises mechanical strength.
Oxidation of bus bars and connectors increases resistance and power loss.

b. Salt Deposition on Glass and Soiling Losses

Salt spray deposits a thin white film on glass surfaces, reducing optical clarity and light transmittance. Combined with dust, bird droppings, and humidity, this leads to:

Reduction in solar irradiance capture by 5–20% depending on location.
Formation of hotspots due to non-uniform soiling.
Increase in panel temperature, reducing module lifespan.

4. Real-World Case Studies

Case Study 1: IIT Madras Study on Coastal PV Degradation

The Indian Institute of Technology Madras conducted a multi-year degradation study of PV modules installed in Chennai, which faces year-round humid and saline conditions.

Key Findings:

10–12% annual power degradation vs 1–2% inland degradation.
Visible corrosion on aluminum frames and junction boxes within 2 years.
Early onset of delamination and yellowing of EVA layer.

Reference: ScienceDirect – Degradation of PV Modules in Coastal Tamil Nadu

Case Study 2: NTPC Simhadri Floating Solar Project

The NTPC’s 25 MW floating solar project in Simhadri, Andhra Pradesh, employed advanced mitigation strategies for saltwater proximity.

Anti-corrosive epoxy-coated structures and marine-grade SS bolts.
Use of PID-resistant bifacial modules.
Performance ratio maintained above 75% after 18 months.

5. Degradation Mechanisms: Summary Table

Degradation Type	Cause	Effect on System
Electrochemical corrosion	Humidity + chloride ions	High resistance, open circuits
Delamination	Moisture ingress	Reduced insulation, power loss
Glass soiling	Salt and dust accumulation	Reduced light absorption
PID (Potential-Induced Degradation)	Humidity + voltage stress	Rapid efficiency loss

6. Mitigation Strategies

a. Material Engineering

Use anodized aluminum frames or SS316-grade steel for mounting.
Choose modules with multi-layer encapsulants and UV-stable backsheet.
Deploy junction boxes and connectors with IP68 ratings.

b. Protective Coatings

Apply hydrophobic and anti-soiling nano-coatings to PV glass.
Use epoxy or polyurethane paints over metallic parts.
Ensure cathodic protection where applicable.

c. Design Best Practices

Elevate PV structures above flood line by at least 1 meter.
Use tilted modules to promote water runoff.
Minimize cable exposure and keep electronics in weather-sealed enclosures.

d. O&M Protocols

Monthly cleaning with demineralized water in high-salinity areas.
Quarterly IR inspections and continuity testing.
Bi-annual re-coating of exposed surfaces.

7. Applicable Standards

IEC 61701: Salt Mist Corrosion Testing of PV Modules.
IEC 60068-2-52: Environmental Testing for Marine Equipment.
MNRE Guidelines: Recommend anti-corrosive certification for coastal projects.

8. Cost Implications

Installing in coastal zones may increase CAPEX by 10–15% due to enhanced materials and protective systems. However, this cost is justified by reduced failure rates and longer asset life.

Conclusion

PV installations in India’s coastal zones demand a high level of engineering foresight, from component selection to maintenance scheduling. While challenges due to humidity and salinity are substantial, they can be mitigated through robust design practices, material resilience, and vigilant O&M. As India expands its solar ambitions, ensuring the long-term sustainability of coastal PV assets will be key to maintaining energy security and investment value.