- As the sun spreads to newer areas including coastal areas, it is important to be prepared for preventive maintenance.
The working environment of a PV system is relatively complex and extreme environments such as high / low temperatures, humidity, salt spray, heavy sand and other harsh environments can test the reliability and environmental adaptability of the PV system. More and more PV systems are being built on water, in the desert and in coastal areas.
2-3 years after a power plant has been built and commissioned, extreme environmental conditions can have serious consequences for the equipment within the system; such as distribution box, assembly and inverter.
In this edition of the Solis seminar, we have analyzed the effects of salt spray and high humidity environments on the operation of solar systems and identified some solutions.
The effects of salt spray and high humidity environments
Salt spray contains a large amount of chloride ions that can easily penetrate the protective layer of a metal surface and cause an electrochemical reaction with the contact metal, leading to failure of a product. Solar power plants built along the coast are susceptible to the effects of high salinity and humid air. The external salt spray particles and humid air affect the components, cables (especially ground cables), metal brackets, inverters and junction boxes.
In addition, high temperature and high humidity environments also affect the PV system, such as:
- In environments with large temperature differences, such as beaches, mountains and other areas, water vapor evaporates and condenses.
- In places with high ambient humidity such as lakes, coastal areas, etc., the ambient air is humid and condensation can easily occur inside the device. This creates internal moisture and can lead to accidents with rollover.
- Exposed conductors can easily corrode in an environment with heavy salt spray and high humidity, which increases impedance and leads to poor contact.
Figure 1: PV terminals are corroded
Figure 2: Corroded PV modules and metal mounting equipment
If salt spray and water vapor are drawn into the junction box, terminal, or inverter, the long-term build-up will corrode the internal structure of the device and cause damage to the device.
Figure 3: Corroded circuit boards and components in the inverter
Figure 4: Corroded PE cable and inside of the mesh box
- The choice of equipment must take into account its ability to be protected
The equipment selected must have strict levels of corrosion protection and protection. Devices such as inverters and junction boxes that are used in areas with high salt spray or high humidity must have higher protection levels and corrosion protection than in other areas. It is recommended to use products with protection class IP65 or higher for the inverter, and the junction box must be galvanized and sprayed with anti-corrosion paint and be 100% airtight. In the case of inverters with IP65 protection, it can effectively prevent moisture from outside penetrating into the interior of the machine.
In addition, the circuit board and the electronic components of the inverter must be provided with a film coating, adhesive or protective lacquer in order to protect the circuit board from moisture, salt spray and mold.
The inverter must pass temperature and humidity tests as well as corrosion resistance tests. Look for the appropriate certification in your area.
We also need to pay attention to products like cables, metal brackets and combiner boxes. Such as:
- Choose PV products and metal mounting devices treated with anti-corrosion products.
- At the same time, the metal parts of the AC / DC / PE cables must not be exposed to air.
- The terminals should be shielded and attached to avoid contact with the metal surface.
Protective treatment during installation and construction
PV, PE and AC cables must be laid in PVC pipes for protection or buried in the ground to prevent the effects of abrasion and salt spray;
The metal bracket and the metal grounding grid must be painted with anti-corrosive paint or galvanized and checked and repaired at regular intervals to prevent subsequent corrosion.
When selecting the screw materials, special attention should be paid to the use of “Al / Zn bolts” to connect stainless steel plates in order to prevent electrochemical corrosion due to contact between different metals.
Plastic seals can be added to isolate the two metals and prevent “contact corrosion”.
For the combiner box or grid box, we need to use refractory slurry at the inlet and outlet to improve protection and prevent water vapor from entering.
Salt spray and high humidity environments can cause major corrosion problems for solar systems and seriously affect the safety, reliability and long-term operation of the power plant. Therefore, special attention should be paid in these environments; Device selection, construction as well as operation and maintenance in order to improve the operational stability of the PV system and reduce system errors.