Material Properties Flashcards

Mounting aluminum rails directly on uncoated copper in a wet environment mainly risks:

Answer: Galvanic corrosion of the aluminum

Aluminum is anodic to copper, so with an electrolyte the aluminum corrodes preferentially.

Aluminum's coefficient of thermal expansion is about 23 ×10⁻⁶/°C. How much does a 10 m rail lengthen over a 50 °C temperature rise?

Answer: 11.5 mm

ΔL = 23e-6 × 10,000 mm × 50 = 11.5 mm.

Hot-dip galvanizing protects steel racking mainly through:

Answer: A sacrificial zinc coating that corrodes before the steel

Zinc is anodic to steel and protects it cathodically even where the coating is scratched.

Ideally, a solar thermal selective absorber surface should have:

Answer: High solar absorptance and low thermal emittance

Selective coatings absorb shortwave sunlight well while radiating little longwave infrared heat.

Why do backsheets often contain a fluoropolymer layer such as PVF (Tedlar)?

Answer: For UV and weathering resistance plus electrical insulation

Fluoropolymers resist UV, moisture and chemicals while keeping the rear of the module insulated.

Which property makes copper preferred over aluminum for small PV string conductors?

Answer: Higher electrical conductivity and better termination reliability

Copper conducts about 60% better than aluminum and has fewer termination creep and oxidation problems.

What does a PV module's NOCT rating describe?

Answer: Cell temperature at 800 W/m², 20 °C ambient and 1 m/s wind

NOCT gives the expected cell temperature under defined field-like conditions, usually about 42–48 °C.