Question 1

What is the temperature coefficient of a solar panel?

Accepted Answer

The temperature coefficient (γ) is the rate at which a panel's power output changes per degree Celsius above the standard test condition of 25°C. Typical crystalline silicon panels have γ ≈ −0.35 to −0.45 %/°C. For example, if cell temperature reaches 60°C in summer, output drops by (60−25)×0.40% = 14%.

Question 2

How is the capacity factor of a solar PV system calculated?

Accepted Answer

Capacity Factor (CF) = Annual Energy Output [kWh] / (System Rated Capacity [kWp] × 8760 h) × 100%. Typical rooftop solar in Japan achieves 10–15%. It depends on panel rated power, installation conditions, irradiance, temperature losses, and inverter efficiency.

Question 3

How is cell temperature estimated?

Accepted Answer

Cell temperature is estimated as T_cell = T_amb + (NOCT − 20) × G/800, where NOCT is the Nominal Operating Cell Temperature (typically 44–48°C) and G is irradiance in W/m². At standard conditions (G=800 W/m²) with ambient temperature 25°C, T_cell ≈ 50°C.

Question 4

What is specific yield (kWh/kWp/year)?

Accepted Answer

Specific yield (SY) = Annual Energy Output [kWh] / System Peak Power [kWp]. It normalizes generation per unit of installed capacity, making it useful for comparing systems of different sizes. In Japan, SY typically ranges from 900 to 1300 kWh/kWp/year depending on location and tilt.

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