Solar PV System Design, Sizing, Load Estimation and Energy Yield
Solar PV System Design, Sizing, Load Estimation and Energy Yield
This domain tests the design chain: load sheet, daily energy, peak sun hours, array and battery sizing, and expected yield.
Core rules
- Build a load sheet: watts × hours per day = Wh/day for each appliance.
- Array size (W) = daily energy (Wh) / (peak sun hours × performance ratio).
- Performance ratio (PR) bundles temperature, soiling, mismatch, cable, inverter and availability losses; 0.70–0.80 is a common design range.
- Battery Ah = (daily Wh × autonomy days) / (battery voltage × DoD × inverter/charge efficiency).
- Inverter continuous rating must exceed total simultaneous AC load; cable voltage drop should be kept low.
- Yield (kWh/year) = array kW × PSH/day × 365 × PR.
Worked example
A load uses 2000 Wh/day. Site PSH = 5, PR = 0.75. Array = 2000/(5 × 0.75) = 533 W; select 2 × 300 W = 600 W. For one day autonomy at 12 V, DoD 0.5: battery = 2000/(12 × 0.5) = 333 Ah; choose 400 Ah. Annual yield estimate = 0.6 × 5 × 365 × 0.75 = 821 kWh.
Traps that cost marks
Using connected load instead of daily energy; forgetting PR or using 1.0; mixing Wh and Ah; sizing battery without DoD; ignoring inverter standby consumption; using summer PSH for a year-round critical load.