CSLB C-46 Solar ContractorPlanning and EstimatingMedium
A C-46 contractor is designing a grid-tied PV system for a residential client. The client's average daily energy consumption is 20 kWh. Assuming 5 peak sun hours per day and a system derate factor of 0.77, what is the approximate DC array size required to meet 100% of the client's energy needs?
- A6.8 kW
- B4.2 kW
- C7.5 kW
- D5.2 kW
Show answer & explanationAnswer & explanation
Correct answer: D. 5.2 kW
To calculate the required DC array size, first determine the daily AC energy needed from the array. Then, divide by the peak sun hours and the system derate factor. (20 kWh / 5 peak sun hours) / 0.77 = 5.19 kW, which is approximately 5.2 kW.
Why the other options are wrong
- A. This value might result from an incorrect application of the derate factor, such as dividing by 1.77 or multiplying by 0.77 instead of dividing.
- B. This value is obtained if the derate factor is incorrectly applied as a multiplier to the daily energy or if the calculation is reversed.
- C. This value is too high and suggests an error in the calculation, possibly multiplying by the derate factor instead of dividing, or an incorrect assumption of peak sun hours.
PV System Sizing (DC Array)
The process of calculating the required DC power output of a solar array to meet a specific energy demand, considering site-specific factors.
- Determines the total wattage needed from solar panels.
- Accounts for daily energy consumption, peak sun hours, and system losses (derate factor).
- Crucial for meeting client energy goals and optimizing system performance.
Memory trick: Sun's Power Calculates Necessary Array.