What Factors Affect Off-Grid Solar Panel Sizing?

Load Calculation and Peak Demand

To size an off-grid solar system, calculate the total load in watt-hours per day (Wh/day). Determine the peak daily demand by adding up the power consumption of all loads (e.g., lights, appliances, and pumps) in watts (W). For instance, a 2 kW refrigerator consumes 2000 W. Calculate the daily load demand by multiplying the peak daily demand (in W) by 24 hours. A sample calculation: a 2 kW refrigerator’s daily load demand is 2 kW * 24 hours = 48 kWh/day.

System Efficiency and Battery Capacity

System efficiency factors, such as inverter efficiency and battery depth of discharge (DOD), also impact solar panel sizing. A common inverter efficiency is 95%. A 12V battery with a 50% DOD can provide 4.8 kWh of usable energy per day. Multiply the daily load demand by the system efficiency factor and battery capacity to determine the required solar panel wattage. For example, a 48 kWh/day load demand requires a 60kW solar panel array, considering a 95% system efficiency and using 12V batteries with 50% DOD.

Worksheet and Calculation Techniques

A worksheet or solar system sizing software can help streamline the calculation process. Key inputs include the daily load demand, system efficiency, battery capacity, and solar irradiance. Use the worksheet to calculate the required solar panel wattage and determine the optimal panel size. A common solar irradiance value is 5-6 peak sun hours (PSH) per day. Multiply the required solar panel wattage by the solar irradiance to determine the required panel area. For instance, a 60 kW solar panel array requires approximately 240-288 square meters of panel area, assuming a 5-6 PSH irradiance value.