Quick Answer
To size solar panels for an EV, calculate the daily energy requirement based on the battery capacity and desired daily mileage, then use the resulting watt-hours per day to determine the required solar panel wattage.
Calculating Daily Energy Requirements
To size solar panels for an EV, you need to calculate the daily energy requirement in watt-hours (Wh). For example, if you have a 60 kWh battery and plan to drive 40 miles per day, assume an EV efficiency of 3 miles/kWh. This means you’ll need 40 / 3 = 13.33 kWh to travel 40 miles. Assuming 8 hours of solar charging, the daily energy requirement would be 13.33 kWh x 1.2 (safety factor for charging efficiency) = 16 kWh. Convert this to watt-hours per day by multiplying by 1000 (since there are 1000 Wh in 1 kWh): 16 kWh x 1000 Wh/kWh = 16,000 Wh or 16 kWh.
Determining Required Solar Panel Wattage
To determine the required solar panel wattage, divide the daily energy requirement by the number of peak sun hours (PSH) available per day. For the southern United States, assume an average of 5 PSH per day. Divide the daily energy requirement of 16 kWh by the number of PSH: 16,000 Wh / 5 PSH = 3200 W. Round up to the nearest 100 W (to account for losses and inefficiencies): 3300 W. Therefore, you would need at least 3300 W of solar panels to meet the daily energy requirement.
Considering Real-World Factors
When sizing solar panels for an EV, consider real-world factors that can affect charging efficiency, such as panel tilt, shading, and temperature. Assume a 10% loss due to these factors and increase the required solar panel wattage by 10%: 3300 W x 1.1 = 3630 W. This will ensure that you have a comfortable buffer to account for any losses or inefficiencies.
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