Quick Answer
Sizing a solar array for grid defection requires careful consideration of factors like energy demand, solar irradiance, inverter efficiency, and battery storage capacity.
Assessing Energy Demand
To size a solar array, start by calculating your daily energy demand in watt-hours (Wh). This involves multiplying the peak daily load by the number of hours it is used. For example, if your peak load is 2 kW and it is used for 8 hours, your daily energy demand is 2 kW x 8 hours = 16 kWh. Next, consider the desired level of autonomy, such as storing 2-3 days’ worth of energy for a comfortable lifestyle.
Evaluating Solar Irradiance and Inverter Efficiency
Solar irradiance varies by location, with average values ranging from 1,000 to 2,000 watts per square meter (W/m²). To determine the required array size, use the National Renewable Energy Laboratory (NREL) PVWatts calculator or a similar tool. Keep in mind that inverter efficiency affects system performance; look for inverters with high DC-to-AC efficiency (e.g., 98-99%) to minimize energy losses. For example, if you’re using a 98% efficient inverter, you’ll need a slightly larger solar array to meet your energy demands.
Considering Battery Storage Capacity
When pairing a solar array with battery storage, consider the depth of discharge (DOD) and cycle life of the batteries. Aim for a 50% DOD to ensure a long battery lifespan and use a battery management system (BMS) to monitor and control the charging and discharging process. For example, if you’re using a 10 kWh battery bank with a 50% DOD, you can store up to 5 kWh of energy. This will help you determine the required solar array size to recharge the batteries during the day.
Find more answers
Browse the full Q&A library by topic, or jump back to the topic this question belongs to.