Quick Answer
Energy storage is not strictly necessary in a well-designed passive solar home, but it can be beneficial in certain situations, such as during extended periods of cloudy weather or at night when the home is not generating power.
Energy Storage for Extended Weather Conditions
In a passive solar home, energy storage can provide a buffer against variability in the weather, ensuring a stable power supply even when the sun is not shining. For example, a well-designed earthship home in a region with frequent cloudy days can benefit from a battery bank to store excess energy generated during sunny periods. A 12-kWh battery bank can be sufficient for an average-sized earthship home, providing 2-3 days of backup power.
Energy Storage for Nighttime Power
Passive solar homes often rely on thermal mass to store heat during the day and release it at night. However, this thermal mass does not provide electricity. In such cases, energy storage can be used to power electric lighting, appliances, and other devices during the night. For a typical earthship home with a 2-kW solar array, a 6-kWh battery bank can provide 3-4 hours of backup power at night.
Selecting Energy Storage for Your Passive Solar Home
When selecting energy storage for your passive solar home, consider the following factors: the size of your solar array, the energy demands of your home, and the local weather patterns. A rule of thumb is to choose a battery bank that can store 2-4 days’ worth of energy. This will ensure a stable power supply even during extended periods of bad weather. Additionally, consider using a battery bank with a high depth of discharge (DOD) to maximize its lifespan.
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