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Step 2 Autonomy / Reliability

Solar power can provide in a reliable power demand. But everybody knows that the sun is not always the most reliable partner. In the wet season, he hides himself behind heavy clouds, sometimes for several days. The concept Autonomy we define as the number of days the system will supply power without sunshine. In most countries a autonomy period of 3 days will be enough for most ordinary applications. There is a statistical chance that the power will drop now and then, but this could be considered as a fact of life. A larger number of autonomy days will decrease the chance. For professional applications sometimes a higher reliability is needed, for example cooling of medicines in a remote health centre. A period of 5-10 days could be considered.

The battery capacity directly results from the determined minimal autonomy period. In the example Step 1: Daily power demand of 2.00 kWh the full battery should be able to provide 6.00 kWh at autonomy requirement of three days.