# African solar systems part 4: A problem on energy usage

Level pending

A person does not only require electrical energy. Consider the following daily typical energy usage:

• Reading and working for four hours after sunset in the light of a 10 Watt LED lamp.
• 3 L of sterilized drinking water. Sterilization of drinking water minimally requires the water temperature to be raised to $$100^\circ$$ C from the ambient temperature of $$25^\circ$$ C.
• 1 hour of cell phone or radio use at 0.5 Watts.

Given these energy requirements, what percentage of the total energy usage per day is made up of heat?

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