As in any energy form, energy can be stored or released from it. For example, we can lift a weight to increase its potential energy and we can recover that energy when the weight is lowered. This is also likely be true with this biological energy entity. This must be achieved by the brain while we are sleeping. After sleeping, we feel refreshed, both physically and mentally, because we have recovered our biological energy.
Animals are very vulnerable during sleep.
Thus there must be a good evolutionary reason for animals to sleep. I next investigate how the brain uses up its energy. The electrical activity in the brain consumes about 15 watts of energy. In Nelson et al.'s model of the brain, the body is treated as a large tank maintained at a constant temperature, the core temperature. The brain is treated as a small container which draws and circulates blood from the body.