Assuming a mage individual has a specific organ or a system (like neural?) that can influence outside material world but in order to do so requires the energy directly fed to the cells in the same manner the muscle and neuron cells do. Meanning that it would only accept ATP or creatine phosphate (CP) and not unrefined glucose, glycogen or fats.
How much energy in joules would be available for such individual to perform an act of magic
in a burst - fraction or couple of seconds.
short time - tens of seconds to couple of minutes.
long period - one or several hours.
Through out the day.
2 - 4 meaning how much energy is available per given time value(second, minute, hour) for said period.
Quick google search says there's only around 5 Kcal worth of energy in ATP/CP on average in the body which equals to mere 20900 joules. Note that rapidly depleting most of it will result in death which implies that a person must have a surplus of it to use in the act of magic. The rest is gradually converted from glucose and glycogen.
There's a lot of similar threads but the answers tend to get carried away into total energy capacity via fat or total energy available through out the day being expended in a single act.
Things to consider:
- Conversion speed between ATP/CP, glucose and glycogen.
- Waste and other byproducts of said reactions like creatinin.
- ATP/CP is either evenly distributed through out body or concentrated in the certain parts of it meaning that the net(gross) value may or may not be used fully for the act.
what constitution a mage should be to have more energy capacity?
Things about diet and possibility of mana potions - something that can quickly add energy(edible glucose) or accelerate the conversion of fat/glycogen(coffeine, creatin or l-carnitine).
What could be achieved with the resulting amount of energy assuming a given amount of efficiency(%) - ie it's unlikely that a mage can simply add up energy freely to someone's brain in order to fry it. There has to be a mechanism of transferring said energy which inevitably introduces waste.