how mach heat can a person produce by his body and activities every day?

Answer 1

Hard to say. It depends heavily on the person, the person's weight, the temperature, etc.

People engaged in very strenuous exercise can go above 5000 KCal/day,

http://www.coolantarctica.com/Antarctica%20fact%20file/science/food.htm
http://www.curewalk.com/northpole.asp

but whether they can do it day in and day out is a different question.

Check out:
http://en.wikipedia.org/wiki/Basal_metabolism
http://en.wikipedia.org/wiki/Metabolic_equivalent

and the links from there