With an average altitude over 4000m, Tibet has been called the “Roof of the World”. Rapid economic growth and booming tourism have Challenged the energy supply system of Tibet greatly, moreover, with the development of peoples living standard, the requirement of improve the indoor thermal environment would put greater pressure on it. On the other hand, solar energy resource in Tibet is the richest where receives an average annual radiation intensity of 7000MJ/ m2 because of its small cloudy, rarified atmosphere, high transparency, low water and dust content.