Alarge oak tree produces 3 tons of wood in 50 years of growth. the tree has a canopy 10 m in diameter and collects solar energy for 6 months of the year. the average solar insolation during this 6 months is 177 w/m2. assuming a wood heating value of 20 mj/kg, what is the tree’s efficiency for converting solar energy?

Awall of 0.5m thickness is to be constructed from a material which has average thermal conductivity of 1.4 w/mk. the wall is to be insulated with a material having an average thermal conductivity of 0.35 w/mk so that heat loss per square meter shall not exceed 1450 w. assume inner wall surface temperature of 1200°c and outer surface temperature of the insulation to be 15°c. calculate the thickness of insulation required.