Solar energy can be the primary source of winter space

Chapter 11, Problem 11.49

(choose chapter or problem)

Solar energy can be the primary source of winter space heating for a typical house (with oor area 130 m2 1 400 ft2) in the north central United States. If the house has very good insulation, you may model it as losing energy by heat steadily at the rate of 1 000 W during the winter, when the average exterior temperature is 5C. The passive solar-energy collector can consist simply of large windows facing south. Sunlight shining in during the daytime is absorbed by the oor, interior walls, and objects in the house, raising their temperature to 30C. As the sun goes down, insulating draperies or shutters are closed over the windows. During the period between 4 PM and 8 AM, the temperature of the house will drop, and a sufciently large thermal mass is required to keep it from dropping too far. The thermal mass can be a large quantity of stone (with specic heat 800 J/kgC) in the oor and the interior walls exposed to sunlight. What mass of stone is required if the temperature is not to drop below 18C overnight?