During the summer solstice sunset, light shines through a porthole and hits the very corner of a doorway into an eastern room. When the sun sets on the day of the winter solstice, it shines through a different porthole onto the corner of the doorway to the tower. The movement of the sun's rays along the wall is noticeable well before the solstice, so the Anasazi sun priests would have had time to plan their ceremonies. When the light first becomes visible in the room early in April, the Anasazi would have known that it was time to get ready to plant their first crops. These are houses made from mud bricks that have tremendous heat absorption ability.
Solar radiation is absorbed during the day and released gradually during the cold nights.
This is the equivalent energy available from 4.25 trillion barrels of oil. Well a typical household in the North Eastern part of the United States uses between 1000 and 2000 gallons of fuel oil per year. A square foot per gallon is based on the calculations below. In other words one square foot of will harvest about two gallon's worth of number 2 fuel oil. Lets be conservative though and simplify things.