EGEE 102
Energy Conservation and Environmental Protection

Solar Energy for Home Heating


Energy that is received on the roof of a house is more than enough to supply the heating needs of the home. The energy reaching the earth from the sun ranges from 600 to 2000 BTUs per square foot per day (averaged over a year). It is a function of the latitude of the place. The amount of solar radiation reaching the earth is called the insolation. This is a short from for incident solar radiation per day.

The earth revolves around the sun with its axis tilted toward the plane of rotation.

  • In June, the North Pole is tilted toward the sun and the solar rays are incident perpendicularly. Therefore, the sun appears to be at a higher angle.
  • In December, the North Pole is tilted away from the sun and therefore days are shorter and the solar rays are incident more obliquely, with lower energy flux (winter).
Illustration of the sun and the Earth during the different seasons.
Illustration of Seasons for Northern Hemisphere

The sun also changes in position and angle from the earth during various times of the year.

Instructions: Press play to observe the movement of the sun as a function of the seasons.

Movement of the Sun with the Seasons

Click here to open a text description of the movement of The Sun with the seasons.

Movement of the Sun with the Seasons

From June through December, the Sun's highest point in a given day moves lower and lower towards the horizon.