Hot Box


In 1760 Horace de Saussure observed that a room covered with glass gets hotter when sunlight passed through it. He determined the effectiveness of trapping heat in this manner by building an insulated, glass-covered pine box. When exposed to sunlight he observed the interior temperature exceeded the boiling temperature of water. His discovery laid the foundation for the development of the solar collector, Trombe Wall, and the solar greenhouse

The Greenhouse Effect is a method of trapping heat. Visible and ultraviolet light passes through a transparent glazing like glass. Once these short wave radiations strike a darkened surface they release some of their energy and are transformed into a long wave IR radiation. These long waves are reflected back from the glazing and trapped inside the greenhouse or collector. 

The Hot Box  is a solar thermal energy project designed to test the greenhouse principle.  Shoe boxes, aluminum foil, black paint, plastic or glass are all that’s needed for this experiment.  

The scientific method requires that we test one variable at a time so we’ll be testing glazing material and absorber plate color separately.  

Step1. Insulate the boxes with cardboard to slow down the heat loss process. Be sure to use the same amount of insulation in both boxes.
Step2. Glue aluminum foil inside the boxes. The boxes should be as identical as possible except for one thing, the inside of one should be painted black and the other should be left alone.
Step3. Cover each box with clear plastic and place them in direct sunlight.

Hot Box EXPERIMENT You'll need a good digital thermometer  to do this experiment. Expose both boxes to sunlight. Record the temperature inside each shoe box at one minute intervals. Some glazing materials work better than others at trapping heat. Always make a note of the date, time, ambient temperature and weather conditions. Also try to run your experiments in direct sunlight on a clear day to be consistent.
1. Which one seems to trap heat better? Why?
2. Replace the plastic lid of both boxes with glass, repeat the experiment, record and explain the results.

Some glazing materials work better than others at trapping heat. The glazing material used in this experiment was Kalwall (fiberglass reinforced plastic). The graph was printed from thermal data collected from an Onset Hobo data logger on January 14, 2004 . It was a partially cloudy day an the ambient temperature was 200 F.  

Please upload the data from this experiment to the Bulletin Board under HOT BOX. Use the following standard format when posting your experimental results:

TIME OF DAY..................................
TYPE OF GLAZING..........................

Summarize your results, suggest methods of improving the accuracy of this experiment, and suggest a practical application.

Notice how rapidly the temperature inside the hot box rose after 10 am . By 11 AM the hot box temperature was about 170 F; eventually the temperature peaked at 200 F. After that some clouds rolled in and the temperature dropped off. Your hot box might not get this hot, but who knows it might get hotter. A hot box is used to demonstrate the greenhouse effect as well as test glazings and absorber plate coatings.