Solar radiation on a typical day at the end of January in Tucson is shown at right. Thus, we must calculate the number of Joules per week. The rest of the light is blocked by the structure of the greenhouse. The average tomato production by the greenhouse is 1,800 tomatoes per week. Each tomato has approximately 70 cal.
Food calories are actually thousands of calories.
Thus, each tomato has 70,000 calories. The internal reaction term in the conservation of energy equation is the amount of solar energy that is successfully converted to tomatoes by photosynthesis. We know that the change in storage term is zero because Dr. Giacomelli does not allow any tomatoes to rot on the vine so there is not an increase in the number of tomatoes on the vine per week. Let us plug numbers into the conservation of energy equation. Of course, L is the energy lost and not used by the tomatoes.