The Energy Conversion Matrix
Forms of energy are interchangeable. When gasoline is burned in an automobile engine, potential energy is first turned into heat. A portion of this heat, say 25%, is then converted into mechanical motion. The remainder of the heat is wasted and must be removed from the engine.
A multitude of processes and devices have been found which make these transformations from one form of energy to another. Many of these are listed in the blocks in [Figure 2]. Asterisks refer to direct conversion processes, the subject matter of this booklet.
To demonstrate how this diagram is to be read, let us use it to trace the energy transformations involved in an automobile engine. We begin with sunlight because all coal and oil deposits (the fossil fuels) received their initial charge of energy in the form of sunlight.
The first conversion, therefore, is from electromagnetic energy to chemical energy via photosynthesis in living things. We trace the transformation by moving down the column marked Electromagnetic Energy until it intersects the horizontal row labeled Chemical Energy. There we see photosynthesis listed in the block. The next conversion is from chemical energy to thermal energy via combustion. We trace this by moving down the Chemical Energy column to the Thermal Energy row; combustion is listed in the appropriate block. The third and final conversion takes place when thermal energy is transformed into mechanical energy via the internal combustion engine.
By the repeated use of the Energy Conversion Matrix in this way, we can chart any energy transformation.
Problem 1
Continue the automobile example by going through the matrix twice more showing how mechanical energy is converted into stored chemical energy in the car’s battery.
Problem 2
If 1 gram of gasoline (about a tablespoonful) yields 48,000 joules of thermal energy when burned with air, how fast can it make a 1000 kilogram car go? Assume the car starts from rest and its engine is 25% efficient.
Answers to problems are on [page 34].