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.