BY JOSE PALU-AY DACUDAO
WHENEVER energy is transformed from one form to another, some of it is always lost as heat energy.
A classic case is the amount of energy lost in the food pyramid. From one trophic level to the next, at least 90% is lost as heat. For example, a plant (say part of a sugar cane) contains 1000 calories. Only 100 calories can be used by the herbivore (say a goat) that eats the sugar cane plant. Only 10 calories can be used by the carnivore (say a leopard) that eats the goat. Poor leopard, but at least it’s on top of the food pyramid.
This an important principle on energy transformation or conversion.
Let us take for another example, electric vehicles. If the electricity comers from batteries that in turn is charged by electricity from a gasoline powered turbine of an electric generator, energy will inevitably be lost as heat. Below is a simplified representation of the process.
Chemical energy in gasoline → heat energy released by combustion of the gasoline → mechanical energy of heated moving gas → mechanical energy of the turbine of an electric generator → electricity (electrical energy) → chemical energy of a battery → mechanical energy that powers the wheels of an electric vehicle
Each arrow above represents a transformation of conversion of energy that loses energy as heat. The efficiency is never 100%. In the physical sciences, power is the rate of transferring energy (or rate of doing work, energy and work having the same unit, the joule) which is energy divided by time or how fast work is done.
In other words, efficiency is ratio of the amount of power, produced by a machine to the amount of power put into it. For example, the internal combustion engine of a car is usually only about 25% efficient. The rest of the energy (75%) is wasted mostly as heat.
There many arrows above. Each arrow represents a process of energy transformation in which some energy is lost, mostly as heat. Such waste of energy! In general, the more processes involved (the more arrows in our representation), the more energy is wasted.
Now note the following (more traditional) process.
Chemical energy in gasoline → heat energy released by combustion of the gasoline in an internal combustion engine → mechanical energy of the heated moving gas → mechanical energy that powers the wheels of a vehicle
Less arrows. Less energy is wasted as heat.
It can be deduced from the above that electric vehicles waste more gasoline if gasoline is the original source of energy.
The same is true for any other fossil fuel, be it coal (made up mostly of carbon), crude oil (from which gasoline is derived) or natural gas (made up mostly of methane). (To be continued)/PN
