Net Energy vs. Efficiency
Hey guys,
Looking over my study guide, I’m confused about the difference between net energy and efficiency. Is there a difference? As I understand it:
Net energy is the amount of energy available minus energy needed to extract/process/etc.
Efficiency is input= output/percent efficient.
Aren’t these definitions basically two different ways of saying the same thing–that the second law of thermodynamics ensures that heat will be lost in all reactions, thus input will never equal output, yet the degree to which energy is lost in the reaction varies?
Thanks!
April 15th, 2010 at 9:11 pm
Net energy has more to do with energy put into getting the fuel versus energy obtained when it is burned. If it takes 3 times more energy to extract and refine oil sands compared to barrel of light crude, then why would we want it?
Efficiency is HOW WELL a device does its job (or a person). So if a light bulb is supposed to make light, but it only converts 5% of the electricity input into light then it is not very efficient is it? Yes, the 2nd Law of Thermodynamics does affect efficiency-input cannot equal output. Note there are some key efficiencies to memorize in the study guide. I’ve seen those on practice exams in the past.