Why We Must Conserve Energy

Today I asked the Oracle of Google about why we must conserve energy.  A smattering of the response:

• In the Wake of the Gulf Oil Disaster, We Must Conserve Energy, 
• Do it all: U.S. must conserve energy in production boost 
• China Must Conserve Energy Or Pay Huge Price, 

To really understand why we have to conserve energy, an introduction to thermodynamics is necessary.

The first thing you have to know about thermodynamics is that it is completely whacked.  In school we used to say that most of the sciences were related, except for thermodynamics which mutated from another universe. 

 The laws of thermodynamics are based on heat experiments conducted by Carnot, Clausius and others in the early 19^th century. Thermodynamics, as its etymology implies, is the science of heat.  What is heat?  Heat is a measure of energy flow between two systems at different temperatures.  Pretty straightforward stuff, but it is amazing how profound the insights from these studies of heat have proven to be.

"Four score and seven years ago..."  Oops!  Wrong guy.
Rudolph Clausius

Let me give you an example of why undergrads flee at the very word Thermodynamics. There's four Laws of Thermodynamics:  The First, Second, Third and Zeroth Law. 

That's right. Zeroth.

Apparently just numbering them up from one would have been too easy.  Also keep in mind that the Second Law was actually discovered before the First Law, and the Zeroth Law was discovered after both of them.  I can't even remember what the Third Law is.  No, no; stick with me, I'm just getting warmed up here.  It gets worse.

The First Law of Thermodynamics you  have definitely heard of.  It’s called the Conservation of Energy (mass-energy, since Einstein, actually).  It states that energy can be neither created nor destroyed; it can only change forms.  Energy must be conserved.  Let's follow Ernest Enviroweenie and Dudley Dorkus:

Ernest Enviroweenie: 

The environment is going to pot, climate change is going to smite us big time, and we're running out of oil.  We have to conserve energy.

Dudley Dorkus: 

You mean we haven't been conserving energy?

Ernest Enviroweenie:

No, we've been wasting it. Do you realize that an incandescent bulb is just a heater that happens to emit 5% of its energy as light? Internal combustion engines operate with a measly efficiency of about 20% It's enormously wasteful.  That's not conserving energy.

Dudley:

Sure it is.  Energy is always conserved.  It's the First Law of Thermodynamics.  As a matter of fact, if you can find a way not to conserve energy, I'm willing to bet there's a Nobel Prize in it for you.

Ernest:

That's not what I meant.

Dudley:

Well, that's what you said.

Ernest: 

This is why you have no friends.

What Dudley is saying is that the First Law of Thermodynamics dictates that energy is conserved.  So, in the case of the light bulb, 100% of the energy going into the system is conserved. It goes in as electrical energy and it comes out transformed as light energy (5%) and infrared energy ("heat").  So all the energy is there, it's just that only 5% is the kind of energy we want in this case.  

In the case of a baseboard heater, electrical energy is converted to thermal energy (infrared radiation). In a fireplace, chemical energy is converted to heat and light.  In a nuclear reactor, nuclear energy is converted to electricity.  In an automobile chemical energy is converted to mechanical work and heat.  In none of these cases is one iota of energy lost.  Energy is conserved. 

So the First Law of Thermodynamics tells us:    

 (Don't tell your kids this yet, it'll just create problems with the teacher.)

So obviously we' re conserving energy.  We have too.  But what is Ernest Enviroweenie really seeking to conserve then?

Well actually, he wants to anti-conserve entropy.  I told you it was going to get worse.

We'll get into that one next time.