The Jevons Principle

I remember my grandmother's refrigerator.  As a small boy I can still remember this massive white object in her small kitchen.  She lived by herself - - so by my current standards it always appeared empty (She weighted less than 100-pounds, threw away less spoiled food than me, and lived to be in her 90s - - modern refrigeration, spoilage, and consumption are highly correlated).  The freezer part had nothing to freeze - - her small country grocery store had less frozen items than the 7-11 near my house.  I remember the frost and my grandmother having to defrost the refrigerator by hand.

The world has changed since my grandmother's refrigerator.  The average refrigerator sold in the U.S. today uses 3/4 less energy than the 1975 average, even though it is 20% larger and costs 60% less (see Energy Vision Update 2010: Towards a More Efficient World).  All of this sounds really great, right?  I am not so sure.  Look at my 2010 refrigeration experience and see what I have done with my energy savings since I was a little boy in my grandmother's house.  It appears that I have actually "consumed" my energy savings - - either partially or fully.  I have one refrigerator in the kitchen, a second one in the laundry room (old refrigerators don't die, they just move to different parts of the house), and a third small refrigerator associated with a bar in the family room.  Yes, I spend less per BTU on refrigeration and my cost per refrigeration space is lower - - but am I actually consuming less energy on refrigeration than my grandmother?  A very interesting and important question for engineers.

My grandfather's first car was a Ford Model T.  According to the Ford Motor Company, its fuel economy ranged between 13 and 21 miles per gallon (so after roughly 100-years, my Dodge Ram is somewhere in the middle of my grandfather's Model T).  My grandfather had one vehicle for a family of four - - I have three vehicles for a family of three.  My family vehicle efficiency is probably double my grandfather's - - yet I consumed my efficiency improvements with additional cars, living farther from work than my grandfather, and vehicular air conditioning (like many southern and western states - - automobiles are really nothing more than a very expensive and complex device for transporting air conditioning between buildings!!).  Increased technological advancement on a miles per gallon basis has actually produced more total consumption for my family.

In both examples, I appear to be consuming efficiencies.  Technological gains and greater efficiency on a per unit basis have actually led to greater consumption of a resource, not less.  A world marked by greater and greater unit efficiencies, yet higher and higher per capita energy and resource consumption - - not a pretty picture for the future of sustainability (By 2014, the U.S, computer network alone will each year require an amount of energy equivalent to the total electricity consumption of Australia).

Enter William Stanley Jevons.  Jevons was a British economist and author of "The Coal Question" in 1865.  The Jevons Principle, that greater per unit efficiency actually produces greater total resource consumption is stated as follows"

"It is wholly a confusion of ideas to suppose that the economical use of fuel is equivalent to a diminished consumption.  The very contrary is the truth."

Engineers will all agree that decreasing reliance on fossil fuels is a pressing global need.  The key question the engineering community faces is whether improving efficiency, rather than reducing total consumption, can possibly bring about the desired result.  The answer might just be with my grandmother's refrigerator.  The primary problem with per unit efficiency gains is that we appear inevitably to "reinvest" savings in additional "things" that ultimately increases total consumption.  In addition, understanding systems is very important for all engineers - - you have some very potent positive feedback loops all over your house.  The ability to chill and freeze more things at lower and lower unit costs has led to me buying more items that need chilling and freezing - - leading to a need for more refrigeration space.

Welcome to the world of Mr. Jevons.