25 Nov '11, 12pm

The Energy Return on Investment Threshold

The Energy Return on Investment Threshold

We must first realize that EROI is a somewhat theoretical concept; it is a unitless ratio that does not describe actual flows of energy. What society really cares about, and what is really used to grow economies around the world, are actual flows of energy. More precisely, the economy utilizes flows of net energy. What, if anything, can EROI tell us about the flow of net energy? To understand how EROI influences the flow of net energy, we must first look at the equation for both net energy and EROI, which are: Net Energy = Eout – Ein EROI = Eout/Ein If we solve the EROI equation for Ein and substitute it into the Net Energy equation, we get: Net Energy = Eout*((EROI-1)/EROI) From this equation Mearns (2008) created the “Net Energy Cliff” graph. The net energy cliff figure relates the percent of energy delivered as net energy (y-axis, dark grey) and the percent of energy us...

Full article: http://www.theoildrum.com/node/8625

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