In the first two posts in this series (1 and 2), I discussed the requirements and challenges of transitioning our global economy to renewable sources of energy. My interim conclusion was that there are serious doubts about our ability to affect any significant transition from fossil fuels to renewable energy. Much of this uncertainty is the result of uncertain systemic energy return on energy invested. In other words, when all inputs are taken into account—as must be done where we’re talking about shifting energy sources on a civilizational level—can a world powered by solar and wind power itself the way it has on oil, gas, and coal?

The key take away is precisely this uncertainty: we simply don’t know if renewables—either current or potential future technology—will be up for the job. Where does that leave us? This discussion—and many others related to Peak Oil—is really a matter of what is known as the “Precautionary Principle,” or what degree of consensus is required before we embark on a course of action that may result in irreversible harm. Because the Precautionary Principle has such broad application in discussions of Peak Oil, I’ve modeled this post as a discussion of the principle itself, using the issue of renewables transition as but one example of its application.

In the first part of this series, I discussed the practicality of a future transition from fossil fuels to renewable energy sources—specifically renewable sources of electricity such as solar and wind power. One little-discussed hurdle is the fact that, because we must invest energy in renewables up front, a rapid transition threatens to greatly impact near-term demand for energy resulting in unwanted economic and political effects. Another is that, because we will initially use fossil fuels to build our renewable infrastructure, the transition to renewables will result in a short-term increase in carbon emissions. The extent to which both of these impacts will be significant, even their potential to foreclose the possibility of such a transition, will turn on the net energy, or Energy Return on Energy Invested (EROEI), of available renewable energy technology.

As I alluded to last time, while there are many EROEI numbers floating about for solar, wind, etc., these numbers are far less accurate or verifiable than is, I believe, commonly assumed. I’ll argue that our measurements of EROEI are fundamentally flawed, at least for some purposes. Most EROEI studies serve as a tool to compare different technologies or to gauge advances in technology--a role for which they are generally well suited. However, when viewed from a complete systems perspective, current EROEI figures fail to provide an inclusive measurement. I’ll argue that, for purposes of planning a civilizational transition, a meaningful meansure must be inclusive of all energy inputs. Finally, I’ll propose a possible proxy-measurement to address the methodological issues surrounding EROEI.

A silver mask that had belonged to a Roman cavalryman of imperial times. It was found on the site of the battle of Teutoburg, fought in September 9 a.d. This year, 2009, marks the 2000th anniversary of the battle that led to the annihilation of three Roman legions and changed forever the history of Europe. It was a tremendous shock for the Romans, who saw their mighty army destroyed by uncivilized barbarians. It was not yet the peak of the Roman Empire, but it was a first hint that something was deeply wrong with it.

Global GDP data from the USDA. Primary energy data and energy prices from the BP statistical reveiw of world energy 2009.

Global GDP has grown steadily and continuously since WWII, in step with a growing global population and primary energy consumption (see below). Oil shocks have caused recessions compensated by higher energy prices that have bolstered global GDP at time of recession in the non-energy economy.