Time to wrap up my "Renewables Hump" series with a few concluding thoughts. Below are links to each of the prior 7 posts. My current plan is to synthesize this series into a shorter set of posts for The Oil Drum--I'll post those links here when they're up.
Renewables Hump 1: Introduction
Renewables Hump 2: Digging Out of a Hole
Renewables Hump 3: The Target
Renewables Hump 4: EROEI Issues
Renewables Hump 5: Proxy EROEI Calculations
Renewables Hump 6: EROEI of Solar and Wind
Renewables Hump 7: Can We Transision?
In wrapping up my thoughts on EROEI and the potential for our civilization to transition to renewable sources of energy, there remains at least one loose end I'd like to address:
Climate change. One of the most frequently-cited arguments in favor of transitioning to renewable sources of energy is that these technologies tend to be zero-carbon soruces of energy. What seems to go unsaid, however, whether we're talking about solar, wind, geothermal, or even (not really renewable) nuclear, is the up-front carbon footprint required to build this infrastructure. Simply put, the vast majority of the energy required to build a renewable energy generation infrastructure will be carbon-heavy fossil fuels. That means, in order to affect a transition, we need to spike carbon emissions in the build-up phase in order to reap lowered carbon emissions at some point in the future.
This necessarily cycles back to the EROEI questions that I have raised in this series. If the EROEI of renewable technology X is 40:1 over a 20-year lifespan, then only a very small amount of fossil fuels must be burned to produce long-lasting clean energy, and after a very short time the remainder of this transition can be financed with clean energy from the renewables build at the outset of the project (here, as fast as 6 months with a maximal investment at startup). Of course, if the EROEI is actually 4:1 over that same 20-year lifespan, for every 4 tons of carbon saved over that lifespan, one ton must be emitted in production, and that carbon emission must be up-front. Additionally, it won't be possible to bootstrap this clean energy to produce more clean energy for years, and likely far longer because it would create an impracticable energy price spike to build enough generation at the very outset of such a transition to allow for complete bootrapping of the next waves of production.
All this boils down to some of the most poorly understood aspects of climate science: are we better off raising carbon levels now in order to better reduce them in the future, or is it more important (from the perspective of various feedback loops, etc.) to keep levels from ever going over a certain threshold, even if that means more overall emission down the road? We simply don't have an answer to this question, but it suggests that the climate/carbon argument for a renewables transition is, at a minimum, built on a shaky and uncertain foundation. The real problem is that--much like broader discussions of the renewables transition--the uncertainty in the carbon-reduction argument for renewable energy flies under the radar because nearly all involved in the discussion use very high EROEI figures for renewables. If these figures, as I have argued, could actually be 10x lower than current estimates, then much of the current debate is off track.
None of this is to suggest that we should use uncertainty to abandon action, to stop efforts to transition to a sustainable society. However, we must accept this uncertainty in deciding HOW to best make that transition. More centralized wind and solar and a better grid might be the answer. It might not. Maybe the answer is decentralization and radical reduction in energy consumption? As I'll address in the future, structurally self-interested participants tend to argue for the former solution--you don't hear GE raising the uncertainties and potential socio-political pitfalls of centralized wind or solar. Unfortunately, we'll only find out if their confidence in our ability to transition was misplaced after such efforts have conclusively failed...