Hi, Nick.

I think it better to look at the relationship between GDP and work, not GDP and BTU's because when we look for some result, the result is a function of work first and BTUs second. If I ask someone to build a house, they base their calculations on how much work is involved, then they split it between their men/women and the machines. The contractor will move jobs between men and machines (assuming the job can be done by either) based on cost, time and quality of the end product.

I view oil as "stored work" in much the same way some people view money as stored work. Converting to BTUs is an interesting exercise but since the various energy forms are not easily converted, or aren't easily converted without significant losses, I think it makes things unnecessarily complex to reduce that far. Work is a better measure for the purpose at hand. This might be why Hirsch chose to go that route.

Regardless, I'd have to go back and look at the context of the 0.14 you cite because it is very suspicious to me. If it turns out that you're using it in the context Ayers intended (which paper and which page?), one way I could see it being valid is with the proviso that much manufacturing continue to be done by other countries. This state of affairs is coming to an end as globalization begins to unwind.

When all is said and done, I'm happy for the moment to say that a 1/10th ratio for oil to work is too small and 10:1 is too great, which leaves 1:1 as the proper order of magnitude.

-André

"once you account for electricity BTUs being more productive than coal BTUs (easier to use precisely) then the "unknowns" drop out of the relationship"

First, I'd note that Hirsch is talking about oil: his hypothesis is that GDP will drop in a 1:1 relationship with oil, as oil declines. The summary of the paper quoted above suggests that Cleveland is talking about the relationship of GDP to all fuels, which is very different. That approach suggests that wind, solar and nuclear (or, god forbid, coal) electricity will substitute for oil quite nicely.

2nd, The paper says: "If we are to sustain current levels of economic growth and productivity as minimum long-run goals, alternative fuel technologies with EROI ratios comparable to petroleum today must be developed, or there must be unprecedented improvements in the efficiency with which we use fuel to produce economic output".

Well, we've done that. Wind, solar and nuclear combined with PHEV/EVs fits the first requirement (alternative fuel technologies with EROI ratios comparable to petroleum today), and the improvements in efficiency are being found.

3rd, this paper is from 1984 (so the data is 25-35 years old), well before it was clear that since that time US (and world) GDP would grow much more quickly than it's energy consumption (even including electricity). The best example of this is California, which has kept per capita electricity consumption flat over the last 25 years, while growing it's GDP relatively quickly.

4th, Ayres used "exergy services", which are not "very close to BTU parity". Exergy services are work performed. So, for instance, a Prius performs the same work as a similar vehicle with half the MPG, but uses half the BTU's. Strictly speaking, a Prius can perform the same work as a Hummer (transporting people), and use 20% of the BTU's. An EV also does the same work as a Hummer, and uses about 1/3 of the BTU's as the Prius, and 1/15 of the Hummer's...and so on.

Please note, this has been revised several times.

Hi, Engineer-Poet.

I think you hit the nail on the head when you point out that the conclusions were drawn several years ago. That means they were formed in a pre-peak world using the typical economic and monetary discount functions we've all come to understand.

What I am saying, however, is that not many people I come across have done the work of reassessing their projects in the light of a post-peak economy. For instance, I think the project will have trouble even getting financing, never mind convincing people (who won't own the cars because we're heading into a depression) that it's in their interest to lend out their batteries.

I think this is fun to think about but has exactly 0% probability of becoming a large-scale reality. If the world economy, suffering from shortages that mess up our just-in-time systems, and sky-high oil prices, is declining at something like 2% to 5% per year, vehicle to grid is, in my view, going to remain one of those good ideas that we just didn't get done in time.

-Andre'