Hi, thanks for the thougful response. You spent quite some time to put things down clearly, and I appreciate that.
I think i can accept your conclusion, for the most part. Saying âa EROI of 2:1 means half your resources go to energy productionâ is indeed a big simplification on my part, which is based on several simplifications I have made and didnât detail :
Currently, energy makes about 6,5% of global GDP (well, that was 2021. For 2022, itâs about 13%). So between 1/â10th and 1/â20th (closer to 1/â20th). This means for every point of GDP invested in energy, between 10 and 20 points of GDP are created.
Currently, the global EROI of energy is between 20:1 and 10:1 (closer to 20:1, but depends on whether you take final or out of the mine well). So for every unit of energy, between 10 and 20 units of energy are created.
From this, I make the overal simplification of âEROI is representative of the share of energy in global GDP, roughlyâ
âHalf of resourcesâ translates roughly to âHalf of GDPâ (since there is a 99% correlation between energy consumption and GDP on a year by year basis, even if this gets bigger over 50 years)
That the current relationship, for fossil fuels, still stands with solar
These are indeed huge simplifications I made in my head, but I can get why you donât see them as valid. I unfortunately didnât really understand your algebra bitâI am not very good at reasoning with equations, it doesnât really âclickâ with the way my brain works. But I understand your overall point.
So ok, letâs drop the assumption that a 2:1 EROI requires half of societyâs resources. I indeed donât really know the exact percentage. This wasnât really my main point, so I removed references to this assumption in the full doc.
However, what empirical data seems to indicate is that society still requires a high EROI to function. As said in another comment :
In the meantime, what Iâm basing myself on is that most of the past societies had quite a high EROI (>10), including hunter-gatherers and agrarian societies (source, page 42). This surplus would allow for the many things a society needs (taking care of children and the ederly, providing for non-productive elites and administration and armies). So itâs uncertain we can really go below that, especially as we are a much more complex society.
For instance, according to this paper, youâd need a minimum of a 3:1 EROI to have transportation, when you take into account its energy needs (making and maintaining roads and trucks). An even higher EROI would be required if we add the needs for food, education, administration, healthcare and stuff like that. I made some changes to the section on EROI in the full document The great energy descentâFull Version, including how the 3:1 measure was calculated, you may find that interesting.
Of course, it may be theoretically possible that a complex society can work out with a EROI<10 or less. Iâm not saying itâs cannot happen. I just think that itâs risky to make this assumption, since the historical record seems to point out that having a high energy surplus was needed in most societies.
On your second section : I do find the calculations interesting. This is well structured.
However, estimating future prices is notoriously tricky. As you put forward, on the short term prices have been decreasing in a quite impressive way, so in this time scale, and for electricity, it should go down.
I could see many reasons, however, that prices will not do that forever, and solar panels could get less affordable in the future. For instance, your calculation does not include:
The cost of upgrading the electric grid (getting the grid in deserts with a lot of sun)
The cost of switching transportation systems to electric (especially as hydrogen requires building much more infrastructure)
The cost of storage, especially seasonal (pumped hydro is good but geographically limited. Batteries, although improving, are much more expensive, and our main options depend a lot on finite materials like lithium. More in the storage section)
Metal smelting relies on coal and gasâitâs far from certain weâll switch to electrified fast enough (or how)
China could increase its prices (80%+ of solar panels are made there)
High-grade silicon and other materials can get scarcer (as you underline)
Solar is not a good option for say Poland or Canada
So far, the best and cheapest spots have been taken, but at a large scale land is going to get expensive, especially in rich countries
I personally do not attempt to calculate prices (as seen with oil prices, itâs really hard), but it sounds likely to me that it will be more expensive than today. This doesnât mean solar is uselessâitâs just that I have trouble seeing how it can be cheap enough to support an âinfinite growthâ economy.
Hi, thanks for the thougful response. You spent quite some time to put things down clearly, and I appreciate that.
I think i can accept your conclusion, for the most part. Saying âa EROI of 2:1 means half your resources go to energy productionâ is indeed a big simplification on my part, which is based on several simplifications I have made and didnât detail :
Currently, energy makes about 6,5% of global GDP (well, that was 2021. For 2022, itâs about 13%). So between 1/â10th and 1/â20th (closer to 1/â20th). This means for every point of GDP invested in energy, between 10 and 20 points of GDP are created.
Currently, the global EROI of energy is between 20:1 and 10:1 (closer to 20:1, but depends on whether you take final or out of the mine well). So for every unit of energy, between 10 and 20 units of energy are created.
From this, I make the overal simplification of âEROI is representative of the share of energy in global GDP, roughlyâ
âHalf of resourcesâ translates roughly to âHalf of GDPâ (since there is a 99% correlation between energy consumption and GDP on a year by year basis, even if this gets bigger over 50 years)
That the current relationship, for fossil fuels, still stands with solar
These are indeed huge simplifications I made in my head, but I can get why you donât see them as valid. I unfortunately didnât really understand your algebra bitâI am not very good at reasoning with equations, it doesnât really âclickâ with the way my brain works. But I understand your overall point.
So ok, letâs drop the assumption that a 2:1 EROI requires half of societyâs resources. I indeed donât really know the exact percentage. This wasnât really my main point, so I removed references to this assumption in the full doc.
However, what empirical data seems to indicate is that society still requires a high EROI to function. As said in another comment :
For instance, according to this paper, youâd need a minimum of a 3:1 EROI to have transportation, when you take into account its energy needs (making and maintaining roads and trucks). An even higher EROI would be required if we add the needs for food, education, administration, healthcare and stuff like that. I made some changes to the section on EROI in the full document The great energy descentâFull Version, including how the 3:1 measure was calculated, you may find that interesting.
Of course, it may be theoretically possible that a complex society can work out with a EROI<10 or less. Iâm not saying itâs cannot happen. I just think that itâs risky to make this assumption, since the historical record seems to point out that having a high energy surplus was needed in most societies.
On your second section : I do find the calculations interesting. This is well structured.
However, estimating future prices is notoriously tricky. As you put forward, on the short term prices have been decreasing in a quite impressive way, so in this time scale, and for electricity, it should go down.
I could see many reasons, however, that prices will not do that forever, and solar panels could get less affordable in the future. For instance, your calculation does not include:
The cost of upgrading the electric grid (getting the grid in deserts with a lot of sun)
The cost of switching transportation systems to electric (especially as hydrogen requires building much more infrastructure)
The cost of storage, especially seasonal (pumped hydro is good but geographically limited. Batteries, although improving, are much more expensive, and our main options depend a lot on finite materials like lithium. More in the storage section)
Metal smelting relies on coal and gasâitâs far from certain weâll switch to electrified fast enough (or how)
China could increase its prices (80%+ of solar panels are made there)
High-grade silicon and other materials can get scarcer (as you underline)
Solar is not a good option for say Poland or Canada
So far, the best and cheapest spots have been taken, but at a large scale land is going to get expensive, especially in rich countries
I personally do not attempt to calculate prices (as seen with oil prices, itâs really hard), but it sounds likely to me that it will be more expensive than today. This doesnât mean solar is uselessâitâs just that I have trouble seeing how it can be cheap enough to support an âinfinite growthâ economy.