102 comments on Understanding the current energy crisis in South Africa
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Hi Nate,
I am reading "Energy & Resource Quality" by Hall & Cleveland, 1986. One of the main points they make is that GNP and Fuel are directly linked. Fuel use and fuel quality (plus smaller factors) can predict GNP to 97% over the enormous range of 1890 to 1980. That leaves 3% for efficiency at best. They seem to explain it by showing that trying to replace fuel use you use more capital and that capital has high embodied energy and outweighs the fuel use.
Do you know if they have done similar studies since the mid 1980's that might show that fuel and GNP have decoupled in any way? Or even show that it has remained just as tightly coupled. I have to admit, I found the news a bit depressing. ...
Forbes keeps featuring economists who say that fuel and GNP have decoupled to a greater degree in recent years in the U.S. But when you really look at the figures, it looks to me like the economic decoupling was based on increased debt, and is not sustainable. I expect we are reverting to the Hall & Cleveland model you cite.
They cite some efficiency improvements:
1. The switch from coal to oil gives a BTU to GNP boost (not good news for a future switch from oil back to coal).
2. The switch from coal or oil to electricity gives a BTU to GNP boost (great news for wind, nuke, solar PV).
But the main differences are explained away by looking at embodied energy in goods, which economists don't care to track, and household uses of energy, which don't impact GNP as much as industrial/commercial energy use.
So it is part hopeful (the future is electric!) and part not (GNP will decline with lower energy). But it would be very nice to have updated papers. I wish there was a 2007 version of the book!
"The switch from coal or oil to electricity gives a BTU to GNP boost"
This defies logic and is not true for coal. In switching from a primary fuel source, such as coal or oil, to a converted form of energy always results in energy losses. For example using electricty for boiler heat requires twice as much base energy (turning coal's btu's into electricity is only 35% efficient considering steam cycle losses, line losses and transformation losses) as compared with burning the coal for that same process heat. Home heating with electric heat pump using ground source would be about same efficiency as burning coal if heat pump has COP of at least 3.
Always? Surely it depends on the end use. Consider a train hauled by a coal fired steam locomotive, a diesel locomotive and an electric locomotive.
If the power station has a higher eficiency than an internal combustion engine or an open coal fire...
Most important.
Electricity is a carrier.
Like Hydrogen.
""The switch from coal or oil to electricity gives a BTU to GNP boost"
To which mbnewtrain replied,
"This defies logic and is not true for coal. In switching from a primary fuel source, such as coal or oil, to a converted form of energy always results in energy losses."
Correct. The primary fuel switch was the one to attribute the gain in BTU to GNP boost, i.e., natural gas.
RC
More recent work by Ayres (1,2) suggests the link is 70% with exergy, which is the amount of useful work derived from the input energy source (meaning 10btu of coal can provide 0-10btu of exergy, depending on how efficiently you use it). It's similar to "fuel quality", in some sense.
He also notes that the exergy-based analysis explains much more of GDP growth than energy-based analyses, so it's likely that the "smaller factors" you mention were pretty significant.
You can see it for yourself in the EIA's data on energy intensity of the economy. The amount of energy required to produce a dollar of GDP fell only 20% from 1949 to 1980, but has fallen by about 45% since then -- nearly triple the previous rate.
You think that might have something to do with the offshoring of US industry?
That's certainly a factor, but far from the only one. Indeed, the tales of US manufacturing's demise are greatly exaggerated.
See also here or here. US manufacturing is still 20% of the world's manufacturing, commensurate to the US economy's 20% share of the world economy.
Of course, it's worth noting that the world's energy intensity (btu/$ of GDP, inflation-adjusted) has fallen 7-15% in the last 10 years (same EIA data, 15% based on PPP, 7% based on market exchange rates), so it's not like the energy consumption has simply been pushed elsewhere.
Thanks! Good links. I had meant to read that paper by Ayres. He does not quote Hall, Cleveland, Odum, or Constanza in any of his references. It seems he discovered the relationship independently. He found the link between quality and GNp but does not have the two other correction factors that they discovered: product mix and household use. I need to read the longer paper. Thanks again!
It's an interesting paper, but obviously it's only one look at the situation. I imagine that both his "exergy" approach and the earlier "quality, product mix, and use" are attempts to quantify the fact that a fixed amount of energy can be used in very different ways to produce very different amounts of things. It's a key thing to examine, but I'm not sure how best to do so.
At any rate, you're more than welcome - finding, exchanging, and disseminating information is, IMHO, the most important (and bestest) function of the internet.