Key words :
energy return on investment,
Charlie Hall's Balloon Graph
19 Dec, 2007 10:11 am
Energy researcher Charlie Hall's balloon graph challenges the notion that alternative energy sources will provide a smooth transition to a post-fossil fuel society. Scale and energy return remain huge obstacles.
Charlie Hall is one the best-known energy researchers you've never heard of. That's because he puts his effort into understanding whole energy systems such as human civilization rather than perfecting headline-grabbing energy panaceas such as corn ethanol. From the early 1980s onward Hall and his colleagues--some of them former students--have been warning that a society hooked on fossil fuels would find itself up against limits not easily breached--probably sooner rather than later.
With the current boom in biofuels, wind, and solar, and even a revival in nuclear power, many people believe that a smooth transition to a post-fossil fuel economy is already a foregone conclusion. But a careful look at Charlie Hall's balloon graph tells a different and much more disconcerting story (1). (To view a larger version of the graph, click here or on the graph itself.)
First, let's look at the components of the chart. On the vertical axis we have energy return on investment (EROI) expressed as the ratio of energy output versus energy input for each energy source. (Hall, an ecologist by training, appears to have coined the term by adapting "yield per effort" concepts from fisheries.) It is not always obvious to modern industrial people that it takes energy to get energy. The more energy we spend on finding, extracting, refining, and transporting energy resources, the less we have for all the other activities of society. The horizontal axis of the graph represents quads or more precisely, quadrillion BTUs (British Thermal Units). The graph depicts energy use in the United States. But the principles it demonstrates apply to the world as a whole.
The various colors put focus on the annual production totals and energy return of oil at different times. The sizes for all the balloons represent a very rough guide to the uncertainties in calculating EROI ranges. (As we shall see, even with these uncertainties there is a very large discernible gap between what we currently get from fossil fuels and what we can expect to get from alternatives.)
Oil, which makes up the largest percentage of U.S. energy consumption today (40%), has shown a substantial increase in its total output even as its EROI has fallen. To see this on the graph look at the blue balloon labeled "Domestic Oil 1930," the purple balloons labeled "Imported Oil 1970" and "Domestic Oil 1970" and the red balloons labeled "Domestic Oil Today" and "Imported Oil Today." That same move to a lower EROI is also being seen for natural gas and coal though the balloon graph does not depict these trends.
Everyone knows that at some point fossil fuel supplies, which are finite, will begin to decline. To replace them we currently have biofuels such as biodiesel; other renewables such as wind, photovoltaic, and hydroelectric; and nuclear power. Oil from tar sands is also shown in the lower left-hand corner, but you have to look hard. And, that's just the point. You have to look pretty hard to see these alternatives on the graph. There are two reasons for this. First, some of these new sources are not very far along in their deployment. As they are more widely deployed, they will supply more total power and move to the right on the graph. Second, the EROI for biofuels such as biodiesel and for unconventional oil such as that extracted from tar sands is extremely low. Given current technology, these alternatives are not likely to move upward very much on the graph anytime soon.
Hall believes we have two problems illustrated by his balloon chart. First, in order for these alternative sources to move rightward on the graph--that is, produce much larger quantities of energy for society--they will have to be deployed on a vast scale which few people contemplate or understand. Two examples come to mind. The worldwide installed capacity of solar photovoltaic cells is 10.9 gigawatts. With the total worldwide installed electrical generating base at 3,872 gigawatts, it would take more than 2,000 years at the current rate of installation (1.74 gigawatts/year) to reach today's capacity. And that's without even considering future growth in electricity demand. If we include the installed base of wind (74.3 gigawatts) and the current rate of wind installations (14.9 gigawatts/year), we can bring the figure all the way down to about 230 years, again without considering growth in demand. Of course, the rates of installation will grow, and there are other renewable and nonrenewable energy sources available. But the challenge of scale remains huge.
When it comes to biofuels, the scale problem gets no better. Biofuels researcher Tad Patzek uses corn ethanol as an example. To fuel the American vehicle fleet using corn ethanol:
[o]ne would have to grow corn on 1.8 billion acres, year-after-year, for decades. There are about 400 million acres of arable land now in cultivation in the U.S. Therefore, one would have to use the land area equal to 4.5 times the current arable land area....If we want to continue living in the kind of energy-drenched civilization we now enjoy, we will have to move simultaneously rightward and upward on the balloon graph. Hall estimates that if society were to average less than a 5 to 1 ratio of EROI, anything resembling our modern civilization would probably not function. The balloon graph suggests a minimum EROI for the United States of around 40 to 1 for 100 quads of energy generated. Therefore, without major breakthroughs in the efficiency of alternative energy sources, no combination of those sources has the prospect of giving us both the high energy returns and the large total production we are accustomed to from our current energy sources.
(It's important to note that nearly all the good sites for hydro power in the world have already been taken. And, turning to firewood for fuel would simply result in the levelling of the world's remaining forests, leaving us with nothing for the future and destroying the habitability of the planet in the bargain. The upshot: Neither of these alternatives is going to move much to the right on the graph.)
Many are saying peak world oil production will soon be upon us with peak natural gas and coal following close behind. To live anything like we now live, we are going to have to see some astounding technical breakthroughs in alternative energy sources soon. And those breakthroughs will have to be followed by dramatic and costly efforts to deploy alternatives rapidly and ubiquitously. For now we appear to be on a course that will require drastic changes in the way we live.
Perhaps we will somehow muddle through. But when you look at Charlie Hall's balloon graph, it's easy to conclude that even muddling through might end up being a very unpleasant affair.
(1) Hall, C.A.S., R. Powers and W. Schoenberg. (in press). Peak oil, EROI, investments and the economy in an uncertain future. Pp. xxx-xxx in Pimentel, David. (ed). Renewable Energy Systems: Environmental and Energetic Issues.
Key words :
energy return on investment,
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[Response] Setting aside whether biofuels on such a scale would be ecologically sustainable in terms of their effects on soil and water or politically feasible in terms of their effects on food prices, the current EROI of such fuels would imply that a huge sector of the economy would have to be devoted to their procurement. Energy researcher Cutler Cleveland provides this example. Assume that we get 10 units of energy for 1 unit consumed for refined petroleum products. For the United States that would mean only 10 exajoules of energy are needed to produce 90 for the rest of the economy. With corn ethanol at a generous ~1.5 to 1 return, the amount of input would have to be at least 270 exajoules and perhaps more just to get the 90 delivered to the rest of the economy. Theoretically, it's possible. But that world is not going to look anything like the one we have now. And, that is Charlie Hall's point.
"The worldwide installed capacity of solar photovoltaic cells is 10.9 gigawatts. With the total worldwide installed electrical generating base at 3,872 gigawatts, it would take more than 2,000 years at the current rate of installation (1.74 gigawatts/year) to reach today's capacity."
I assume you speak of ONLY electricity already installed, not including other energy demands.
Do you refer to installed electricity but only the portion based on fossil fuel? Hydro power obviously does not need to be replaced.
How much more solar electricity would we need in addition if we want to reduce oil consumption, say by 20% for those uses which do not generate electricity, like transportation?
My guess is that the amount of solar panels would be much higher still. There is some good info out showing that very likely there are not enough special rare elements needed for this, ie the limiting factor will also be from material needs to construct panels.
[Response] Yes, I am speaking only about electricity and this figure does include hydro which, of course, we wouldn't be trying necessarily to replace. But the scale problem would remain huge even if you subtract hydro from the total. If we want to use electricity to run our transportation system, then, of course, you are talking about a huge increase in needed capacity, though I haven't worked that number out. Like you I'm very concerned that the rare elements needed for photovoltaic may prove a limiting factor for constructing solar panels the way we construct them now.
The revelation is the total photosynth line. It's roughly correct and means solar just won't suffice. Ditto for bio which is only solar reduced to solids and liquids.
So it'll be nuclear or nothing. Nukes 10-15x is certainly possible even if currently politically unpalateable. They'd better be thorium fast breeders because we are also running out of yellowcake.
Nukes aren't great on EROI, but that's because most of the energy is thermal for concrete and steel. We _do_ have enough coal to build the nukes. We will for quite some time.
Drastic conservation will be the first step, voluntary, or forced by events, price, shortages...
It would seem to me that simple things.
- Changes to zoning laws to prevent sprawl
- Require carpooling and public transportation
- Forced introduction in improvements of energy efficient appliances, automobiles and heating/cooling devices.
We know we could reduce our energy usages by 40% without suffering a serious drop in standard of living (we know, because the European countries already do it).
It's even possible in the US (look at California)
Many American's are too stupid to see what's coming, and too ignorant to elect leaders that will tell them anything they don't want to hear.
Ultimately we'll hit a wall, create a crisis, and we'll all come together to solve this "sudden emergency"
It'll probably work out all right in the end, and 30 years from now, we'll be talking about the "Greatest generation". Ignorant of the generation before that got us into this mess in the first place (just like the last greatest generation).
In that case, 40 million people died.
I believe your figures for replacement periods with PV and wind are too optimistic.
You quote installed solar PV at 10.9 GW and Wind at 74.3 GW. These are I believe the theoretical peaks ie, assuming perfect 24 hour sunshine and 24 hour winds, 365. In practice the average for wind is 20-30% and PV 10 to 20% rated peak output.
As an example for PV, until relatively recently the largest PV array in the world was at Serre in Southern Italy with a rated Peak Output of 3.3 Megawatt and in operation in 1993.
Data for recent years (98-2000) averaged output to grid was under 10% Peak module rating.
Data available at
I thus suspect your figure of 2,000 years to replace existing energy systems with PV at current rates should be nearer 20,000 years.
Peculiarly I am a PV and RE enthusiast having run a small PV business for 15 years in Middle East. Unfortunately this experience has taught me the limitations of Renewable Technologies when compared to our current fossil fuel based lifestyles.
United Arab Emirates
PS I have been following your excellent articles on PO for a number of years, and have met Charlie Hall on a few occasions at ASPO Conferences in Europe latest being in Cork in September. Seasons Greetings from Dubai and keep up the good work.
[Response] You are surely correct that my figures are far too optimistic when it comes to actual production of electricity which is why I was careful to mention only capacity. But that, of course, doesn't tell the whole story. I too remain a staunch advocate of PV and wind, but recognize that any hope of maintaining an electrically based society in the long run will likely mean drastic reductions in total energy use through increased efficiency and most certainly simple curtailment.
Instead of getting our selves into another resource pickle where you rely on Australia and Russia to supply uranium for the next 40 years (because that's how long it will last) why not bit the bullet and go hell for leather on PV, solar Thermal and wind, tidal... oh that's right, it's hard to trade in wind and light, where as there are killings to be made in uranium.
Tarring industrial scale solar PV/thermal and wind with the brush that we apply to home/hobby solar/wind systems is just silly. It's like comparing the reliability of a coal fired power station generator with a camping generator. With national grids, and countries/continent's with 17+ hours of sunlight we should be able to achieve amazing things it's 2008 for god's sake. Where's the spirit that saw people build continent spanning railways!
[Response] The key words in most estimates are "at current rates of consumption." Exponential growth in coal use would, therefore, mean that the peak is brought considerably forward. The German-based Energy Working Group believes we are already on a trajectory for peak around 2025. But they aren't alone in their concern. The National Academy of Sciences has downgraded U. S. reserves to 100 years, but, of course, this is "at current rates of consumption." Perhaps most compelling is the re-evaluation of coal reserves done strictly from publicly available data by Cal Tech's David Rutledge who persuasively argues that actual reserves are half stated worldwide reserves. Surprisingly, the reserves collapse in the official statistics has been going on for some time. When the NAS looked at the outdated methods for reserve estimated still in use, it concluded,"Present estimates of coal reserves are based upon methods that have not been reviewed or revised since their inception in 1974, and much of the input data were compiled in the early 1970s. Recent programs to assess reserves in limited areas using updated methods indicate that only a small fraction of previously estimated reserves are actually minable reserves."
Charlie Hall?s balloon graph fails to provide meaningful insight into the role of energy efficiency, except when it plays a role in mineral extraction or some of the heavy industry production whose output is reflected in this graph. Skip Laitner?s examination of this question finds that since 1970, 77% of all new energy service added to the U.S. economy was efficiency. The testimony is available at http://www.aceee.org/tstimony/0709HouseScience_Laitner.pdf .
This means a lot of things, but for this discussion it means that three quarters of the energy service growth in the U.S. is coming from a source which is too cheap to meter, and which is almost completely unrecognized by the mainstream forces who do this sort of projecting and reporting. Even if you don?t accept Laitner?s methodology (which is pretty robust) a simple comparison of energy/GDP provides support for efficiency having contributed more than half the energy added to the U.S. economy over this period.
Start with the knowledge that there is a very large untapped reservoir of efficiency technology which is cheaper than existing resources. Add the knowledge that existing resources have tripled in cost in the last five years, while efficiency has not increased much. Most decisions to purchase efficiency do not properly account for the true economic savings, and did not capture the old economic benefits, and are wildly off the mark for capturing the true savings today. If we correct these flaws, the simple act of investing appropriately in efficiency products and services will reduce their cost and make a larger efficiency resource more available.
Several experts have mapped out carbon strategies with money-saving and above-market resources, showing a complete strategy that looks sort of like a break-even. None of those properly reflect the fact that if you do the efficiency components first, the renewable components will probably be money saving components, even if they are not today, because the fossil fuels they are compared with will rise in cost by the time we need them.
Wind is cheaper than coal today. PV is cheaper than coal today, if you properly econometrize the value of peak power in a summer peaking utility, when PV works best.
If it takes 230 years to replace the world?s current consumption of energy with wind and PV at current rates, that ignores the current growth rates of those industries. 15% is a good conservative value. Ignore those who claim higher values for recent years. It would take 39 years at 15% growth rates for wind and solar energy to displace all existing energy resources. This ignores new growth, which has been only population growth since the early 1980?s, and it ignores the fact that there will be other renewable technologies and it ignores the fact that these industries will not add 15% new construction capacity in the last decade of this effort because they won?t build factories with no future.
This only touches on the high points. Zero energy buildings is the meat of the matter, but it will take ten years for the nation to have a proper dialogue on them. Biofuels are not really important, and many of them are counterproductive if we don?t figure out how to put sustainable agriculture first. Solar thermal may be more important than PV. Some transportation fuels do not yet have apparent sustainable options which are cheaper than existing fossil fuels, but electricity and natural gas do, and can balance that out.
The single most important element of any effective climate strategy is an early start on steady net reductions of about 2% per year.
Increased energy efficiency and increased production of alternative, sustainable energy converters will never enable us to avoid energy disasters or climate change. PV might reach 40-50% tops, solar thermal 30-35% using tracking and focussing tools and wind energy, which actually is a thermal process as the heating by the sun creates wind, only has a thermal efficiency far less than 1% (given how much solar energy is needed to create the power converted by the wind turbine).
There is only one option that very few dare to mention: world population must decrease. There are other websites available stating how big a world population can be maintained used sustainable energy and agriculture. That amount appears to be somewhere in between 1.5 and 2 billion entities. At this moment, there are almost 7 billion people on this globe...