Among critics of renewable energy, one key idea is that of Energy Returned On Energy Invested (EROEI). The central idea can be illustrated by the case of ethanol produced from corn in the US. It’s argued by critics that the production of ethanol from corn uses more fossil fuel inputs than it displaces. The US Department of Agriculture has an EROEI slightly greater than 1, but it’s still clear that corn ethanol is not going to do much to solve the carbon dioxide problem.

Now lets look at the case of solar PV. The energy-intensive component of a solar PV module is the polysilicon used to produce the wafer, which is produced using an electric furnace. Clearly, if more electricity is used in this process than is generated by cell, EROEI < 1, and the idea does not work. We can do a rough check by observing that a typical wafer uses 5 grams/watt of polysilicon. The cost of polysilicon is $20/kg. To be conservative let's assume this is all electricity, at a cost of 5c/Kwh. Then a quick calculation shows that each watt of PV requires 2 KWh of electricity in production or about 1 year's generation in a favorable location. So, for a panel with a 10-year lifetime, the EROEI is 10. Clearly not much of a problem. The estimate omits the energy costs of the rest of the module, but that's almost certainly more than offset by the conservative assumptions about polysilicon.

Some EROEI fans don't like this calculation. They want to include all sorts of other costs, going as far as the food energy used by the workers who instal the panel. At this point, the exercise becomes one of trying to price all economic activity in terms of energy, an idea that has been tried without success for decades. For everything except energy-intensive activities like smelting, energy costs are a small part of the total, and imputing such costs to any particular energy source is a fools errand.

35 thoughts on “EROEI

  1. I agree with this conclusion, Prof John. If the purpose of the analysis is to demonstrate how our society is heading for energy cliff, then there may be merit in examining the total drawdown needed to produce industrial products, from all direct and indirect inputs. However, the more peripheral activities that are drawn into the calculation, the less significant becomes the relative contribution of the core energy production process.

    I have recently submitted a scientific paper on EROEI. I concluded that the boundary assumptions adopted by different analysts vary so much that it is difficult to compare any two figures in the literature in quantitative terms. Also, it is only an indirect proxy for greenhouse emissions, which is the more critical index.

  2. I’ll mention that current solar panels have about half a gram of silicon per watt. However, due to wastage in the cell making process the amount of silicon used would be closer to 1 gram. And I’ll also mention that perovskite cells that don’t require the energy intensive process needed to make silicon ingots may be commercial in a few years time, which I am sure will please all those who are not happy with PV’s current EROEI of about 30.

  3. So many comments one can make on this devil in the detail issue which lies at the heart of limits to growth and needs far more work. Though a couple of your comments are puzzling full marks for putting it up. And apologies in advance for recycling as I’ve put these up before.

    1. This is a critical issue because historically its treatment by mainstream stream economists v. ecological economists (not to be confused with environmental economists) seems still stuck in the warring silos mode since the broader ‘limits to growth’ was originally dumped on by the mainstream back in the 1970s. This is evidenced by conventional economics still being wedded to growth with the caveat that we can (easily??) decouple growth from increasing energy use and environmental impact. Yeah right…………..

    2. EROEI is a conundrum for all fuels, not just renewables, which seems to be the focus here. There is a nice analysis of unconventional oil production in MURPHY, D. J. 2014. The implications of the declining energy return on investment of oil production. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 372. One perverse response is that the scarcer and more expensive the resource the more resources and hence power need to be thrown at the energy companies?! What is clear from this paper is liquid energy production is moving toward serious unviability even leaving aside carbon taxes. The timing though is uncertain.

    3. A different EROEI story is BARDI, U. 2010. Extracting minerals from seawater: an energy analysis. Sustainability, 2, 980-992. The calculations do have a couple of problems if you look closely but once you correct them, his thesis seems essentially correct – mining Uranium and most everything else is a joke because of the energy and infrastructure needs – it can never be viable precisely because of the unfavourable EROEI and related issues. Still it makes a good baby engineer bed-time story – like the promise of cold fusion repeated on the tele again just the other night – where you can produce loads of energy for a flying DeLorean without being fried by the massive flux of high energy neutrons emitted by deuterium fusion. Again…yeah right.

    4. A further favorite is STEEN, B. & BORG, G. 2002. An estimation of the cost of sustainable production of metal concentrates from the earth’s crust. Ecological Economics, 42, 401-413.

    I wonder how many remember that old Dr Strangelove model Herman Kahn explaining how many resources there is locked up in bedrock so we will never run out. Certainly there are plenty of resources and Kahn was no fool in many other respects, but this paper provides a useful analysis of the resources including energy required to do mine the ultimate mineral – bedrock. When you compare the levels and our current usage in U.S. GEOLOGICAL SURVEY 2011. Mineral commodity summaries 2011. U.S. Geological Survey. you find quickly there are a host of key resources whose extraction would require more energy than the current total global output and leave an excavation hole and hydrochloric acid problem you dont want to think about.

    One calculation that impressed me particularly was for phosphorus (a successor paper by Steen). Now P is present in rock in quite high concentrations – about 1000 ppm – which sustains ecosystems as they breakdown bedrock to soil. But to use this as a source instead of fossil guano would again require the entire worlds resources of energy given these authors calculations.

    I leave asteroid mining for another time.

    The point here is at some point in the future many key resources will become too expensive energy, cost, impact, or logistics wise to continue. But we dont have a handle on these points yet in large part I think because mainstream economist refuse to engage with the issue holistically still – though LtG had a pretty good go and there are plenty of examples which indicate they are right (see HALL, C. A. S. & DAY, J. W. 2009 Revisiting the Limits to Growth: After Peak Oil. American Scientist, 97 230-237.) including our old friend carbon emissions.

    5. So overall

    For everything except energy-intensive activities like smelting, energy costs are a small part of the total

    looks like a very questionable throwaway line. It would be more useful to compare and contrast on which activities are energy intensive and which arent directly and indirectly.

    Certainly we can be a lot more energy efficient than we are in Australia – conceptually – but there are always limits to the latter.

    6. Finally a comment on this funny comment

    “the exercise becomes one of trying to price all economic activity in terms of energy, an idea that has been tried without success for decades.

    If truth be told no statistical indicator measures are ideal. GDP is great example of a flawed indicator, counting as it does pollution clean up as a positive, counting the growth of the financial parasite industry as a good, ignoring obesity, ignoring environmental externalities left right and centre – and not just Cecil but critical survival issues like topsoil erosion and acidification. But economists happily ignore the externalities or deem them trivial.

    GDP is though arguably useful as an order of magnitude measure of wealth and its growth – but then if you plot energy against GDP there is also a not too bad log log correlation from plots I’ve seen.

  4. EROEI does matter. But it’s simply now the case that solar and wind do pass the test with energy profit ratios in the region of 20:1 to 30:1. I was wrong a while ago as I didn’t think solar and wind would get this good.

    There is some argument from some quarters that our economy needs anywhere from an energy profit of 10:1 to run at all to an energy profit of 100:1 to run really well and not have recessions etc. Let us entertain the worst case scenario for the heck of it. Assume we need 100:1 energy profit from our best sources to run the economy really well and not have recessions (ignoring all other possible problems for the economy.)

    Let us assume renewables make an energy profit of 33.3 (recurring) to 1 to make the maths easy. This puts us at 1/3 of what we need. But hang on, practical IC motors have an energy efficiency of about 20% on a good day. Electric motors have an energy efficiency of about 80% on a bad day.

    Let these ratings stand in as proxies for the fossil fuel economy and the electrical economy. Thus we get only 1/3 the energy profit ratio from renewables compared to the very top quality, easy to access fossil fuels which are mostly gone now anyway, but we only need 1/4 of the power to run the same economy fully electrically. This is clearly an improvement so on the energy score at least we are looking good.

  5. From the OP: “The US Department of Agriculture has an EROEI slightly greater than 1..”

    No. The D of Ag uses energy to heat and cool its offices, fly and drive around its inspectors, run its computers and so on. Its activities produce zero energy. So its EROEI is zero. According to the line followed by some commentators here, that would mean it should be closed down as unsustainable, along with universities, schools, hospitals, public administration, and the military. I’m no friend of Ministries of Agriculture, which are almost universally exemplars of regulatory capture, but EROEI isn’t the reason why they need reform.

  6. @James Wimberley

    Are being droll? You do realise the sentence meant “The US Department of Agriculture has calculated an EROEI ratio of slightly greater than 1 to 1 on corn ethanol.”

    Obviously, all our economic activities other than energy “production”, use net energy for useful work. They do not “produce” energy as such except as a waste by-product.

  7. Prof. J.Q. says:

    “Some EROEI fans don’t like this calculation. They want to include all sorts of other costs, going as far as the food energy used by the workers who instal the panel.”

    I agree that energy accounting to this degree becomes absurd and so difficult as to be well nigh impossible. If EROEI “fanatics” (as opposed to EROEI “sensibles” like me) want to apply this type of calculation to renewable energy, then they must also apply it to all other forms of production. Thus coal miners and oil riggers must also have their food energy costs imputed.

    It probably makes more sense to count energy costs in energy units at the mine gate and at the factory gate. I simply mean the direct energy costs in energy units of the mine or factory within the perimeter fence are what should be counted. This should give us a workable EROEI ratio.

    As for the rest, the embedded energy in trucks and humans etc. can be regarded as the energy cost in energy units of the rest of our economy which needs to “funded” by a positive EROEI at our energy “production” centres.

    After all, straight energy production for useful work is the only economic activity which needs to return a positive EROEI to run everything else. Everything else is a user of energy for useful work not a net energy source.

    To put this another way, EROEI is of importance when the corn ethanol is used for fuel in an engine. However, EROEI is not of importance when the corn ethanol is used for drinking. A whiskey distillery can use much more energy than it “embeds” in its whiskey and still make a money profit.

  8. Solar PV is a clear standout for this particular calculation because EROEI only needs to be >1 for there to be significant gains by the energy intensive manufactures of the devices/components to utilise the tech for their own power generation.

  9. Transportation energy is also a relatively small component of the embodied energy of a PV module. It’s really not a big deal to bring a high efficiency module from Germany to Australia on a ship.

  10. Uncle Milty, just with solar PV, the location of wind affects its ERoEI but modern wind power should have an ERoEI of about 18, perhaps higher. Australia’s ratio is probably quite high as we have good wind resources and the direct drive turbines that make up our two largest wind farms mass less than geared turbines.

  11. > fools errand.

    Some people are stupid

    Politics-that-is-stupid is largely — not entirely — supported by people who support other stupid things, who can be defined by this as “people who do stupid things”, or “people who are stupid”.

  12. I’m pretty sure that any overall measure (GDP, EROI or whatever) is fairly useless analytically. It’s the detail that counts. For instance, one chapter in Adam Tooze’s The Wages of Destruction looks at one critical part of the German war economy – coal and steel production. This involved movement of grain to feed pigs to produce pork to feed miners to produce coal to fuel trains to move grain and meat and coal to steel mills….A multi-part chain the Germans could not get right, and which led to a spiral of failure (less pork, less coal, less fuel…). What counts is how tightly coupled the systems are, and what the specific points of failure are.

  13. I support the idea of EROEI calculations, but I do not regard myself as a critic of alternative energy. EROEI analysis was first used by proponents of the Peak Oil hypothesis to show that some claims of existing fossil fuel reserves were greatly exaggerated. They included some deep deposits of oil that would take more energy to extract than they could produce. Hence regardless of the oil price those reserves would never be extracted.

    That being said, it is obviously false to add in numerous indirect energy “costs” to an activity to argue its real EROEI ratio is poor. There is also a time dimension to the problem. The entire electricity transmission grid is a sunk cost built largely to favour existing coal fired power station sand coal reserves. Do we count that energy in the EROEI calculation for coal power? I doubt it.

  14. Products are made to maximize profit; this generally includes lowering costs, and energy is just one of the costs. A set amount of energy isn’t sucked out of the universe into a solar cell. A solar cell factory does require heat to cook up the silicon but the amount of energy used will depend on the industrial process.

    As far as I know, no one has demonstrated the lowest achievable limit of the energy required to mass produce silicon cells. If that number was less than one we could declare silicon cells dead right now but that obviously aint so. If there actually was a lower limit it would be, I bet, a lot lower than the numbers floated in various EROEI calculations. Markets happily produce all sorts of inefficiencies when they don’t matter. In the normal process of improving technologies and production efficiencies, EROEI will typically improve.

  15. The EROEI of corn ethanol is one of the most dishonest political arguments in the US. The key factors are that US farmers use less than optimal farming practices, the energy content of the corn stover is not used in the calculation, the corn husks are used as stock feed and not included in energy calculation, rather than use the bio fuel energy from the corn husks to fuel the ethanol production process the mill use gas, and all farming vehicles use petrol or diesel rather than ethanol to power the farming process. Everything that can be done wrong in US ethanol production is done wrong, to the total delight of ethanol’s detractors. In the US this is a political debate that goes right back to Henry Ford who wanted vehicles to run on Ethanol, the cola lobby, and Rockefeller who most definitely wanted ethanol to die the death that it did for eighty odd years.

    Australian cane ethanol is very profitable, more than double the return for sugar. And we certainly do not need more sugar. The field costs of cane ethanol are 5% of the return and the energy for the ethanol production comes from the biofuel content of the bagasse, and the whole process exports electricity as well.

    The whole EROEI argument for biofuels is an overheated crock of manure. As are the similar arguments for solar panels.

    The last thing that solar energy detractors want is for solar PV’s to become solar PVT’s as this blows their already falacious argument into insignificance. A PVT uses a small amount of material behind the solar array to collect the heat energy that is not used by the solar panel in the electrical cycle, for water heating. This adds an additional 30% efficiency to the panel, more than tripling the energy performance of these panels where the thermal energy can be used for heating water, heating air, powering absorptive air conditioners for cooling in summer. Detractors will attempt to steer the argument to grid scale PV arrays where the potential thermal energy cannot be conveniently used, and build their EROEI argument around this ONLY.

  16. The skewiff aspect to the eroei argument against solar pv panelz is that if their solar energy output is used for their production effectively reducing their factor from 30 to 29, and all of their materials are recycled, then the entire eroei argument is pointless. The only remaining considerations lay with the value to the user of the products performance over cost, oh, and the product’s contribution to reducing carbon emissions.

    I got home this afternoon as the two installers were leaving having fitted my first 4kw of solar panels to the house. Everything done, two guys seven hours each. So here I am enjoying the warmth of the log fire reading this article (hat tip to Geof Henderson at Climate Plus) here…..

    Is there no end to the stupidity in this country?

  17. Peter T :
    Adam Tooze’s The Wages of Destruction.

    A most excellent book. Open it at any page for a riveting read. I liked the part about the highs and lows of production of ammunition (vital!) caused by the competing priorities of other production. Or the collapse of the flow of resources from conquered France after the Deutsche Reichsbahn plundered the French rolling stock. Or the frantic claw back of expert workers from the front lines after they were hoovered up by the army.

  18. I’ve just done the EROEI of the thermal panel component in a PVT based on the material embodied energy of the stainless steel content and it comes to a return of 238, which when the PVT is calculated as one complete module brings the PVT EROEI to well over 100. And if you consider the economic benefit to the household in all of increase in living standard quality of life and environmental CO2 emission reduction contribution, then it is game over for coal. Where additional panels are installed to charge electric hybrid vehicle 8.5 kw hour batteries, then it is game over for petrol as well.

    What we need are hybride cars with the 8.5 kw hour for 50 klms of electric only driving where the beyond electric range engine is powered by E85 ethanol. With this change Australia easily has the capacity to produce all of its commuter fleet energy for all range driving from solar energy as well as all domestic energy from solar PVT’s, Summer and Winter.

  19. Another argument which is becoming increasingly popular with the anti-renewables crowd who are trying to give it the status of an immutable law is discussed in this article by David Roberts.

    “It is increasingly difficult for the market share of variable renewable energy sources at the system-wide level to exceed the capacity factor of the energy source”

    The argument is being promoted by among others a couple of BTI researchers and it has some superficial appeal but given the disruption that low cost renewables approaching 30-40% would generate in the electricity market, it seems unlikely that it would be a restriction in practice.

    I would be interested in your comments if you get a chance to look it.

  20. MikeH,

    Part 1 Domestic and Light Commercial

    The safest statement to make is that the future of renewable energy is substantially unpredictable. Just a few months ago distributed energy storage was problematic at best. Then the announcement by one entrepreneur has turned that around to be that distributed energy storage with Tesla’s Power Wall is as stable certainty. Suddenly rooftop solar can power through the night.

    Photo Voltaic Thermal (PVT’s) panels are not even part of the discussion (beyond my own comments) yet as people do not really understand the impact that they will have, so any projections made by commentators on factors involving distributed energy and rooftop solar are automatically incorrect as they are only calculating the direct electrical production, completely missing the indirect electrical offsets.

    Backup power generation to bridge the low solar periods has been left in the “too hard” basket as people’s perceptions (justifiably) are of clackety costly devices that one uses if there is absolutely no choice. This has been low hanging fruit for contrarians to pick off renewable reliability arguments. Here again there are entrepreneurial initiatives afoot that will elegantly eliminate this problem area for rooftop solar renewables. The Liquid Piston 70cc engine developer now has DARPA funding to further the development of this awesomely compact little power plant that will operate utilising natural gas to deliver backup energy directly into Tesla Power Wall modules and heat energy for water heating during extended periods of grey days.

    There are a raft of other innovations yet to make their appearance. Each will serve to stabilise local micro grids. This covers domestic and light commercial distributed rooftop energy systems for household energy and commuter energy. This sector on its own has sufficient capacity to supply all of Australia’s energy needs, but there is an issue of timing. So the reality will be that the distributed energy sector will have substantial over capacity which will deliver stability.

    What of Heavy Commercial, Heavy Industry, High Rise Commercial and High Rise residential? And what does this mean for the Grid? That will be in part 2

  21. MikeH, the article you linked to states, “At a certain point, in a given grid system, the cost of integrating more VRE exceeds the benefits.” Well, yeah, if the benefit is defined as the wholesale price received for electricity it produces. And it is exactly the same with coal and nuclear power. South Australia is going to shut down its last operating coal plant because the cost of keeping it going exceeds the benefits in terms of the average wholesale price received for the electricity it generates. No one is ever going to build a new coal plant in South Australia because the cost of integrating more coal power exceeds the payment they will receive, thanks to the current lower cost of renewables.

    This is even more the case for nuclear power. It’s a mark of how stupid the article is that it mentions that the capacity factor of nuclear power is 90%, giving the impression that perhaps nuclear power can meet 90% of electricity demand while failing to mention that new nuclear power is uneconomic everywhere and the amount that can be intergrated before the costs start exceeding the benefits is zero.

    Since there is economic value in not destroying the climate, it might be a good idea to factor that in with a carbon price. With a suitable carbon price electricity generation will become carbon neutral, and without nuclear power as that can’t compete against renewables regardless of what the carbon price may be. And even without a carbon price electricity generation could become emission free provided the cost of renewables and/or storage falls low enough.

    So yeah, a pretty dumb article that ignores the fact that new coal capacity and definitely new nuclear capacity are uneconomic.

  22. @MikeH

    Roughly speaking the position may be stated as follows. Conditional on existing pricing policies, and in the absence of storage or a grid large enough to even out fluctuations, if the proportion of a specific kind of renewable exceeds the capacity factor, some electricity will be wasted.

    The qualifications I’ve stated indicate the ways in which the problem may be addressed. I think Roberts is going to go on and spell this out.

  23. My understanding of coal fired power is that there is significant waste (fly ash, sludge etc) and by product (heat energy etc). It’s been said that an overwhelming percentage of energy produced by coal powered stations is wasted ie it is lost by heated water, heated air. There would also be other losses incurred during extraction, processing and transport.

    Difficult to flesh out the real cost as govt is ready with handouts to the supply chain.

  24. Rog, about a third of the heat energy in coal will be converted into electricity. Victoria’s brown coal power stations do worse than this modern super critical coal plants can do better, but were not going to get any modern new coal power stations here and fortunately neither is most of the rest of the world. In additon, about 7% of the electricity generated will be lost in transmission, but this is the case with any utility scale generation.

  25. Japan has field tested fabric and sponge based methods of extracting uranium from seawater. These methods adsorb uranium oxide onto their surface. They are estimated to operate at around $240 per kilogram of yellowcake(55). The normal price of yellowcake is around $110 per kilogram.

    There is approximately 4.2 billion tons of uranium dissolved in the world ocean. Because of the vast amount of uranium in the ocean, there is enough U-235 in Tokyo Bay to build 20-25 Hiroshima-sized bombs. (How much depends on the degree of freshwater dilution.

    55. M Tamada. Current status of technology for collection of uranium from seawater. Erice seminar 2009:; 2009

  26. The exciting thing about that technology, Brian, is that it could actually have a practical use as there are places where ground water used for drinking is contaminated with uranium. Of course, safely disposing of the material in a low level waste dump once it has become saturated might be a costly problem.

  27. Ah, the economist’s EROEI without any energy calculations involved.

    I’m looking forward to the day that solar power powers solar panel production 100% and at a profit. In the same way I look forward to seeing unicorns.

  28. Personally I’m looking forward to the day when South Australia generates electricity equal to 40% of its total consumption from wind and solar. Oh wait, that’s already happened.

  29. “Ah, the economist’s EROEI without any energy calculations involved.”

    Say what? I calculated the electricity produced by a solar cell, and divided it by an estimate of the electricity used to produce it. The only place I used prices was to derive the second estimate. As has already been pointed out in comments, you can find lower numbers for new technologies like fluidized bed reactors

  30. @iain

    I see that Ian Plimer is writing a book called “Heaven and Hell: The Pope condemns the poor to eternal poverty”.

    You probly like his thoughts and calculations.

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