Energy return: ratio or net value (revised)

Quite a while back we had a discussion of the idea of Energy Return On Energy Invested (EROEI) as a measure of the viability of solar and wind energy. I did the numbers for solar (including battery backup) and came to the conclusion that EROEI was at least 10 and therefore not a problem.

The issue has come up in an email discussion I’ve been having. Thinking about it, I concluded that using a ratio of energy generated to energy invested is incorrect. As a starting point, I assume that we want to consider energy separately from market goods in general. Producing new energy requires inputs of both energy and market goods (including labour and capital). Think about this example

Technology A uses 1 Mwh of energy input and $180 of market inputs to produce 10 MWh of energy output

Technology B uses 1 Mwh of energy input and $600 of market inputs to produce 20 MWh of energy output

Technology B has an EROEI of 20, while that for A is 10. But using technology B with 1 MWh of energy input, we produce 20 MWh yielding a net output of 19MWh, at a cost of more than $30/MWh. By contrast, using A, with 2.1 MWh of input, we can produce 21 MWh of output for net generation of 19 MWh at a cost of less than $20/MWh

How can we capture this. The calculation implied above is (EREOI – 1)/$ where $ is the cost of market inputs associated with a unit of energy input. In the absence of constraints on how much of each technology we can deploy, this gives us the lowest cost way of generating a given amount of additional net energy.

Where did the idea of using a ratio come from? I think it’s because ratios can be used to derive a payback period, which is commonly used in the evaluation of private investments. But the payback period is a kludge even in this case, and has no relevance when we are evaluating an energy strategy.

An EROEI criterion would make sense if we had a fixed amount of energy available as input to new energy generation and didn’t care about market costs. More generally EROEI would be relevant if we were seeking an energy transition so rapid that the construction of new generating sources was a major part of total energy use. But that isn’t the case. I don’t have data for the share of total energy use going into the manufacture and installation of solar and wind power. But that’s because this share is too small to be broken out from general industrial uses of energy,

I thank commenter MartinK for pointing out problems with the original version of this post, which used much lower EROEI numbers for both technologies.

59 thoughts on “Energy return: ratio or net value (revised)

  1. “We decided to combine our energy innovation study’s best-case scenario results with Hansen’s climate model to see whether a 55 percent emission cut by 2050 would bring the world back below that 350-ppm threshold.”

    Sure, it’s pretty obvious that a 55 per cent cut won’t be enough. Even Scomo is talking about a 100 per cent cut by 2050 (that is, net zero). EU is going for a 60 per cent cut by 2030 – that’s clearly feasible in technical terms. So, the “best-case scenario” must be way out of date.

  2. “So, the “best-case scenario” must be way out of date”

    And the best case scenario that can be mustered now is net zero emissions for some by 2030, or maybe 2050.

    Sure, yet China says 2060. And the EU and so many others outsource and shift emissions to China and elsewhere and will continue to do so. And Russia and Canada will somehow extinguish the perpetual wildfires in their thawed Arctic peat soils and similarly all the never ending burning elsewhere shall cease.

    The current best case scenario also falls short. Way short of <350ppm by 2050 and climbing. Way short of 400ppm by 2050 and still climbing… Use by dates keep being put off. The big fossils have just inserted their man into the top OECD job… Do you really believe global net zero emissions will occur by 2050? And whenever that occurs, if it occurs, what will the long lasting level of atmospheric CO2e be by that date after continuing exponential growth in added emissions for some time yet followed then by tapering additions out to the net zero day?

    However, the cutting of emissions was seen to be and still is in fact only half the problem. As the Google RE<C engineers found, and as the Hansen graph plot they referred to made clear, the other half of the problem of avoiding severe climate change is rapidly removing long lived CO2 from the atmosphere and lowering the concentration to 350ppm. I know of no newly discovered technology that has been developed since the plug was pulled on RE<C a decade ago that can rapidly be deployed and rapidly accomplish such a reduction. Without that scale of reduction severe climate change is assured for some time which raises a real prospect of triggering natural tipping points that the RE<C engineers also surely would have considered before the plug was pulled on their funding. The take out from the RE<C study in large parts still holds.

  3. With thanks to JQ et al. for the interesting discussion – as someone who is far from well versed in EROI-type calculations, it is useful to see the discussion here.

    As previously noted, it is a complex situation to grapple with – there are differences in methodology which often make comparisons between values difficult or impossible, and there has been a lot of discussion regarding “what minimum [energy] is required for civilisation?” (where [energy] can be any number of EROEI/GExRR/etc. calculations).

    My impression is that one should be extremely cautious when trying to make comparisons between different research (perhaps particularly when trying to compare “what is the [energy] of a system?” and “what minimum [energy] is required for civilisation?”). Unfortunately, as far as I am aware there is not yet published research which answers both these questions with a unified methodology for the range of low-emissions (e.g. RE, VRE, etc.) technologies (if there is, I´d certainly appreciate it being highlighted).

    However, just to attempt to give an overview, here is my current understanding of the cross-section of literature:

    One paper investigating biofuels suggests a minimum EROIext of 3:1 would be necessary to maintain civilisation, but leave little “surplus” (1); another suggests a minimum EROI of 7 is needed, but does not show how that figure was arrived at (2) and so perhaps should be considered with great care; one calculation based on correlations between ERR and HDI suggests a minimum primary energy ERR of 15 is needed for an HDI of 0.7 (3); and an indirect approach using US energy expenditures (which should be treated with caution, of course, due to the indirect nature) seems to show a yearly ERRgross 12-15 is required to support an equivalent modern society (4). However, it should also be noted that recent publications suggest that the ERRnet of China has declined to 5.5 in 2012 (and that the EROIpou has similarly declined to ca. 5) while still maintaining civilisation (5) and that the EROIfin of fossil fuels has decreased from 6 to 5.4 between 1995 and 2011 (6).

    Again, to be clear, I would be very wary of a straightforward comparison of these values (particularly with respect to those calculated for renewables – such as those noted in my previous posts) as it is by no means clear that this is methodologically sound. But on the basis of an examination of the literature, I would venture that it is by no means clear whether or not a high degree of RE (and VRE) penetration would lead to “falling off the net energy cliff”.

    In short, it would seem to me that “what is the [energy] of any given technology?”, “what minimum [energy] is required for civilisation?”, and “is it possible to sustain [value for civilisation] using [energy production/storage/transmission/etc. system]?” are questions yet to be satisfactorily addressed.

    References:
    (1) What is the minimum EROI that a sustainable society must have?, C A S Hall et al., Energies (2009), 2, 25; doi: 10.3390/en20100025

    (2) Energy intensities, EROIs (energy returned on invested), and energy payback times of electricity generating power plants, D Weissbach et al., Energies (2013), 52, 210; doi.org/10.1016/j.energy.2013.01.029

    (3) Energy, EROI and quality of life, J G Lambert et al., Energy Policy (2014), 64, 153; doi.org/10.1016/j.enpol.2013.07.001

    (4) Energy expenditure, economic growth, and the minimum EROI of society, F. Fizaine et al., Energy Policy (2016), 95, 172; http://dx.doi.org/10.1016/j.enpol.2016.04.039

    (5) Modeling the point of use EROI and its implications for economic growth in China, J. Feng et al., Energy (2018), 144, 232; https://doi.org/10.1016/j.energy.2017.11.061

    (6) Estimation of global final stage energy return-on-investment for fossil fuels with comparison to renewable energy sources, P E Brockway et al., Nature Energy (2019), 4, 612; https://doi.org/10.1038/s41560-019-0425-z

  4. Even Scomo is talking about a 100 per cent cut by 2050 (that is, net zero). EU is going for a 60 per cent cut by 2030

    I tend to treat IPCC “worst case” numbers as “most nations will try to do worse than this” targets, because that’s been the pattern since they started issuing predictions. So we’re currently on track for 3-5 degrees of warming, assuming the current level of comittments are met (a very shaky assumption). Best case, the post-2050 promises to go seriously net negative will bring us back down to less than 2 degrees over the next 5000-20000 years.

    Maybe I should read less David Spratt and more David Brin?

  5. JQ: – “Sure, it’s pretty obvious that a 55 per cent cut won’t be enough. Even Scomo is talking about a 100 per cent cut by 2050 (that is, net zero). EU is going for a 60 per cent cut by 2030 – that’s clearly feasible in technical terms. So, the “best-case scenario” must be way out of date.”

    It sure is – per a Climate Code Red post headlined “Zero by 2050 or 2030? 1.5°C or 2°C? Overshoot or not? Demystifying carbon budgets”, dated Mar 2, re IPCC carbon budgets and the Paris Agreement:

    “The problem is that carbon budgets, picked out of thin air by underestimating warming, using low climate sensitivity figures, making assumptions about technologies that don’t exist in a functioning manner now, and similar sleights of hand, have become a foundation for mythologies about the Paris Agreement and excuses for delay.

    In demystifying carbon budgets, we also need a frank conversation about Paris. More than five years after the agreement was signed, current national emission reduction commitments will lead to emission levels in 2030 just 1% below the 2010 level.

    When will the penny drop that Paris has failed catastrophically?”
    http://www.climatecodered.org/2021/03/zero-by-2050-or-2030-15c-or-2c.html

    Posted earlier today at The Conversation is a piece by Lesley Hughes, Professor, Department of Biological Sciences, Macquarie University; John Hewson, Professor and Chair, Tax and Transfer Policy Institute, Crawford School of Public Policy, Australian National University; Malte Meinshausen, A/Prof., School of Earth Sciences, The University of Melbourne; and Will Steffen, Emeritus Professor, Fenner School of Environment & Society, Australian National University; headlined “Wake up, Mr Morrison: Australia’s slack climate effort leaves our children 10 times more work to do”.
    https://theconversation.com/wake-up-mr-morrison-australias-slack-climate-effort-leaves-our-children-10-times-more-work-to-do-157136

  6. Carbon dioxide emissions need to be cut by over 80% to stabilize CO2 levels. This will slow, but not stop global warming. Rapidly reaching zero net emissions from humanity will result in a a fairly modest drop in emissions as oceans and other sinks absorb some of the CO2 in the atmosphere, but this will slow and stop. The world will still be left warmer than it was unless we actively to something to counter that. The sooner and the faster we cut emissions, the less saturated these natural carbon sinks will be and the better the effect.

  7. Geoff, we appear to be in agreement here. The problem isn’t technical, it’s political.

    In this context, quibbling about difficulties with decarbonization only helps the denialists and do-nothingists.

    Ben, I think that’s right. Hopefully, we’ll get down to the Pledges and Targets (2.6) line at Glasgow, which will still leave a lot of work to be done if we are to get below 2.

  8. JQ: – “Geoff, we appear to be in agreement here. The problem isn’t technical, it’s political.”

    Based on what I’ve stated here at this blog, I don’t see how you arrive at that conclusion.

    I think a very substantial part of the problem is political – profound ignorance or is it ‘predatory delay’?

    I see some timely technical solutions to eliminate the majority of humanity’s GHG emissions, but not ALL – we need to do ALL, and time is against us. Carbon drawdown is also now vital.

    The evidence I see indicates the Earth’s climate system is likely to overshoot +2 °C global mean warming (relative to Holocene Epoch pre-industrial age) within this century.

    Per ERA5 data, Earth’s climate state was at +1.3 °C global mean warming in 2020. Land was at 1.94 °C.

    It’s inevitable an overshoot of +1.5 °C global mean warming will occur, probably before 2030 – modeling suggests best estimates for around 2026 to 2028, regardless of future human-induced GHG emissions.

    Per “Climate Reality Check 2020”, the current Earth energy imbalance (EEI) – the radiative imbalance at
    the top of the atmosphere (between outgoing and incoming radiation), which is driving global warming – is +0.6–0.75 °C for the current level of greenhouse gases ALREADY in the atmosphere. So that means we are already ‘locked-in’ for a global mean warming, at equilibrium, at +1.9–2.05 °C with no further human-induced GHG emissions. Humanity won’t be cutting GHG emissions overnight, so it’s almost a certainty that +2 °C will be breached, and on current GHG emissions trajectory, probably by around 2050, or perhaps earlier. If humanity can rapidly reduce GHG emissions – greater than 50% before 2030 and net zero before 2040, then overshoot of +2 °C global mean warming will probably be delayed to the later part of this century. So, per the evidence I see, we have already failed the Paris Agreement goal for keeping “well below 2 °C”.

    Yet our political, business and media elites are still talking about keeping below 1.5 °C – the disconnect from reality is breathtaking – or is it deliberate misdirection?

    Evidence I see indicates it’s a big mistake to think we can “park” the Earth System at any given temperature rise – say at +2 °C global mean warming – and expect it to stay there. Former NASA climate chief Professor James Hansen said that it is “well understood by the scientific community” that goals to limit human-made warming to +2 °C are “prescriptions for disaster”. Professor Schellnhuber has said similar.

    The “Hothouse Earth” scenario is one in which climate system feedbacks and their mutual interaction drive the Earth System climate to a point of no return, whereby further warming would become self-sustaining (that is, without further human perturbations). This planetary threshold could exist at a temperature rise as low as +2 °C, possibly even in the +1.5 °C–2 °C range.
    https://www.pnas.org/content/115/33/8252

    Per Scripps Mauna Loa Observatory readings over the last 12 months, atmospheric CO2 readings ranged from a monthly average low of around 411 ppm to a peak of around 417 ppm.
    https://keelingcurve.ucsd.edu/

    Stabilisation (at current climate state) would require carbon drawdown of around 65 ppm (back to ~350 ppm) to stop further warming of ~0.7 °C. Drawdown is a slow process that will not provide active cooling until it is greater than the level of emissions.

    Large-scale carbon drawdown technologies do not currently exist. Large-scale R&D and deployment is crucial, but there are also significant risks of unintended consequences.

    The collapse of civilisation is not inevitable, but emergency-level action right now is critical to minimise the rate and magnitude of warming.

    Even substantial emission reductions will have no significant impact on the warming trend over the next 20-25 years, due to the offsetting effect of aerosols.

    IMO, these are the inconvenient truths that are not being acknowledged by our political, business and media elites.

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