I have ‘known’ Pedro Prieto online for many many years, and have featured his work here, and here on DTM. Pedro is an expert on renewable energy, and is one of the few engineers I’ve ever read who understands ERoEI (Energy Return on Energy Invested), and has practical experience in deploying both wind and solar energy system in his native Spain. Pedro has recently dropped a bombshell in a book he co authored with Charles Hall (EROEI is the ratio of energy output over energy input, a measure that was developed by Professor Charles Hall). This book, titled “Tilting at Windmills, Spain’s disastrous attempt to replace fossil fuels with Solar Photovoltaics”, is the first in-depth look at the ERoEI of large-scale PV in any developed nation. And the results do not bode well……
This is the first time an estimate of Energy Returned on Energy Invested (EROI) of solar Photovoltaics (PV) has been based on real data from the sunniest European country, with accurate measures of generated energy from over 50,000 installations using several years of real-life data from optimized, efficient, multi-megawatt and well oriented facilities.
Other life cycle and energy payback time analyses used models that left out dozens of energy inputs, leading to overestimates of energy such as payback time of 1-2 years (Fthenakis), EROI 8.3 (Bankier), and EROI of 5.9 to 11.8 (Raugei et al).
Prieto and Hall added dozens of energy inputs missing from past solar PV analyses. Perhaps previous studies missed these inputs because their authors weren’t overseeing several large photovoltaic projects and signing every purchase order like author Pedro Prieto. Charles A. S. Hall is one of the foremost experts in the world on the calculation of EROI. Together they’re a formidable team with data, methodology, and expertise that will be hard to refute.
Prieto and Hall conclude that the EROI of solar photovoltaic is only 2.45, very low despite Spain’s ideal sunny climate. Germany’s EROI is probably 20 to 33% less (1.6 to 2), due to less sunlight and efficient rooftop installations.
Here is what Gail Tverberg has to say on ERoEI…
Commenters frequently remark that such-and-such an energy source has an Energy Return on Energy Invested (EROI) ratio of greater than 5:1, so must be a helpful addition to our current energy supply. My finding that the overall energy return is already too low seems to run counter to this belief.
Adequate Return for All Elements Required for Energy Investment
In order to extract oil or create biofuels, or to make any other type of energy investment, at least four distinct elements described in Figure 1: (1) adequate payback on energy invested, (2) sufficient wages for humans, (3) sufficient credit availability and (4) sufficient funds for government services. If any of these is lacking, the whole system has a tendency to seize up.
EROI analyses tend to look primarily at the first item on the list, comparing “energy available to society” as the result of a given process to “energy required for extraction” (all in units of energy). While this comparison can be helpful for some purposes, it seems to me that we should also be looking at whether the dollars collected at the end-product level are sufficient to provide an adequate financial return to meet the financial needs of all four areas simultaneously.
My list of the four distinct elements necessary to enable energy extraction and to keep the economy functioning is really an abbreviated list. Clearly one needs other items, such as profits for businesses. In a sense, the whole world economy is an energy delivery system. This is why it is important to understand what the system needs to function properly.
Source of the EROI 5:1 Threshold
To my knowledge, no one has directly proven that a 5:1 threshold is sufficient for an energy source to be helpful to an economy. The study that is often referred to is the 2009 paper, What is the Minimum EROI that a Sustainable Society Must Have? (Free for download), by Charles A. S. Hall, Steven Balogh, and David Murphy. This paper analyzes how much energy needs to be provided by oil and coal, if the energy provided by those fuels is to be sufficient to pay not just for the energy used in its own extraction, but also for the energy required for pipeline and truck or train transportation to its destination of use. The conclusion of that paper was that in order to include these energy transportation costs for oil or coal, an EROI of at least 3:1 was needed.
Clearly this figure is not high enough to cover all costs of using the fuels, including the energy costs to build devices that actually use the fuels, such as private passenger cars, electrical power plants and transmission lines, and devices to use electricity, such as refrigerators. The ratio required would probably need to be higher for harder-to-transport fuels, such as natural gas and ethanol. The ratio would also need to include the energy cost of schools, if there are to be engineers to design all of these devices, and factory workers who can read basic instructions. If the cost of government in general were added, the cost would be higher yet. One could theoretically add other systems as well, such as the cost of maintaining the financial system.
The way I understood the 5:1 ratio was that it was more or less a lower bound, below which even looking at an energy product did not make sense. Given the diversity of what is needed to support the current economy, the small increment between 3 and 5 is probably not enough–the minimum ratio probably needs to be much higher. The ratio also seems to need to change for different fuels, with many quite a bit higher.
So there you have it folks……. solar will never keep civilisation as we know it going. But you already knew that. And before Eclipse jumps in, I found this on Nuclear Power…:
The seemingly most reliable information on ERoEI is quite old and is summarized in chapter 12 of Hall et al. (1986). Newer information tends to fall into the wildly optimistic camp (high EROI, e.g. 10:1 or more, sometimes wildly more) or the extremely pessimistic (low or even negative EROI) camp (Tyner et al. 1998, Tyner 2002, Fleay 2006 and Caldicamp 2006). One recent PhD analysis from Sweden undertook an emergy analysis (a kind of comprehensive energy analysis including all environmental inputs and quality corrections as per Howard Odum) and found an emergy return on emergy invested of 11:1 (with a high quality factor for electricity) but it was not possible to undertake an energy analysis from the data presented (Kindburg, 2007). Nevertheless that final number is similar to many of the older analyses when a quality correction is included.
Notice this was written in 1986. As the quality of Uranium ores worsen, (they’ve worsen rapidly since 1986…), nuclear will be no more able to keep Business as Usual running than solar.
As extraction and depletion have operated over time, the average ore grade has decreased and the uranium has become more and more dispersed within the background substrate, plus the total amount of uranium we can extract can decrease as well. Leuwen (2005) argues that the empirical extraction yield declines much more sharply than the hypothetical one, which could come into play if there is a large increase in nuclear capacity in the coming decades.
Just enjoy life in the quiet lane……. it’s not that bead, really…..