Turning Trees Into Enemies. The New War on Forests

The San Marco Square in Florence in 2017. You can see the ancient trees of the square being cut as part of a plan that involved the removal of several hundred trees in the whole city. The action was accompanied by a propaganda campaign against trees that looked curiously similar to that used to justify the invasion of Iraq, in 2003. "Trees are a threat to citizens,", "There is no alternative," "Killer Trees," and the like.

The war on trees seems to be starting. I don't know about what's happening where you live, but here, in Italy, we see it clearly, accompanied by all the propaganda tricks normally used to start wars. So, we have seen a string of accusations in the media against "killer trees," supposed to be a danger for the citizens because they can fall on them or on their beloved shiny cars. The image on the right, here shows the first page of an Italian newspaper in 2014 informing us there are "50,000 killer trees" in Rome. Truly an invading army to be fought with the appropriate weaponry in the form of chainsaws.

One century ago, city administrations were proud of planting trees, today they are proud of cutting them. What happened that changed their attitude so much is hard to say. Maybe it is the general degradation of the ecosystem that has turned trees into monsters, but that doesn't explain how administrations are starting also a war on forests - surely not threatening citizens or their cars. In a previous post, I commented on a recent piece of legislation in Italy that forces land owners to cut their woods even if they don't want to. From the comments I received to that post and from what I can read on the Web, I think I can say that the war on trees is not just an Italian phenomenon, it is worldwide.

I interpreted this war as the result of the diminishing returns of our energy sources - mainly fossil fuels. The returns of an energy source, as you may know, can be expressed in terms of EROI (energy return on energy invested). It is the ratio of result to effort. Extracting oil, for instance, implies digging a well, using pumps, and many more things which have an energy cost. The energy obtained from oil need be much larger than the energy spent on oil, otherwise the whole effort would be useless. And, historically, it has been the case. At the height of the oil age, an oil well in the US provided perhaps 50 times the energy spent to extract the oil. But not anymore: it is the harsh law of the EROI: it declines with time. The consequence is a well-known law in economics: diminishing returns on investments.

What's happening worldwide is that the EROI of fossil fuels has been going down. It was expected: it is a result of the gradual depletion of the resources. Obviously people will look first for the best resources, then progressively move to less good ones. This has consequences: the worldwide search for oil and other fuels leads to conflicts for what's left - the invasion of Iraq in 2003 is a good example. But even the Iraqi oil is subjected to the harsh law of EROI. The result is that some energy resources which, once, looked old and outfashioned, now start looking good again. Wood, for instance.

And here is the reason for the war on trees. As all wars, it is a war on resources. And, as it is normal in our times, before going to war, you demonize your enemies - hence the "killer trees." It is also traditional to state that wars are done in the name of lofty and noble principles, in this case in the name of ecology, since wood is said to be a "carbon neutral" energy resource and therefore cutting trees somehow fights global warming.

Alas, no. Wood burning is NOT carbon neutral. It is true that the CO2 generated by burning biomass will eventually become biomass again, but it takes time. A recent study estimates that it takes several decades, even a century, for the CO2 generated by burning trees to be reabsorbed from the atmosphere in the form of new trees. And that assumes that the forest reforms while, in practice, forest razing is often an irreversible phenomenon, at least on the century time scale. According to some recent studies, the Sahara may be a human-made desert.

So, the harsh law of the EROI holds also for wood. If the current rush to wood cutting continues, the best resources will soon be exhausted and cutters will move to more expensive ones. At some moment, the cycle that's leading from fossils to wood will repeat itself: after wood, what? How about burning furniture?

Why EROEI matters: the role of net energy in the survival of civilization

The image above was shown by Charlie Hall in a recent presentation that he gave in Princeton. It seems logic that the more net energy is available for a civilization, the more that civilization can do, say, build cathedrals, create art, explore space, and more. But what's needed, exactly, for a civilization to exist? Maybe very high values of the EROEI (energy return on energy invested) are not necessary.

A lively debate is ongoing on what should be the minimum energy return for energy invested (EROEI) in order to sustain a civilization. Clearly, one always wants the best returns for one's investments. And, of course, investing in something that provides a return smaller than the investment is a bad idea. So, a civilization grows and prosper on the net energy it receives, that is the energy produced minus the energy required to sustain production. The question is whether the transition from fossil fuels to renewables could provide enough energy to keep civilization alive in a form not too different from the present one.

It is often said that the prosperity of our society is the result of the high EROEI of crude oil as it was in mid 20th century. Values as high as 100 are often cited, but these are probably widely off the mark. The data reported in a 2014 study by Dave Murphy indicate that the average EROEI of crude oil worldwide could have been around 35 in the past, declining to around 20 at present. Dale et al. estimate (2011) that the average EROEI of crude oil could have been, at most, around 45 in the 1960s Data for the US production indicate an EROEI around 20 in the 1950s; down to about 10 today.

We see that the EROEI of oil is not easy to estimate but we can say at least two things: 1) our civilization was built on an energy source with an EROEI around 30-40. 2) the EROEI of oil has been going down, owing to the depletion of the most profitable (high EROEI) wells. Today, we may be producing crude oil at EROEIs between 10 and 20 on the average, and the net energy yield keeps going down.

Let's move to renewables. Here, the debate often becomes dominated by emotional or political factors that seem to bring people to try to disparage renewables as much as possible. Some evidently wrong assessments, for instance, claim EROEIs smaller than one for the most promising renewable technology, photovoltaics (PV). In other cases, the game consists in enlarging the boundaries of the calculation, adding costs not directly related to the exploitation of the resource. That's why we should compare what's comparable; that is, use the same rules for evaluating the EROEI of fossil fuels and of renewable energy. If we do that, we find that, for instance, photovoltaics has an EROEI around 10. Wind energy does better than that, with an average EROEI around 20. Not bad, but not as large as crude oil in the good old days.

Now, for the mother of all questions: on the basis of these data, can renewables replace the increasing energy expensive oil and sustain civilization? Here, we venture into a difficult field: what do we mean exactly as a "civilization"? What kind of civilization? Could it build cathedrals? Would it include driving SUVs? How about plane trips to Hawaii?

Here, some people are very pessimistic and not just about SUVs and plane trips. On the basis of the fact that the EROEI of renewables is smaller than that of crude oil, considering also the expense of the infrastructure needed to adapt our society to the kind of energy produced by renewables, they conclude that "renewables cannot sustain a civilization that can sustain renewables." (a little like Groucho Marx's joke, "I wouldn't want to belong to a club that accepts people like me as members.").

Maybe, but I beg to differ. Let me explain with an example. Suppose, just for the sake of argument, that the energy source that powers society has an EROEI equal to 2. You would think that this is an abysmally low value and that it couldn't support anything more than a society of mountain shepherds or not even that. But think about what an EROEI of 2 implies: for each energy producing plant in operation there must be a second one of the same size that only produces the energy that will be used to replace both plants after that they have gone through their lifetime. And the energy produced by the first plant is net energy fully available to society for all the needed uses, including cathedrals if needed. Now, consider a power source that has an EROEI= infinity; then you don't need the second plant or, if you have it, you can make twice as many cathedrals. In the end, the difference between two and infinity in terms the investments necessary to maintain the energy producing system is only a factor of two.

It is like that: the EROEI is a strongly non-linear measurement. You can see that in the well-known diagram below (here in a simplified version, some people trace a vertical line in the graph indicating the "minimum EROEI needed for civilization", which I think is unjustified)):

You see that oil, wind, coal, and solar are all in the same range. As long as the EROEI is higher than about 5-10, the energy return is reasonably good, at most you have to re-invest 10% of the production to keep the system going. It is only when the EROEI becomes smaller than ca. 2 that things become awkward. So, it doesn't seem to be so difficult to support a complex civilization with the technologies we have. Maybe trips to Hawaii and SUVs wouldn't be included in a PV-based society (note the low EROEI of biofuels) but about art, science, health care, and the like, well, what's the problem?

Actually, there is a problem. It has to do with growth. Let me go back to the example I made before, that of a hypothetical energy technology that has an EROEI = 2. If this energy return is calculated over a lifetime of 25 years, it means that the best that can be done in terms of growth is to double the number of plants over 25 years, a yearly growth rate of less than 3%. And that in the hypothesis that all the energy produced by the plants would go to make more plants which, of course, makes no sense. If we assume that, say, 10% of the energy produced is invested in new plants then, with EROEI=2, growth can be at most of the order of 0.3%. Even with an EROEI =10, we can't reasonably expect renewables to push their own growth at rates higher than 1%-2%(*). Things were different in the good old days, up to about 1970, when, with an EROEI around 40, crude oil production grew at a yearly rate of 7%. It seemed normal, at that time, but it was the result of very special conditions.

Our society is fixated on growth and people seem to be unable to conceive that it could be otherwise. But renewables, with the present values of the EROEI, can't support a fast growing society. But is that a bad thing? I wouldn't say so. We have grown enough with crude oil, actually way too much. Slowing down, and even going back a little, can only improve the situation.





(*) The present problem is not to keep the unsustainable growth rates that society is accustomed to. It is how to grow renewable energy fast enough to replace fossil fuels before depletion or climate change (or both) destroy us. This is a difficult but not impossible task. The current fraction of energy produced by wind and solar combined is less than 2% of the final consumption (see p. 28 of the REN21 report), so we need a yearly growth of more than 10% to replace fossils by 2050. Right now, both solar and wind are growing at more than a 20% yearly rate, but this high rate is obtained using energy from fossil fuels. The calculations indicate that it is possible to keep these growth rates while gradually phasing out fossil fuels by 2050, as described here

Catastrophism is popular, but not necessarily right. Debunking the "Hill's Group" analysis of the future of the oil industry

"The Hill's Group" has been arguing for the rapid demise of the world's oil industry on the basis of a calculation of the entropy of the oil extraction process. While it is true that the oil industry is in trouble, the calculations by the Hill's group are, at best, irrelevant and probably simply plain wrong. Entropy is an important concept, but it must be correctly understood to be useful. It is no good to use it as an excuse to pander unbridled catastrophism. 

Catastrophism is popular. I can see that with the "Cassandra's Legacy" blog. Every time I publish something that says that we are all going to die soon, it gets many more hits than when I publish posts arguing that we can do something to avoid the incoming disaster. The latest confirmation of this trend came from three posts by Louis Arnoux that I published last summer (link to the first one). All three are in the list of the ten most successful posts ever published here.

Arnoux argues that the problems we have today are caused by the diminishing energy yield (or net energy, or EROI) of fossil fuels. This is a correct observation, but Arnoux bases his case on a report released by a rather obscure organization called "The Hill's Group." They use calculations based on the evaluation of the entropy of the extraction process in order to predict a dire future for the world's oil production. And they sell their report for $28 (shipping included).

Neither Arnoux nor the "Hill's Group" are the first to argue that diminishing EROEI is at the basis of most of our troubles. But the Hill's report gained a certain popularity and it has been favorably commented on many blogs and websites. It is t is understandable: the report has an aura of scientific correctness that comes from its use of basic thermodynamic principles and of the concept of entropy, correctly understood as the force behind the depletion problem. There is just a small problem: the report is badly flawed.

When I published Arnoux's posts on this blog, I thought they were qualitatively correct, and I still think they are. But I didn't have the time to look at the details of the report of Hill's group. Now, some people did that and their analysis clearly shows the many fundamental flaws of the treatment. You can read the results in English by Seppo Korpela, and in Spanish by Carlos De Castro and Antonio Turiel.

Entropy is a complex subject and delving into the Hill's report and into the criticism to it requires a certain effort. I won't go into details, here. Let me just say that it simply makes no sense to start from the textbook definition of entropy to calculate the net energy of oil production. The approximations made in the report are so large to make the whole treatment useless (to say nothing of the errors it contains). Using the definition of entropy to analyze oil production is like using quantum mechanics to design a plane. It is true that all the electrons in a plane have to obey Schroedinger's equation, but that's not the way engineers design planes.

Of course, the problem of diminishing EROEI exists and can be studied. The way to do that is known and it is based on the "life cycle analysis" (LCA) of the process. This method takes into account entropy indirectly, in terms of heat losses, without attempting the impossible task of calculating it from first principles. By means of this method we can see that, at present, the EROEI of oil production is not so bad as described by Hill/Arnoux. It still provides a reasonable energy return on investment (EROEI) as you can read, for instance, in a recent paper by Brandt et al

But if producing oil still provides an energy return, why is the oil industry in such dire troubles? (see this post on the SRSrocco report, for instance). Well, let me cite a post by Nate Hagens:

In the last 10 years the global credit market has grown at 12% per year allowing GDP growth of only 3.5% and increasing global crude oil production less than 1% annually. We're so used to running on various treadmills that the landscape doesn't look all too scary. But since 2008, despite energies fundamental role in economic growth, it is access to credit that is supporting our economies, in a surreal, permanent, Faustian bargain sort of way. As long as interest rates (govt borrowing costs) are low and market participants accept it, this can go on for quite a long time, all the while burning through the next higher cost tranche of extractable carbon fuel in turn getting reduced benefits from the "Trade" creating other societal pressures.

Society runs on energy, but thinks it runs on money. In such a scenario, there will be some paradoxical results from the end of cheap (to extract) oil. Instead of higher prices, the global economy will first lose the ability to continue to service both the principal and the interest on the large amounts of newly created money/debt, and we will then probably first face deflation. Under this scenario, the casualty will not be higher and higher prices to consumers that most in peak oil community expect, but rather the high and medium cost producers gradually going out of business due to market prices significantly below extraction costs. Peak oil will come about from the high cost tranches of production gradually disappearing.

I don't expect the government takeover of the credit mechanism to stop, but if it does, both oil production and oil prices will be quite a bit lower. In the long run it's all about the energy. For the foreseeable future, it's mostly about the credit

In the end, it is simply dumb to think that the system will automatically collapse when and because the net energy of the oil production process becomes negative (or the EROEI smaller than one). No, it will crash much earlier because of factors correlated to the control system that we call "the economy". It is a behavior typical of complex adaptative systems that are never understandable in terms of mere energy return considerations. Complex systems always kick back.

The final consideration of this post would simply be to avoid losing time with the Hill's report (to say nothing about paying $28 for it). But there remains a problem: a report that claims to be based on thermodynamics and uses resounding words such as "entropy" plays into the human tendency of believing what one wants to believe. Catastrophism is popular for various reasons, some perfectly good. Actually, we should all be cautious catastrophists in the sense of being worried about the catastrophes we risk to see as the result of climate change and mineral depletion. But we should also be careful about crying wolf too early. Unfortunately, that's exactly what Hill&Arnoux did and now they are being debunked, as they should be. That puts in a bad light all the people who are seriously trying to alert the public of the risks ahead.

Catastrophism is the other face of cornucopianism; both are human reactions to a difficult situation. Cornucopianism denies the existence of the problem, catastrophism denies that it can be solved or even just mitigated. Both attitudes lead to inaction. But there exists a middle way in which we don't exaggerate the problem but we don't deny it, either, and we do something about it!

Another failure of scientific peer-review: a wrong paper on the energy return of photovoltaic energy

Theoretically, whatever is published in a scientific journal should go through a rigorous review process that ensures that it is correct and reliable. Unfortunately, it doesn't work that way.

If you follow the debate on renewable energy, you know how important is the question of the energy return (or EROEI) of the various sources. An EROEI lower than one would make the source - PV, wind, or whatever, an energy sink, not a source. And this is exactly what Ferruccio Ferroni and Richard Hopkirk have been claimed with a paper recently published in "Energy Policy" that arrives to results that are completely different than to those of all the other studies on the subject.

The paper by Ferroni and Hopkirk is simply wrong. You can read below a complete demolition of their arguments performed by Maury Markowitz. But, no matter how wrong is the paper - and it is wrong - this story raises some disturbing points about how scientific information is validated and diffused.


1. Any paper, no matter how bad, poorly conceived, and ultimately totally wrong, can be published in a scientific journal if the authors are persistent enough and try many times. Eventually, they will find a combination of editors and reviewers sufficiently incompetent, sloppy, or biased that they will accept it.

2. There is no way to correct the mistakes of a wrong paper once it is published. The journal will retract it only if it is possible to prove that the authors are guilty of evident fraud or plagiarism. But "simple" mistakes, things such as wrong citations, misinterpreted data, inappropriate data treatment and the like are rarely sufficient to force retraction.

3. The only way to protest against a wrong paper is to ask to the journal to publish a rebuttal. They will do that with the same degree of willingness that you feel about having a tooth pulled, but they will do that, asking also to the authors of the original paper to write a counter-rebuttal. The whole task is long, painful, and ultimately useless as it may end up giving more visibility to the initial paper.

4. Mark Twain is reported to have said that "A Lie Can Travel Halfway Around the World While the Truth Is Putting On Its Shoes". That's exactly what happens when a wrong paper sees the light in a scientific journal. It will spread fast with the people who are seeking for whatever can help them with their confirmation bias. And the rebuttals will be considered as proof of the conspiracy by the PTBs to suppress the Truth.


That's exactly what's happening with the F&H paper, gleefully paraded around as proof that photovoltaic energy is a scam and a waste of money. A rebuttal to the paper is in preparation by a group of scientists, but it will arrive late and will do little to correct the wrong information already diffused on the Web. The problem is that this information affects choices that will determine our future: we can't afford to base them on wrong studies that somehow managed to get published.

So, how did we find ourselves into this mess? Who created a scientific review system that has no quality standards, no independent quality control, no audits, no nothing? I have no idea, but it is clear that the system badly needs a serious reform.


Here is the demolition of the Ferroni and Hopkirk paper, reproduced from Markowits's blog

__________________________________________________________________

From Energy Matters by Maury Markowitz

Another PV ERoEI debacle May 17, 2016

Posted by Maury Markowitz in balonium, solar.
Tags: bolognium, solar power trackback

Your face should have this expression when you read Ferroni and Hopkirk’s paper.

A recent report by Ferroni and Hopkirk explores the energy balance of solar power, and concludes that using PV is energy negative. That is, building PV requires more energy than the panel will produce over its lifetime.
 
Claims like these pop up from time to time, and normally end up being based on definitional tricks on the part of the authors. This example is no different in that respect, but in this case they also add a liberal dose of bad data.
 
The paper is so filled with errors and omissions that’s it’s almost breathtaking. Once again, dear reader, it’s time for the deep dive.

The sincerest flattery

While googling myself (I can’t remember my URL any more than you can) I found to my delight that the name of this blog has been taken up by a pair of bloggers from Aberdeen. How I never came across this previously is something of a mystery; I guess the web is deeper than one would imagine.
 
In any event, a May 9 post by one of the authors pointed me to the paper that is the topic of the rest of this article. After stating that the topic of ERoEI is new to the blog, he goes on to note that when he came across this paper, “the findings are so stunning that I felt compelled to write this post immediately.”
 
When I come across a study in the renewables field with findings that are “stunning”, I normally hold it at arm’s length until I can run the numbers myself. That’s because the field is utterly filled with bogus information from thinly disguised coal company shills to the nuclear true believers. 

Don’t get me wrong, there’s just as much BS going the other way, from the usual suspects to the space heads, which is all the more reason to be super-skeptical. While Mr. Mearns does make some comments about the validity of certain inputs in theoretical terms, in the end, he quotes the bottom line:

Solar panels will produce only 0.83 times the amount of energy they take to produce… If correct, that means more energy is used to make the PV panels than will ever be recovered from them during their 25 year lifetime.

That’s a big “if correct.”
 
And guess what, it’s not correct.

Start bad…

So let’s get into the meat of it. The paper starts with the authors having examined 28 other papers on the topic and found they had a wide variability of Cumulative Energy Demand (CED), the amount of energy used by a product over its lifetime. They conclude that “the authors … were not following the same criteria in determining the boundaries of the PV system.”

Now getting the CED is important, because the overall energy balance, ERoEI,i s basically energy out divided by energy in. So you’re going to need to have a good value for that CED, and there’re all over the map. So their solution is to define an entirely new version – yay!
 
But now they change gears, and work on the other side of the equation, the total energy produced. 

And they attempt to do this in per-square-meter terms.
 
Now stop right there.
 
The industry, and I mean the entire power industry here, not just the renewables industry, measures everything in either per-watt or per-kilowatt-hour terms. That’s because the physical mechanisms of the generators differ wildly, but a watt is a watt, so when you convert to those terms you have a real apples-to-apples comparison.
 
Consider an example; if I tell you a hydro dam cost $2/Watt and a new wind turbine costs $1.50/W,well, there you have it. Now what if I told you that the dam cost $2 per square meter and the turbine $10? Well, does that area include the reservoir? Does the turbine include all the area around it, or just the actual footprint on the ground? See the problem? Area is tough to pin down. Dollars are not.

So why would the authors pick such an odd unit? I can’t say for sure, but in the abstract they mention something about how “solar radiation exhibits a rather low power density”. Well, sure, and that’s important why? Apparently it’s not, because it only figures in very peripherally in the calculations, and has no effect on the bottom line.
Whatever, let’s get to the numbers at hand:

The data are available in the Swiss annual energy statistics … and show an average value of 400 kW ht/m2 yr (suffix “t” means “thermal”) for the last 10 years. This is an indication of the rather low effective level of the insolation in Switzerland. … The uptake from the incoming solar radiation is converted into electrical energy by the photovoltaic effect. The conversion process is subject to the Shockley-Queisser Limit, which indicates for the silicon technology a maximum theoretical energy conversion ef- ficiency of 31%. Since the maximum measured efficiency under standard test conditions (vertical irradiation and temperature below 25 °C) is lower, at approximately 20%, the yearly energy return derived by this first method in the form of electricity gen- erated, amounts to only 80 kW he/m2 yr.

Ok, if you don’t really know much about solar power, you might not immediately see the problem with this statement. What they’re doing is a double conversion – they’re not calculating the amount of energy produced by a PV panel, they’re taking the amount of heat collected by a thermal panel, then applying a formula to convert that to expected electrical power production.

 

But that conversion is totally wrong. The Shockley-Queisser Limit doesn’t work on thermal energy, it works on the original solar energy. And no, the thermal energy is not a good proxy for the original solar energy. The main contribution to the losses in PV, the SQ limit, is wavelength, which doesn’t come into play in thermal collectors at all. And the main contributor to losses in thermal collectors is ambient temperature, which has a minor effect on PV.
 
The two are just not the same, you can’t do that.
 
But more to the point, why would they do that? Because the same source they quote for the thermal value publishes actual electrical output figures as well, which they then go on to quote:

According to the official Swiss energy statistics (Swiss Federal Office of Energy, 2015), an average for the last 10 years of 106 kWhe/m2 yr is obtained for relatively new modules.

This number is 30% higher than their calculation based on thermal, a discrepancy they don’t even try to explain.
 
Beyond that, any number that is “an average for the last 10 years” is, by definition, not talking about “relatively new modules”. Ten years ago the average panel was about 160 Watts and cost about $5.00/Wp. Today they’re around 280 Watts and cost about $0.45/Wp. The vast majority of the world’s PV was installed in the last three years, so any calculation based on data older than that is just plain wrong.

 

And even this number, 106, is significantly lower than 

I would expect given that Switzerland has fairly average insolation for mid-latitude Europe. So what’s up with that?
 
Well when I checked the cited source I found that no such number is actually reported. One can only find total output numbers and then work back from there, but the authors fail to give their calculation. And those totals  -wait for it- go back over a decade, so we’re right back to that problem again.
 
Which is all the more funny when you consider that such data is trivially available on the ‘net. Anyone who wants do to do this calculation should do what we all do; use NREL’s PVWatts. It has highly accurate weather data going back 30 years taken only from first-class sensors.
 
I typed in Zurich for the location, and selected the TMY3 data set. For the system size, I considered a typical modern 280 Watt panel at 1.6 m², or 175 W/m², and typed 0.175 into the System Size. I also changed the tilt from 20, which is good for California, to 30, which is good for Zurich. And here it is:


 
They said 106. We’re at the very first number in the paper, and they’re already off by a factor of 60% from what the industry standard tool suggests.No attempt is made to explain this, except for dismissive comments about industry calculators.

 …get worse…

Now the authors turn their attention to expected lifetime of the panels, which is needed in order to calculate the overall lifetime energy production. They do so in a rather convoluted fashion, starting by considering the amount of panels recycled in Germany:

This was 7637 t. A module of 1 m2 weighs 16 kg and 1 kWp peak rating needs 9 m2 and consequently, scaling this up, a 1 MWp module will weigh approximately 144 t.

Hmmm. A SolarWorld 280, a typical modern panel, masses 17.9 kg. That’s 17.9/1.6 = 11.2 kg/m². I really have no idea where they got their value, and they don’t include any sort of reference. A 1 MWp system using these panels would require 1 million / 280 ~= 3570 panels, or 3570 x 17.9 = 63,903 kg = 64 t. So now we’re at calculation number two, and we find they’re off by another factor of two.
 
The paper goes on to use these numbers to suggest a real lifetime is about 17 years. Now the problem is that if older panels are heavier, then the number on a per-kg basis is automatically skewed towards older panels again. Or to put it another way, if you had 10 panels from each year since 1990 and scrapped one from each year, when measured by weight it would seem that more older panels are dying.
 
And once again I’m left scratching my head why they would use this convoluted magic, when one can find real values in seconds. In fact, one of the most quoted examples is right up the road from them on the LEEE-TISO buildings. The vast majority of these panels, apparently the first grid-tie system in the world, are still running fine after almost 35 years now. They calculate the losses at 0.2 to 0.5% a year, which corresponds to a panel lifetime on the order of 60 years.

…a little more…

They then ignore their previous calculations, and use a 25 year lifetime. So apparently all of that was for nothing! And that brings us to this:

Experience has shown that, on average, efficiency and hence performance de- gradations of around 1% per year of operation must be expected (Jordan and Kurtz, 2012).

Now we go from bad to terrible. They claim this 1% number comes from a paper by Jordan and Kurtz. Well that paper is available online, and actually states the measured rate varies widely, from 0.23% to as much as 2%. And the mode among that data is between 0.4 and 0.5%, which you can see on page 4 of the paper.
 
So if the paper they quote says it is 0.5%, how do they get 1% from the same report? Because they chose the figure on the right of page 4, which includes low-quality data. And what is the difference between the two? Well, the low-quality data is:

very sensitive to several sources of error that could skew the results. Soiling, maintaining calibration and cleanliness of irradiance sensors, module baseline data (nameplate vs. flash test), and not appropriately accounting for LID are just a few major sources of data errors.

In other words, the high-quality data is based on controlled measurements, where they account for these effects and report only the actual panel degradation. In contrast, the low-quality data does not account for these issues, so it includes all sorts of external environmental effects. They fail to mention any of this, they knowingly use the bad data.

They also fail to mention that while the 1% value was indeed used by the industry in the past, they number the industry now uses is 0.5%. And that’s because a number of long-period studies demonstrated 1% was too high. In particular, a NREL study found that panels made before 2000 had a degradation rate of 0.5%, and those after 2000 fell to 0.4%. That indicates the sorts of improvement processes that continue to this day. And, of course, they have the LEEE-TISO numbers, which strongly agree with both of the sources quoted above.
Ferroni and Hopkirk then claim:

There are also other, external factors, which can reduce PV module lifetime, for instance the site, the weather and indeed climatic conditions. These aspects do not appear to have been treated in the scientific literature in connection with photovoltaic energy usage.

Oh come on! They actually talk about these factors in the paper they’re quoting! These sorts of effects are also considered in every tool that predicts output, including PVWatts. And what, do they think their weather would be any different than the LEEE-TISO install down the road from them? Ugh.

…which brings us to…

Ok so now all of this feeds into this equation:

What this does is add up all the yearly power production figures over the lifetime of the panel to produce the total energy output of the panel. And using their figures they get 2203 kWhe/m².

Ok, just for funzies, let’s run the exact same equation,but we’ll use NREL’s 30-year climatic data, and the industry-standard 0.5% degradation. That gets you 3795 kWhe/m². Almost double.
And I need to point out that I’m using industry standard numbers, and in one case, from the same paper they quote. Their result is lower simply because they have selected worst-case-scenarios for all of these numbers. Normally one would indicate this with error bars or using the mode or mean values, like I’m doing here, but they haven’t done that. They just say these numbers are correct. They aren’t.

So, now, the other side of the equation

Ok, so the authors have now developed a number for the total output of the panel, now it’s time to consider the total energy input. And that starts like this:

The average weight of a photovoltaic module is 16 kg/m2

As I noted earlier, the SolarWorld example I linked to above is 17.9 kg for 1.6 m², or 11 kg/m². I assure you this is typical, but feel free to Google “solar panel weight” if you don’t believe me. And then they go on to state:

and the weight of the support system, inverter and the balance of the system is at least 25 kg/m2

25 kg for every square meter? I’ve installed a number of crazy systems, and I can assure you, we never came even close to that. Invariably the heaviest part was the panel.

So let’s check on their sources. Well, first of all they don’t actually quote the original source for those numbers, they quote a University of Toronto thesis from 2009 where you’ll find that:

Support structures for PV panels are made from aluminum or steel, with the majority of systems using steel.

The majority use steel? Uhh, no. And the 25 kg/m² figure in there? It comes from two even earlier papers from 2007. And when I looked there, the one that did have the 25 figure was quoting that from the other, which didn’t have that number in it. I really have no idea where it comes from.

There’s only so much time we can spend on that madness. So let’s just use the power of the internet to find modern values. Check out page 6 of this fairly modern product guide to mountings, which puts the total weight of mounts and panels at 16 kg/m². If we use the modern figure of 11 kg/m² for the panel, that puts the weight of the support structure at 5 kg/m². That same guide also includes values up to 50 kg/m², but that’s for ballast on flat roofs, which are concrete blocks, not steel. This is not used on sloped roofs or ground mounts, but as it might represent as much as 15% of the market, you can factor that in as you wish.

Ok, let’s keep going.

16 kg (module) + 25 kg (balance of plant) + 3.5 kg (significant chemicals) = 44.5 kg/m2

Ok, let’s use our numbers from real sources instead: 11 + 5 + 3.5 = 19.5 kg/m²
Which brings us to:

Since the total lifetime energy return is 2203 kW he/m2, we obtain a material flow of 20.2 g per kWhe

Maybe. Or maybe it’s 19,500 / 3795 = 5.1 g/kWh? Once again, using numbers from the industry I get a number four times “better” than they do.

Now why is this important? Because that number is basically how you calculate the energy needed to make the panel and rest of the system. So much weight of steel takes so much energy to make, and so forth. So if you reduce that by four, you’re almost reducing the CED by four, right off the bat.

Show me da money!

So now the authors move onto the “use of capital.” The basic idea here is that money embodies energy, in a way. Basically everything requires energy to build and ship to you, so if you spend $1 on something, some of that is paying for that energy. So, on average, you can say that a dollar of capital has a certain average energy content, which for convenience, we’ll express in kWh.

So if we’re going to start down that road, we need to have some sort of value for how much capital we need. Here’s the relevant part:

The actual capital cost for a sample group of fully installed PV units, 2/3 roof-mounted and 1/3 free-field-mounted, in Switzerland lies at or above 1000 CHF/m2 with large cost variations of up to 30%, due principally to the uncertainty in the price develop- ments of PV modules. The NREL (National Renewable Energy Laboratory of the U.S. DOE) reports capital cost for fully installed PV units in the lower end of the price range given above. The 1000 CHF/m2 cost, translated into specific cost for installed peak power is 6000 CHF/kWp and is a result of personal experience of the authors.

Ok ok, let’s take this bit by bit. First they have a 2/3 roof and 1/3 field split. They don’t provide a source,of course. I’ve never seen numbers anything like this, and it is trivially easy to find industry values that show the opposite.

For instance, even in Germany where the majority of installs were residential, they represent only 35% of the total buildout. In the US, where the split used to be about 50/50, utility installations now far outnumber residential. Now I mention this because utility installs are ground-mount, so according to these recent sources, the total installed base should be at least the opposite of what they use in this paper.

And this is important, because the capital cost of the system is roughly double for roof mounts, especially residential. That’s because you’re installing far less panels per job, so setup and administration is a lot more on a percentage basis. And for that reason, utility scale installs are dwarfing residential these days, a move that continues to accelerate every year.

Which brings us to the second number, the actual capex value they will use from here on in. That number is 1000 CHF/m2, but that translates into 6000 CHF/kWp based on the “personal experience of the authors”?!

Really. In a peer reviewed paper, we’re being told just to take their word for it. Wow.

Well they can’t be bothered to cite their numbers, but I’ll cite mine. I will refer to the most comprehensive and up-to-date industry-measured values one can easily get, the yearly Lazard LCoE report. And that number, averaged across the western world, is found on page 11, and it is $1500/kWp for utility and $3500/kWp for residential.

Using the modern 1/3rd residential, 2/3rds commercial split, that gives us (3.5*.33)+(1.5*.66) = $2145/kWp average. Now to make a kWp of panel using those SolarWorlds, we need 1000 / 280 = 3.57 panels, and since each panel is 1.6 m², we need 3.57 x 1.6 = 5.7 m², so on a per-m² basis that’s $2145 / 5.7m² = $376 / m².

That’s less than 1/3rd the number they’re quoting, although they do so out of thin air. Even this number overestimates the contribution of residential installs moving forward. I prefer to use the utility rate as more indicative of the real capex of PV; $1500 / 5.7m² = $263 / m².

Working in a coal mine

The paper then moves onto breaking out the various components of that cost and calculating the energy value of each one. They start with labour. After quoting four year old figures, they say:

Based upon the authors’ experiences for typical local labour costs per square meter of PV module are: project management (10% of capital cost), installation (506 CHF per m2), operation for 25 years, including insurance (1.67% of capital cost per year for 25 years) and decommissioning (30% of installation). The total labour costs amount to 1175 CHF/m2.

Now in case it’s not obvious, I want to point out that all of these measurements are based on the capital cost. So if your capital cost is off, this is too. And their capex is off by a factor of three to four. Because, once again, it’s just “the authors’ experiences”.

And to make my point, consider that value in the middle, the installation costs. They’ve already said that the total capex for the system is 1100 CHF / m², and here they say that installation labour is over 500 of that, roughly half.

Really? According to these numbers, published only months ago, all soft costs put together cost around 52% of the system price. And you’ll note that number puts all-in prices at 1300 Euro, basically identical to the Lazard number at $1500 US, and, once again, 1/4 the number Ferroni and Hopkirk create out of thin air.

So for the moment, lets ignore their made-up numbers and use these industry standard ones. They calculate 505 kWhe/m² based on 1175 CHF/m² of labour. Using these figures we see that all the soft costs are 52% of 1300 Euro per kWp, or 748 CHF/kWp, or 209 kWhe/m².

But what’s another factor of two between frenemies?

And finally, in section 5.5.3, the duo calculate the energy value of the capital itself. Basically the idea here is that if you have to borrow the money (or you can flip that to opportunity cost, same thing) then you could express that in terms of panels you could have bought with that interest (so to speak). You can think of that as “lost energy” in a way…

• Using their rate of 1100 CHF/m², they get a value of 420.
• Using the industry rate above, 1300 Euro/kWp, that gets us around 120.

Show me da money (again)!

Which brings us, finally, to their totals in Table 4:

Now let’s do the exact same thing using the numbers we’ve calculated:

CED	1300
Integration	349
Labour	209
Faulty equipment	90
Capital	120
Total	2068

So basically, just considering the known-good, widely-available capex number, we’ve reduced the “energy investment” by 22%.

All of this goes back to the original claim. They claim that the ERoEI is 2203/2664 = 83%. But a whole lot of that is made up by the cost of capital, based on a bogus number. By changing that one number to the one actually measured in the field, we get 2203/2068 = ERoEI 1.06.

And if we instead insert NREL’s number for the insolation, and use the industry standard degradation, it becomes 3795/2203 = ERoEI 1.7. That’s better than fracked oil in the US.

And we haven’t even touched that CED number, which, as you can see above, is based on some rather odd numbers about system weights.

That’s not all folks…

Now we come to the issue of recycling. In the calculations in the paper, the authors consider the panels to have a 30% decommissioning fee, which is added in the labour term.

But they totally ignore the salvage value of the panels. Panels are basically glass, aluminum, some silver and some copper. People pay for these things, which is precisely why the Europeans have a recycling program for panels.

Given an average 50% energy recovery for recycling, we can reduce the CED of a 2nd generation panel to 650. Running the same calculation gets us 1419, so 2203/1419 = 1.55, or 3795/1419 = 2.7.

And if you do consider the recycling as a potential revenue stream, then the labour line is reduced by some portion of that 30%, which brings the denominator to 1340. And that gives 2203/1340 = 1.64 or 3795/1340 = 2.83.

So in the end

Consider this: the calculation they use in their paper would produce different results if the interest rate changes, the FX rate between the Yuan and Swiss Franc changes, or the price of installations continues its astonishing downward fall.

So, what exactly is this figure measuring?


It’s certainly not measuring anything like the “embedded energy content” of the panels. That wouldn’t change just because someone types a number into a Bloomberg terminal. Yet that’s precisely what happens using their calculation.
 
And finally, I need to point out the glaring fact that the authors don’t run the same calculation on any other power source. Given that sources like nuclear are far more capital intensive than PV (which is why no one is building them) their calculation of “ERoEI” is worse.

 This paper is just plain bogus. The entire methodology is based on numbers that have no physical reality (money) and the authors deliberately cherry pick data to make those numbers “prove” their point, or just make up values out of the air. All of this is glaringly obvious, and is simply yet another example of the sorts of attacks renewables face at the hands of the true believers in the nuclear field.

Photovoltaic is an Energy Source, not a Sink!

This is a comment by Luis De Souza on a recent paper by Ferroni and Hopkirk who reported a negative energy yield for photovoltaic plants in Switzerland (in other words, an energy return, EROEI, smaller than one). It is an anomalous result, considering that a comprehensive meta-analysis of the field reported values of 11-12 for the EROEI of the most common PV technology. So, what's wrong with the paper by Ferroni and Hopkirk? A lot of things, it seems. Here, De Souza shows that photovoltaics is a source of energy, even in a not so sunny country as Switzerland. He concludes that something went badly wrong with the review procedure with the journal that published the paper by F&H, "Energy Policy". That seems to be correct and you may be interested to know that an extensive rebuttal of that paper has been prepared and submitted to the journal by a group of researchers expert in the field of energy calculations. That rebuttal finds a lot more wrong things in F&H's paper than those identified by De Souza. In short, Energy Policy managed to publish a flawed study that should never have been published in a scientific journal. Unfortunately, it was done and now a lot of people are using it to support the war against renewable energy.

Photo-Voltaics is not an energy sink in Switzerland

by Luis De Souza

Energy Policy recently published a study conducted on the EROEI of Photo-Voltaics (PV) technologies installed in Switzerland. The end result is a remarkably low figure of 0.8:1, well below any EROEI assessments ever conducted on this energy technology.

Such a figure naturally made the delight of those campaigning against renewable energy, who take at face value any hints of negative performance. However, from this study a number immediately stands out: average lifetime energy yield of 106 kWh/m2/a. As it turns out, a closer look at this single figure is enough to disprove the hypothesis of PV being an energy sink in Switzerland.

Basic check

The first check one can conduct on this EROEI study is to compare it with previous assessments. Pedro Prieto and Charles Hall produced what is possibly the most conservative EROEI study on PV, concluding on a figure of 2.4:1 for Spain. There is much to question in this study, in particularly the arbitrary translation of non physical requirements of a PV system into energy inputs, but for the purpose of comparison let this low figure be taken at face value.

Yearly solar radiation at the latitude of Madrid (40 ºN) is in the range of 2 000 kWh/m2. At the latitude of Bern (47 ºN) this value is down to 1 500 kWh/m2. Assuming the extraordinarily high energy inputs computed by Prieto and Hall for Spain also apply to Switzerland one can directly apply the rule of three to compute an EROEI figure of 1.8:1.

Mind here that EROEI is a logarithmic measurement. Therefore 1.8:1 is considerably closer to 2.4:1 than to 0.8:1. These simple figures start showing that something is fundamentally awkward with the results presented by Ferroni & Hopkirk.

Why energy per unit of area?

The article in itself is not very detailed and leaves much for the reader to guess. However, there is a key figure that plays into this EROEI study that immediately stands out: an average lifetime energy output of 106 kWh/m2/a for solar panels installed in Switzerland. Upfront, it appears a strangely low figure, but there is something more problematic with it. Each solar panel model is designed and built differently, with cells distributed in different ways; even among those produced by the same manufacturer the capacities per unit of area can be quite different.

The graph below shows capacities per unit of area for different models presently on sale by various manufacturers, including the world's top three.

While Ferroni & Hopkirk never indicate what energy output per installed capacity they use, this sample of panel capacity per unit area allows for some investigation into it. The figure below presents this calculation for these same panel models. 

Again, the figures vary widely, with the average under 700 Wh/Wp/a.


Comparison with PVGIS

PVGIS is a web application developed by the Joint Research Centre (JRC) that calculates the energy output of a PV system taking into account yearly solar insulation, panel orientation and system losses to cabling, the inverter, temperature, angular reflectance and more. PVGIS has not been updated in a few years and for the most recent systems I have been involved with it underestimates first year output by 5% to 10%. But for this exercise its results are taken at face value.

The table below is the result produced by PVGIS for an hypothetical system rated at 1 kWp, optimally oriented and installed around where I live, in the Canton of Zürich (47 ºN, in the Northwest of Switzerland). The most relevant figure in this report is the energy output estimate: 1090 Wh/Wp/a. While this is an estimate for an optimally oriented system, it provides a good measure of where the annual energy yield figure used by Ferroni & Hopkirk actually lays. 

PVGIS © European Communities, 2001-2012
Reproduction is authorised, provided the source is acknowledged
See the disclaimer here


Comparison with Swiss statistics

Ferroni & Hopkirk cite the statistics compiled by Swiss Federal Office of Energy (SFOE) as the source of their 106 kWh/m2/a figure. There are a number of different documents available from theSFOE website covering all matters of energy generation and consumption.

In recent years the SFOE has produced a yearly report of renewable energy with a series of important figures. The report for 2015 is not available yet, therefore the figures used here refer only up to 2014. These are all aggregate values, but are already enough to provide another investigation path into Ferroni & Hopkirk's figure.

After going through these reports, one thing becomes evident: the SFOE does not use the energy output per unit area measure cited by Ferroni & Hopkirk. As expected, average electricity generation figures are rather provided in energy output per installed capacity (Wh/Wp/a).

Secondly it is important to note that PV is something relatively new in Switzerland, installed capacity has picked up only recently, almost tripling from 2012 to 2014. At the end of 2014 there were 1060 MWp of PV panels installed in Switzerland, a figure that grew 40% that year alone. During 2014 electricity generation from PV reached 841 GWh.

Assuming that all the new systems installed in 2014 were connected to the grid on the 1st of January a figure 794 Wh/Wp comes out for the year. This is already on the high side of the possible generation per installed capacity figures used by Ferroni & Hopkirk. However, assuming that these new systems where connected to the grid at a regular pace throughout the year, this number rises to 927 Wh/Wp. This is less than 15% off the PVGIS estimate, and possibly explainable by non optimal orientation of some systems and a small fraction of older and likely less efficient systems. Usually, systems tend to be installed towards the end of the year, to take up the most favourable legislative framework.

Possible causes

The first cause that comes to mind for such low energy yield figure is an erroneous cell efficiency factor. PV cells are rated in control experiments where their energy output is assessed at a temperature of 25 ºC and a constant radiation of 1 kW/m2. This assessment is very useful to compare different cell technologies. Modern day wholesale crystalline cells reach efficiency factors between 14% and 16%, i.e. they convert that fraction of incident radiation into electrical current.

Since Ferroni & Hopkirk present average lifetime yield in energy per unit area, these authors might have converted incident radiation in Switzerland directly into an energy yield. However, instead of using the figures above, the efficiency factor they used must have been in the order of 8% to 9% to result in an energy per installed capacity value around 690 Wh/Wp/a. Such low conversion factors are more common with thin film technologies.

A second hypothesis is the employment of an unusually high cell degradation rate. PV cells loose their properties over time, both to the heat they are exposed to, as to the solar radiation itself. While tools such as PVGIS can easily model system losses, they usually leave this degradation rate out. Research centres such as the JRC have assessed PV technologies for decades, concluding on an energy yield degradation rate in the order of 0.5 %/a. Moreover, these long term studies also indicate that cells tend to degrade in a linear fashion.

The following figure presents two hypothetical degradation rates that bring down a PV panel from 1090 Wh/Wp/a to an average yield of 690 Wh/Wp/a over a 25 year lifetime: a liner degradation of 33.5 Wh/Wp/a and a logarithm decline of 4 %/a. In both cases the energy yield dives under half before the end of system life.

While this latter hypothesis is my favourite, it does not explain the employment of the strange energy per unit area figure. Also, these degradation rates would assume that in the face of a fast collapse in energy output owners would never activate panel warranty. 

Final remarks

Replacing the inexplicably low energy yield figures used in this study by those available from the SFOE is already enough to bring the Swiss PV park into positive net energy territory. However, such result is still far from previous PV EROEI assessments, even the highly conservative estimate produced by Prieto & Hall. Just as the energy yield assumptions proved problematic in this study, I expect similar awkwardness to be found on the energy input side of the equation. However, I leave this aspect to be assessed by someone else.

The publication of such a study by a relatively renowned outlet begs for deep reflection. The last article I authored in a scientific journal was over two years in review; this is usually a slow and painstaking process. Being myself an editor and reviewer at scientific publications, I am at a loss to explain how could such a problematic figure of 106 kWh/m2/a have possibly made through the peer review process. It should have immediately raised a red flag to whoever is slightly acquainted with PV technology and economics, calling for close scrutiny by reviewers and editors alike. Something fundamental has failed in the review process at Energy Policy. 

The Take Away

The EROEI figure concluded by Ferroni & Kopkirk for PV is the lowest ever and far below any previous studies.

These authors use awkward units that largely obfuscate their assumptions on yearly energy yield.

A sample of various panel models points to an energy yield under 700 Wh/Wp/a used in this study.

Official statistics point to an average yield well above 900 Wh/Wp/a for the Swiss PV park; this is in line with values from assessment tools like PVGIS.

The peer review process is not functioning properly at Energy Policy.

The real EROI of photovoltaic systems: professor Hall weighs in.

Charles Hall is known for his multiple and important contributions in the field of sustainability, and in particular for having introduced the concept of Energy Return on Energy Investment, EROI or EROEI. He is now emeritus and still active in research; among other things as chief editor of the new Springer journal: "Biophysical Economics and Resource Quality, BERQ. Here, he intervenes in the recent debate on the EROI of photovoltaic systems, sending me this note that I am happy to publish, with some comments of mine at the end.






by Charles Hall


The EROI of our various energy options, and its associated issues, may be the most important issues that will face future civilizations.  The present discussion tends to vacillate between people who accept (or advocate) very high EROIs for solar vs people who accept (or advocate) very low such EROIs.   I trust only one study, the one I did with Pedro Prieto, who has a great deal of real world experience and data. This study attempted to (conservatively) estimate all the energy used to generate PV electricity in Spain by following all the money spent (per GW) and using physical analysis where possible, and energy intensity of money where necessary. We found that the panels and inverters, which are the only parts measured in most studies, were only about a third of the energy cost of the system.  As noted in the responses to Ugo’s last post we estimated an EROI of 2.45:1 in 2008 assuming a lifetime of 25 years and at the juncture with the distribution system.   Studies that we think used more or less appropriate boundaries (Palmer, Weissbach) got similar results.

We recognize that subsequent studies to ours would probably have generated higher EROIs because of using panels of lower energy costs or higher efficiency.  But there are many ways that it might be lower too.  For example Ferroni and Hopkirk, who (despite, perhaps, some issues) have done us a good service by attempting to get actual lifetimes for modules, which were much closer to 18 years than infinity.  This agrees with what happened in Spain when, due to post-2008 financial turmoil, manufacturers did not honor their guarantees and legally "disappeared", leaving broken systems unfixed.   (And what happened to all those "surplus" Chinese panels that were never used?   Should we factor in their energy costs, as we factor in dry holes for oil analysis?)  My point is that we need to include empirical, not theoretical, estimates of ALL the energy used to make these systems work.

This is what Prieto and Hall did, imperfectly I am sure, using conservative assumptions of energy costs, many of which now appear too low.  Mostly I do not see others doing this, so I mistrust their analyses. I do not know whether Bandhari et al. included only studies using appropriate boundaries, but I would guess that many are for just the panels (and maybe converters), not the whole system required to deliver the electricity.  Another way that we were conservative was to not include the (pro-rated) distribution system, as Ferroni and Hopkirk did (i.e. EROIpou, for point of use).  It seems to me that we should do this routinely, at least as sensitivity analysis. If you are really analyzing the EROI of solar you need to get the electricity to the factory, the gravel and panels to the installation site etc. etc,

There are at least three reasons that EROI estimates appear much wider than they probably really are:

1) They are often done by advocates one way or another, not by experienced, objective (and peer reviewed) analysts.

2) a common protocol is not followed.  Murphy et al. 2011  should be followed or good reasons given for not doing so. They recommend that all investigators generate a "standard EROI (EROIst) so that different studies can be compared, but then suggest that investigators may define in addition other criteria/boundaries as long as they are well defined and the reason for their inclusion given.    This protocol is being updated at this time to deal with various concerns.

3) Related to above appropriate boundaries are  often not used.  For a start "follow the money" as money is a lien on energy.  Where there is controversy (e.g. include labor or not, and how) this should be dealt with through sensitivity analysis.   Energy quality (e.g. electricity vs fossil) also needs to be considered, as Prieto and Hall did in their final chapter.

The largest problem with EROI studies is that although the concept has been around and even lauded since at least 1977 it has essentially never been supported by legitimate and objective funding sources such as the US National Science Foundation (which however has recognized this as a large failure and is starting a new program on EROI.)  As any investigator knows it takes money to do a good job, and this we have not had.  Most of the best work has been done on a shoestring or pro bono. This appears to be changing now, especially in Europe, and we hope to see some kind of objective, high-quality Institute/Program in the future.  We also need better governmental statistics on energy use and the development of appropriate energy I-O analyses to get a better handle on energy costs.  These had been done to high quality in the US 40 years ago but the official Bureau of Census energy use data has degraded, and we have ceased undertaking appropriate energy I-O analyses while the real experts have retired or died.

If these issues can be resolved, which is not too difficult at least in principle, and if the protocols are followed, then I think we will narrow the range of published EROI estimates considerably.  In the meantime I have done a fair amount of sensitivity analysis (e.g. Guilford et al 2011; Prieto and Hall 2012) that suggest that at least for the studies I have been involved with the range of uncertainty is well within plus or minus 25 percent (except when using the assumptions of using the energy cost of the full salary of labor or electricity is multiplied by a quality factor of three, in which case the range is two to three).   At this time, we do not recommend either of those two factors for general use.   This range of uncertainty is much less than the EROI range among the different technologies, as shown in Euan Mearns most recent post.

Guilford, M., C.A.S., Hall, P. O’Conner, and C.J., Cleveland. 2011. A new long term assessment of EROI for U.S. oil and gas: Sustainability: Special Issue on EROI. Pages 1866-1887. 

Murphy, D., Hall, C.A.S., Cleveland, C., P. O’Conner. 2011. Order from chaos: A Preliminary Protocol for Determining EROI for Fuels. Sustainability: Special Issue on EROI. 2011. Pages 1888-1907.

Prieto, P., C.A.S. Hall. 2012 Spain’s Photovoltaic Revolution: The energy return on investment. Springer, NY. (about $50) 


A comment by Ugo Bardi

This note by professor Hall highlights some elements of the debate and let me comment on it. Basically, I think that there is nothing wrong in the work by Hall and Prieto that arrived at relatively low values of the EROI of PV (note, however, that there is a lot that's wrong in the recent paper by Ferroni and Hopkirk, but that will be addressed elsewhere). The discrepancies are due to different initial assumptions, as Hall correctly states here, and, obviously, different assumptions lead to different numbers.

Then, the question is, what are the "right" assumptions in these estimates? Evidently, it depends on what one is trying to measure. Here lie the problem and the remarkable confusion surrounding the debate. Basically, there are two main possible aims for an EROI calculation: 1) determining whether a technology is an energy source or an energy sink and 2) determining whether a technology can support an industrial civilization similar to ours (maybe including SUVs and plane trips to Hawai'i for middle-class families).

Once this point is clarified, we see that answering these different questions requires different assumptions. For the first question, energy source or sink, the estimate is defined by the life-cycle analysis (LCA) of the plant. For PV, that includes the cycle of all the components of the plant (surely not just the cells!). Within the LCA framework, the result is an EROI of about 11-12 for the most common technologies available today. There is no doubt that a PV plant is an energy source, not a sink.

For the second question, can PV support a civilization, we are dealing with something very different and it is for this purpose that professor Hall defines  the "extended EROI" (EROIext). However, how the term "extended" is to be understood is open for discussion. If you think that a civilization should include plane trips to Hawai'i for middle-class people, then the energy required should be factored in the calculation. Without arriving at these extremes, the more elements you add to the energy cost, the lower the final EROI turns out to be and it is not surprising that Hall and Prieto arrive at values between 2-3. These values still make PV an energy source and not a sink, but find it to be hardly able to support plane trips to Hawai'i. But that should have been obvious from the beginning!

There are a few fundamental problems with the concept of "EROIext" that I think make it a scarcely viable idea, but it might become a standard if we all find an agreement on it. The main problem, I believe, is that when we deal with such a thing as the survival of our civilization we move into a very slippery set of questions. One problem is that EROI is not the only parameter that we need to consider, and PV not the only renewable technology available; to say nothing about defining what we mean as "our civilization". So, claiming that PV, alone, cannot support the present civilization may be true, but it is also totally irrelevant. If our civilization has to survive the ongoing crisis it has to go through profound changes that are difficult even to imagine for us. For sure, however, all the renewable technologies able to produce a positive net energy, such as PV, have a role to play in our future.




Note: the current standards of EROI measurements are described in this document.