Saturday, May 28, 2016

Adrastia interviews Ugo Bardi






The French Association "Adrastia" has been interested enough in my modest work that they asked me a series of questions. The original interview was in French, here is the text, kindly translated into English by Florence Mitchell.









Ugo Bardi is a researcher and Professor in Chemistry. He contributes to The Oil Drum, is a member of the scientific committee of the Association for the Study of Peak Oil and Gas (ASPO) and author of several books, including one on energy and mineral resources (The Limits to Growth Revisited).


Our sincere thanks to Mr. Bardi for agreeing to talk to us.

Adrastia: You have built a theory called The Seneca Cliff. It revisits the Hubbert peak and bell curve though in this case its descent is much steeper than its ascent. Originally this curve applied to oil production. Could you explain in what way it applies to many other key factors of our civilisation?

Ugo Bardi: The point of the Seneca Cliff is clear to most of us: many things go down faster than they went up. Just think of a house of cards, for instance. It’s one of those obvious things which happens not to be easy to explain according to the fundamentals of physics. In Newton’s time, for instance, everyone knew that apples fell from trees, but the law of universal gravity had yet to be discovered. With the Seneca Cliff we are still in what we could call a ‘pre-Newtonian situation’. Roughly speaking, the curve is observed in systems where there is a kind of correlation between their constituents. It is a ‘‘collective phenomenon’’ typical of systems that are described as complex, for example at times of rapid collective changes in phase transitions, but also in the mechanics of the breakdown of materials, and also when civilisations collapse. Systems are always complex when the internal elements are inter-correlated. Let’s say that if one likes the theory of networks as well as system dynamics modeling there is much fun to be had with them. In fact, it’s so much fun that I am working on a book which will be called The Seneca Cliff and which I hope to publish before the end of the year – perhaps…


A: What do you think are the weak points of our civilisation, its main vulnerabilities? If there was to be a collapse what would you see as the first chain of events typical of the phenomenon? And do you have a sense of what will then happen as resources get depleted and the climate goes awry?

U. B.: I have thought quite a bit about these issues, and I find the study of the theory of networks combined with system dynamics modeling very helpful. When I started working on this topic, I thought that the depletion of resources might be the main reason why civilisations collapse. I still think that might be the case, just as it might also be the case that civilisations have been destroyed by outside forces such as climate change or military invasions. But it seems to me that very often something more subtle may be going on: it’s loss of control which leads to the collapse of civilisations. A civilisation is a system made up of elements that are closely linked, and their correlation has to be controlled in one way or another. Besides, the control mechanism needs resources, and if fewer resources are available there may be loss of control leading in turn to a risk of collapse, even before the exhaustion of resources or climate change brings about this result.


A: You have named your blog Cassandra’s Legacy. Do you get the impression that you’re not heard?

U.B.: Never… How could you possibly think such a thing?! (smile)


A: How did you come to the realisation that our civilisation is reaching the end of the road? Do you remember a particular moment when your conscience reached a tipping point?

U.B.: Yes, definitely. On September 11 I was in the States, in Berkeley, and I saw the Twin Towers collapse on TV. That same morning, in quite a state, I went for a walk, and in a bookshop in Berkeley I found a book called The Hubbert Peak, written by the American geologist Kenneth Deffeyes (who I later got to know personally). These two events, the book and the New York attacks, seemed to me to be correlated that day, even though I couldn’t quite explain it to myself. It was later that I realised how they were indeed connected.


A.: How do you deal with this theory of collapse that we are going to experience – that we are already experiencing in some ways – when it comes to those around you, your family and friends, who don’t have the same awareness or may even reject the theory? Very generally, what impact has it had on your social interaction, and how do you live with the knowledge?

U.B.: People often ask me this. I am not sure I have an answer, but one thing is obvious to me: “catastrophists” (and I am one of them) are not unhappier in their daily life than “cornucopians”. I should add that the risks that we, the catastrophists, see coming in the future mean that we also take a rather philosophical approach to the world and we have a strong urge to take action. It’s the very same vision that the “Stoics” had, Seneca being one of them. It’s a philosophical vision which emerges in difficult times. Japanese Samurais used to practise a very similar philosophy to Stoicism, I believe. A good Stoic (or a good Samurai) knows his limits, but he also knows he has a duty to act or to fight for the general good. Nowadays, of course, we don’t use a sword in our daily life, although I am learning Japanese swordsmanship, as well as traditional archery. You never know…


A: Do you talk about these issues with your children, who will have to face these difficult and possibly dangerous times to come? If so, how do you broach the topic?

U.B.: This is the hardest thing. I think it’s not for me to push my children (they are grown-up now) towards my own vision of the world. They have the right and the ability to develop their own vision. And I believe they are well adjusted to a world which is becoming more and more difficult, especially for young people.


A: Many members of the Adrastia association are literally consumed by the issue of the end of the industrial and fossil-fuel civilisation, to such a point that they think of nothing else. Is it a kind of obsession for you, and if so, how do you cope?

U.B.: It may be so. There is a risk that one’s ideas become an obsession but, in my experience, one can’t do for long: it’s too stressful. People forget and go back to watching TV. It’s normal, it’s human. In my case, I have other interests which prevent me, I hope, from turning my life into a catastrophist saga! (I’ve written a sci-fi novel, for example. It’s a bit catastrophist, I have to admit…)


A: Do you already have a clear idea of how you are going to live through this period of energy decline? How are you preparing for it? Are you ready to live without oil?

U. B.: One makes long-term predictions that often turn out to be correct, but it’s difficult to translate them into daily life, very difficult. One thing I have learned is that the future is never what you expect, so you get there, I think, by following a long winding path that you create one step at a time.


A: Do you belong to a group, collective, association or NGO aiming to lay the foundations of resilience, even autonomy (local energy transition, alternative currencies, permaculture…)? How do you view these initiatives, and what would you recommend to individuals or groups who want to prepare themselves?

U.B.: These are interesting things which I have tried to put into practice several times. At the moment I think my job is above all to communicate certain ideas, and that’s what I am doing. I am privileged to have been able to focus on those things which I believe are the right things to do. It’s a privilege, I know. If I was unable to do this, I would surely be more active in the local community, in the Transition Town Movement or similar movements. In the future, I might possibly be more involved in this kind of activity.


A: You travel on a regular basis to give talks, and your books are translated in several languages. Among the countries or regions you have visited, are you aware of major cultural differences – in nature or degree – in the way that people tackle the notion of collapse, in their individual or collective awareness, or the way they listen to your message?

U.B.: In the West (Western Europe and the United States) I don’t notice many differences: in many places in these countries there is a fraction of the population that is aware of certain problems and tries to work on them. But, of course, I am rarely invited to those countries where these problems are not at all understood. For instance, it seems to me extremely difficult to convey certain ideas in Eastern European countries and especially in Russia. It seems that in Russia the idea that mineral resources are destined to become exhausted at some point is seen as a form of Western propaganda against Russia and its vast mineral resources. And they won’t be taken in, will they? They aren’t stupid… What is to be done? I don’t know. In fact, nothing changes; governments in the West and the East are doing the same thing and couldn’t care less about catastrophist forecasts. It’s well known throughout history: human societies are not very good at managing the future. And, by the way, that’s why I called my blog “Cassandra’s legacy”!


A: In the face of environmental constraints which we understand better these days, and in view of the considerable research in neuroscience which challenges our usual definition of personal freedom, do you think we could have chosen to avoid the risks? Is mankind inevitably headed towards a tragic destiny that it won’t be able to escape?

U.B.: Clearly it’s extremely difficult to convey messages that are perceived as “catastrophist”. Climate change is a good example: it’s a horrific message to be giving. We are really talking about the possibility of an end to mankind and maybe life on earth. It’s understandable that instead of listening to the message, many people prefer to flee with their hands over their ears while singing “la-la-la!”. We’re dealing, obviously, with the limits of human intelligence. How could we do better than that? Many people have tried to find an answer in neuroscience, others in philosophy, in religion, or even in slightly esoteric fields like “memetics”. Finding the answer proves to be very difficult, if not completely impossible. The only thing we can say is that the future will surprise us. We have arrived here after a journey of some ten thousand years, through the Holocene period. We are only starting to understand the huge transformations that human beings have gone through, thanks to developments and changes during this period which are not only cultural but also genetic. Mankind, hopefully, still has several thousands of years to adapt, and this in a world of constant change. The evolution of mankind is probably far from over. Where this evolution will take us, it’s impossible to say at this point. But evolving means adapting, and the theorists of infinite growth are clearly ill-adapted to the future – they are bound to disappear. In the future, we won’t be able to bypass the need to adapt to a finite world.



Thursday, May 26, 2016

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.  




Monday, May 23, 2016

But what's the REAL energy return of photovoltaic energy?




According to a recent, comprehensive study of the scientific literature (1), the average energy return on energy invested (EROEI) of the most common photovoltaic technology (polycrystalline Si) is 11-12. A far cry from the legend of the "EROI smaller than one" that's making the rounds in the Web



Some time ago, a colleague of mine told me the story of when he had been in charge of the installation of one of the first photovoltaic plants in Italy, in 1984 (shown in the figure, on the right). He told me that, shortly after the installation, a high-ranking politician came to visit the plant. As a demonstration, my colleague connected the plant output to an electric heater, lighting up the internal heating elements.

The politician refused to believe that the heater was being powered by the PV plant. "There has to be a trick," he said, "this is not possible. It must be a scam." My colleague tried to describe to him how PV cells work, but imagine trying to explain quantum mechanics to a politician! Apparently, he left still unconvinced.

More than 30 years have passed from the installation of that old plant, but the general attitude about photovoltaic energy doesn't seem to have changed a lot. Not that people think that photovoltaic is a scientific hoax in the same league as the many proposals about such things as "free energy" or "cold fusion" (or maybe yes). But it seems that many people just can't believe that those small blue things can produce energy in any significant amount. Come on: in order to produce energy you need an engine, a boiler, a smokestack, a turbine, something like that.....

Indeed, most of the current discussions on photovoltaic energy seem to turn around one or another kind of legend. The most recent one seems to be that photovoltaics has a low energy return (EROI or EROEI), sometimes said to be even smaller than one. If it were true, it would mean that photovoltaic plants are not producing energy, they are just consuming it! But it is not true. It is just one more example of confirmation bias: cherry-picking the data that confirm one's pre-conceived ideas.

It is true that you can find a few studies (very few) that look serious (perhaps) and that maintain that PV has a low EROI. However, in a recent study, Bhandari et al. (1)⁠ surveyed 231 articles on photovoltaic technologies, finding that, under average Southern European irradiation, the mean EROI of the most common PV technology (polycrystalline Si) is about 11-12. Other technologies (e.g. CdTe) were found to have even better EROIs. Maybe these values are still lower than those of some fossil fuels, but surely not much lower (if they are lower) and a far cry from the legend of the "EROI smaller than one" that's making the rounds on the Web.

Then, if you are worried about another common legend, the one that says that PV cells degrade rapidly, think that those of the plant described at the beginning of this article were found to be still working after 30 years of operation, having lost just about 10% of their initial efficiency! In addition, consider that the most common kind of cells use only common elements of the earth's crust: silicon and aluminum (and a little silver, but that's not essential). What more can you ask from a technology that's efficient, sustainable, and long lasting?


All that doesn't mean that a world powered by renewable energy will come for free. On the contrary, it will take a very large financial effort if we want to create it before it is too late to avoid a climate disaster (quantitative calculations here). But a better world is possible if we really want it.




(1) Bhandari, Khagendra P., Jennifer M. Collier, Randy J. Ellingson, and Defne S. Apul. 2015. “Energy Payback Time (EPBT) and Energy Return on Energy Invested (EROI) of Solar Photovoltaic Systems: A Systematic Review and Meta-Analysis.” Renewable and Sustainable Energy Reviews 47 (July): 133–41. doi:10.1016/j.rser.2015.02.057. 

Here is the relevant figure from the article:







h/t Domenico Coiante, Marco Raugei, and Sgouris Sgouridis

Thursday, May 19, 2016

A 100% renewable world is possible? A poll among experts

Image source



I am reporting here the results of a small survey that I carried out last week among the members of a discussion forum; mainly experts in renewable energy (*). It was a very informal poll; not meant to have statistical value. But some 70 people responded out of a total of 167 members; so I think these results have a certain value in telling us how the experts feel in this field. And I was surprised by the remarkable optimism that resulted from the poll.

This is what I asked the members of the list (note: this poll is now on line at the Doomstead Diner)

The question is about  the possibility of a society not too different from ours (**) but 100% based on renewable energy sources, and on the possibility of obtaining it before it is too late to avoid the climate disaster. This said, what statement best describes your position?


1.  It is impossible for technical reasons. (Renewables have too low EROEIs, need too large amounts of natural resources, we'll run out of fossil fuels first, climate change will destroy us first, etc.)

2. It is technically possible but so expensive to be unthinkable.

3. It is technically possible and not so expensive to be beyond our means. However, it is still expensive enough that most likely people will not want to pay the costs of the transition before it will be too late to achieve it, unless we move to a global emergency status.

4. It is technically possible and inexpensive enough that it can be done smoothly, by means of targeted government intervention, such as a carbon tax.

5. It is technically possible and technological progress will soon make it so inexpensive that normal market mechanisms will bring us there nearly effortlessly.



As I said, it was a very informal poll and these questions could have been phrased differently, and probably in a better way. And, indeed, many people thought that their position was best described by something intermediate, some saying, for instance, "I am between 4 and 5". Because of this, it was rather difficult to make a precise counting of the results. But the trend was clear anyway.

Out of some 70 answers, the overwhelming majority was for option 4, that is, the transition is not only technologically possible, but within reach at a reasonable cost and fast enough to avoid major damage from climate change. The second best choice was option 3 (the transition is possible but very expensive). Only a few respondents say that the transition is technologically impossible without truly radical changes of society. Some opted for option 5, even suggesting an "option 6", something like "it will be faster than anyone expects".

I must confess that I was a little surprised by this diffuse optimism, being myself set on option 3. In part, it is because I tend to frequent "doomer" groups, but also on the basis of the quantitative calculations that I performed with some colleagues. But I think that these results are indicative of a trend that's developing among energy experts. It is an attitude that would have been unthinkable just a few years ago, but the experts are clearly perceiving the rapid strides forward of renewable technologies and reacting accordingly. They feel that there is a concrete chance to be able to create a cleaner world fast enough to avoid the worst.

I understand that this is the opinion of just a tiny group of experts, I understand that experts may well be wrong, I understand that there exist such things as the "bandwagon effect" and the "confirmation bias." I know all this. Yet, I believe that, in the difficult situation in which we find ourselves, we can't go anywhere if we keep telling people that we are doomed, no matter what we do. What we need in order to keep going and fight the climate crisis is a healthy dose of hope and of optimism. And these results show that there is hope, that there is reason for optimism. Whether the transition will turn out to be very difficult, or not so difficult, it seems to be within reach if we really want it.




(*) Note: the forum mentioned in this post is a private discussion group meant to be a tool for professionals in renewable energy. It is not a place to discuss whether renewable energy is a good thing or not, nor to discuss such thing as the incoming near term extinction of humankind and the like. Rather, the idea of the forum is to discuss how to make the renewable energy transition happen as fast as possible; hopefully fast enough to avoid a climate disaster. If you are interested in joining this forum, please write me privately at ugo.bardi(zingything)unifi.it telling me in a few lines who you are and why you would like to join. It is not necessary that you are a researcher or a professional. People of good will who think they have something to contribute to the discussion are welcome.

(**) The concept of a society "not too different from ours" is left purposefully vague, because it is, obviously subjected to many different interpretations.Personally, I would tend to define it in terms of what such a society would NOT be. A non-exhaustive list could be, in no particular order,

  • Not a Mayan style theocracy, complete with human sacrifices
  • Not a military dictatorship, Roman style, complete with a semi-divine imperial ruler
  • Not a proletarian paradise, complete with a secret police sending dissenters to very cold places
  • Not a hunting and gathering society, complete with hunting rituals and initiation rites
  • Not a society where you are hanged upside down if you tell a joke about the dear leader
  • Not a society where, if you can't afford health care, you are left to die in the street
  • Not a society where you are worried every day about whether you and your children will have something to eat
  • Not a society where slavery is legal and the obvious way things ought to be
  • Not a society where women are supposed to be the property of men
  • Not a society where most people spend most of their life tilling the fields
  • Not a society where you are burned at the stake if you belong to a different sect than the dominant one

Many other things are, I think, negotiable, such as having vacations in Hawai'i, owning an SUV, watering the lawn in summer, and more.




Monday, May 16, 2016

An energy miracle? But we already have it!



Silicon is a material with properties close to the optimal for a solar cell. It is also one of the most abundant elements in the earth's crust, and, finally, we know how to use it to manufacture cells with efficiency close to the theoretical maximum. Isn't it a miracle?


"EnergySkeptic" recently commented on an article appeared in "Nature" in 2014 on the possibility of cheap photovoltaic cells entering the market of solar energy. The post is short enough that I can reproduce it in full, below. It is interesting because it shows the problems with the idea of the "miracle breakthrough" in energy that Bill Gates advocates.

Here, the discussion is on perovskite solar cells; a technology that promises to be cheaper than that based on silicon. Perovskites are a large class of materials; those being studied as solar cell materials have several advantages, including the fact that they can be manufactured in the form of thin films, don't need to be so extremely pure as silicon, have a band gap close to the theoretical optimum.

That, however, doesn't necessarily make perovskites a "breakthrough" in the field. Even assuming that perovskite cells could reach an efficiency high enough to be marketable, the problem is that, at present, the cost of the cells is only about 30% of the total cost of a solar plant. Even if perovskite cells were to cost half as much in comparison to silicon ones, that would be no improvement unless their efficiency were to match or exceed that of silicon. Otherwise, the whole plant would probably cost more because it would have to occupy more space.

In practice, to have a breakthrough in solar power, we would need a technology which is 1) significantly cheaper than silicon, 2) much more efficient, 3) that uses no rare and non-renewable elements (that rules out, in the long run, cells that use tellurium or gallium). That's a tall order, especially considering that we are bumping into the physical limits of single-junction cells; which cannot have efficiencies higher than a little more than 30%. Silicon, because of some quirks of the way the universe works, happens to be placed almost in an optimal position in terms of band-gap and, at the same time, to be a widely available element in the earth's crust. So, it is, in many respects, an optimal choice for solar cells, and already not so far away from its theoretical limits. I think that we'll stay with silicon for a long, long time. Surely we will improve the technology, but don't expect miracles. That silicon works so well is already a miracle!

_______________________

Further notes:

1. Here, in Florence, a colleague of mine has built a nice solar plant that uses multi-junction GaAs cells and concentrating mirrors, attaining, I think, around 50% efficiency. I saw it: it is a wonder of technology, full of gears, motors, optics, sensors, computers, and things. But I didn't dare to ask him how much it would cost to buy one for the roof of my house!

2. True breakthroughs may occur "downstream" with respect to energy production; for instance with batteries and the diffusion of a new generation of electric vehicles. There is no thermodynamic limit to the number of times that a battery can be recharged without degrading.

3. "heavy-duty trucks, locomotives, and ships run on diesel fuel" in the article below is, in part, a canard. Here in Europe, locomotives already run on electricity. Trucks can run on electricity, too, (http://mondoelettrico.blogspot.it/2014/08/ehighway-il-filocarro-elettrico.html). For ships, the problem is not so much how to push them on, there are ways. It is another one, much more difficult (see e.g. https://blogdredd.blogspot.it/2015/08/why-sea-level-rise-may-be-greatest.html). And the only way to solve that problem is to rush into renewable energy as fast as possible.


_________________________

Van Noorden, R. September 24, 2014. Cheap solar cells tempt businesses. Nature #513 470-471.

[Excerpts. Of interest because rarely do obstacles get mentioned in the news. Most are optimistic hype making it sound like a solution to the energy crisis is just around the corner. And forget that electricity does not solve our main problem — heavy-duty trucks, locomotives, and ships run on diesel fuel ]
Large, commercial silicon modules convert 17–25% of solar radiation into electricity, and much smaller perovskite cells have already reached a widely reproduced rate of 16–18% in the lab — occasionally spiking higher.
The cells, composed of perovskite film sandwiched between conducting layers, are still about the size of postage stamps. To be practical, they must be scaled up, which causes efficiency to drop. Seok says that he has achieved 12% efficiency with 10 small cells wired together.
Doubts remain over whether the materials can survive for years when exposed to conditions outside the lab, such as humidity, temperature fluctuations and ultraviolet light. Researchers have also reported that ions inside some perovskite structures might shift positions in response to cycles of light and dark, potentially degrading performance.
The need for complex engineering might create another setback, says Arthur Nozik, a chemist at the University of Colorado Boulder. After plummeting in past years, the price of crystalline silicon modules — which make up 90% of the solar-cell market — has leveled off but is expected to keep falling slowly. As a result, most of the cost of today’s photovoltaic systems is not in the material itself, but in the protective glass and wiring, racking, cabling and engineering work.
When all these costs are factored in, perov­skites might save money only if they can overtake silicon in efficiency. In the short term, firms are focusing on depositing the films on silicon wafers, with the perovskites tuned to capture wavelengths of light that silicon does not. On 10 September, Oxford PV announced that it was working with companies to make prototypes of these ‘tandem’ cells by 2015, and that this could boost silicon solar cells’ efficiencies by one-fifth, so that they approach 30%. Malinkiewicz’s hope is to find a niche that silicon cannot fill: ultra-cheap, flexible solar cells that might not last for years, but could be rolled out on roof tiles, or used as a portable back-up power source.
There is another potential snag: perovskites contain a small amount of toxic lead, in a form that would be soluble in any water leaching through the cells’ protection. Although Snaith and others have made films with tin instead, the efficiency of these cells is only just above 6%.

Sunday, May 15, 2016

How to destroy an empire by getting rid of its best generals




In 408 CE, Emperor Honorius ordered the execution of the "magister militum," Flavius Stilicho, commander in chief of the Roman Army. Stilicho was the man who had stopped several times the invading Goths. He had commanded what Gibbon defined "the last army of the Republic" that had defeated the Goths at the battle of Faesulae, in 406 CE. Two years after the death of Stilicho, in 410 CE, the Visigoths sacked Rome. That was the beginning of the end for the Roman Empire, that would disappear forever some decades later.


By Sou of the Hot Whopper

MONDAY, MAY 16, 2016


Shock and furious anger at the vandalism of CSIRO: Larry Marshall wants to tear it down before anyone can stop him

Sou 1:24 AM
The Australian Government is now in caretaker mode. After declaring an election is to be held on 2 July, the government will not be making any substantive decisions before the election, other than is absolutely necessary. All seats in both houses of Parliament are up for grabs in what is known here as a double dissolution. That sets the scene for who knows what. The current government is probably ahead slightly, but a lot can happen in the next 46 days.

...

You have probably read of the work of Dr John Church here at HotWhopper and elsewhere. Many of his sea level papers were prepared with his long-time colleague Dr Neil White, who retired last year.

Today Peter Hannam at the Sydney Morning Herald has reported that Dr Church, a living treasure here in Australia, and one of the world's leading authorities on sea level change, got a phone call to tell him that he's out on his ear. He's got the sack. It was reported that he has a couple of weeks (while he's on a ship doing research) to justify his position. Right! As if his major contribution to science in Australia and the world isn't enough. As if it isn't enough of a reason that Australia, with most of its population living on or near the coast, is in desperate need of a very good understanding of sea level changes to come. As if it isn't enough that Australia is totally surrounded by sea, that our shipping infrastructure, on which exporters are almost completely dependent, needs to be able to plan properly for sea level rise.t.)

Friday, May 13, 2016

We asked for an energy miracle and all what we are getting are lousy killer robots




If you have four minutes, turn down the horrible background music and watch this clip up to the end, which is truly revealing. So, maybe you were hoping that science would bring to us a technological miracle that could solve the energy problem. But this is what we are getting. Oh, wait.... at least this may solve the overpopulation problem. (source)



h/t Luis de Souza

Who

Ugo Bardi is a member of the Club of Rome and the author of "Extracted: how the quest for mineral resources is plundering the Planet" (Chelsea Green 2014)