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

Thursday, May 12, 2016

Why Joe the plumber doesn't want renewable energy



Joe the plumber is a real person, but also an abstraction for the troubled American blue collar worker. 



In a previous post, I argued that a global transition to 100% renewable energy would be very expensive, but possible and that it could also be fast enough to avoid exceeding the emission targets set by the COP21. This opinion triggered the usual flow of negative comments; mainly based on old canards or motivated reasoning. It also generated a discussion in a private forum where it was argued that we could have the transition if we could convince the general public that renewable energy is a good thing. I found myself in partial disagreement with this interpretation and I responded with a comment that I am reproducing here, with minimal edits. 


All polls indicate that the "public" is largely favorable to renewable energy, apart from a minority of diehards who vent their frustrations by commenting the posts they don't like. So, we don't need a big effort to convince Joe the plumber that solar energy is a good idea.

Unfortunately, most likely Joe doesn't have enough money to install solar panels in his backyard. On the contrary, he is probably deep in the red, and if somebody comes up and tells him, "look, your high electricity bill is the result of the subsidies to renewable energy", he is going to believe that. He'll probably keep thinking that solar energy is a good idea, but he won't want to pay any money for it. (nor, in general, for anything related to "sustainability" or "fighting climate change").

In the end, it doesn't matter so much what Joe thinks or does. The point is how to convince that nebulous entity that we call "The Financial System" to funnel large amounts of money into renewable energy before it is too late And with large, I mean LARGE: If the big investors don't move, and fast, we are doomed.

The difficulty of the problem is evident if we consider what happened during the past decade, when the "financial system" poured gigantic amounts of money into the shale gas and oil industry. And we all know the story of the great bubble that's bursting out right now. But it is not just a question of money: it has been an incredible misuse of resources affecting a whole civilization; something that may well have doomed it for good, also in terms of the large quantity of greenhouse gases emitted and that didn't need to be emitted.

And I can't avoid thinking, "what if all that money and resources had been used for renewables, instead?" The world, today, would be completely different. So, who decided to push all that money in the wrong direction?  The Gnomes of Zurich? The Trolls of Budapest? The Goblins of Southampton? The Orcs of Bratislava? Who?

I think this is the crux of the matter. As you can see in my post,  investments in renewable energy seem to have plateaued after 2011.



And that's VERY worrisome. On the other hand, it is also true that we see a trend of increase during the past two years; that may indicate a return of interest of the financial system to renewables. And the impression is that, yes, there is a clear trend in that direction. So, maybe we have a chance, but we must move on.



h/t Adam Siegel

Saturday, May 7, 2016

How much for the sustainable energy transition? A "back of the envelope" calculation



Image source. "Back of the Envelope" calculations are a tradition in science and often turn out to be able to provide plenty of useful information, at the same time avoiding the common pitfall of complex models, that of being able to fit anything provided that one has enough adjustable parameters.


The world's economy can be seen as a giant heat engine. It consumes energy, mainly in the form of fossil fuels, and uses it to produce services and goods. No matter how fine-tuned and efficient the engine is, it still needs energy to run. So, if we want to do the big switch that we call the "energy transition" from fossil fuels to renewables, we can't rely just on efficiency and on energy saving. We need to feed the big beast with something it can run on, energy produced by renewable sources such as photovoltaics (PV) and wind in the form of electric power.

Here are a few notes on the kind of effort we need in order to move to a completely renewable energy infrastructure before it is too late to avoid the double threat of climate disruption and resource depletion. It is a tall order: we need to do it, basically, in some 50 years from now, possibly less, otherwise it will be too late to avoid a climate disaster. So, let's try a "back of the envelope" calculation that should provide an order of magnitude estimate. For a complete treatment, see this article by Sgouridis et al.

Let's start: first of all, the average power generation worldwide is estimated as around 18 TW in terms of primary energy. Of these, about 81% is the fraction generated by fossil fuels, that is 14.5 TW. This can be taken as the power that we need to replace using renewable sources, assuming to leave everything else as it is.

We need, however, also to take into account that these 14.5 TW are the result of primary energy generation, that is the heat generated by the combustion of these fuels. A lot of this heat is waste heat, whereas renewables (excluding biofuels) directly generate electric power.  If we take into account this factor, we could divide the total by a factor of ca. 3. So, we may say that we might be able to keep the engine running with 5 TW of average renewable power. This may be optimistic because a lot of heat generated by fossil fuels is used for indoor heating, but it is based on the idea that civilization needs electricity more than anything else in order to survive. In terms of indoor heating, civilization survives even if we turn down the thermostat, wear a multi-layer of wool, and light up a small wood fire.

Renewable installations are normally described in terms of "capacity", measured in "peak-Watt" (Wp), that is the power that the plant can generate in optimal conditions. That depends on the technologies used. Starting from the NREL data, a reasonable average capacity factor a mix of renewables can be taken as about 20%. So, 5 TW of average power need 25 TWp of installed capacity. We need to take into account many other factors, such as intermittency, which may require storage and/or some spare power, but also better efficiency, demand management, and storage. On the whole, we may say that these requirements cancel each other. So, 25 TWp can be seen as a bare minimum for survival, but still a reasonable order of magnitude estimate. Then, what do we have? The present installed renewable capacity is ca. 1.8 TWp; around 7%. Clearly, we need to grow, and to grow a lot.

Let's see how we have been doing so far. (The values in the figure below appear to exclude large hydropower plants, which anyway have a limited growth potential).



Image source

As you can see, we have been increasing the installed power every year. According to Bloomberg, the installed capacity reached about 134 GWp in 2015. If this value is compared with the IRENA data, above, we see that the growth of installations is slowing down. Still, 134 GWp/year is not bad. The renewable energy industry is alive and doing well, worldwide.

Now, let's go to the core of the matter: what do we need to do in order to attain the transition, and to attain it fast enough? (*)

Clearly, 130 GWp/year, is not enough. At this rate, we would need two centuries to arrive at 25 TWp. Actually, we would never get there: assuming an average lifespan of the plants of 30 years, we would reach only about 4 TWp and all the new installations would be used to replace the old plants as they wear out. But we could get to 25 TWp in 30 years if we could reach and maintain an installation rate of 800 GWp per year, about 6 times larger than what we are doing today. (note that this doesn't take into account the need of replacing old plants but, if we assume an average lifetime of 30 years, the calculation remains approximately valid from now to 2050.)

We may not need to reach 100% renewable power by 2050; 80% or even less may be enough. In such case, we could make it with something like 500 GWp/year; still a much larger rate than what we are doing today. And if we manage to arrive to  - say - even just 50% renewable power by 2050, then we will have created a renewable juggernaut that will lead to 100% in a relatively short time. On the other hand, as I said before, 25 TWp may be optimistic and we may well need more than that. On the whole, I'd say that 1TWp/year is as good as it can be as an order of magnitude estimate of the energy needed for the survival of civilization as we know it. Approximately a factor of 8 higher than what we have been doing so far.

This back of the envelope calculations arrives at results compatible to those of the more detailed calculations by  Sgouridis et al. That study makes more stringent and detailed assumptions, such as the need of increasing the supply of energy for a growing human population, a lower capacity factor, the need of a gradual build-up of the production facilities, the need of oversized capacity to account for intermittency, the energy yield of the plants (*) and more. In the end, it arrives at the conclusion that we need to install at least 5 TWp per year for a successful transition (and, by the way, that, if we do so, we can avoid crossing the 2 degrees C warming threshold). That's certainly more realistic than the present calculation, but let's stay with this scribbled envelope as a minimalistic approach. Let's say that, just in order for civilization to survive, we need to install 1 TWp per year  for the next 30 years, how much would that cost?

Let's see how much we have been spending so far, again from Bloomberg:


Image from Bloomberg Global clean energy investment 2004-15, $bn

As you can see, investments in renewable energy were rapidly increasing up to 2011, then they plateaued with the value for 2015 only marginally higher than it was in 2011. However, if we compare with the previous figure, we see that we have been getting more Watt for the buck. In part, it is because of previously made investments, in part because of the improvements in renewable technologies that have reduced the cost per kWp. But note that technological improvements tend to show diminishing returns. The cost of renewable energy in terms of watt/dollar has gone down so fast and so much that from now on it may be difficult to attain the same kind of radical improvements, barring the development of some new, miracle technology. For instance, at present solar cells represent only about 30% of the total cost of a PV plant. Even if we were able to halve that cost once more, that would result in just a 15% lower cost of installations. Take also into account that technological improvement may be offset by the increasing costs of the mineral resources needed for the plants.

We said that we need to increase the installation rate of about a factor of 8 in energy terms. Assuming that the cost of renewable energy won't radically change in the future, monetary investments should of about the same factor. It means that we need to go from the present value of about 300 billion dollars per year to some 2 trillion dollars/year. This is a lot of money, but not an unthinkable: amount. If we sum up what we are investing for fossils (about $1 trillion/year), for renewables ($300 billions/year) and nuclear (perhaps around $200 billions/year) we see that we are not far from there, as we can see in the image below. The total amount yearly invested in the world for energy supply is about 2% of the Gross World Product, today totaling about US$78 trillion.



And there we are. The final result of this exercise is, I think, to frame the transition as a "mind-sized" model (to use a term coined by Seymour Papert). Basically, it turns out that, barring technological miracles, a smooth transition from fossils to renewables is probably impossible; simply because the current way of seeing humankind's problems makes it impossible even to conceive such a massive shift of investments as it would be needed (noting also that investments in renewables have not been significantly increasing from 2011 - that's bad).

This calculation also tells us that it is not unthinkable to advance in the right direction and attain a transition that would allow us to maintain at least some of the features of the present civilization. That is, if we are willing to invest in renewable energy, our destiny is not necessarily that of going back to middle ages or to hunting and gathering (or even to extinction, as it seems to be a fashionable future in certain circles). The transition will be rough, it will be difficult, but it will not necessarily be the Apocalypse that many predict.

In any case, some kind of transition is unavoidable; fossil fuels just have no future. But civilization may still have a future: all the investments in renewable energy we can manage to make today for the transition will make the difference for the future. This is a choice that we can still make.



(*) Note: In this simplified calculation, I haven't specified where the energy needed for building the new infrastructure will come from and I haven't used the concept of EROEI (energy return on energy invested). It is taken into account in detail in the calculations by Sgouridis et al in terms of the concept of the "Sower's Strategy", that is assuming that fossil fuels provide the necessary energy during the initial stages of the transition, then they are gradually replaced by renewable energy. 





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)