Cassandra has moved. Ugo Bardi publishes now on a new site called "The Seneca Effect."

Monday, October 3, 2011

The renewable revolution - II

After that I published in "Cassandra's Legacy" a post titled "The renewable revolution" I was surprised at discovering that many of the commenters reacted negatively to it, taking for granted the fact that renewables, in the form of photovoltaics or wind, "have a low EROEI" and, as a consequence, are unable to exist without a subsidy from fossil fuels. This view has its origins in the 1990s, when it was commonplace to state that "A renewable plant cannot provide enough energy to repay the energy needed to build the plant." That is, the EROEI of renewables was supposed to be smaller than one. We can find this concept, for instance, in the 2001 book by Howard Odum titled "A prosperous way down." 

Perhaps the "low EROEI" of renewables was true in the 1990s, but it is not true any longer. There are various recent estimates of the EROEIs of wind and photovoltaics; but none that I know gives values smaller than one and several give high values, for instance in the range of 30-40 for the new generation of thin film PV. With such EROEIs,  renewables are perfectly able to get on without the support of fossil fuels. If fossil fuels are used to build renewable plants, then the energy invested is returned several times; making it an excellent investment for the remaining fossil resources we have.

But that doesn't seem to be common knowledge, yet, and some people reacted aggressively to my post in a classic display of refusal of accepting new data that challenge one's established world view (e.g. one Harquebus). It seems that some people have concluded long ago that we are heading back to Middle Ages (or to the Olduvai Gorge) and that nothing can (or even should) be done to avoid it.

To keep my role of Cassandra, let me say that it is perfectly possible that we are moving towards such a destiny, but that doesn't mean it is unavoidable or that we shouldn't try to do something to avoid it. Let me also say that the fact that we can have now high EROEI renewables doesn't mean that we can keep the economy growing, it doesn't mean that we can run around in SUVs, it doesn't mean we can fly to Hawai'i every year. It only means that in the declining phase of the Hubbert curve we can keep electric power in relative abundance. As a consequence, we can keep the Internet, digital computation, worldwide communications, scientific research and many other things that could make the future substantially different than a return to Middle Ages. But, if we want that, we must invest on renewables now.

This said, I thought it was  appropriate to reproduce another very un-Cassandric post that I published on this subject on "The Oil Drum" about one year ago. Here it is.

Renewables out of the bottle

From "The Oil Drum," April 2010

There is an old zen koan that says that a baby goose was placed inside a glass bottle and raised inside it. When it was fully grown it could no longer pass through the neck of the bottle. How can we get the goose out of the bottle without breaking it? It is the concept of "satori," "revelation". It is something that shakes you out of your old views and takes you to a new vision. It happens when you see something apparently impossible suddenly coming true, like the goose in the bottle suddenly appearing outside, free. Renewables have been growing as inside a bottle so far; a bottle made of disbelief, red tape and not enough financing. It is time for a little satori in renewable energy. Renewables can hold on their own with new and more efficient technologies, in particular the CdTe thin film version which may have an EROEI of 40. With such EROEIs, we can start thinking of renewable energy as abundant and cheap. 

A few years ago, at a meeting on energy, I met a lady who turned out to be the environment minister for one of the county governments in Italy. Talking with her, I started feeling a sort of cognitive dissonance. We were using the same words: solar, wind, and the like, but with different meanings. At some point it dawned on me: she was fully convinced that renewables don't really produce any energy; that wind towers and photovoltaic plants are nice toys to make environmentalists happy but that their main purpose is to create business and transfer money from one place to another. So, she saw that her duty as environment minister was to make sure that some of the money would find its way to the goverment of her region, in exchange for the permission they gave to build the plants.

I can't really fault this lady for the way she had understood the situation; not after I have seen expensive "cash for clunkers" programs being implemented in Italy and elsewhere. If a government is willing to pay cash for destroying perfectly good cars in the name of the environment, one wouldn't be surprised if wind turbines were to turn out to be little more than souped up lava lamps. Machines that turn and turn, but produce nothing.

This is an attitude that I have often seen in politicians and the public alike: renewables are nice toys, but little more. When it is time to get serious, you need something real. You can't produce energy without burning something. You need a smokestack, somewhere, that's why you need coal, or oil, or gas. That explains another story I was told: that of the national minister of industry who was shown an electric heater (about 1 kW) powered by a 300 kW photovoltaic plant and who refused to believe what he was seeing. "Where is the trick?" he kept asking. No smokestack, no energy, apparently. You can't power the world with little blue squares facing the sun or with propellers that turn in the wind, sometimes.

Even promoters of renewables seem to see renewable energy as at best a marginal source. Most environmentalits seem to think that the right way to go is energy saving. That's the real, untapped energy source that we need to exploit. This is a respectable opinion, but I think it doesn't take into account the real potential of renewables. And that potential is truly gigantic: think of the amount of sunlight that arrives on earth everyday - you probably have heard that it is almost 10,000 times larger than the primary energy we produce today (see here ). So, what prevents us from using it? Once you start thinking about the possibilities, you may experience a little satori , an illumination where you see renewable energy suddenly breaking free out of the bottle. Renewables can provide as much energy as we need and it doesn't have to be expensive. After all, sunlight and wind are free and there is plenty of both.

But even a Zen satori has to be based on some good physics when it is about energy. And, when talking renewables, the good physics is mostly contained in the concept of EROEI - energy returned for energy invested. It is the ratio of the energy that a plant can produce over its lifetime divided by the energy needed to build it, maintain it, and dismantle it when its useful life is over. A good energy source must have an EROEI larger than one; obviously. But that is not enough; it must have an energy much larger than one if it has to provide that surplus that we need to keep up what we call "civilization".

Now, if you look at Charles Hall's balloon graph with a list of EROEIs for various sources, you'll probably think that there is not much hope for renewables. In the graph, the EROEI of PV is given as under 10 and that of wind as under 20. The graph is dominated by the blue balloon of "Oil, domestic, 1930") which is rated as having EROEI= 100. If our economy has been built on oil and if oil's EROEI is so large (or, at least it was at that time) then we can't expect that renewables could substitute oil and fossil fuels. Renewables, it seems, are a marginal source at best and surely can't give us back the good times of old.

But things move on. Charlie Hall's graph is already outdated in some points. The EROEI of renewables is increasing, it is actually shooting up. Realizing how fast that is happening was a little satori for me, not more than a few months ago. It came when I found a 2007 paper by Raugei, Bargigli and Ulgiati that evaluated the LCA of various photovoltaic technologies (See the references at the end). Then, the same authors published another paper in 2009 and in a few years the change has been remarkable. They don't report the EROEIs directly, but these can be approximately calculated from the values of the EPBT (energy payback time). I discussed the results with one of the authors, Marco Raugei (incidentally, a former student of mine), and we arrived to the conclusion that, in favorable conditions of illumination (1700 kWh/(m2*year) and assuming a lifetime of 30 years, polycrystalline silicon has an EROEI of 15, while CdTe thin film cells have an EROEI of 40. 

Now, tell me if this is not enough for a good satori. An EROEI of 40? And that with a "state of the art" system? Yes, with CdTe cells that you can buy on the market! I can almost hear the objections - that I am too optimistic, that the EROEI depends on the initial assumptions, and how about intermittency, and don't you know that we passed peak tellurium? And so on. But let me discuss these objections in a note at the end of this post. For the time being, let's take this large value of the EROEI as a working hypothesis and let's see how we got there and what are the perspectives.

First of all, this high EROEI is the result of a breakthrough in thin film cells. There are many ways of making thin film cells; the advantage is that the amount of material needed is very small and that reduces the cost. The problem is that in some cases it is the manufacturing of the cells that is expensive; requiring, for instance, vacuum processing. In other cases, making the cell may be cheap, but it is the efficiency of light conversion that is low; that's the case of many kinds of organic cells. The low efficiency of the cells increases the cost of the installation (called "BOS", "balance of system") because larger areas are needed.

So far, thin film cells have been either too expensive or too inefficient (or both). However, in the past few years, CdTe (cadmium telluride) cells have reached conversion efficiencies of the order of 11% and that has led to a commercial boom all over the world. A breakthrough, indeed, compounded by further advantages of the CdTe technology: that of being less sensitive than silicon cells to high temperatures, and that of being more efficient in capturing diffuse light. First Solar , the company that makes CdTe cells, is now the second largest producer of solar cells in the world, with a yearly production corresponding to about 1.2 GW peak power. Plans have been announced for reaching 1.8 GW by 2012.

So, we aren't yet at the EROEI = 100 of oil in the 1930s, but the progress in this area has been remarkable. And if PV based on CdTe can have an EROEI of 40, what prevents us from getting much higher values, using the same or other thin film PV technologies? And not just photovoltaic cells are susceptible of breakthroughs. Not long ago, I had another satori when I reviewed the situation with Airborne Wind Energy (AWE) and in particular the implementation called Kitegen. Here, we are talking of prototypes still under costruction, but the simulations are extremely promising - the EROEI could well be over 100 .

At these EROEI levels, well, the goose is really out of the bottle (and the bottle is not broken). Of course we can't yet claim that the energy problem is solved. We may have high EROEI renewable sources, but we still have to build up the infrastructure needed to build and deploy the plants; we need to build up a "smart grid" system that can manage power production in such a way to overcome the intermittency problem; we need also to restructure our economy in such a way that it can use electric power instead of fossil fuels for such things as transportation. It can be done, but it is not at all obvious that it can be done before running out of the resources needed for doing it, that is of fossil fuels. But it is not impossible. It is a fighting chance, but it is there.

Note: The calculation of the EROEI depends on where exactly you take the "boundaries" of the system and that we still don't have rules on this point (see this paper by Charles Hall ). But as long as we compare different technologies then we can compare the relative EROEIs and that has a meaning if the same methodologies have been applied; which is the case here. About PV in general, I know that we need to take into account the question of storage, but that is very often overstated and PV is not supposed to be the only technology used for energy production. PV would be embedded in a mix of different sources over large areas that would compensate each other. The concept of of "smart grid" would provide the necessary management of the energy produced and consumed. Then, I know that the value of EROEI=40 it is obtained under rather optimistic assumptions: that the plant is located in a well irradiated area (e.g. Southern Europe or North Africa) and that it has a lifetime of 30 years. Optimistic, perhaps, but realistic as well. You CAN place these plants in Southern Europe, North Africa or Southern US and their lifetime can exceed thirty years if they are decently maintained. So, we are not talking futuristic applications - it is reality. Then, there are other objections that one can make to CdTe technology; that it needs the rare element tellurium, that cadmium is toxic and what happens in case of fire; etc. All reasonable objections, but notice that these very problems imply that there is a tremendous stimulus to recover and recycle the materials used. Finally, if one thin film technology can be made commercial, it is reasonable to think that there are more that can reach the same level.


"Life cycle assessment and energy pay-back time of advanced photovoltaic modules: CdTe and CIS compared to poly-Si", by Marco Raugei, Silvia Bargiglia and Sergio Ulgiati at Energy Volume 32, Issue 8, August 2007, Pages 1310-1318

"Update of PV energy payback times and life-cycle greenhouse gas emissions" V. Fthenakis, H.C. Kim, M. Held, M. Raugei and J. Krones, 24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany


  1. Thanks for an interesting post on renewables. What I really do wonder though is what effect the unfolding economic crises will have on the large capital investments required now to deploy renewables at the necessary scale. I suspect that the global economy and our way of life will need substantial transformations (through some kind of collapse) before communities can start to prosper on renewable energy.

  2. "Most environmentalits seem to think that the right way to go is energy saving. That's the real, untapped energy source that we need to exploit."

    When you look at the starting point it is indeed clear that the lowest hanging fruits are there, but anyway alternative production and conservation are for sure not mutually exclusive, and on this D MacKay approach in his book "Sustainable Energy – without the hot air" seems to me the right one : looking at what we can do with renewables and what it means in terms of infrastructure at the level of a country, with also having pushed quite hard on the conservation side, and the summary scenarios clearly show that we would need "really a lot" of infrastructure... (even keeping some nuclear).

    But currently what seems to me the most important aspect is to define the policies for pushing in the right direction, and on this I'm clearly convinced that volume based taxes on fossile fuels, with a high level of redistribution as proposed in (2) below for instance is the right way to go :
    (here with the CO2 rationale but it works exactly the same with the "we need to consume less fossile" rationale).

    Volume based taxes have this huge advantage over subsidies : you do not have to define the "good solution" but it favors any "good solution" be it on alternative production or conservation side. And it is very easy to make mistakes in this "good solution labelling" activity (besides various cheats or lobbying behind subsidies schmas).

    Take cars for instance, almost all the progress in engine efficiency has been eaten up by cars getting in fact bigger and heavier since the sixties.

    Not to forget that simple things like south facing windows are also renewables energy gathering devices (in winter)

  3. Unfortunately, most windows leak so much heat that they are net energy sinks.  Technologies like aerogels are required to make them net energy collectors.

    The EROEI-related objections to renewables apply just as much to nuclear power.  A nuclear plant requires less concrete and steel than a wind farm of the same nameplate rating, and has much higher capacity factor.  The objections are either in the "goose out of the bottle" category (enrichment for LWRs has switched from gaseous diffusion, consuming about 5% of net electric generation, to gas centrifuges consuming about 0.2% of net generation) or are completely bogus (ridiculously high claims of energy required to mine uranium).

    The only explanation I have for this phenomenon is that a lot of people do not want solutions.  They want a collapse.  They'll have their vision of a train wreck even if they have to pry up the rails themselves.

  4. You are right, EP, with the train wreck image. We could also say that some people are like the Trojans who demolished their own walls to let their enemies into the city

  5. ERoEI is only one part of the ‘renewable’ energy equation. The renewable energy crowd creates a dangerous illusion. The illusion that middle class life can continue at some level of luxury and ease. That electricity for motors, electronics and lights will be available continually. That using “renewable” energy, we are not assaulting the earth’s resources and other life forms. That because it is “renewable”, it is clean and green. That because it is “sustainable”, it can go on indefinitely.

    The panels or wind turbines, the control electronics, and the batteries are not renewable. To create these devices, we use fossil fuels and toxic chemicals to mine, process, fabricate, manufacture and transport materials. The earth is gouged, rivers polluted, and air sullied. Given the amount and type of energy needed to get the end products, these devices are not renewable or green or clean or environmentally safe or sustainable.

    In order to make good energy decision we must look at the total process, not just pretty high tech pictures. To be sustainable, to be renewable it must be able to create all the equipment, manufacturing facilities and transportation that goes into creating these devices from the beginning. These devices simply will not reproduce themselves without fossil fuels. For those who foster this belief, prove it. Not on paper. Do a demonstration project of tons of materials and multiple square meters of arrays.

    These installation will take decades to replace the fossil fuel energy expended to create all this equipment. With replacement batteries and potential equipment malfunctions the energy debt may never be repaid. Given the price, environmental costs and geologic limits of fossil fuels, poor decisions take from the next generations.

    For pictures of mining equipment see: Energy in the Real World with pictures of proof.

  6. John, I looked at your site and I see that you are clearly a good person who put a lot of thought on this matter. Just for this reason, I invite you to make an extra step and accept that renewables CAN do us a lot of good.

    Think of one barrel of oil, what is the best use for it? You can burn it in a SUV and it will be gone forever. Use it to build a fraction of a renewable plant, and you'll see it return in the form of clean energy in a few years (or perhaps less than a year). And from then on, the plant will keep producing clean energy for free for at least a couple of decades.

    It is a moral imperative: if we don't set up an alternative, people will burn oil for nothing, until there is some left. If we use it to build a renewable systems, not only we'll give energy to our descendants, but we have a chance to create a mechanism that will allow us to say "enough" to oil and to stop using it while there is still some left in the ground. The same is true for coal and gas. If we can stop burning we still have a chance to avoid planetary overheating. A small chance, I know, but we must fight for it.

    Think of Cassandra, the prophetess. There was a prophecy that said that Troy would fall to the Greeks, she knew it. But that didn't prevent her from fighting for her city; she did what she could and, eventually, she paid with her life her failure. But it was her duty to do it.

  7. BTW, John, there is a chapter in my new book titled "A world without mines" where I discuss exactly the theme you are mentioning: the disaster which is modern mining, with all those huge machines, mountaintop removal, and all the rest.

    Then, in another chapter, I discuss how you can make mining (partly) sustainable, using those minerals which are abundant on the earth's crust and recycling to the utmost level possible. The result is that renewables don't really need large amounts of rare metals. Conventional PV panels, for instance, get by mainly with silicon and aluminium; both materials which are abundant in the crust. It is true that right now they use some silver for the back contact, but that is not crucial. Silver can be removed at the price of just a marginal reduction in efficiency. Then there is the question of the conducting cables, of the electronics, and many other things, but if we have energy, we can substitute rare metals with common ones; for instance copper can be substituted with aluminum - it can be done.

    The book will be published this month. Only problem: it is in Italian (sorry!)

  8. In your eyes (?Cassandra's eyes?) our only problem is if we can build out renewables fast enough? We might also have a problem of needing to move everyone where the renewable energy is. There were reports from last winter of the UK wind farms producing almost no net energy and having to actually heat the motors to keep them from freezing and I am sure that any solar plants they had also didn't produce much energy at that time of year. Can a smart grid fix the problems in the UK and other climes when the earth isn't tilted their way? What about manufacturing processes that are only efficient when run all the time in these countries and how does that feed into EROI? EROI and fungibility remain problems in my mind, I guess I will have to read your book when it comes out in English.

  9. Maybe I am identifying myself too much with Cassandra. But I see that I have problems in explaining my position. I am not seeing that renewables will "solve the problems" caused by running out of fossil fuels. It depends on what we define as "problems". If the definition is "how can we keep growing and running around in SUVs", then the answer is definitely "no". If the problem is defined "avoiding to go back to a depopulated, purely agrarian society from which we'll never be able to restart a new industrial revolution", then my answer is "probably yes - but only if we work on it"

    Generally (answer good also for Yves's point) society adapt to the available resources. We'll see how we'll adapt to renewables. We can adapt if we have energy. If we have no energy, we'll have no choice. If we have some, some things that used to be difficult will turn out to be easy, others will turn out to be impossible.

    In the Circle of Life
    It's the wheel of fortune
    It's the leap of faith
    It's the band of hope
    Till we find our place
    On the path unwinding
    In the Circle, the Circle of Life

  10. I guess where I am confused is when you are saying EROI is 40:1 or a potential 100:1, that sounds like business as usual to me or even better. We will be able to do everything we do today with EROI of 40:1 and much more with 100:1, so you must believe that those are not the societal costs and ultimate costs of these energies (and I understand that fossil fuels have massive externalities not calculated in their EROIs). I agree that energy sources will not go away after peak, but a more powered down world would be in line with what we expect to see from renewables with true EROIs of 3:1 or 10:1.

  11. Some additional resources worth taking a look at:

    Energy Payback of Roof Mounted Photovoltaic Cells

    The conventional wisdom about energy payback for solar seems to be based on a misconception: Odum's analysis was for a utility grade solar collector plant - and so included the physical plant, which skewed the emergy calcs.

    The excellent physics blog do-the-math weighs in on the issue of PV efficiency:

    But as this same blog makes clear, energy storage - necessary for a practical wind or solar basis - would a major challenge:

    And, again from the same blog (sorry - as an engineer, these quantitative perspectives are the flame to my moth!), the macro scale view of the historical growth of energy supply and demand:

    This latter makes the crucial point that no energy source - renewable or not - will allow BAU to persist in anything like the way we are used to. Renewables may be able to provide significant amounts of energy, as Prof Bardi suggests, but they are certainly no 'replacement' for current energy usage regimes in the industrial part of the world.

    Frankly, I am not as sanguine as Professor Bardi, and I think there are very good non-technical reasons to expect that the vast majority of solar panels and wind turbines that will ever exist are already manufactured and installed, but if sociopolitical and economic conditions manage to shift in certain dramatic and unexpected ways, it is certainly possible that renewables could play the kind of role the good professor imagines.

    The only way I do see such a thing as remotely plausible is if our entire energy infrastructure follows a highly decentralized model - essentially a point-of-use model - thus negating the need for the oft-fantasized 'smart grid' which I'm confident cannot possibly be implemented now, due to a lack of financial, temporal and other resources.

    I also think that under any plausible such model, electricity will provide only a portion of the energy used by individuals, households and businesses. The efficiency losses for, say, heating, or doing mechanical work by means of electricity are a source of huge waste, and I'd expect a number of other types of energy to take over tasks to which they are better suited. I look forward to the fitness level I will be able to achieve with my pedal powered washing machine, for instance. :)

    - Oz

  12. As I posted a comment to your previous post disagreeing with some of what you exposed, I guess that I am included among those you say that responded negatively to your post. However, I don't consider myself to be among those who are already convinced we will head back to the Middle Ages, although most of what is being done and said seems to bring us there. For now I hope there is still hope for us.

    Regarding renewables, I have never opposed spending in R&D to obtain higher EROEI and lower costs, for instance. However I do not agree with wasting time, money, energy and efforts to build those renewable sources that do not yet have appropriate EROEI ratios and costs. And above all I do not agree with creating a perception that easy solutions to our energy problems do exist just by making use of renewables, which in my opinion is currently the most widespread idea among the general population. Moreover, I think that the lack of awareness and the underestimation of the treat that an energy crisis constitutes to human civilization is at least as dangerous as the decrease in energy resources availability itself. And in my opinion, it would be more tragic that the fall of human civilization was not to be caused by physical limitations but by misconceptions or even plain stupidity. And most of what has been said about renewables in previous years could probably be included in the category that brings us there.

    When seeing arguments such as "sunlight and wind are free" so let's use them, I begin to wonder, and only two options came to my mind. Either I am being fooled or who write this has not even stopped to thing about it for a couple of seconds. It should not even be necessary to say so, but ALL natural resources are free, even oil, gas and coal. What costs money (and energy) is their conversion into useful energy. In some cases it involves mining or drilling and subsequent burning, while in others it may require mining and processing materials to build devices that can transform light or wind directly into electricity, for instance. In any case, they cost money (and energy) and consume natural resources. What it is relevant is to do it in an efficient manner, and being aware of the resources availability and the needs that they have to cover.

    When hearing statements such as PV have an EROEI of 40, it makes me think that some renewables subsidies are not just an unsound policy but an embezzlement of public funds instead. However, even professedly having such high EROEI index they are still expensive and need subsidies to become competitive. Isn't that odd?. The reasons suggested seem to be that, despite the low energy investment required for their fabrication, their manufacturing is expensive due to the need of vacuum processing or other techniques. And why is this processing expensive if not because it consumes a lot of energy or large amounts of energy are invested in the fabrication of the required equipment? A certain amount of distortion exists, due to the financial system and some other issues, upon the ratio between economic cost and energy consumption, but costs are ultimately related to energy. It makes no sense to me that something that requires a small energy investment compared to the energy it produces, ends up producing that energy at a substantially higher cost than the energy used to build it. There is something missing somewhere.

  13. I agree also with Engineer-Poet about the underestimation of nuclear energy EROEI, and with John Weber regarding the mythologizing of renewables, usually being called green or clean energy sources. It is past time for people to realize that there is no such thing as clean energy. All energy production, and in fact all human activities, have an environmental impact, but it is for us to choose which are the most sensible decisions to make to limit that impact and to allow a decent living standard if possible. To date, renewable claims have mainly contributed to reduce energy scarcity awareness and to keep the business as usual model that has brought us to be much more dependent on fossil fuels than we were while having substantially reduced their availability.

    I will be glad to see cheap PV panels installed to fulfill our energy needs, but till then these boasts keeps sounding to me like more of the same song that has brought us where we are, and it is not a very comfortable position.

    Finally, I find yvesT comment "even keeping some nuclear" strangely amusing. I wonder if most people still think they can afford to be picky about the energy sources they use to power their needs, even when already burning like crazy the same resources they would later need to feed themselves, and pumping huge amounts of GHGs into the atmosphere amidst a context of global warming.

  14. Quoth Oz:

    "The efficiency losses for, say, heating, or doing mechanical work by means of electricity are a source of huge waste"

    I am skeptical of his claim to be an engineer, unless he is some sort of narrow specialist.  Electricity is pure work, and the losses involved in conversion to and from mechanical forms are a few percent in large machines.  He ought to know that point-of-use machinery is the least efficient; combined-cycle gas turbines regularly beat 60% (LHV), while heat engines under 10 HP are lucky to scrape 30%.

    Such a switch from central to distributed engines would cut the available energy from a given amount of fuel in half (CHP excepted).  Anyone with an engineering education ought to know better.  While the ignorant can be excused, I have to question the impartiality of anyone who ought to know better and wonder what other goal they could be trying to advance.

    ZZR, did you realize that the USA has several hundred years worth of energy, already mined, refined and sitting in warehouses?  Our current energy and climate crises are largely the work of Hazel O'Leary (dead and beyond retribution) and Patrick Leahy (still in the Senate).  Oh, and our nuclear waste "crisis" also.

    There's also Flibe Energy.  It's not too late to reverse course.

  15. Prof Bardi, i fully support a renewable revolution. However from my overview in the PV field i think that it would not be easy to have that many candidates for thin film solar cells that can be as good as CdTe. There is of course CIGSSe but In are not that abundant. If you look into the literature, high efficiency CdTe along with CIGSSe(19.6%) was known almost 10-20 years but only CdTe was successful to compete with silicon and CIGSSe is still way behind. There is an emerging material, CZTSSe(Copper zin tin sulfide selenide)which has relatively earth abundant material which reach around 7-10% efficiency last year but for real commercialization, at least 12-15% and preferably 20% is needed. Other cells like Graztel cells have been stagnating at 12% with a host of problems and polymer cells are still too low efficiency.
    In my view, research into CZTSSe is still in the early stages and i do not think that a commercial product is very likely in 5-10 years. Based on the literature from CdTe and CIGSSE development, at least 10-15 years are needed before they can start to compete against Crystalline ,amorphous si and CdTe. Even then to scale up to the TW capacity will take another decade. Thus in my opinion, i am not that hopeful that it can be scaled up fast enough to offset the decline phase unless a drastic reduction of growth in energy usage is implemented which is basically impossible since the huge demand from the Asian poor ( i am from Asia) aspiring to reach middle class will overwhelm any demand destruction from the west. My point is that unless the oil shock occurs in the later part of 2020s instead of 2012-15 as suggested by many groups, it would be better to base any realistic actions based on the Si and CdTe and possibly CIGSSe we have now and do not rely on the future possibilities.

    Thus to answer "what prevents us from getting much higher values, using the same or other thin film PV technologies?: My answer is nothing we can get higher values using thin film PV technologies but they will only be large scale commercially viable if we are lucky in the late 2020 to 2030s. The difficulties is to reach then with an intact economical and world which is not plagued by war and economical and social crisis.

  16. I hate to be be the bringer of bad news bu CdTe thin film photovoltaïcs have the same problem as nuclear fission : namely lack of raw material. Tellurium is one of the rarest element in Earth crust, roughly one the same level as platinium. Selenium is also quite uncommon.

    Since tellurium has little use (mostly metalurgy) so it is cheap... for now, but it won't stay so if demand ramps up and we will quickly hit the wall.

    For wind, the problem is rare earth (for magnets), not that uncommon, but a pain to mine

  17. Well, I agree that I might have been somewhat optimistic with that line in my post of last year. Indeed, I think that PV technology is basically mature by now. Whatever we do, we'll have to be happy with efficiencies under 20%, at least for the foreseeable future. But that is more than enough for what we need.

    About the various technologies, CIGS is growing rapidly, I think it has some chances to catch up with the others. CdTe is doing very well, but I see it as a sort of bootstrapping technology. It will allow us to grow rapidly in an initial phase, but then we have to settle on technologies that do not use rare materials such as tellurium.

    I think silicon PV is an excellent technology that doesn't use rare materials (well, a bit of silver in the back contacts, but it can be eliminated). It is not the most performing one, but enough for what we need. I give some chances to Graetzel cells; in a different kind of world they could find interesting uses. Not right now, though.

  18. Damien, I posted the above comment before seeing yours. The problem with finite tellurium resources is well known and it is known that we can't raise production over a certain limit. It does not seem that the limit is close, right now, but it surely exists. But the technology is very efficient, tellurium can be recycled to over 95%. As I said in my previous comment, it is a way to grow in the present phase. At some point, obviously, we'll have to move to something else.

  19. Ugo, I haven't gotten many questions about my Systems Energy Assessment (SEA) paper, on what is necessary to accurately measure the total energy costs for producing energy. It seems to be the systems thinking that stumps people. What it exposes is a major omission from the the standard measures. The true scale of EROI for wind is about 1/5 what people have been measuring.

    The difference is that I count ALL the energy needed for bringing wind energy to market, and not just the energy used in making and running the turbines. It's a major conceptual mistake in systems energy accounting, that the true energy demand on the earth is often about five times the energy consumed by the technology.

    That said, the real limits on wind energy are much the same (usually overlooked) limits on fossil fuel energy. For our economy to remain stable it has to continually expand in scale, but ever increasing scales of energy from either fossil or wind sources becomes prohibitively expensive.

  20. "Quoth Oz:

    "The efficiency losses for, say, heating, or doing mechanical work by means of electricity are a source of huge waste"

    I am skeptical of his claim to be an engineer, unless he is some sort of narrow specialist. Electricity is pure work, and the losses involved in conversion to and from mechanical forms are a few percent in large machines. He ought to know that point-of-use machinery is the least efficient; combined-cycle gas turbines regularly beat 60% (LHV), while heat engines under 10 HP are lucky to scrape 30%.

    ...I have to question the impartiality of anyone who ought to know better and wonder what other goal they could be trying to advance."

    In fact, your suspicions regarding nefarious agendas aside, that aspect of my comment which you quoted was admittedly poorly worded. It's not the electrical-to-mechanical conversion efficiency that I am complaining about so much as the entire cycle, from fossil fuel to end-user mechanical use. But that's not the real issue here. The gulf between our worldviews, is.

    From your standpoint, 60% is a 'good' efficiency figure. From my standpoint, it is an intolerable waste of an almost incalculably precious finite supply of fossil fuels. Your argument is a relative one, mine is an absolute one.

    You see, in my book, 40% loss (in that single stage, not counting all the further losses across the entire system, which your argument treats as negligible) is in fact in and of itself what I termed a 'huge waste' - while for you it is, apparently, an acceptable loss, simply because other systems capable of accomplishing the same ends exhibit even more egregious waste. Terrific illustration of the mindset difference between you and I, methinks.

    In a sense, your argument derives from a set of assumptions with which I disagree. To you, this makes me a 'bad engineer with an agenda' - which I suspect says more about your psyche than it does about the quality of my education.

    The notion that 60% efficiency is better than 30% efficiency - all other things being equal - is inarguable. What you seem unwilling to grasp is that all other things are not equal, and that is in fact the core of my position. It is in the area of which ends are being accomplished that I am focused, while you simply accept them as a constant.

    For example, is it really sensible, in light of the reality of resource depletion and carbon pollution, for someone to burn any amount at all of fossil fuels to run a tanning bed in their home?? I would argue that this is in fact recklessly irresponsible from both a social and ecological standpoint, while your position might involve calculating the consumption of various brands of tanning bulbs to determine the most efficient.

    I'm well aware of your cornucopian outlook, which of course means you would be reluctant to accept the premise I state in the question above. I've seen your positions refuted any number of times on ToD, often based on the same approach you've taken here: restrict your focus to an isolated technical component of a systems level problem, make assumptions about the frame of reference which in fact are debatable, while ignoring the aspects - especially non-technical ones - which don't fit neatly with your view - and then ascribe unspecified 'agendas' to those who disagree with any of the above.

    Fundamentally, we are starting from different premises, and so it does not surprise me that we'd wind up with different conclusions, even if the reasoning for each position is sound. But, your ad hominem approach is one which refuses to acknowledge that other premises than your own may in fact be legitimate, and this means that dialectic rather than debate is probably not really possible between us.

    - Oz

  21. Given that the response to a pointed criticism amounts to handwaving, and is followed by the erection of several straw men, I think my suspicion is quite adequately proven a posteriori.



Ugo Bardi is a member of the Club of Rome, faculty member of the University of Florence, and the author of "Extracted" (Chelsea Green 2014), "The Seneca Effect" (Springer 2017), and Before the Collapse (Springer 2019)