Monday, June 01, 2009

The Renewables Hump 3: The Target

In he last post in this series, I discussed the criticality of accurately measuring EROEI of potential alternative energy technologies.  If the EROEI of a renewable energy is high enough, then a relatively small initial investment of energy can lead to the rapid scale-up of renewable generation by bootstrapping its own energy production to finance (in energy terms) its own growth.  However, if EROEI is too low, then the amount of energy that society must invest to meet a renewable target would be so great as to be effectively impracticable (because it would cause sufficient energy price spikes as to threaten so much immediate economic damage as to be politically impossible).

Before proceeding with this discussion of EROEI, I thought it would be worth defining what this target for a renewable transition actually looks like:

First, it's important to recognize that there are a variety of possible targets.  Some include: a general transition target (either total transition to renewables, or transition to some arbitrary %), a peak-oil mitigation target, a peak fossil-fuel mitigation target, and a climate change mitigation target.  All have differences and similarities.  Clearly, its one can define a "target" that is plainly achievable, as can one define a "target" that simply can't be done (e.g. 100% transition in 5 years).  As such, the definition of "transition target" represents an easily manipulable variable in any discussion of renewables transition.  If two people or organizations don't recognize the same target, they'll be constantly talking past each other in discussing renewables and the practicality of transition.  While I certainly don't think that I'll be able to convince all parties to adopt a unified transition target in this blog post, I do plan to argue for a threshold target that, in my opinion, represents a minimum rate of transition to keep the "viridian vision" of a renewable future possible:  a peak oil mitigation target.

So, it seems clear that a renewable energy transition will need to, at a minimum, replace the decline in oil production with renewable energy generation.  I'll elaborate on why I draw this line in the sand below, but in brief the viridian vision (by which I mean a general continuation of our current neo-liberal, capitalist/market-socialist civilizational structure into the distant future by leveraging technological advances and a transition to a renewable energy base and "green" economic foundation) requires that we maintain generally the same level of present energy consumption into the foreseeable future.

Why this focus on the "viridian vision"?  I think my personal biases are clear:  I'm very skeptical about the practicality of viridian vision--to be more plain, I don't think it's realistic, and further I think it's the modern opiate of the masses when it comes to confronting current energy issues.  That said, I think anyone who refuses to recognize that both 1) the viridian may be possible, and that 2) it may be fundamentally impossible is taking a faith-based and irrational position.  I don't want anyone to accuse me of hiding the ball as this series progresses--my own studies to date suggest that the renewables transition necessary to fuel the viridian vision is most likely not realistic, and my purpose in this series is to build an argument to this effect.  I'm not trying to be pessimistic.  Rather, I'm trying to prevent a waste of effort, focus, and our limited (and dwindling) supply of surplus energy on an epochal folly.  For lack of a better analogy, it's a bit like our childhood fantasies:  at some point, the little league baseball player needs to give up on the dream of becoming a star professional athlete and focus on a more realistic plan for the future.  Sure, for any given kid it's a possibility to become the next big star, but it would be folly to advise all of them to pursue that dream at all expense.

It's also important to point out the obvious, that there are significant differences between the energy produced by renewable technologies (that, for our purposes, produce electricity) and the energy lost by declining oil production.  In general terms, in order to use the electric energy produced by renewables to replace oil, there will be an additional energy cost required to transition the energy-consuming infrastructure to utilize electricity rather than oil.  This will increase the overall amount of energy required to affect this transition.  For the time being, I'll ignore this additional cost--the result is that my estimates will be more conservative than an estimate that would account for these additional transition demands.

One key argument in favor of the viridian vision is that we can mitigate peak oil with increases in efficiency and energy conservation.  These arguments generally don't, however, address how we're going to meet the energy demands of 1) a growing population, and 2) a huge third-world population that wants to live at Western standards of energy consumption.  The more optimistic population estimates show the Earth's population peaking at 8.3 billion, and more pessimistic estimates show population peaks between 9 and 13 billion.  It's important to point out that may population estimates reason that population will stabilize--and then decline--because of the effect of bringing the standard of living of the world's poor closer to Western standards.  Will the energy pressures presented by population growth and efforts to improve living standards roughly balance out any improvements in efficiency and conservation?  I think so.  In fact, I think that this is overly optimistic, and that demographic pressures will more than eat up any energy savings from efficiency and conservation.  For this reason, I think that we must increase renewable generation capacity at the same rate that oil production declines--we can't count on efficiency and conservation to make up any of this decline.

Additionally, any renewables transition that attempts to mitigate peak oil must cope with the disparity between effective ramp-up rates and effective oil decline rates.  It's nothing more than a simple issue of math:  if you use a post-peak decline rate of 5% for oil decline, then that works out to about 4.4 million barrels per day of decline per year, gradually decreasing over time.  Conversely, because the current renewable generation base is so small (excluding hydropower, which can't be easily ramped up), even a 100% per year increase in renewable generation comes nowhere close to mitigating this 4.4 million barrel per day decline in the early years.  At some point, a 100% annual increase in renewable generation overtakes the declining annual oil production decline figure, but there is a significant gap, especially if we are currently at or very near peak oil.  For this reason, we can't necessarily look at the rate of increase of renewables generation over a 20 or 30 year window, because this long-term view alone may overlook a very significant energy gap.  It's possible that this gap can be filled with fossil alternatives that are not yet at peak--specifically coal and gas--but that's probably the best we can expect from such fossil alternatives given that they are already experiencing significant EROEI declines (and cost increases) and that their climate consequences may be incompatible with the viridian vision...

All of these values--renewable generation, population growth, conservation, efficiency--are arbitrary decisions.  There are simply too many variables to produce a single, agreed set of assumptions on which to base a target estimate.  Here, my goal is simply to make my assumptions (and their rationale) clear so that others can question them and change them if they wish.  Ultimately, I'll continue with this Renewables Hump series using this peak oil mitigation transition target outlined below.  If others have alternative targets, it should be relatively simple to apply the remainder of this series to those different targets...


In looking at these figures, I'm choosing to ignore hydropower, which has a current generation capacity of approximately 800 GW.  My rationale is that hydropower is largely location constrained, and is not scalable in the way that other renewables (especially wind and solar) are.  For example, only about 10 GW of hydropower were added in 2008.  Compare this to a rough doubling in wind generation capacity.

The world consumes roughly  500 Quads per year (Quadrillion BTUs) from all energy sources.  Of this roughly 186 Quads come from oil consumption.  If you accept a post-peak decline rate of 5% per year, then that represents a decline of 9.3 Quads per year.  9.3 Quads equates to roughly 102.3 GW-years, or 896,000 GWh.  To round that off, let's call it 100 GW-years, or 900,000 GW-hours.  That's how much new renewable generation must be added each year going forward.  That's the transition target.  How does that compare with current renewable generation rates? 

The current global installed (nameplate) solar capacity is about 15 GW, including about 5.5 GW added in 2008.  That works out to roughly 1 GW-year of solar generation capacity added in 2008.  One EIA study estimates that, under an "aggressive" growth scenario, total all sources of solar power could displace a total of 22 Quads of fossil fuel consumption by 2050 (that's the total from present to 2050, to an annual rate).  Clearly this rate of transition is woefully insufficient to mitigate peak oil.

At the end of 2008, global (nameplate) wind generation capacity was 121 GW.  That works out to roughly 42 GW-years of total global wind generation, of which 35 GW, or about 12 GW-years of wind generation was added in 2008.  Combining solar and wind, we added about 13 GW-years of renewable generation capacity in 2008.  That's a bit over 10% of the rate at which we'll need to add new renewable capacity each year just to compensate for a 5% global oil production decline rate (not to mention future natural gas decline, coal decline, etc.).  There are two take-aways from this:  1) the current rate at which we are increasing renewable energy generation is an order of magnitude lower than that necessary to mitigate peak oil, and 2) the amount of energy invested in renewable energy projects at present does not pose the kind of energy drain that will be presented by investment sufficient to mitigate peak oil.

On this last point, mitigating a decline of 4.4 million barrels of oil per day each year with new renewable generation capacity will impose a significant up-front energy cost.  If the energy payback time is 1 year for the mitigating renewable source, and this represents a 90% increase in current renewable energy investment, then we need to invest the equivalent of an additional 3.96 million barrels of oil each day to facilitate the transition.  That's like adding another half of China to global demand, and that 1-year payback time assumes an EROEI of 40:1 on a 40-year generating life.  If the energy payback time is 2 years (or a 20:1 EROEI) then you can add another full China to global demand.  If it's 10 years (an EROEi of 4:1), then go ahead and add 5 Chinas.  You can see where this is going--getting an accurate measure of EROEI, and properly understanding the mechanics of scalability, are critical before we can determine if it's possible to mitigate peak oil with renewables...


Neil1947 said...

I agree that we will need to replace 4.4 million barrels of oil per day every year, but not that will need the same energy contained in oil. Oil used for heating delivers 65-70% of energy, while elctric heat pumps 250-400%, oil used for electricty genreation is at most 50% efficient and oil used for motor vehicles 15-20% efficient. Ten kWh of electric energy can replace 1 gallon of gasoline so need about 500kWh per barrel. Thus all told probably only need about one third of the energy contained on oil to be replaced with renewable electricity.

Neil1947 said...

If oil production starts to decline in next few years, we would expect perhaps 5-10years of slower decline and then a more rapid 5% decline, so we possibly have a few more years in which wind and solar capacity can grow.
If we just consider wind energy, world wide the growth rate has been 30% for more than a decade, but not under the type of pressure we would expect when oil decline begins. None the less lets see what wind could be in 5 years at a 30%per year growth rate, using the 12GW average increase for 2008. In 5 years (Jan 2014)that 12 GW increase should be an increase of 45GW average per year more than one third of the energy in 4.4 million barrels, and the following year will have increased by another 59GW. It seems likely that the limitation will be building a lot of PHEV and EV cars to take advantage of the additional electricity, however, I understand there is a large surplus of car manufacturing capacity and labour, so would not ahve to include the additional energy to build these facilities or train labour only the re-tooling costs and the EROEI of new wind and transmission lines.

Rice Farmer said...

The implications are staggering. Actually, I can't imagine that it will go well. There are various problems to take into account. For example:

First, there is financing. We are at the point where the amount of debt in the world is far greater than actual assets, and the strain is more than evident. Yet, to build lots of renewable equipment requires us to take on a whole lot more debt. There are plenty of news stories about how financing difficulties are crimping renewables. Adding still more debt to the creaking world financial system can only make things worse.

Second, human society is already incapable of maintaining existing infrastructure (because energy is now much more expensive than when most of it was built), and developed countries are literally falling apart. But, the large-scale deployment of renewables is about adding a huge amount of new infrastructure. Obviously, anything we manage to build can never be maintained.

Third, there is the matter of energy fungibility. Of course it works to a point. But whereas we can convert coal into electricity, we can't convert electricity into coal. In truth, renewable energy infrastructure (and that for nuclear) needs coal and oil for maintenance and replacement because electricity and piddling amounts of biofuels could never run blast furnaces, forge steel, found machine parts, build roads, and do so many of the other things that coal and oil do.

But don't get me wrong -- I think we should pull out all the stops and build all the renewables we can right now because that will help us achieve a soft landing.

Robert Martini said...
This comment has been removed by the author.
Robert Martini said...


explain to me how 45 GW per year is one third of 4.4 million per day?

45 Gw = 45*10^9 joules/sec
there are 31 milliom seconds in a year

45 gw of generation for a year entails a total of 1.4*10^18 joules produced in one year

the energy density of crude oil is 37*10^6 joules per litre, one barrel has 159 litres in it, aka 42 gallons.
so that multiplied by 4.4 million, per day, but its in a year so multiply again by 365 and you get, 9.3*10^21

which is actually 6667 times greater than the 45 GW for a year.... I believer you forgot to multiply 4.4 million barrels by 365 days per year or something..

To all:

The bane of renewable energy is it is several orders of magnitude less energy dense than fossil fuels...

How in the bloody hell do we expect, to replace millions of years of stored sunlight per year, with a single year of sunlight per year? I would be incredibly grateful to the first man to give me a logical well thought out argument as to how this is possible. We forget that the only reason we can harness all this renewable energy is because we can spend copious amounts of fossil fuel to make it possible.

The current paradigm of renewable energy, is like, someone adding a solar panel to a Nissan Titan, and then arguing that because the truck will still run fine with a solar panel, that it would still run fine, if i were to take away the god knows how much horsepower diesel engine and add a second solar panel.. we can't get a realistic hold on how feasible renewable energy is because were still in the fossil fuel era.

Wind energy cannot survive without subsidies and huge tax benefits. I have a theory that as fossil fuel cost rise that industrial wind farms will NEVER be competitive with fossil fuel industries without subsidies and other free market maladies. Why, because the cost of building a wind turbine and maintaining it with rise just as fossil fuel cost rise, because we need fossil fuels to build them. Looking at future revenue based on future fossil fuel prices and using PRESENT costs, labor and overhead will be the doom of us all.. By the time fossil fuels decline to a shadow of their former selves, people will not have the discretionary income to support large electrical power demand. We forget that widespread electricity is a phenomena unique to the past 100 years or so. what do you need electricity for when your only motivations that is food, water, shelter and safety which are barely in your means to begin with, like at east 2 billion of the worlds people..

Thoughts and comments would be appreaciated..

Robert Martini said...
This comment has been removed by the author.
Robert Martini said...

Also, I believe as you may see from my comment, that I think that perhaps the discoveries and dramatic increase in "Human Knowledge and Discoveries" are not to be credited to true progress as much with an abundance of energy, I believe many of the practices and discoveries are only relics of an era of abundant energy, that may become the lost knowledge of the future. If you don't have an abundance of energy, what use is quantum mechanics, astrophysics, advanced statistics, highly complex mathematical proofs and axioms to you. What good to you is the mathematical knowledge to be able to figure out a three dimensional representation of the stresses in a support or structure, if you don't have the energy to make possible an advanced web of networks, computer programs and an electrical grid to run all of it. Our ancestors were just as capable of discovering mathematical proofs that could predict the probable frequency of gamma ray emissions from a quasar 60 million light years away, however, because they lacked a huge accessible energy endowment, they could not afford this level of societal specialization nor the time and resources to spend on something so irrelevant to their immediate survival. I question how much truly useful knowledge has been gleaned from this era that could make a better future for humanity without our limited time endowment of energy?

Neil1947 said...

Robert Martini,
I was using Jeff's figure of needing 100GW years new energy production. Each 10kWh(36MJ) replaces 1gallon gasoline(130MJ) so would only need 100GWx 36/130 =30GW years. Last year the world added 12GWyears, so needs to increase this by X2.5, wind energy is growing by 30% per year, so doubles every 2.4 years, thus 45GWyears in 6 years.

Your comments about energy density of wind or solar energy is not relevant unless you compare them with the energy density of oil bearing strata, not refined gasoline. We don't run an electric car on wind or sunlight, we use electricty just as we don't shovel in 500 Kg of oil shale or oil sands into an ICE vehicle. Batteries have a lower energy density than gasoline, but we need a large ICE to use that energy and in any case batteries can do the job for most transport needs which is short distances each day. It won't work on air transport(5%of oil use)

Rice Farmer said...

Robert Martini remarked: "How in the bloody hell do we expect, to replace millions of years of stored sunlight per year, with a single year of sunlight per year?"

This is an excellent observation. It is exactly what I am talking about when I use the terms "stored solar energy" and "real-time solar energy." It should be obvious to anyone with a functioning brain that real-time solar energy cannot replace the HUGE amount of solar energy stored in fossil fuels.

One other observation I'd like to add: The second point in my previous comment noted the problem of maintaining infrastructure. In fact, Oil Drum Europe has a good post on "peak capital" that bolsters my argument.

Existing infrastructure is already crumbling, and we're rapidly falling behind on maintenance. So the idea that we can build a vast new infrastructure for renewables and maintain it is a fantasy. The "smart grid" is a pipe dream.

Neil1947 said...

Rice Farmer,
Jeff's post provides the world energy use of 500 QUADS or 5,500GW years.
If we just consider the desert regions within 35degrees of equator, we have 20Million km^2.
Each meter^2 receives 8kWh/day or 2.7kW continuos(0.3kWyears/year), meaning 0.3GW per km^2 or 6 Million GW about X1,000 times the energy we obtain from all FF per year.
The problem is harvesting this energy, not the availability of the resource.
I am hoping that Jeff will be examing the energy used(invested) to obtain this energy. By the way, it's not really that diffuse, the roof of a typical home is 150meters ^2 so receives about 750kWh per day( assuming a lower value of 5kWh/day in US). This is more than X10 average family electricty consumption(both domestic and by industry)

Robert Martini said...


Good points! In my mind however, methods for obtaining the resource are in fact are directly related to the availability of the resource, in a sense they are or make the availability of the resource. Also, Oil bearing strata are still orders of magnitude more energy dense than sunlight and wind coal has a similar energy density to oil bearing strata I believe.

Also there is a huge difference between how much solar energy hits the roof and how much you can actually gather due to changes in the angle of the sun and cloud cover. Also typical solar technology is only 10-12% efficient. which means your figure is at least 10 times too high. Who can afford to cover their entire roof in pv panels?

terrapraeta said...

Hey Jeff --

I think you probably know that I have little to no expectation of "solving" peak oil on any kind of global scale... still, it is interesting to follow the discussion.

One question... I recently read something about the huge hydro system China is building on, what is it? the Yellow River? Know anything about that and the expectations for energy output? Is it significant enough to make a difference in any of this?


Roger Brown said...

EROI is not really a good parameter for analyzing the growth limitations of various energy sources. You are right, of course, that long energy payback times do place limits on energy growth, but that is a separate issue from energy balance.

For example suppose you have two renewable energy technologies with an energy back time of 4 years. One of them as an expected mean life time of 40 years and the the other a mean life time of 20 years. The EROI values are 10 and 5 respectively (assuming constant output over time). Nevertheless over a twenty year period starting from zero (or near zero) capacity the growth limitation due to the long pay back time is identical for both technologies. On the other hand in long term equilbrium, where only worn out generation units are replaced, the net energy provided by the first technology is 90% of the gross output while the net energy of the second technology is 80% of the gross output.

If the second technology has a two year energy payback time and a 20 year life time, then both technologies have EROI=10 and both would provide the same net energy in long term equilibrium for a fixed generating capacity. However, during a period of growth the shorter energy payback time of the second technology would give it an advantage over the first.

Now consider the other extreme of very short payback times. Suppose that energy investment in growing algae payed off in one day's time (Yes, I know that the energy embedded in ponds and biomass processing equipment would not pay off in this length of time. I am not trying to be realistic; I am examining a limiting case.) Suppose that EROI=2 so that 1 unit of energy today produces 2 units of energy tommorow. We sell 0.5 units and reinvest 1.5 units. If we make the same proportional split every day our gross energy output after n days will be 0.5+1.5**n. After 1 year our gross energy output will have increased by a factor of approximate 1.88+E64. Clearly this rate of increase in energy production is absurd and some other factor of production such as labor, land, water, nutrients, etc. will limit the growth actually achieved. In the limit of very short payback times the energy "cost" of energy production is irrelevant.

Net energy accounting is important, but EROI is not a natural parameter for doing such accounting.

Jeff Vail said...


You said "Ten kWh of electric energy can replace 1 gallon of gasoline so need about 500kWh per barrel. Thus all told probably only need about one third of the energy contained on oil to be replaced with renewable electricity."

I agree that there are differences between the value of oil and electricity to society. However, I disagree that the end result will be that we can mitigate peak oil with 1/3 the energy equivalent of electricity.

First, IF we're mitigating the specific oil used to generate electricity with renewables that directly produce electricity, then I agree that we should probably use the EIA's estimate of 33% efficiency (and that, therefore, we only need 1/3 the amount of electricity to mitigate). However, that still assumes that the renewable generation locations (wind or solar farms) are as well situated relative to the grid as current oil-fired powerplants, and that also assumes that there are no intermittency issues with wind and solar. In reality, even to just replace the oil (which, in the US, is a very small %) used to generate electricity, we will need to 1) invest in significant transmission infrastructure, and 2) invest in storage capacity (or even greater transmission infrastructure to smooth out the intermittency of wind and solar). I haven't seen any good studies that compare this additional investment to the 33% efficiency of oil-fired electricity, but it may well make up the difference (meaning that there is no savings by generating electricity directly), and at a minimum it will mean that the net effect is less than a 3:1 savings. I think this issue will become more critical to the extent that we're looking to also replace coal with renewables (which will also be necessary--preferably sooner than later), but that's outside the scope of a focus on mitigating peak oil specifically.

But, because we use a relatively small amount of oil to directly generate electricity, the real issue will come in where renewable electricity must substitute for other uses of oil--primarily heating and transportation. Here, I think the situation is worse--meaning that I think the net savings by generating electricity will be far lower than 3:1, and may actually be negative (meaning we'll actually need to generate more joules of electricity than the number of joules of oil that we hope to displace).

It seems my comment is too long, so I'll continue it below...

Jeff Vail said...

When it comes to use of oil for heating, the initial savings are already lower (closer to 2:1, as you point out). We still have to deal with the infrastructure and intermittency issues, and these will be exacerbated by the increased seasonality of oil-based heating (meaning less intensive use of the infrastructure, making it relatively more expensive).

When it comes to use of oil for transportation, I think we're also looking at much lower than a 3:1 savings--and even more likely to be negative in reality. Here, not only do we need the infrastrusture investment, but making electricity portable (as in personal electric vehicles) will result in huge additional energy costs. While I agree with you that there may well be vast idle car manufacturing capacity that won't require new energy investment, and that could largely be converted to manufacturing PEVs, the embodied energy in the batteries will be massive. Of course, light rail and high-speed regional rail could avoid this battery issue, and I think actually pose a real potential for reaping the kind of savings that you talk about. However, that would require a near-term decision to effectively abandon the personal vehicle model and adopt a public transit vehicle. I think that's a decision we're very unlikely to make as a society (at least in the US), and as a result I think we'll go down the path of very inefficient (comparatively) PEVs.

So, when you look at the adaptation required to displace oil with electricity, I think we come out close to a wash when comparing joule to joule of energy input required. There may be some small savings based on the factors you point out, but I personally don't think we'll see anything on the order of 3:1, or even 1.5:1 savings. However, I think you raise an excellent point, and one that demonstrates the very complexity of this issue--one that deserves a great deal of further study...

Jeff Vail said...


I disagree that EROEI and energy payback times are really separate issues--different, certainly, but highly related. See my discussion on this point earlier in this series.

The reasons are several. First, our most promising technologies (wind, solar, tidal, geothermal) all seem to have useful lifespans on par with most industrial machinery--in the neighborhood of 25 to 40 years. I'm not a "believer" in thin film solar yet, but that may be an exception with significantly shorter lifespan. That said, if there is great variability of "true" EROEI, then your point may be valid. I don't think, however, that renewables actually exhibit a "true" EROEI range that is nearly as broad as you suggest--I think that reality is a range from less than 1 (industrial biofuels, algae, etc.) to perhaps as high as 4:1 or 5:1 for wind. I realize that most people will immediately point to various studies that show much, much higher EROEI values--that's one of the points of this series to show that these high figures are largely misguided to the extent that they purport to represent "true" (no system boundaries) EROEI calculations.

If you accept that renewables last 25-40 years, and have EROEIs between 1 and 5, then EROEI is very significant when it comes to scalability. If a wind technology has a generating lifespan of 35 years, there is a huge scalability difference between an EROEI of 2 and 5. Your point on the difference between EROEI and energy payback time is still well taken, but I maintain that we these figures are in no way superfluous. Instead, they are critical to understanding the practicality of any transition plan--we need to study them, both of them with an understanding of their differences, very carefully.

Jeff Vail said...


I think the huge hydropower plans in China represent ancillary dams in the Yellow River basin (mostly). My understanding is that hydropower works very much like oilfields--there are a few supergiants (with great EROEI), then several giants, a large number of small dam locations, and a huge number of micro-hydro viable sites. We simply can't double the number of supergiants (Grand Coulee, Three Gorges, etc.) each year the way that we theoretically can with solar, for example. We can double the number of microhydro locations for some time, but the sum total of this production will be relatively minor--much like you can't makeup for a few declining wells in Cantarell with hundreds of wells in KMZ that are closer to stripper wells...

So, long way of saying that I'm sure China will be able to double its number of dams in the next decade, but all of these new dams combined will generate less than Three Gorges. There are relatively few viable super-giant hydropower sites left in the world (even if you discount the environmental and cultural/human impacts of their placement). Hydropower can be great--by in my opinion its future role is more along the lines of pumped storage than peak oil mitigation.

Rice Farmer said...

Neil1947 -- Indeed the Earth receives much solar energy in a day, but due to factors such as intermittency and efficiency, we can only capture a tiny portion of it.

Also, the argument that we can generate all the electricity we need by putting up vast solar arrays in the desert completely ignores the points I have made about infrastructure maintenance and replacement, and the impossibility of bootstrapping -- factors which translate into continued dependence on fossil fuels. The bottom line is, real-time solar energy is simply not dense enough to replace fossil fuels.

Finally, here's an article everyone will find of interest.

Solar panels 'take 100 years to pay back installation costs'

Neil1947 said...

I await with anticipation your ananlysis of "true EROEI values" for wind energy. I will be very surprised if the values are as low as 20:1, and interested in what you consider are the system bouindaries.

Neven said...

Rice Farmer, I've read many articles like the one you posted. It's not that interesting wrt what Jeff Vail is writing, as it's more about money EROI than about energy EROI.

For me personally, I couldn't care less how many years it takes to have my solar panels paid back financially, as long as they compensate for the energy it took to produce, transport and install them and after a few years start producing surplus energy.

Nobody is talking about externalities in the article you linked to, such as the cost of climate change or peak oil. I have the money to spend, my next car will be less big (if and when I buy a new one). Besides, I live in Germany, and (financial) pay back time isn't that long here.

Rice Farmer said...

Hi Neven. I posted the article for everyone's interest; people can agree or disagree if they wish. I have a solar hot water heather. I figure it will eventually pay itself off, which is why I bought it, but the point I am making is, in the big picture it doesn't matter if solar equipment pays itself off or not. The important consideration is that we cannot manufacture, deploy, maintain, and replace renewable-energy infrastructure without fossil fuels. Calculating the EROEI is useful for knowing how long it will take a piece of equipment to recoup the investment, but that's all. Without access to energy-dense fossil fuels, the expansion of renewables comes to a halt. As Jeff once pointed out, if you send people to an island and give them lots of renewable-energy infrastructure and then ask them to recreate industrial civilization, it can't be done.

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AutumnPhoenix said...

Hahaha that last comment was certainly informative. Anyways, my question to Jeff, or anyone else who might know, is about the lifecycle and recycle-ability of the solar panel technology that would most likely be attempted to be rapidly scaled up. I heard somewhere that current solar panels only have a lifecycle of approximately 30 years before they're done for, and I know that recycling programs usually only have something along the lines of a paltry 30% conversion of waste back to usable material. I think these are important considerations to factor in, but I'd like to actually verify those claims first.

Jeff Vail said...


Good questions. I don't think we have very good, hard data on the life-span of solar photovoltaics, in part because it's a moving target, and the estimates for current production runs are just that.

However, the data on old panels (e.g. those produced in the 70s and 80s) suggests that the energy generation half-life (e.g. the number of years before they're producing only half their initial generation) is around 25 years. Newer panels are--I'm told--much better. In most cases, with new panels, the manufacturers warranty their products for 25 or 30 years, so that seems like a good, albeit conservative, estimate for modern technology. I think the engineering target is closer to 40-50 years, though with some degredation in generation. I've used 40 years at 100% generation in my calculations as I think this is realistic but conservative.

As for the recycling, there are two critical issues here: rare earth metals and energy. I've heard numbers somewhat close to what you've suggested: you can get around 25-50% of the rare earth elements out of photovoltaics with current reclycling methods. However, I've seen no numbers on energy for recycling. My guess is that you can get an even higher % of rare earth elements out if you put enough energy in, but I think you're going to rapidly invest more energy in recycling these rare earth elements than the next generation of photovoltaics they'll make will produce. This would be a great topic for a research project...