Posted: Wed Jun 23, 2004 2:54 pm Post subject: EROEI: Energy Returned on Energy Invested (merged)
While I can't argue with the stated EROEI numbers for renewable technologies, they are admittedly low, couldn't one argue that over time the EROEI for renewables will only increase, whereas, over time, the EROEI of fossil fuels will only decrease?
Can this be another argument in support of public support for renewables?
Joined: May 23, 2004 Posts: 276 Location: Melbourne, Australia
Posted: Fri Jul 09, 2004 4:32 am Post subject: Re: renewables EROEI
tkn317071 wrote:
While I can't argue with the stated EROEI numbers for renewable technologies, they are admittedly low, couldn't one argue that over time the EROEI for renewables will only increase, whereas, over time, the EROEI of fossil fuels will only decrease?
Can this be another argument in support of public support for renewables?
Well, for starters, it's not true. That may not stop uninformed people from trying to use it as an argument (not that arguments actually result in homes being heated during cold weather or people moving from A to B).
Without ready access to fossil fuels, production of solar panels and other renewable energy collectors will become very very hard.
Do you know how high the temperatures needed to (for example) crack silicon are? Do you therefore appreciate how unlikely it is that renewables could be used to make more renewables? If you assume that it basically won't be a self-sustaining process, what happens to the process when the competing demands for high value energy sources are too high? _________________ The purpose of human life revolves around an endless need to extract ever increasing amounts of carbon out of the ground and then release it into the atmosphere.
Posted: Fri Jul 09, 2004 5:47 am Post subject: Re: renewables EROEI
MrPC wrote:
Without ready access to fossil fuels, production of solar panels and other renewable energy collectors will become very very hard.
Do you know how high the temperatures needed to (for example) crack silicon are?
The next generation of solar cells are not based on silicon.
Why not silicon? I mean, organic solar cells are exiting technology and should be pursued, but at the moment silicon is the better option.
The disadvantages of silicon are obvious, being the high production costs, and low energy yield. On the other hand the advantages are that the technology is commercially proven, the materials used (silicon, boron and phosphorus) are among the most abundant in the world and are non-toxic.
Organic solar cells have the advantage that they can perhaps be mass-produced cheaply and could in theory have a very high efficiency. On the other hand it is unproven technology. There are prototypes, which have a high yield and there are prototypes, which have a high durability. None of them have both. It will at least take several years to tackle this problem.
http://soe.stanford.edu/AR01-02/pr_m.html
There are also some other disadvantages, which are rarely mentioned. The organic molecules, which are used, are often complex (like fullerenes).
An organic solar cell is only partly organic. Nanocrystalline semiconductors are incorporated to catch the sunlight. Current high-yield prototypes are based on arsenides (Toxic and in most countries forbidden) and rare (and expensive) metals like Indium.
TiO2 is a low cost and non-toxic alternative, but this will never give a high yield since the bandgap is too large. So it is by no standard easy technology and a lot of work has still to be done. It is doubtful whether the final product will match the very optimistic forecasts, which are made at the moment.
I wouldn’t put all my eggs in that basket. There is plenty of room to optimize the silicon panels and their production, so I would give that priority. A second research track would be the development of organic solar cells.
Well, for starters, it's not true. That may not stop uninformed people from trying to use it as an argument (not that arguments actually result in homes being heated during cold weather or people moving from A to B).
Admittedly, I am not fully informed of all the intricacies of solar cell production and I'm sure it does take a lot of energy to make them. (they do,nevertheless, have a positive EROEI do they not?)
But for the sake of argument, what I am suggesting is that while we still have some oil/gas left if we use it in a focussed way to improve RE technology production...just as every technology (e.g. computers) has improved over time, why wouldn't RE technologies? Also, I wouldn't be so naive as to suggest that solar technology exclusively be used to make solar technology. Methane from cow manure or landfill gas or ethanol could be used (all renewable, high heat content). True, it might temporarily boost the cost of production, but OVER TIME wouldn't that cost naturally decline as improvements and innovations are found?
I'm not suggesting that renewables will be able to replace fossil fuels, I'm pretty convinced that nothing will ever be able to perfectly substitute for the stored energy of millions of years of organic life, but I am suggesting that renewables must be strongly emphasized now and in the future.
Joined: May 23, 2004 Posts: 276 Location: Melbourne, Australia
Posted: Sat Jul 10, 2004 3:56 am Post subject:
tkn317071 wrote:
Admittedly, I am not fully informed of all the intricacies of solar cell production and I'm sure it does take a lot of energy to make them. (they do,nevertheless, have a positive EROEI do they not?)
Barely. Nowhere near what's needed. Just having a positive EROEI (self-contained process) is a different question to having 10+ EROEI (genuinely positive)
tkn317071 wrote:
But for the sake of argument, what I am suggesting is that while we still have some oil/gas left if we use it in a focussed way to improve RE technology production...just as every technology (e.g. computers) has improved over time, why wouldn't RE technologies?
Well, what we make now will probably last 20-40 years. If TSHTF in about 5 years, what happens in 25-45 years? _________________ The purpose of human life revolves around an endless need to extract ever increasing amounts of carbon out of the ground and then release it into the atmosphere.
Silicon is the most likely future technogy for solar cells. They promise reasonable efficiency 15 - 20%, the materials are abundant and non-toxic as stated earlier and technological improvements are continuously reducing the amount of silicon required. Remember, silicon is the 2nd most abundant element on earth behind oxygen, we will never run out of silicon.
Think monocrystalline thin films, spherical bead silicon and other technologies that reduce the need for silicon and in some cases the required purity level. Most solar cells are presently made from electronics grade silicon which require much higher purity than solar grade applications. Solar grade silicon using less energy intensive processing will eventually take over the task.
It must also be noted with regards to solar cell manufacturing that high temperature metallurgical silicon manufacture may be feasible using concentrated solar heat especially in desert locations. In fact purity levels would likely exceed electric furnace purity levels given the absence of carbon anodes etc.
According to most estimates that I have read, solar cells in general have EROEIs between 5 and 10 which certainly is a useful figure. It certainly beats the EROEI of tar sands oil (2), the EROEI of lower 48 U.S. oil (~ 4 - 5), ethanol production (1.3), biodiesel production (3) etc. The alternative energy technologies better than solar photovoltaics are: solar thermal, nuclear if associated long term costs are ignored, wind and hydro. It must be noted as well that the solar cell technologies I mentioned above have the technical potential to have EROEIs of 10 - 20% in the same region with wind and the others.
Joined: May 21, 2004 Posts: 158 Location: Melbourne, Australia
Posted: Sun Jul 18, 2004 12:54 am Post subject:
MrPC wrote:
Barely. Nowhere near what's needed. Just having a positive EROEI (self-contained process) is a different question to having 10+ EROEI (genuinely positive)
Am I the only one who thinks all this debate about EROEI's is a bit of a sideshow? Mainly because it's a nonsense concept.
The problem is not a shortage of energy generally. It is the approaching peak and decline of one particular energy source - oil - and its cousin natural gas a couple of decades thereafter.
The fact that plants only convert into biological matter less than 1% of the energy in the sunlight that falls on them does not mean that plants are worthless as a source of energy (and I use the word broadly, to include food). Trying to add up all the energy used in setting up a particular energy-harvesting system assumes all energy is created equal when it isn't.
I am not saying energy inputs are irrelevant. It is important to look at what inputs are required and what the opportunity costs of particular systems are. But the fact that manufacturing solar cells might require a lot of heat - indeed, on paper more heat than the electricity they produce over their lifespam - tells us nothing about whether solar panels are a worthwhile technology to deploy.
If, for example, solar panels were made, and could only be made, from a particular oil-based plastic, and this plastic was not recyclable, and there was no other product that could replace it, that would severely limit their utility. But they're not. I don't doubt you need a lot of heat to manufacture the silicon, but there are plenty of ways to get heat.
Posted: Sun Jul 18, 2004 6:59 am Post subject: New Mindset
Right now the new mindset needed for myself is just joining a forum and using the Internet for such discussions. It does well in bringing like minded people together, even if we would likely not pay any heed to eachother in anyway, otherwise. As a "new guy" or "cherry" to this group should preclude that I sit in the background for sometime, I cannot but make one observation so far and that is one of fear and a demand to get all the facts on Peakoil so that we may better able to defend ourselves and loved ones from the "New World Order' that senior Bush warned of 14 years ago. It seems the basic theme behind all that is being discussed. Denial, anger, depression, acceptance, is the norm for humans facing traumatic events. Anyone studing not only Peak Oil but also the present human condition cannot but feel something is not right with the currant state of affairs. If we could be more honest about our personel fears in such discussions, it would give us a better basis for understanding the whole equation, and to promote a better understanding. I believe our greatest enemy will be ourselves and our own present circumstances as this new reality unfolds.
It's not that solar EROI is so crummy... it's that hydrocarbon's EROI is so great that constitutes the problem.
If we stipulate that Oil has a return of around 50:1 and compare this to the "alternatives" EROI the problem becomes clear.
I'm not doubting that alternatives (solar) can produce energy on an individual basis, but the "heavy lifting" which supports our world culture comes from fossil fuels. Fine, econo boxes can run on hydrogen. PV can trickle electric to some battery storage. Algae can produce some bio fuel.
It's the order of magnitude that counts.
An analogy: A train traveling at 50 mph using coal for power runs out of coal halfway to it's destination. The conductor is forced to burn wood to continue the journey. Since wood burns at a lower temperature than coal, the best speed we can now achieve is 10 mph. The trip that started off as a 2 week journey now takes a month and a half. Meanwhile I have a train full of passengers expecting a 2 week trip, and only enough supplies on board for that timetable. So what do we do? We will never all make it on the food & water we have... not with that many people. We have a choice... keep going as normal, and everyone starves or we kick off some of the passengers to reduce our needs.
Alternatives assume that along the train tracks somewhere, we will find a coal alternate which equals the EROI of coal, and propel us back up to 50 mph. Perhaps we will find this power source... & perhaps not. _________________ "When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours." - Stephen F Roberts.
Joined: May 21, 2004 Posts: 158 Location: Melbourne, Australia
Posted: Sun Jul 18, 2004 8:23 am Post subject:
Aaron wrote:
If we stipulate that Oil has a return of around 50:1 and compare this to the "alternatives" EROI the problem becomes clear.
I'm not doubting that alternatives (solar) can produce energy on an individual basis, but the "heavy lifting" which supports our world culture comes from fossil fuels. Fine, econo boxes can run on hydrogen. PV can trickle electric to some battery storage. Algae can produce some bio fuel.
It's the order of magnitude that counts.
I don't think I agree. All this means is that we can't go on being as prolific as we have been in consumption of energy, particularly in the sectors which are less able to switch away from oil (predominantly transport).
The suggestion that this will bring down civilisation as we know it and cause millions to die is just fanciful. It will cause economic disruption - and that disruption will be relatively worse in the places that rely most heavily on oil and gas, and have not bothered to put alternatives in place before the crisis.
Barely. Nowhere near what's needed. Just having a positive EROEI (self-contained process) is a different question to having 10+ EROEI (genuinely positive)
Am I the only one who thinks all this debate about EROEI's is a bit of a sideshow? Mainly because it's a nonsense concept.
The problem is not a shortage of energy generally. It is the approaching peak and decline of one particular energy source - oil - and its cousin natural gas a couple of decades thereafter.
The fact that plants only convert into biological matter less than 1% of the energy in the sunlight that falls on them does not mean that plants are worthless as a source of energy (and I use the word broadly, to include food). Trying to add up all the energy used in setting up a particular energy-harvesting system assumes all energy is created equal when it isn't.
I am not saying energy inputs are irrelevant. It is important to look at what inputs are required and what the opportunity costs of particular systems are. But the fact that manufacturing solar cells might require a lot of heat - indeed, on paper more heat than the electricity they produce over their lifespam - tells us nothing about whether solar panels are a worthwhile technology to deploy.
If, for example, solar panels were made, and could only be made, from a particular oil-based plastic, and this plastic was not recyclable, and there was no other product that could replace it, that would severely limit their utility. But they're not. I don't doubt you need a lot of heat to manufacture the silicon, but there are plenty of ways to get heat.
I think exactly the opposite. EROEI is the central piece of information.
It is true that you could "get heat" from some other operation...but that would be part of the "energy return" of that operation.
As far as solar, the question is "can it stand on its own" or is it dependent upon cheap energy in its construction. If a solar cell takes x units of energy to make and delivers x over its life, then it is no solution to the problem of declining energy sources.
As for plants, alot of people make that analogy but it's wrong. Plants get 1% of energy, but this is free energy for them, that's all they do. How much energy do they expend to obain that 1% energy from the sun? Not much! That is why they are viable. Now how much energy do WE spend harvesting them? Maybe less energy than they provide. But since we can eat plants and not oil, it doesn't matter.
If you invest a barrel of oil into the ground and get 30 back, then it is easy to see that no matter how wastefully you use that 30 barrels, it's positive EROEI of 30 is worthwhile. IE you can always sink 1 of the 30 barrels into the ground and get another 30. Even if you waste most of teh resultant energy in wasteful ways...it's still easy to get more.
Maybe you can use waste heat and thus increase that operations (the one that produced the waste heat)'s energy return. Or maybe you could just "not count" that energy requirement (energy in) when making solar. Solar energy would be kind of a way of storing that heat and distributing it slowly.
As long as there are sources of waste heat which would otherwise be discarded, it makes sense.
However, without waste heat, if solar has a EROEI of 1, then it is doomed. Right now they make solar with cheap coal energy, etc. So what if there is no coal, gas, oil...can you use solar energy to create electricity with which it not only replaces itself but is a net generator of power to the grid or wherever? If so, then great. If not, then it is at best, dependent on other energy sources and people who claim it will solve all our problems are simply mistaken.
As the price of coal goes up, the price of the PV electricity will go up too. When there is no coal and no other energy, PV wil have infinite expense.
Joined: Jun 26, 2004 Posts: 1189 Location: Madison,Wisconsin
Posted: Sun Jul 18, 2004 3:54 pm Post subject:
I was just talking with someone with the Chat name Madrid about peak oil on the peak chat function of the website. ( definte need for improvement there in both the function and the amount of people using it) But one thing we both agreed on is it is not so much a problem of actual production of food as it is the transport of that food. Your telling me that all the food you eat in a day is near enough that it would be easily transported without cheap oil? I don t know if that is true for u, but I know for me it is definatly the opposite. Most of the food I eat comes from thousands of miles away, and if the just the stuff i get from inside the US starts getting harder and harder to ship because of fuel costs, it will suddenly become ALOT less expensive to just go to my local farmers market and get some food rather than hit the grocery store. _________________ Azreal60
Posted: Wed Jul 21, 2004 4:58 am Post subject: EROEI: Energy Returned on Energy Invested
Hi there. I am sure we are all aware that there is no point in extracting a barrel of oil when it takes a barrel of oil to extract it. Can any one shed light on how much oil is used converting a barrel of oil to usable products e.g. petrol?
How much sooner would a well become un economic because of this factor?
thanks, Laurie
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