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Post by Jesus R on Jul 24, 2012 4:22:46 GMT 9.5
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Post by anonposter on Jul 24, 2012 4:53:25 GMT 9.5
It's only more efficient if you ignore the fact that PV doesn't work when we need it to (i.e. when we want power, which is not necessarily when the sun is shining, unless of course you are in space well away from a planet where solar actually does make sense). Besides, had you bothered to read that study you'd have noticed: Hence, taken in isolation, EROI is arguably a rather poor indicator of the long-term sustainability of an energy exploitation system, and making far-reaching policy decisions only based on this one metric is not recommendable. Ultimately energy return on investment is mainly relevant to the question of whether a technology can do the job (if the EROI is less than 1 then it doesn't have a chance at primary energy) though of course we would also expect EROI to correlate with economic viability as well though even there any correlation would be weak. Of course for PV you'd have to take account of the storage and the need for massively excess generation capacity (we're talking of the order of 5 times peak usage) due to the low capacity factor of the solar panels. Once you do that I wouldn't be surprised if the EROI dropped down way down (though still at a point at which you'd get more energy out than you put in). |
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Post by Graham Palmer on Jul 24, 2012 12:14:15 GMT 9.5
The paper notes (pg 580/1)
On the other hand, PV is not a base-load technology,and deploying it on a large scale, beyond approximately 20% of grid penetration, may require building an extensive energy storage infrastructure....Most importantly, a fully-fledged long-term analysis of the EROI of PV vs conventional energy generation cannot be done by analysing the individual systems in isolation. Such analysis would instead require accounting for combinations of different renewable energy generation systems, their interconnections and storage to satisfy regional or global load demands. Also, as deployment increases, minor additional losses in life cycle efficiency might at times be caused by the necessity to compensate for intermittency with lower-efficiency marginal technologies.
Hence the paper is deliberately only taking a narrow look at the EROI of PV. To me, the problem of EROI is not the biggest challenge for PV anyway, so I don't think there is too much that can be read into the conclusions other than that improvements in the fabrication of PV has resulted in substantial improvements in the EROI, which is sort of a mute point given that PV cannot function in a grid without large scale conventional energy.
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Post by davidm on Jul 24, 2012 12:50:01 GMT 9.5
Frankly it's not clear to me why intermittency is treated as such an overwhelming problem. Overseas empires were built on the intermittency of the wind. One of the marks of great building construction is averaging out the intermittency of the sun. Intermittency is how our whole daily and seasonal life cycle works. It defines natural process. We couldn't survive without it.
"Roll on Columbia, roll on. Your power is turning the darkness to dawn." It's like we have some God impulse inside and we don't know how to humbly back off and adapt like normal creatures. So we're killing the goose that lays the golden eggs.
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Post by Graham Palmer on Jul 24, 2012 15:17:27 GMT 9.5
Overseas empires were built on the intermittency of the wind. My g.g.g.g.grandfather was shipped out from England for stealing in the 1840s, the trip taking about 250 days. Why would any rational person choose to waste a day in a newfangled Airbus A380 when they could enjoy a leisurely cruise on a sail boat taking 6 months? ;D |
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Post by proteos on Jul 24, 2012 17:44:18 GMT 9.5
Frankly it's not clear to me why intermittency is treated as such an overwhelming problem. Because we can't store electricity at very large scale. Every example you give are case where any energy goes into a store, with sometimes disappointing results (such as sail boats). Wind mills were well known before the Industrial Revolution. But they were superseded by machines working with coal, a reliable store of energy. Hydropower survived because it allows to store energy (dams) or the power variations are smooth (run of the mill). Beside whatever you do, storing energy means you stand to lose some and the infrastructure will cost you something. Alternatively you can rest on some existing store of energy and today, it's fossil fuels! The infrastructure needed is also more extensive than with dispatchable sources. You just have to look at the crazy transmission needs of 100% renewables scenarios. |
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Post by davidm on Jul 24, 2012 21:23:24 GMT 9.5
Overseas empires were built on the intermittency of the wind. Hmmm the Aussie convict bit.  He obviously wasn't acquainted with fast boats to China like the clipper ships. In any case what's the rush? There are things to do when the wind isn't blowing like fish and swim and read and repair stuff. A lot of this seems to be a matter of philosophy. Adapting to conditions or changing conditions to adapt to you. To keep us from going off the cliff it would seem to be we have to consider shifting our emphasis more to the former, the more natural intermittent way. I think it will be after I die when we start seriously shifting back to sail transport but I think it will eventually happen. Hard to beat that free nonpolluting wind, when we start scaling down. |
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Post by davidm on Jul 24, 2012 21:30:35 GMT 9.5
Frankly it's not clear to me why intermittency is treated as such an overwhelming problem. .... Wind mills were well known before the Industrial Revolution. But they were superseded by machines working with coal Coal isn't looking very good these days. |
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Post by anonposter on Jul 24, 2012 21:48:18 GMT 9.5
Whilst the clippers were fast when the wind was blowing (and the wind does tend to be less unreliable over the ocean than on land) they had a speed of zero when the wind died down (and it did happen from time to time). One other thing you'd need to deal with if you want to switch back to sails is labour, the old style sailing ships simply require too many crew to be viable (though I imagine you could have the rigging done by electric motors).
Looking at the history of shipping pretty much as soon as fossil fuels developed to the point at which they could get near the performance of sail they took over completely to the point at which the only use of sailing ships these days is recreation. Most likely fossil fuels will be replaced in large ships with nuclear which we already know can be economical for merchant shipping (for serious icebreaking it's already better than fossil fuels).
At the very least we don't tend to see a switch back to sail when oil prices go up.
In the early days of steam it was common for the fossil fuels to be an auxiliary power source used in battle or when winds were low with sails used as the primary propulsion to get a ship where it needed to go and this could be a viable solution to shipping though will probably not end up being used much in the long term (even though we should probably expect a lot of fossil fuel powered ships to supplement their diesel engines with some form of sail as a form of greenwashing, it might even save more in fuel costs than the sails cost to install).
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Post by proteos on Jul 24, 2012 23:09:02 GMT 9.5
.... Wind mills were well known before the Industrial Revolution. But they were superseded by machines working with coal Coal isn't looking very good these days. Depends who you're talking to. I posted an IEA report showing that really dirty coal power plants were built in droves in China this past few years. Germany prefers lignite to nuclear power. It's true coal was abandonned in many uses, mainly because oil and natural gas replaced it. |
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Post by davidm on Jul 25, 2012 2:50:23 GMT 9.5
Coal isn't looking very good these days.
Depends who you're talking to. I posted an IEA report showing that really dirty coal power plants were built in droves in China this past few years. Germany prefers lignite to nuclear power.
It's true coal was abandonned in many uses, mainly because oil and natural gas replaced it. I meant in environmental terms. An angry Mother Nature is coming for fossil fuel even if the peak might be delayed a decade or so. Wind enjoys her favor. ;D |
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Post by davidm on Jul 25, 2012 3:10:58 GMT 9.5
One other thing you'd need to deal with if you want to switch back to sails is labour, the old style sailing ships simply require too many crew to be viable. With a lot of unemployed youth high labor could be a positive. What a glorious way to get into the work force. On the other hand I sailed a good part of the pacific by myself in a 35 food sailboat. Fossil fuel dominance came at the expense of downstream costs. Those costs are starting to come due. For smaller shipping sailing should become dominant. Diesel may be kept as a backup to power through the doldrums. ;D |
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Post by anonposter on Jul 25, 2012 4:01:04 GMT 9.5
With a lot of unemployed youth high labor could be a positive. OTOH it would likely come at the expense of the rest of the economy. Though it might be worth coming up with a contingency in case Marshall Brain turns out to be right but that's a whole other flamewar. What a glorious way to get into the work force. For some people, maybe, but it's not for everyone. On the other hand I sailed a good part of the pacific by myself in a 35 food sailboat. Would you want to spend most of your working life doing it? Likely with a boss and deadlines (though of course with sail the customer is just going to have to be a bit flexible about when their stuff arrives). Fossil fuel dominance came at the expense of downstream costs. Those costs are starting to come due. A better assessment would be that there a limit to how much we can use fossil fuels before having an adverse environmental effect on the planet. The downstream costs could have been mostly avoided if we got off them sooner. For smaller shipping sailing should become dominant. Even that is doubtful, nuclear probably can't scale down enough for a speedboat (though the high power density and good neutron economy of MSRs should allow them to go pretty small, at least technically, economically is another matter) but synthetic hydrocarbons or biofuels (if they would otherwise go to waste, I don't think we should be specifically growing them) should be able to do the job for smaller boats. As I noted before, there wasn't any shift back to sailing during past oil price shocks. Ferries used for public transport might be able to use batteries (with all boats in service during the peaks and some charging outside peak). Diesel may be kept as a backup to power through the doldrums. ;D I understand a lot of sailing vessels do have a diesel engine of some kind, either as just a generator or for propulsion when the wind isn't blowing (I understand a lot of the live-aboard sub-culture does things like that). Of course it isn't so much the smaller boats which matter, it's the big ones our civilisation depends on (they also use more fuel and cause more emissions, not just of CO 2, marine diesel is incredibly dirty). |
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Post by davidm on Jul 25, 2012 5:11:08 GMT 9.5
With a lot of unemployed youth high labor could be a positive. OTOH it would likely come at the expense of the rest of the economy. Not my version of it. Civilizations sometimes change from big to small. Ask the Mayans. |
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Post by anonposter on Jul 25, 2012 5:28:32 GMT 9.5
Civilizations sometimes change from big to small. Ask the Mayans. An example of what we want to avoid. |
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Post by proteos on Jul 26, 2012 0:14:04 GMT 9.5
I meant in environmental terms. An angry Mother Nature is coming for fossil fuel even if the peak might be delayed a decade or so. Wind enjoys her favor. ;D Yes: in environmental terms everyone agrees with you. Just with the SO2 pollution and others dangers of coal, everyone knows that coal has a dark side  But some people are ready to cope with all those woes, just because coal is a practical store of energy. This shows, I think why intermittency is such a problem! We want things done when we need them, so we want to be able to harness energy mostly anytime we want. |
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He obviously wasn't acquainted with fast boats to China like the clipper ships. In any case what's the rush? There are things to do when the wind isn't blowing like fish and swim and read and repair stuff.