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dv82matt
SFN Regular
760 Posts |
 Posted - 08/18/2005 : 11:16:56 [Permalink]
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From Exit Mundi's page on the oil peak. (click on 'oil peak in the science section of the sidebar)quote:
...it costs more energy (oil) to actually build a windmill, than a windmill will ever generate during its entire lifetime!
This seems unlikely to me. If it were true then wind generators would make no sense at all. But I was wondering what the ratio of the energy input to output actually is, and how well does wind energy compare to other energy sources? |
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BigPapaSmurf
SFN Die Hard
3192 Posts |
Posted - 08/18/2005 : 12:19:10 [Permalink]
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| I would like to rescind my previous calculations, they may be faulty. |
"...things I have neither seen nor experienced nor heard tell of from anybody else; things, what is more, that do not in fact exist and could not ever exist at all. So my readers must not believe a word I say." -Lucian on his book True History
"...They accept such things on faith alone, without any evidence. So if a fraudulent and cunning person who knows how to take advantage of a situation comes among them, he can make himself rich in a short time." -Lucian critical of early Christians c.166 AD From his book, De Morte Peregrini |
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H. Humbert
SFN Die Hard
USA
4574 Posts |
Posted - 08/18/2005 : 12:41:26 [Permalink]
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Why can't they set up a wind farm in the Midwest that would supply a plant with the electricity to convert water from the Great Lakes to hydrogen. The hydrogen could then be stockpiled and used to run a conventional power plant to supply electricity to the grid. Extra hydrogen could be dispersed to local filling stations for vehicles.
What is wrong with this idea?
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"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes
"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman
"Face facts with dignity." --found inside a fortune cookie |
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dv82matt
SFN Regular
760 Posts |
Posted - 08/18/2005 : 14:03:39 [Permalink]
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quote:
Originally posted by H. Humbert
Why can't they set up a wind farm in the Midwest that would supply a plant with the electricity to convert water from the Great Lakes to hydrogen. The hydrogen could then be stockpiled and used to run a conventional power plant to supply electricity to the grid. Extra hydrogen could be dispersed to local filling stations for vehicles.
What is wrong with this idea?
I don't really know how to do the calculations but I think the problems boil down to efficiency and expense. Oil would have to be a lot more expensive that it is, in order for such a scenario to make economic sense.
First consider the energy cost of building and maintaining the wind tubines. Then add in the energy losses from converting mechanical energy to electricity and then to chemical energy (burning the hydrogen to produce electricity doesn't make sense to me since electricity is already produced in an earlier step). The hydrogen also has to be compressed into pressurised tanks, this also uses energy. In the end there's not much energy left over to actually power anything. |
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H. Humbert
SFN Die Hard
USA
4574 Posts |
Posted - 08/18/2005 : 14:18:27 [Permalink]
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quote:
Originally posted by dv82matt
(burning the hydrogen to produce electricity doesn't make sense to me since electricity is already produced in an earlier step).
Earlier it was said that wind turbines couldn't supply all the energy for the grid since wind is unreliable. Using wind to make hydrogen allows you to power a generator in a more consistant manner, increase output to meet demand as needed, and most importantly store excess energy.
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"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes
"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman
"Face facts with dignity." --found inside a fortune cookie |
| Edited by - H. Humbert on 08/18/2005 15:45:09 |
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dv82matt
SFN Regular
760 Posts |
Posted - 08/18/2005 : 15:04:08 [Permalink]
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quote:
Originally posted by H. Humbert
Earlier it was said that wind turbines couldn't supply all the energy for the grid since wind is unreliable. Using wind to make hydrogen allows you to power a generator in a consistant manner, as well as to increase output to meet demand as needed, and most importantly store excess.
Good point.
It's a very inefficient process though (about 25% efficient at present). You'd be better off using the electricity to pump water into the reservoirs of hydro-electric plants. |
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 08/18/2005 : 15:30:25 [Permalink]
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quote:
It's a very inefficient process though (about 25% efficient at present). You'd be better off using the electricity to pump water into the reservoirs of hydro-electric plants.
None of our current power sources are what you'd call efficient, really.
We just compensate by massive use of resources.
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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dv82matt
SFN Regular
760 Posts |
Posted - 08/18/2005 : 23:08:34 [Permalink]
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quote:
Originally posted by Dude
None of our current power sources are what you'd call efficient, really.
We just compensate by massive use of resources.
I don't know. I'd say that in general our power sources (including coal and oil) are as efficient as we can make them.
Different power sources obviously face different challenges. For example hydrogen burns cleanly and efficiently, but has low energy density and is expensive to transport and store. Oil burns less efficiently, but has a much higher energy density and is cheap and easy to transport and store. Right now the advantages of oil far outweigh its disadvantages (speaking economically here, not environmentally).
As technology improves and the price of oil continues to climb the hydrogen economy becomes more and more feasible, but it's unlikely to ever bring about a return to super cheap energy. |
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R.Wreck
SFN Regular
USA
1191 Posts |
Posted - 08/19/2005 : 05:36:39 [Permalink]
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quote:
Originally posted by Dave W.:
R.Wreck, how does one properly convert between kWh and required generation wattage? Assuming a steady flow and no peaks, is it as simple as multiplying, say, 3.6 Mw by 24 for kwh in a day's use, or by 24*365.24 for kwh for a year's use? I mean, is it the case that if that 3.66 trillion kwh were evenly spread over a year and over geography, we'd need 418 Gw of generating capacity going 24/7?
Yes, your calcs are correct. Due to actual usage patterns of peaks and valleys, time for maintenance, the need for spinning reserve, etc., you need to install more capacity than the average usage. Installed US generating capacity in 2003 was 932GW. So the system needs about twice the generation of the average use based on how our grid is actually built. Based on what I've seen for my company's peak and average load patterns, that seems about right.
quote:
If so (going back to dreaming, here), with your generous 50% capacity factor, and a 30% availability factor for wind, then we'd really need 2790 Gw of generation, or about 620,000 of those 4.5 Mw monsters. Guessing at 4 per square km, we can install all of them on 155,000 km2 of land (or sea), or about the size of Georgia. Yeah, 2% of the US - including Hawaii and Alaska.
My 50% capacity factor was the amount of generation compared to the theoretical maximum for all factors, including wind availability. That's why I considered it generous. A little googling came up with actual capacity factors averaging around 30% for wind. I'm not sure how much wind power you would need to install to ensure you met your peak load, given the variability of its production, but I believe it would be substantially higher than the currently installed 932 GW, a good portion of which operates with much higher capacity factors. 2000 or more GW is probably in the ballpark. |
The foundation of morality is to . . . give up pretending to believe that for which there is no evidence, and repeating unintelligible propositions about things beyond the possibliities of knowledge.
T. H. Huxley
The Cattle Prod of Enlightened Compassion
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 08/19/2005 : 07:55:10 [Permalink]
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quote:
I don't know. I'd say that in general our power sources (including coal and oil) are as efficient as we can make them.
Which isn't the same thing as actually being efficient. The actual % of potential power from a chunk of coal that gets delivered as usable power to the grid is a fraction of the total potential power of that chunk. I don't recall what the % is, its been a while since I've read anything on it, but its certainly not high enough to call the process efficient.
quote:
For example hydrogen burns cleanly and efficiently
There are many issues with hydrogen as a fuel source. And, overall, as a source of motive power for automobiles via hydrogen fuel cells it is far less efficient than oil, in terms of the potential energy that actually can be converted into force to move your car.
IF efficiency were the only concern or issue it would make far more sense to continue to use fossil fuels.
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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BigPapaSmurf
SFN Die Hard
3192 Posts |
Posted - 08/19/2005 : 10:02:31 [Permalink]
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I never knew about the solar power generators which use mirrors to focus sunlight onto a tower full of molten salt, which in turn boils water, very cool.
http://www.boeing.com/assocproducts/energy/powertower.html |
"...things I have neither seen nor experienced nor heard tell of from anybody else; things, what is more, that do not in fact exist and could not ever exist at all. So my readers must not believe a word I say." -Lucian on his book True History
"...They accept such things on faith alone, without any evidence. So if a fraudulent and cunning person who knows how to take advantage of a situation comes among them, he can make himself rich in a short time." -Lucian critical of early Christians c.166 AD From his book, De Morte Peregrini |
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Robb
SFN Regular
USA
1223 Posts |
Posted - 08/19/2005 : 10:28:35 [Permalink]
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quote:
Originally posted by Dude
Which isn't the same thing as actually being efficient. The actual % of potential power from a chunk of coal that gets delivered as usable power to the grid is a fraction of the total potential power of that chunk. I don't recall what the % is, its been a while since I've read anything on it, but its certainly not high enough to call the process efficient.
Most coal plants are around 35% efficient. An efficiency in the high 30's is very good. A combined cycle natural gas plant can be greater than 50% efficient with efficiencies in th emid 50's being very good. For plants of any type, there is a maximum theoretical efficiency that can be achieved and it is not 100%. It depends on the heat source and heat sink temperatures. With this in mind our plants are highly efficient. With an increase in only 1% efficiency in some plants millions of dollars can be saved in operating costs. This is a big incentive for these plants to develop technology to improve efficiency.
quote:
There are many issues with hydrogen as a fuel source. And, overall, as a source of motive power for automobiles via hydrogen fuel cells it is far less efficient than oil, in terms of the potential energy that actually can be converted into force to move your car.
Some issues are how do we distribute the hydrogen, there are not any hydrogen pipelines throughout the country. Also, with the amount of hydrogen we would need, we would have to make plants that make hydrogen from seawater. What would we run these plants with?
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Government is not reason; it is not eloquent; it is force. Like fire, it is a dangerous servant and a fearful master. - George Washington |
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Dave W.
Info Junkie
USA
26020 Posts |
Posted - 08/19/2005 : 11:53:28 [Permalink]
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quote:
Originally posted by Robb
Also, with the amount of hydrogen we would need, we would have to make plants that make hydrogen from seawater. What would we run these plants with?
Big honking windmills and/or molten-salt boilers.
Seriously, without tremendously huge batteries, converting electricity to hydrogen for storage makes some amount of sense. It'll sit for long periods (mostly without disturbing anyone), and it's transportable by a variety of methods (pipeline, truck, ship, etc.).
Small-scale power-generation windmills for underdeveloped areas typically don't generate electricity directly, but instead just pump water up to a big tank. It is water draining from that tank which turns a generator. This is done so that it's still possible to have power without wind, as the water tank acts as power storage.
Similarly, storing power derived from wind, solar or other sources as hydrogen makes sense. A power-storage medium with better efficiency than hydrogen would make more sense, but does one exist for which the source material is as ubiquitous as water?
I mean, it'd be great if the currently-under-test reprocessing of chicken guts into not-so-fossil fuels could do the job better than hydrogen (thus also eliminating the need to refit gas stations as hydrogen stations), but it would mean putting the windmills or other primary power sources next to poultry processing plants, and not anywhere near a large body of water.
By the way, if one includes the burning of coal (or other fuel) as a power source for the electrolysis of sea water for conversion to hydrogen, the oxygen "byproduct" may (I'm not sure) be useful to "supercharge" the fuel-burning process. Maybe? |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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dv82matt
SFN Regular
760 Posts |
Posted - 08/19/2005 : 17:57:51 [Permalink]
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quote:
Originally posted by Dave W.
Seriously, without tremendously huge batteries, converting electricity to hydrogen for storage makes some amount of sense. It'll sit for long periods (mostly without disturbing anyone), and it's transportable by a variety of methods (pipeline, truck, ship, etc.).
Wikipedia has a good article on the hydrogen economy that explains some of the problems with storing and transporting hydrogen.quote:
Small-scale power-generation windmills for underdeveloped areas typically don't generate electricity directly, but instead just pump water up to a big tank. It is water draining from that tank which turns a generator. This is done so that it's still possible to have power without wind, as the water tank acts as power storage.
Similarly, storing power derived from wind, solar or other sources as hydrogen makes sense. A power-storage medium with better efficiency than hydrogen would make more sense, but does one exist for which the source material is as ubiquitous as water?
I think you answered your own question. Pumped storage %70 to %85 efficient. 
Transmission losses from remote locations would have to be pretty steep before it would make economic sense to use hydrogen for general purpose energy storage. |
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Dave W.
Info Junkie
USA
26020 Posts |
Posted - 08/19/2005 : 22:02:47 [Permalink]
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Obviously, Matt, I wasn't thinking about the economic aspects of hydrogen storage and transport, which apparently are fairly dismal. Also obviously, I was unaware of other possible power-storage solutions.
Though the idea that pumped storage is that efficient was news to me. So now, the idea would be to empty Washington state ('cause it's rainy there), dump up to a mile of dirt onto it to build a giant basin, line the basin's edges with windmills (and rows of them out into the ocean) to power pumps sucking up sea water from the Pacific, and then let the water drain through some massive generators so that there's a more-or-less constant over-supply of power, enough to overcome long-distance transmission losses, even. I mean, according to the Wiki article you linked to, Matt, there's a pumped storage facility in New York capable of churning out over 2.8 Gw, which is more than my wind estimate for the whole of the U.S. at a 15% capacity factor.
Yeah, that'll do it. When do we start?
Edited to add: one wonders (well, I wonder) how much of the inefficiency of pumped storage is due to simple evaporation. Some of the water you expend energy pumping up just floats away on the wind. |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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