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07/18/2008 05:52:56 PM · #51 |
Originally posted by kenskid:
Seems like it was using electricity from the solar panels to strip Hydrogen off of "rain"...this process is "electrolysis".
From your discription I don't know how hydrogen was used to heat the home. Was it "burned" to produce heat or did they use the hydrogen in a "fuel cell" to produce electricity?
EDIT: However, it seems strange to have a solar powered house and use almost 2/3 of the solar power to strip hydrogen to produce electricity. It's like using one source of electricity to produce another source.
Originally posted by togtog:
This is somewhat off topic but it is also completely on topic so I apologize...
Several months ago on a home improvement show they had a solar powered house. However it appeared from what I understood not hearing the whole story, that instead of having a battery bank to charge up, it instead used the solar to produce electricity then used that to convert rain water into hydrogen and oxygen which were stored, compressed somehow it appeared, in tanks, then when power was required, the hydrogen and oxygen would be recombined producing optional heat for the home. They did not explain why they went this way instead of with more standard lead-acid batteries.
Has anyone heard of a system like this? |
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07/18/2008 05:57:40 PM · #52 |
"The electricity from the solar feeds into this box that regulates it, and here is where the water is separated into the hydrogen and oxygen and stored in these tanks until needed." "That's a great set up I can see how it can really be useful to have a system like this."
Paraphrased, sadly that is about the extent to what they said about it :/
ETA: Forgot a detail...
"This white line here this carries the water produced back into the holding tank." "Where the rain water is collected, so nothing is wasted. Good deal!"
Message edited by author 2008-07-18 18:01:21. |
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07/18/2008 06:03:25 PM · #53 |
Originally posted by kenskid:
But did you see this:
"For example, electrolysis consumes a lot of electricity to free up hydrogen that then has to undergo expensive processing and transport, only to be turned back into electricity via the fuel cell. By one estimate you've wasted three quarters of the energy that was initially available just to get it to the car."
That's pretty close to being inefficient. |
And what do all the other estimates (besides your "one") say? Right now, that electricity produced by coal-fired plants (and hydro and all other centrally-generated electricty) is transported over high-tension power lines to the places it's needed with a loss of something like 90%. That's pretty inefficient too.
One of the reasons Edison lost out to Tesla in the battle over whether to electrify the nation with DC or AC was that AC could be transported over long distances -- even though at a significant loss -- allowing for the existence of central generating plants, which could only be built and owned by large corporations, and would require a huge transmission inrastructure (and grants or rights-of way over public lands -- they learned from the railroad barons).
DC requires a nearby generating source -- windmills and the like -- and therefore would require a dispersed and decentralized power system which would be impossible to monopolize.
Message edited by author 2008-07-18 18:16:13. |
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07/18/2008 06:45:42 PM · #54 |
Originally posted by GeneralE:
Originally posted by kenskid:
But did you see this:
That's pretty close to being inefficient. |
And what do all the other estimates (besides your "one") say? Right now, that electricity produced by coal-fired plants (and hydro and all other centrally-generated electricty) is transported over high-tension power lines to the places it's needed with a loss of something like 90%. That's pretty inefficient too. |
Where did you get this number? It's more like 7.2% in the US and 7.4% in the UK. |
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07/18/2008 11:01:35 PM · #55 |
Originally posted by GeneralE:
Originally posted by Spazmo99:
Most of the electricity in the US comes from non-renewable sources, like coal. Since the process for extracting hydrogen is very inefficient ... |
This is true at present. However, if you check up this Solar Energy Roundup at Science Friday you'll see that the potential for shifting electric generation to a combination of photo-voltaic and solar-thermal is not that far off, and requires only off-the-shelf* technologies. Creating hydrogen and oxygen by electrolysis isn't that inefficient, and of course it makes a completely non-polluting, portable fuel.
*Solar-thermal electric generator with parabolic mirror developed 1915
*Hydrogen fuel cell developed 1839 |
Commercial grade available photovoltaic solar cells are, at best, about %20 efficient converting light into electricity. While it's true that higher efficiency cells are available or in development, they are presently not in commercial production or are cost prohibitive.
Assuming that you live in an area that gets peak solar radiation (~1000 W/m^2), that gives you a peak power output of 200W/m^2. To equal the output of one 800MW power plant, you'd need 4 million square meters of solar panel area or roughly 1000 acres of power producing solar cells. You also would not be able to simply take an area that size and cover it with solar panels, there need to be access areas, spaces between panels, tilting the panels, etc will give you a packing factor around 0.75, which means that to get 1000 acres of power production, you'll need about 1330 acres of space. Of course, this plant will only produce that much power when the sun is high in the sky and shining directly on the panel. As the sun sets or clouds come and go, output will drop precipitously. You have to also consider the ecological impact of removing the solar radiation from such a huge area.
This is only comparing the peak output of each facility and, unlike coal or nuclear energy, the sun is variable, and disappears for half of the day or more. A good rule of thumb is that the average power capacity of a solar plant is about %20 of its peak capacity. If you consider the average coal fired plant's average output is around 500MW, that would require a solar plant with a peak capacity of 2.5 GW if you apply the %20 efficiency of the cells and consider the packing factor, your plant would need an area 16.7 million square meters (a bit more that 4100 acres or 6.5 square miles). That's really big. Too big. And, what about those of us while live away from the sunny part of the country?
There's no reason solar power can't be part of the solution. but it's not the solution.
Message edited by author 2008-07-18 23:01:56. |
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07/19/2008 03:41:03 AM · #56 |
Originally posted by GeneralE:
Originally posted by kenskid:
But did you see this:
"For example, electrolysis consumes a lot of electricity to free up hydrogen that then has to undergo expensive processing and transport, only to be turned back into electricity via the fuel cell. By one estimate you've wasted three quarters of the energy that was initially available just to get it to the car."
That's pretty close to being inefficient. |
And what do all the other estimates (besides your "one") say? Right now, that electricity produced by coal-fired plants (and hydro and all other centrally-generated electricty) is transported over high-tension power lines to the places it's needed with a loss of something like 90%. That's pretty inefficient too.
One of the reasons Edison lost out to Tesla in the battle over whether to electrify the nation with DC or AC was that AC could be transported over long distances -- even though at a significant loss -- allowing for the existence of central generating plants, which could only be built and owned by large corporations, and would require a huge transmission inrastructure (and grants or rights-of way over public lands -- they learned from the railroad barons).
DC requires a nearby generating source -- windmills and the like -- and therefore would require a dispersed and decentralized power system which would be impossible to monopolize. |
The reason that it's the standard to use AC for transmission and distribution is the ease with which it can be transformed. Transforming up at power plants and then transforming down nearer the point of usage results in fewer transmission losses. Much less, in fact, than the 90% referred to above.
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07/19/2008 03:35:50 PM · #57 |
I have the same 7.2% in an old (few years) text book. Says the transmission/distribution loss is 7.2%.
Are we and GeneralE talking about the same "loss"? 90% loss seems really out of line with 7.4%.
Originally posted by ambaker:
Originally posted by GeneralE:
Originally posted by kenskid:
But did you see this:
That's pretty close to being inefficient. |
And what do all the other estimates (besides your "one") say? Right now, that electricity produced by coal-fired plants (and hydro and all other centrally-generated electricty) is transported over high-tension power lines to the places it's needed with a loss of something like 90%. That's pretty inefficient too. |
Where did you get this number? It's more like 7.2% in the US and 7.4% in the UK. |
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07/19/2008 03:42:23 PM · #58 |
I must have mis-heard something then ... I'm pretty sure whatever it was was on a radio report. Maybe that's the loss for DC transmission ...
Over what kinds of distances is that 7%? Seems to me that sending electricity over 1000 miles of wire might lose more than that in resistance/heat, but perhaps not.
However, that means it makes even more sense to start generating pollutionless electricity in the sunny and windy desert than by burning coal in the northeast. T. Boone Pickens knows something about the energy business, and he's getting out of oil and into wind-farming ... |
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07/19/2008 05:58:06 PM · #59 |
I guess Wind to produce electricity would be nice.
How many wind turbines and how much "windy area" would you need in order to produce the power of one coal burning plant?
Here is info on a currently operating windfarm.
Seventeen 73 ton towers are used to power 3,300 homes.
Originally posted by GeneralE:
I must have mis-heard something then ... I'm pretty sure whatever it was was on a radio report. Maybe that's the loss for DC transmission ...
Over what kinds of distances is that 7%? Seems to me that sending electricity over 1000 miles of wire might lose more than that in resistance/heat, but perhaps not.
However, that means it makes even more sense to start generating pollutionless electricity in the sunny and windy desert than by burning coal in the northeast. T. Boone Pickens knows something about the energy business, and he's getting out of oil and into wind-farming ... |
Message edited by author 2008-07-19 18:01:48.
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07/19/2008 06:11:14 PM · #60 |
Unlike a coal-fired power plant, the land used by wind turbines is mostly still usable for other purposes as well -- farmers can plow around the tower base and collect about $2000/year rent. I don't see any reason you couldn't mingle wind turbines with the solar installations as well -- they don't cast that much shade, and there are plenty of places which are both sunny and windy.
  
Message edited by author 2008-07-19 18:22:05. |
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07/19/2008 06:18:29 PM · #61 |
The current problem limiting implementation of wind energy is energy transport. It costs $$$$ to build the transmission lines to transport energy from locations favorable to wind farms to the power grid. A wind farm can be built in less than a year, but transmission lines take several years. No power company wants to build a transmission line when there is still debate on approval for a wind farm. So it becomes a "chicken and egg" problem.
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07/19/2008 06:20:29 PM · #62 |
Originally posted by GeneralE:
...ny reason you couldn't mingle wind turbines with the solar installations as well -- they don't cast that much shade, and there are plenty of places which are both sunny and windy. |
Like, for instance, the top of my head! No shade up there either, and the wind blows unobstructed! I think I'll put it up for rent... |
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07/19/2008 06:32:30 PM · #63 |
Originally posted by kirbic:
Like, for instance, the top of my head! No shade up there either, and the wind blows unobstructed! I think I'll put it up for rent... |
Cover one of these with some of that new photo-voltaic film and you can probably power your cell phone or iPod ... |
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07/19/2008 07:35:44 PM · #64 |
| whenever i get into a discussion like this, i simply ask them "when you brake, and the brakes get hot, and then the heat gets dissipated to the air, where does that energy come from?" |
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07/19/2008 07:45:19 PM · #65 |
Originally posted by kirbic:
The current problem limiting implementation of wind energy is energy transport. It costs $$$$ to build the transmission lines to transport energy from locations favorable to wind farms to the power grid. A wind farm can be built in less than a year, but transmission lines take several years. No power company wants to build a transmission line when there is still debate on approval for a wind farm. So it becomes a "chicken and egg" problem. |
There's that and the NIMBY syndrome. The windmills produce a surprising amount of noise and while one is not harsh or particularly loud, it is annoying. Put dozens of them together and you'll need to shout to be heard. Also these windmills are quite tall and in a flat area they are visible for miles and miles. Many people who already live in areas that would be ideal locations for wind farms have no desire to have their scenery disrupted.
They also have a tendency to kill birds, creating some more environmental concerns. |
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07/19/2008 08:17:13 PM · #66 |
Originally posted by Spazmo99:
There's that and the NIMBY syndrome. The windmills produce a surprising amount of noise and while one is not harsh or particularly loud, it is annoying. Put dozens of them together and you'll need to shout to be heard. Also these windmills are quite tall and in a flat area they are visible for miles and miles. Many people who already live in areas that would be ideal locations for wind farms have no desire to have their scenery disrupted.
They also have a tendency to kill birds, creating some more environmental concerns. |
The NIMBY syndrome is real, no doubt. As energy costs rise, and the real (minimal) impact of wind farms is better understood, much of that will evaporate, IMO.
I'll very much debate the noise issue. Look at the link provided earlier by  kenskid, that wind farm is a couple hours drive from my home, and there is a much larger one about 30 minutes from home that DPCer  ironworker helped erect. I've been in the middle of the latter one many times, and you can't even hear them over normal rural daytime background noise levels. I expect they would be audible at night.
The bird-kill question is one that will be interesting to watch. The farm near my home sits a few miles from the Horicon Marsh, one of the larger migratory bird havens on the northern part of the mississippi flyway. A large part of the opposition to that farm was driven by concern over bird kills. I suspect it will be monitored closely.
In CA, they took down some wind turbines that were killing large numbers of birds. The issue was that the smaller, fast-turning units were much more dangerous to birds than the taller, slower-turning ones. |
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07/19/2008 08:45:00 PM · #67 |
| If they covered those windmills with solar cells, then the reflections might scare off the birds, while producing power even when the winds die down. |
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07/19/2008 10:54:38 PM · #68 |
What "energy" are you talking about? The "heat" energy that is getting "dissipated" into the air?
I'm pretty sure that the heat generated by your brake is coming directly from the gasoline that is moving your car. The burning of gasoline moves your car...the brakes stop it so ultimatly the "heat" from the brakes is coming from "gasoline".
If you want to trace it back further then the "heat" from the brakes is coming from gasoline...that came from oil...that came from organic material that ultimatly got it's "energy" from where.......
....the SUN !
Originally posted by k4ffy:
whenever i get into a discussion like this, i simply ask them "when you brake, and the brakes get hot, and then the heat gets dissipated to the air, where does that energy come from?" |
Message edited by author 2008-07-19 22:55:13.
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07/19/2008 11:30:09 PM · #69 |
Sun->Oil->Fuel->Combustion->Propulsion->Momentum->Friction->Heat->Nikon->Ponies
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07/19/2008 11:58:12 PM · #70 |
Originally posted by togtog:
Sun->Plants->Animals->60,000,000 years->Oil->Fuel->Combustion->Propulsion->Momentum->Friction->Heat->Nikon->Ponies |
I've filled-in some steps you must've inadvertently omitted ... |
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07/20/2008 12:38:37 AM · #71 |
Originally posted by kirbic:
Originally posted by Spazmo99:
There's that and the NIMBY syndrome. The windmills produce a surprising amount of noise and while one is not harsh or particularly loud, it is annoying. Put dozens of them together and you'll need to shout to be heard. Also these windmills are quite tall and in a flat area they are visible for miles and miles. Many people who already live in areas that would be ideal locations for wind farms have no desire to have their scenery disrupted.
They also have a tendency to kill birds, creating some more environmental concerns. |
The NIMBY syndrome is real, no doubt. As energy costs rise, and the real (minimal) impact of wind farms is better understood, much of that will evaporate, IMO.
I'll very much debate the noise issue. Look at the link provided earlier by kenskid, that wind farm is a couple hours drive from my home, and there is a much larger one about 30 minutes from home that DPCer ironworker helped erect. I've been in the middle of the latter one many times, and you can't even hear them over normal rural daytime background noise levels. I expect they would be audible at night.
The bird-kill question is one that will be interesting to watch. The farm near my home sits a few miles from the Horicon Marsh, one of the larger migratory bird havens on the northern part of the mississippi flyway. A large part of the opposition to that farm was driven by concern over bird kills. I suspect it will be monitored closely.
In CA, they took down some wind turbines that were killing large numbers of birds. The issue was that the smaller, fast-turning units were much more dangerous to birds than the taller, slower-turning ones. |
My experience with wind turbine noise dates back to my visit to the Tehachapi Wind farm back in the 90's they were far from silent.
It seems that the issues now are mainly nocturnal with typical windfarm noise at 350m being about 10dB louder than the rural night background noise level. In other words, if your house were close to the turbine, it would be, by far, the loudest sound you would hear at night. There also seems to be the possibility of infrasound (below audible range) being transmitted through the earth and causing resonant behavior in houses. Some people have reported hearing a low hum coming through their basements/foundations. If such sound is being generated by a wind-turbine, it's not unlikely that it would be transmitted that way through the ground.
Other studies have shown that those who can't see the turbine can't hear it. Those that stand to benefit financially from the turbine also report no annoyance due to the turbine operating. |
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07/20/2008 09:52:36 AM · #72 |
Someone had mentioned the cost of transmission lines for wind power ... which, in my naiveté, caught me by surprise. Coincidentally enough, yesterday there was a story in the newspaper about Texas approving a $4.93B (that's capital B) project to provide transmission lines for the wind-rich state. The story is in the New York Times.
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07/21/2008 09:40:23 AM · #73 |
Combustion - Not energy
Propulsion - Not energy
Momentum - Not energy
Friction - Not energy
Heat - Is an energy
Nikon - ?
Ponies - ?
Originally posted by togtog:
Sun->Oil->Fuel->Combustion->Propulsion->Momentum->Friction->Heat->Nikon->Ponies |
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07/21/2008 01:37:30 PM · #74 |
Originally posted by kenskid:
Combustion - Not energy
Propulsion - Not energy
Momentum - Not energy
Friction - Not energy
Heat - Is an energy
Nikon - ?
Ponies - ?
Originally posted by togtog:
Sun->Oil->Fuel->Combustion->Propulsion->Momentum->Friction->Heat->Nikon->Ponies |
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I was attempting to more clearly answer where the heat in the brakes comes from. I have absolutely no idea how either Nikon or Ponies got in there though. |
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07/21/2008 02:48:07 PM · #75 |
The brakes of a car turn the kinetic energy provided by combustion of the fuel (potential energy) which when ignited turns into heat energy and is then rapidly expanded to produce the kinetic energy used to propel your car into heat energy by way of friction and dissipating it to the surrounding air.
Returning to the OP
The "scientific" way of explaining to your friend about why he's very wrong is through the idea of exergy. Exergy is the "usefulness" of energy. Energy is conserved, we all know that, but in any REAL process exergy is destroyed. This, in turn, means that there is a limited amount of exergy in the universe and after it is all used up...well that's beyond my means of understanding. Either way, when you burn fuel to run your car, you are destroying part of the exergy in the process because it is dissipating to other sources than the one you want to use. For example, the desired effect of burning the fuel in your car is to heat and rapidly expand the air in the cylinders to achieve the desired effect of force on the piston downwards (or sideways if you have a subaru and/or porsche) which in turn drives the crankshaft and your car moves. However, part of the useful energy is lost by means of heat which is not the desired effect. In order to improve the overall exergy efficiency the heat energy lost can be used to, for example, heat your car (making it useful) which is regeneration. Regeneration is used all the time in power generation cycles in order to improve exergy efficiency.
In the means of one battery to drive a car and the motion of the car to charge the other one, there is exergy loss in that cycle. That means that it will not work because there is not a 100% power recovery. If 100% of the energy was conserved WITHIN the cycle, you would have a reversible cycle and that is impossible.
I love thermodynamics! Don't you?
PS: If any of you manages to invent a process where exergy is not destroyed, let me know. I will invest heavily...
Message edited by author 2008-07-21 14:51:23.
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