attn peak oil fearmongers: fuel cell cars take a leap forward

[Jamougha]

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Figures I've seen for running costs per mile given hydrogen from steam methane refoming are similar to those for petrol. The carbon can be sequestered.

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Ok, pretend peak oil has occurred. Where are we going to get enough methane to replace our entire oil infrastructure?

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Useful methane supplies are expected to outlast oil by some time. There are new sources like methane hydrates being considered for exploitation. Also it's to be hoped that carbon neutral sources will begin to replace some of our mains generation infrastructure.

When methane runs out, hydrogen could be produced via high-temperature electrolysis. Some of the new designs for nuclear plants operate at a high coolant temperature and can provide the required thermal energy for on-site hydrogen production. It would make great use of off-peak capacity. Costs are being estimated as similar to steam reforming, and although the process has not yet been comercialised R&D is complete.

Or, ideally, we may have a breathrough battery technology by this point.

[frizzfreeling]

But is it better than petroleum? I mean, it takes 300 million years to turn plants into crude, right? And what kind of efficiency are we talking about there, it's got to be way lower than simple electrolysis. So how did petroleum ever get to where it is now? It's obviously a piss poor way of storing and transporting energy.

All he is really saying is that when you go to the pump, you are not actually paying for the energy content of the gasoline you pump. All you are paying for is the transportation cost, from the aquifer to the well head, through a pipeline, onto a tanker, through a CAT plant that uses the energy already in the oil to crack it, onto a tanker truck and finally into your car. All of these steps, even though they seem vast, pale in comparison to the energy that you are getting free from the fuel itself.

Contrast that with, say, hydrogen fuel, which must in itself be created by YOU (or us) from another fuel source, then be transported much like I described above, but in reality much more complicated and voluminous transport, before it gets to you. If you make the hydrogen out of natural gas, then the process has inherent inefficiency and the hydrogen product has less energy content than the initial content of the natural gas. So why not use the natural gas as a fuel instead? Why use the intervening steps to hydrogen and the associated transport and infrastructure difficulties? The hydrogen from this process cannot become cheaper than the original product. This is just an example...

[Jamougha]

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if we are talking about powering the world with solar power, I'd be curious to see an estimate of the effect on our climate of absorbing that much sunlight.

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'None' would be a pretty accurate ballpark assesment.

[frizzfreeling]

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if we are talking about powering the world with solar power, I'd be curious to see an estimate of the effect on our climate of absorbing that much sunlight.

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'None' would be a pretty accurate ballpark assesment.

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This is false. If you cover desert, which reflects much of the sun's rays, with a dark-blue/black surface that absorbs say 90%+ of the sun's rays and takes 20% of that energy, converting it to electricity, you still have a body that absorbs much more thermal solar energy than a typical desert environment. This works on the same general principle as that used to describe why its usually hotter over a blacktop surface than over a white surface.

Compared to a typical environment, deserts absorb less radiation per unit area from the sun, causing wild fluctuations in temperature from night and day versus, say a piece of forrest, which changes temperature more slowly and maintains temp better at night due to its increase absorbtion of radiation during the daytime.

If you live in Phoenix, Arizona, and replace your white roof with dark shingles, your roof/attic will become much hotter. Simply taking part of that radiation and converting it to electricity does not make up for the added heat load.

[Al68]

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if we are talking about powering the world with solar power, I'd be curious to see an estimate of the effect on our climate of absorbing that much sunlight.

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'None' would be a pretty accurate ballpark assesment.

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Maybe you're right, maybe it's insignificant. I was just suggesting we consider it.
It just seemed like absorbing 76 square meters of sunlight per person to convert to electricity might be significant, since this sunlight is currently being (partially) absorbed and converted to heat at the earth's surface.

[ADDboy]

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This means that to be competitive in construction alone, given a bulk efficiency of 20%

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Try doubling that:
http://www.energy.gov/news/4503.htm

We are at 40% now and there's plenty of unexplored techs for increasing efficiency left.

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I think the only reasonable thing to do is assume 100% efficiency. Average sunlight is 300 watts per square meter. Assuming we solve the storage problem and can store energy from day to night, and from summer to winter, also with 100% efficiency, we could average 150 watts/sq. meter of solar cell. That's still 76 square meters per person in the U.S., assuming our current usage of 11,400 watts per person.

We still have a significant obstacle here besides the storage problem.

At least if the goal is to replace fossil fuels altogether, which should be our goal, since we will have to eventually.

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Is 76 square meters per person supposed to be a lot? That fits inside a 9 meter by 9 meter square; to get 300 million people, 18,000^2=324 million, so 76 m^2 per person fits inside a 160 km by 160 km square, which could easily fit into the desert.

[Jamougha]

frizz,

Yah I understand basic physics. [img]/images/graemlins/smile.gif[/img] The area of solar cells that we're talking about is almost certainly too small to have a significant effect on global climate.

If it's not then we just need to get a few people to paint their roof slates white to compensate. [img]/images/graemlins/tongue.gif[/img]

[Al68]

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Is 76 square meters per person supposed to be a lot? That fits inside a 9 meter by 9 meter square; to get 300 million people, 18,000^2=324 million, so 76 m^2 per person fits inside a 160 km by 160 km square, which could easily fit into the desert.

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Well, "a lot" depends on perspective. I wasn't suggesting that we physically did not have the room, just that it is a factor.

[Al68]

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frizz,

Yah I understand basic physics. [img]/images/graemlins/smile.gif[/img] The area of solar cells that we're talking about is almost certainly too small to have a significant effect on global climate.

If it's not then we just need to get a few people to paint their roof slates white to compensate. [img]/images/graemlins/tongue.gif[/img]

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Dude, you just found the cure for global warming. [img]/images/graemlins/grin.gif[/img]

[frizzfreeling]

If it's not then we just need to get a few people to paint their roof slates white to compensate.

On a large enough scale, all jokes aside, yes this would solve global warming. White reflects all visible wavelengths of the spectrum with moderately high efficiency. That's why its white... because white is the color of all visible colors combined. Of course "a few people" wouldnt even come close to doing the trick. However, there is evidence stating that if all houses in large desert cities were painted white, those houses would use markedly less electriciy for cooling and the city as a whole would more temperature neutral compared to it surroundings. A large plot of solar cells many KM in diameter would be at a much higher average temperature than its surroundings. A tiny percentage of the earth's surface covered with solar cells will not have a big impact on global temperatures, however, to say that it is "none" is based on opinion and not fact. Heat pollution is already a problem in many areas, so globally it may not be a major problem, but locally, it may. Phoenix would have a massive heat problem if you built a 1000km^2 solar farm nearby, which just happens to be one of the best places in the U.S. to build a solar farm as climate stability and terrain are concerned.