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• #### Re:Nanowires are nice and everything... (Score:4, Interesting)

on Monday May 19, 2008 @06:21PM (#23468106)
Barely related... but as a South Texas resident, I wonder how much less I could run my A/C every year just because of the shade provided by solar cells on my roof? I believe I first used my A/C this year in February, so even a small decrease could be significant over the year.

I also always wondered why people don't advertise how much cooler CFL bulbs are than incandescent bulbs. I replaced 480W of lighting in a bathroom with 72W (replaced 60W clear bulbs with 9W vanity CFLs) and not only is it brighter and the light softer (and thus makes ladies feel prettier when doing whatever it is they do for hours in bathrooms) but it's a lot cooler. And they will pay for themselves in roughly 13 months.

And similar swaps make a really significant difference when sitting under the 5-bulb light that is just above the dining table. A friend of mine used to unscrew some of the bulbs when she did homework.

So basically now I save electricity while saving electricity.
• #### Re: (Score:3, Interesting)

Ahh, but that's because you live in Texas. Residents of lesser states are often concerned primarily with heating a room instead of cooling it. The difference is particularly huge in a batroom with a well-lit mirror, where 300W of heating in a small poorly-ventilated room could send the temperature over 100 in minutes - the CFLs are a glorious change, and available in whatever color temperature suits your fancy.

Now we just need affordable dimmable CFLs for that dining table fixture, and low-wattage CFLs wi
• #### Re:Nanowires are nice and everything... (Score:5, Funny)

on Monday May 19, 2008 @06:45PM (#23468366) Journal

I believe I first used my A/C this year in February
You own an Anonymous Coward? That would be sweet. I would task mine to read and summarize /. for me.
• #### Re: (Score:2)

I wonder how much less I could run my A/C every year just because of the shade provided by solar cells on my roof?

Your average silicon PV cell is 12% efficient. That means that for every watt of electricity out, 7 watts goes into heating up the cell, and very little gets reflected back out (since they are black).

A white or light-shaded composition shingle roof would reflect about 30% of the light energy hitting it. While an asphalt shingle generates no electricity, it would absorb 20% less heat than the

• #### Re: (Score:2)

I wonder how much less I could run my A/C every year just because of the shade provided by solar cells on my roof?

Probably fairly little. You could get the same effect by putting something that's not solar panels (and therefore much cheaper) on your roof, or a larger effect by spending the money you'd spent on solar cells to improve the insulation of your house (provided that there's still potential to do so, i.e. the house isn't wrapped in 12 inches of insulation yet).

• #### Re: (Score:3, Informative)

Now it's been a while since I dealt with Physics and all that, but... release 2 electrons for one photon? How would that work? Photons knock electrons out of their bonds by imparting enough energy into the electron so that it moves into the conduction band. However, photons are either absorbed or not - this is not billiards.
• #### Dramatic efficiency improvements unlikely. (Score:5, Informative)

on Monday May 19, 2008 @05:58PM (#23467904)
If I am not completely mistaken "classical" semi conductor cells can reach efficiencies of 40%, meaning that even with perfect 100% efficiency you would get at best a factor 2.5 improvement. Of course, 100% efficiency is an impossibility and thus I think we can safely assume that these cells will never reach more than 80%-90% efficiency, which would be an improvement of a factor of 2 over current technology. Now last estimate I saw was that in Europe solar cells work out to be about 4 times as expensive as wind power (which is itself rather pricey ), so even assuming the 100% efficiency, efficiency gains alone cannot make solar economical.

Add in to this that a large part of the cost of solar is the energy needed to produce the cells, which means that if you get that energy from a more expensive power source, the price of the cells will increase. I.e, if one started to replace relatively cheap generation capacity with more expensive solar cells, then the cost of energy, and hence the cost of the cells, would increase.

It would therefore appear to me that for solar to have a chance to become competitive what is needed is focus on lowering the cost of producing the cells, because the gains from improving their efficiency cannot offset their presently large price, and it appears unlikely that pushing for higher and higher efficiencies will be possible without making the cells more expensive.
• #### Re:Dramatic efficiency improvements unlikely. (Score:5, Informative)

on Monday May 19, 2008 @06:07PM (#23467982)
Currently availible non-specialty cells (the cells used for space etc are not used for general power) are typically between 5 and 15%.

Therefore getting to the 80-90% range would result in a 5-18X improvment.

Since solar is currently 4X, that means it will drop to .2-.8X of CURRENT power costs.

Now remember that hydro is essentially 100% tapped. Wind has a much more limited range and is already approaching the likley maximum efficiency. Nuclear is great but will take some time to spin up. Oil/natural gas prices are climbing rapidly and coal is becoming more expensive to mine and or clean.

Solar PV provides a great load matching power source that will help reduce an individuals demand on the system even if it doesn't complely remove the need for other power sources as well.
• #### Re: (Score:2, Interesting)

solar could maybe provide 10% of our needs at most. it can't supply base load, which is something nuclear can do very well. don't tell the tree huggers that though, they want to continue to live in their dream world.
• #### Re: (Score:2)

personally I would love to see throium reactors until fusion actually shows up.

While I am not a "tree-hugger" I am a "tree-shacker-hander"
• #### Re: (Score:3, Funny)

Yeah, but who's gonna build the catchium reactors?
• #### Re:Dramatic efficiency improvements unlikely. (Score:4, Informative)

by Anonymous Coward on Monday May 19, 2008 @06:31PM (#23468200)
Photovoltaics can't supply base load now, but that doesn't that you can't get a solar plant to supply base load. The trick is to instead, use thermal energy. We can store the excess thermal energy overnight to continue generating power in the dark, until the sun shines again. Check it out http://en.wikipedia.org/wiki/Solar_thermal_energy [wikipedia.org]
• #### Re: (Score:2)

The primary benifit to solar thermal is that it is a mature technology and is about 40 percent efficiency plus we are decent at storing heat energy without loss.

The downside is that we are unlikley to improve much because of Karnat restrictions.

PV has a Karnat limit of about 98 percent. Therefore while at the moment thermal is better for large power plants, PV will eventually pass thermal. We are already pretty close efficiency wise to storing electricity cost effectivly.

Thermal is great for now.
• #### Re: (Score:2)

PV has a Karnat limit of about 98 percent.

Maybe you mean Carnot [wikipedia.org]? More importantly, if you have a source for this assertion, I'd be very interested in reading it.

• #### Re: (Score:2)

Sorry about that...I sent the message on a palm pilot with not checking :-)

take a look here http://www.ese.iitb.ac.in/aer2006_files/papers/086.pdf [iitb.ac.in]

While local temperatures don't effct the PV Carnot efficiency, the surface temperature of the sun does.

The sun is about 6000K. Locally we are 300K calculate it out and you get a maximum efficiency of about 95% (my mistake...off by 3)

However 80% is a much more realistic end point for consumer grade equipment. Even 50% would bring the cost down to less than ANYTHI
• #### Re: (Score:2)

Also besides storing the power, the sun is up somewhere in the
world and can make power, so spread the power generation
across all 24 time zones and use long haul transmission.

The long haul losses for the US are about 7.2%

http://en.wikipedia.org/wiki/Electric_power_transmission#Losses [wikipedia.org]

So all those Anti-solar idiots out there can stop fondling
their fossil fuel shares, and face the fact that 3% of
the Sahara at 40% efficiency could replace all other forms
of power on earth alone.

Spread it across all 24 time zones
• #### Re:Dramatic efficiency improvements unlikely. (Score:5, Interesting)

on Monday May 19, 2008 @08:03PM (#23469088)

solar could maybe provide 10% of our needs at most. it can't supply base load, which is something nuclear can do very well. don't tell the tree huggers that though, they want to continue to live in their dream world.

Just to be contrary: at least in theory, solar COULD supply base-load. All you need to do is integrate the Earth's power grids. Then you'd have a more or less constant amount of current available throughout the grid.

Of course, this isn't practical - even ignoring the political implications, transmission losses would create serious problems. Getting away from AC current and using DC for all grid transmission could fix part of that problem, but that's not likely to happen any time soon.

And yes, you're certainly right about nuclear. Realistically, it's our best option at this point in time. That's one thing that France got right.
• #### Re: (Score:2)

Of course, this isn't practical - even ignoring the political implications, transmission losses would create serious problems. Getting away from AC current and using DC for all grid transmission could fix part of that problem, but that's not likely to happen any time soon.
Westinghouse isn't dead, he's just posting nonsense on Slashdot!
• #### Re: (Score:2)

solar could maybe provide 10% of our needs at most.

Yeah, not much solar power hits the earth:

http://en.wikipedia.org/wiki/Solar_energy#Energy_from_the_Sun [wikipedia.org]

2.5 acres makes 354 Mega Watts

http://en.wikipedia.org/wiki/SEGS [wikipedia.org]

I swear your daddy must work for big oil, or you are just
as smart as a bag of hammers.
• #### Re:Dramatic efficiency improvements unlikely. (Score:4, Informative)

on Monday May 19, 2008 @06:48PM (#23468382)

Currently availible non-specialty cells (the cells used for space etc are not used for general power) are typically between 5 and 15%.

Therefore getting to the 80-90% range would result in a 5-18X improvment.

Since solar is currently 4X, that means it will drop to .2-.8X of CURRENT power costs..

I said 4X WIND POWER costs. Not current power costs. Britain's Royal Academy of Engineering estimates the cost of wind power at roughly 3 times that of nuclear, so even if you achieve 90% efficiency that would put you at roughly twice the cost of nuclear generation ( assuming 15% efficiency for present cells ). Now, to give an idea of how hard 90% efficiency would be to reach, the Sun's average surface temperature is 5778K , meaning a solar cell at 300K could at best reach 95% efficiency without violating the laws of thermodynamics.

That is, ignoring ANY other problems you are closing in on the theoretical limits allowed by the laws of physics if you are to get such efficiencies, and you have to do this without increasing the costs of your cells. Any dust on the cells and you can forget it. Protective glass coating is a no-no since it would absorb in the UV range. Heck, simply finding a material that is reasonably transparent at all the relevant wavelengths could be tricky. Add in to this that you cannot use any expensive/toxic/rare elements, that the cells should have to last for a long time, that they should survive a wide range of temperatures and be able to handle a reasonable level of abuse, and it becomes far from certain that it is even possible to reach 80% efficiency, let alone to do so in the foreseeable future.

• #### Re: (Score:2)

You are correct..You did say Wind power.

But the cost of power is based on more than cell efficiency.

For instance, nanocell solar cells are proven and produce power at 0.15 cents a KWH. this is done at about 7 percent efficiency. Coal power typically costs about 0.10 cents a KWH. This is possible because the cells are so cheap and can be placed in "useless" areas like residential siding and roofs. This tech is expected to reach rf percent efficiency at the current price point in 5-10 years.

There is enou
• #### Re: (Score:2)

Coal power doesn't cost 10 cents a kwh. It's more like 4-6 cents, before distribution grid costs. Unless you go off the grid, you're still going to have that, as the power lines need to be maintained.

Of course, clean coal is much more expensive, quite possibly making it more expensive than building nuclear plants. The level of cleaning/scrubbing making coal clean is expensive.
• #### Re: (Score:2)

Argue with my electric bill.... I pay 10.5 cents per KWH and I am slightly better than my state (Georgia).

Coal prices vary but the average has NEVER been below 7 cents a KWH (adjusted to today's dollar) before distribution costs. Those that are that low are typically from non-profit co-op type organizations.

For profit power companies charge anywhere from 8 cents up to 15 depending on market forces (again average).

Finally even is you WERE right and it did cost 4-6 cents before distribution costs, we are ta
• #### Re: (Score:2)

10.5 cents per KWH? Man, I wish I could get power that cheap. My last bill had me paying 23 cents KWH for a good portion of the bill.
• #### Re: (Score:2)

Man I wish I could get power that cheap. My last bill (converting @ \$2 = Â£1) would put it at 28 cents / KWH! Dropping to 25 cents after using several hundred KWH.
• #### Re: (Score:2)

Pretty lucky here as well, 7.68 cents a KWh and it is
natural gas here in Oklahoma.

• #### Lots of NG electricity for you... (Score:2)

I find it interesting that you're 40% NG(20% cola) and that you're getting 7.68 c/KWh.

NG generally has cheap construction costs and expensive running costs. But you probably have substantional cheap NG deposits.
• #### Re: (Score:2)

Oh yeah, Oklahoma has massive natural gas wells.

Some were so massive when they came in they caused minor earthquakes.

There are literally dozens if not hundreds of them.

Oklahoma is the 3rd largest Natural Gas producer in the US.

Suprised we use any coal at all.
• #### Re: (Score:2)

hydro isn't 100% tapped, there are tons of places around the world where new hydro electric plants are going up, maybe in America the market was saturated early, but if we put in hydro plants in many countries in Africa, those countries won't have to put in as many coal fired plants at technology gets cheaper, etc.

wind is nowhere near tapped.... i think the Department of energy once found in a study that wind power plants could provide up to 40% of the energy needs of the US, overall, the problem though, i
• #### Re: (Score:2)

High power tornadoes are extremely rare.

I live in the center of tornado alley, and my house
is 55 years old, and my friend's house is 70+ years old.

Neither of these houses have been hit by a F0-F5.

Some day that will happen, but I may not be alive to see it.

There are lots of homes around me that are over 50 years
old and none of them have been hit.

A few areas in central Oklahoma seems to be a tornado magnet
Moore and Edmond, some areas almost never get hit,like Norman.

I have no idea why, just a observation of t
• #### Re: (Score:2)

Since solar is currently 4X, that means it will drop to .2-.8X of CURRENT power costs.

Do you happen to have a source on this? All the times I've figured it, it's around 10X as much.

4X might be with some of the high levels of subsidies and such. Or a large solar thermal installation, which photovoltiacs don't figure into.

Or maybe it's compared to retail electrical prices, and doesn't include support equipment such as the inverter.
• #### Re: (Score:2)

I was quoting the parent of my comment.

However with nanosolar's thin film cells the price can drop to about 1.5X coal (although space could become an issue).

Currently the payback period for a full off-grid residential solar system is on the order of 7-10 years. (Cited all over the place) This is in line with the roughly 4X for conventional silicon cells.
• #### Re: (Score:2)

Even given your calculations (and I don't think I'm really happy with all the assumptions) solar power is often usable where wind power isn't, and vice versa, so it's not an "either or" situation.
• #### Re: (Score:2)

If you're talking strictly about the monetary economics, then I think what we really need to do is rethink the world's concept of economics.

At SOME point the bullet has to bitten as far as cost goes somewhere. Oil and coal aren't going to stick around for ever.
• #### Re: (Score:2)

While increasing the efficiency of a solar cell can indeed make it cheaper, in that if the increase in efficiency doesn't significantly increase the cost of a cell, making it so you need half as many, half as much mounting equipment, etc... It doesn't really matter.

I agree with you, the significant obstacle isn't the efficiency of solar panels. It's the cost of them, more so than the space they take up.

If we could produce solar panels that were half as efficient as current panels for the cost of a ream of
• #### Re: (Score:2)

so even assuming the 100% efficiency, efficiency gains alone cannot make solar economical.

Add the long term cost of the Iraq war, and the future
war in Iran onto the cost of your petro power.

It is not so cheap anymore.

If the long term projected trillions of dollars went to a
Solar Thermal array like the SEGS system we could
power the earth with 10% of the Sahara Desert
3 times over replacing all forms of power including
oil, coal, nuclear, wind, hydro.

In 2005 total world energy usage was 15 Tera Watts,
the 10% se
• #### Fraud alert ... (Score:5, Funny)

on Monday May 19, 2008 @07:46PM (#23468940)
These guys are scammers ... it's the old When Hairy Met Sili Con.
• #### Wow, ANOTHER solar cell breakthrough (Score:5, Insightful)

on Monday May 19, 2008 @08:39PM (#23469368)
Wake me up when there's actually a cheap product. These articles need their own icon; maybe Bigfoot, the Easter Bunny, Santa Claus, the Loch Ness Monster, or La Chupacabra.

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