Photovoltaic cells

[Sxotty]

As the other thread was hijacked I thought I would start a new one about it. My opinion is that we should make a huge effort to implement solar cell power generation. Why? Because then energy is free, it would take a long time to pay for it though >10 years at current prices but prices are going up so it will pay for itself more quickly.

The following is in relation to PV cells with 10% efficiency

How much space does PV take?
The most common modules (using cells made from crystalline silicon) generate 100-120 watts per square meter (W/m2) (per 10 square feef). Thus, one (Square meter) module generates enough electricity to pwer a 100-w light bulb. At the other end of the range, a PV power plant laid out on a square piece of land measuring approximately 160km (100mi) on a side could supply all the electricity consumed annually be the entire United States.

http://www.nrel.gov/research/pv/tapsun.html

I think mayhaps it would be easier to convince nevadans to place a huge solar farm instead of to use yucca mountain.

In addition there is new discoveries constantly being made that make much more efficient cells than those listed above, but they are still expensive.

a single system of alloys incorporating indium, gallium, and nitrogen can convert virtually the full spectrum of sunlight -- from the near infrared to the far ultraviolet -- to electrical current.
....

The maximum efficiency a solar cell made from a single material can achieve in converting light to electrical power is about 30 percent; the best efficiency actually achieved is about 25 percent. To do better, researchers and manufacturers stack different band gap materials in multijunction cells.

Dozens of different layers could be stacked to catch photons at all energies, reaching efficiencies better than 70 percent, but too many problems intervene. When crystal lattices differ too much, for example, strain damages the crystals. The most efficient multijunction solar cell yet made -- 30 percent, out of a possible 50 percent efficiency -- has just two layers.

http://www.lbl.gov/Science-Articles/Archive/MSD-full-spectrum-solar-cell.html
The article is worth a read, b/c as always it promises tantilizingly cheap and efficient solar cells. Also as you might notice by using the full spectrum of EM (electromagnetic) radiation we would use infrared energy to make electricty and this could conteract global warming, in addition to less use of fossil fuels. Currently we use about 70% fossilfuels to generate electricity.


Our current infrastructure would be very helpful, b/c solar cells could produce energy and ship it to another place to store it.http://www.eia.doe.gov/emeu/cabs/usa.html#elec

 

[zidane1strife]

Good post.

Say yes to sol!!! say no to nukes!!!!

 

[Dr. Ffreeze]

Sxotty,

Thankx for the post and links. It has been a long day, I will read up on them later in a few days.

Thankx,
Dr. Ffreeze

 

[Fruitfrenzy]

I was once told that the energy required to manufacturer a solar cell is more than they typically generate in their lifetime. Although I don't have any evidence to back that up at all it does sound potentially correct.

I would imagine that the semiconductor processes involved require a lot of juice.

 

[Sxotty]

FruitFrenzy, I will look into that sometime today, I have never heard that I kind of doubt it though to be honest, perhaps it would take a year to produce the energy required to make one, but I think in 20 years they could easily do it.

 

[davefb]

It wouldnt just be the power used to make them, a key issue is the poisons used to create the semiconductors used. To be honest, i quite like the idea of having less-efficient but much cheaper/cleaner solar cells, which in theory householders could put across windows // or on rooftops ,, just for "topping up".. I don't think large scale generation using solar cells makes any sense because you'd have to create a method of storing the electrity... but thats just me

To be honest i also always think it's ironic people talking about 'being nice to the planet by having solar cells' , what would save the planet better would be to turn lights off !!!!

btw, are you sure that the 160km*160km issue isnt a bit of a give away that solar cells arent exactly a solution! ! ! and theres still the problem that everyones lights would go at night!!!

-dave-

err or not have a 100w cpu burning away whilst all i'm doing is surfin' the web

 

[Sxotty]

the problems with solar panels are efficiency
This is not a problem b/c the sunlight is free

Recycleability: When they wear out the are hard to deal with if they could be easily recycled it would help

Night?
Well obviously take a machine that drill subway tunnels drill a tunnel in a hill, fill it with water in the day and then at night let the water drain out thru generators.

So basically although it would be a massive investment it would pay for itself eventually b/c sunlight is free. In alaska the power company is required to pay consumers for electricty they add to the grid, many states do not as yet do this but it would certainly encourage people to get solar cells if they could not only get free electricty in the day but also get paid for the excess.


As follows below a quote saying typically in 10years a solar system pays for itself. Of course this is in ridiculous california...

So a key feature of the new BP customer site is a savings calculator, allowing customers to plug in their area codes and monthly electricity bills for a calculation of how long it would take for the system to pay for itself.

Those paybacks typically extend more than 10 years, but BP and other manufacturers say their systems should last twice that long. They say that means dividends for years on a photovoltaic investment. And Postles notes BP calculations assume utility power prices remain flat

http://www.powertothepeople.org/newswire/020703.shtml

Less obvious than solar panels are photovoltaic roof shingles. The shingles are indistinguishable from normal roof shingles. By performing double duty, they make the cost of solar cells competitive over the life of the shingles, according to the National Renewable Energy Lab, an arm of the Energy Department. The shingles produce about five watts per square foot, based on the average sun hours per day.

http://www.irecusa.org/articles/static/1/1010741387_987100817.html

This is from the other thread that I said was "hijacked" So yes I realize that solar cells are poluting to manufacture and dispose of.

Another way to store the energy effectively is, convert H2O (water ) to hydrogen and oxygen, then burn hydrogen to create water. I am not sure which of these methods would be most effective as a way to store energy, I actually think that the hydrogen one might be better, but hydrogen gas is explosive and water in tunnels isn't. (electrolysis of water youguys have heard of I assume)

 

[Sticky]

I think something should be devloped here in the next ten years... That would allow a new home builder to give you an option of placing solar cells on your roof to supplement your electricity. Something I think in the 10K category might get things going. How ever innefficient they are... Someon needs to start selling these bad boys in some sort of volume before things will start to progress like computers do... $$$$ speaks... Obviously we would never have just one source of energy... but if we cover the day time sources.... with renewable energy... the night time is a piece of cake.... wind, natural gas, nuke. etc Way less useage at night obviously.

Hydrogen Fuel cells have great potential... They are something like halfing the size of these every 5 years or something... I heard that froma friend in my company whos job it is to look at altenative sources of energy and how my company can get involved. I am going to have to check some links out and see if I can post some.

 

[davefb]

w.r.t. pumped hyrdo,, i think you underestimate just how much water you need..

dinoriwc in the uk is such a scheme and to work you dont just need the tunnels ,, you need somewhere to store the water..
http://www.bbc.co.uk/dna/ww2/A958818

http://www.fhc.co.uk/DIN.htm

frankly, i just dont believe dinorwic would be built now,,, it's too long term for shareholders AND in the uk since coal/nuclear are being priced out due to gas(*) powered stations which can come onstream/offstream 'moderately' quickly,, i can't see a new dinorwic ever being built... also note, you need a lake in a nice area where nobody will care if the water rises//lowers,,,
dinorwic IS fantastic though

-dave-
(*)i really hate the current way that gas is being used to generate electricity... i think it's disgusting ...
ps photovoltaic shingles might be okay in california,, but if they only get 5watts per sqft there,, i really don't see them ever being usefull where i live... more likely would be a hydro-scheme

 

[Sxotty]

Dave, thanks. There is a few differences with what I propose.

I want the system sealed so water is not lost thru evaporation. This would be especially important in places like Nevada where solar power is best. Thus that gets rid of the water level issues (ie lowering/raising thru day) the problem is of course this would cost even more than what they did, but it should also be pretty maintanace free. I mean it could easily last over a 100 years.

But yes hydrogen gas may be the way to go, I am not really sure though how efficient this way would be.

 

[mboeller]

Solar cells with an efficiency of 70% are nothing new.

Have You heard about the Lumeloid-film? This tech promised 36% / 72% conversion efficiency back in 1984 !

Links :

http://www.techno-preneur.net/timeis/techtrends/chemical/1311Solar.html

http://science.slashdot.org/science/03/01/08/0323237.shtml


But until now nothing came out of this tech.

 

[Basic]

The water level will go up and down because of the massive amounts of water that need to be pumped in and out of the reservoir. The upper reservoir water level in Dinorwig can vary 34 meter. That has nothing to do with evaporation. Even if the same system vere located in Nevada, evaporation would be insignificant.

The "working volume" in Dinorwig is 7M m^3. That's a *huge* cave to make. And if you can't find a suitable place to put the reservoirs with a height difference as high as in Dinorwig (500m), you'll have to compensate that by pumping even more water.

 

[Sxotty]

I understood about the water level, I was just saying that if the system was enclosed it would not matter. Actually the amount of evaporation in a place like nevada I think would surprise you. The reason I wanted it enclosed is so that water would not be wasted, fresh water is another resource which is becoming less abundant. Finding a place with 500m, or 1600feet of difference really would not be hard at all in the western US, in the central part it might be a problem. Yes that is definitely a huge cave, bigger than I thought necessary I must admit i.e. I had not done any calculations just seat of the pants guesstimates. I would rather not have one cave though but a series of tunnels. I have no idea like I said whether this would be that good. After I get through some writeups and a test in analytical instrumentation, I will do some research on how the electrolysis of water to make hydrogen would fare as an energy storage technique.

 

[Dave H]

As an alternative to pumping/draining water, I've seen it proposed to compress/release air (again in a big cavern). Not sure how this compares w.r.t. energy efficiency, the ease of constructing a large enough sealed system, etc, but it certainly addresses the issue of locating the plant by a proper reservoir.

 

[Crusher]

Why don't we just bore a hole through the side of Mount St. Helens, divert the Columbia river into it, and put steam powered generators on top? I'm pretty sure that would be cheaper than covering 1/10th of Nevada with solar generators.

 

[Sxotty]

Dave H.
I have never heard of that idea I have no idea about the efficiency, but I do know that it would be much easier to implement for many reasons such as no geological constraints (ie the need for mountains). Plus there tends to be air around

Crusher
I think people should honestly think about stuff like that, except that in that case it would be horrible for many reasons, but seriously what is wrong with trying to think up new ideas. Here is another unusual power generation idea.
http://www.sustdev.org/energy/articles/energy/edition3/SDI3-10.pdf

Talks about using temperature differences in the Ocean to create power. If solar cells pay for themselves in just over 10 years I fail to see how it would be unfeasible to install them on a large basis. There are a ton of different interesting and likely scenarios.

 

[Crusher]

If solar cells pay for themselves in just over 10 years I fail to see how it would be unfeasible to install them on a large basis.

Well, besides the fact that a 10,000 square mile solar panel farm would be a giant bullseye for terrorist attacks, one good hail storm, lightning strike, flood, mudslide, tornado, etc. etc. would simultaneously destroy a multi-billion dollar investment and cut off the power to most of the nation. Not to mention the vast acreage it would rend useless for any other purpose (contrary to what people think, deserts are not completely barren, and do provide a home to many forms of life).

Also, as was pointed out earlier, there's no real way to store electricity, so they'd only be able to provide power during the day (and their efficiency would be dictated by the weather). Then you have to consider the transmission lines necessary to carry the electricity from this giant solar farm to anywhere else in the nation. People complain about the radiation eminating from local transmission lines now, just wait until they see the gigantic 10 million volt cables carrying it from Nevada to New York.

Solar cells are too weak, too fragile, and too unreliable to be a major power source, IMO. Honestly, nuclear reactors are the best technology we have today, in any aspect. Unfortunately Chernobyl and all the "goddamn tree hugging hippies" (as Cartman would call them) have pretty much ruined the chances of power companies being able to build them within the U.S.

And don't even get me started on wind farms...

 

[3dilettante]

Well, a 10,000 square mile solar array may be a big target, but it would take one heck of a massive storm system to take it all down.

I also don't think destroying something like a couple hundred panels out of tens of millions is exactly the kind of high-impact target a terrorist would pick. I think just one nuclear core offers much more terror/effort ratio.

Not that I disagree with other reasons you cited.

 

[ByteMe]

Fusion would be a MUCH better way to go.