It is currently Sun Oct 22, 2017 7:47 am

All times are UTC - 8 hours




 Page 1 of 10 [ 142 posts ]  Go to page 1, 2, 3, 4, 5 ... 10  Next
Author Message
 Post subject: Solar cells down to details...
PostPosted: Wed Apr 06, 2005 2:26 pm 
User avatar

Joined: Fri Feb 01, 2002 1:01 am
Posts: 1738
Location: Mideast USA
Hello everyone.
A solar cell is a PN junction of silicon.
There is amorphous and crystaline types, thus crystaline is not a mandatory structure.<p>How can some ink with anions dopant be applied to a conductive foil; and when dry, a second ink with cations dopant applied on top (plus a clear conductive collector overlay)?<p>¿Is the chemistry to produce a paintable compound of the same effect as in doped silicon so elusive to achieve comparatively decent efficiencies ?<p>Just as reference, the basics is here:
http://library.thinkquest.org/17658/sol/solelecht.html<p>Obtaining the same with simple compounds other than silicon; is that difficult ?<p>(Yes, I have already deeply searched the web with many interesting results) Maybe this should go to a specialized forum but I prefer YOU, fellows.<p>Miguel



_________________
- Abolish the deciBel ! -
Offline
 Profile Send private message  
 
 Post subject: Re: Solar cells down to details...
PostPosted: Wed Apr 06, 2005 2:49 pm 

Joined: Sat Feb 28, 2004 1:01 am
Posts: 28
<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr> Obtaining the same with simple compounds other than silicon; is that difficult ?<p> <hr></blockquote>
Nope. Research into alternative solar cell designs have seen promise. Solar cells from spinach proteins is one example. I also participated in a demonstration that involved creating a solar cell from black berry juice.


Offline
 Profile Send private message  
 
 Post subject: Re: Solar cells down to details...
PostPosted: Wed Apr 06, 2005 3:31 pm 
User avatar

Joined: Mon Feb 09, 2004 1:01 am
Posts: 2126
Location: NY
Silicon is certainly not the only photovoltaic.
Check out these sites for a few alternatives:
http://www.tfp.ethz.ch/HESC/HESC.html
http://www.siemenssolar.com/facts.html
There is no simple explanation for photon-to-power conversion in amorphous or crystalline materials, and the potential list of ingredients goes on and on!
As an alternative to fossil fuel power, it gets better looking every day!
:D


Offline
 Profile Send private message  
 
 Post subject: Re: Solar cells down to details...
PostPosted: Wed Apr 06, 2005 3:31 pm 
User avatar

Joined: Thu Aug 01, 2002 12:01 am
Posts: 2780
Location: San Jose CA
"Obtaining the same with simple compounds other than silicon; is that difficult ?"<p>If it were easy, we would not need Oil.<p>You have to think in terms of a chemical reaction or material wherein one or more photons enter and move electrons up to a higher energy level where they are collected and sent through a circuit before returning to the original energy state.<p>Though scientists have come up with many materials that atr photo sensitive, creating an efficient way of connecting all those little things up so that the electrons can be gathered and used is just as big a challenge. <p>Let just say we can do it the way you described. What keeps the whole thing from becoming a big short circuit if you build it on a continuous conductive sheet? With only one electrode, where does the current return? how do you prevent oxygen or water vapor from reacting with your electron deprived material without creating a non conductive barrior?<p>My favorite fantasy solar generator consists of two fine wires held in parallel, crystals are grown between the two by immersing in a solution while a bias voltage is applied to the wires. The resulting threads are coated with a polymer for stability and flexibility and can be woven and wired together to make a cloth. Of course, I have no idea what material to grow the crystals from.


Offline
 Profile Send private message  
 
 Post subject: Re: Solar cells down to details...
PostPosted: Thu Apr 07, 2005 1:44 am 

Joined: Tue Mar 04, 2003 1:01 am
Posts: 1286
Actually, some of the earlier solar cells were amorphous and were not made of silicon. Photographic exposure meters used in the 1950's and possibly earlier used selenium cells. Many transistor projects were described powered by the International Rectifier B2M, a small selenium cell with leads and a mounting bracket attached. The total area was a couple of square centimeters and the output was possibly 100 or so microamps in full daylight.<p>These cells were made by using very crude techniques by present standards. The selenium was melted and then applied to a substrate. The cooling conditions may have been such as to give an amorphous structure rather than a crystalline one. Electrodes were some form of conductive paint.<p>Actually, an plate taken from a selenium rectifier would give a few microamps of photocurrent.<p>The basic problem was poor efficiency and low output currents.<p>Single crystal silicon cells seem to be the most efficient. Amorphous silicon cells are less efficient and easier to make and are actually quite common in devices such as solar powered calculators. Polycrystalline cells are also fairly common. I suspect that the polycrystalline cells work only because the individual crystals are fairly large. The grain boundaries between the crystals will probably cause leakage currents, which would reduce the output. If the crystals are large, this might be tolerable, since the area of a single grain would increase faster than the periphery of the grain as the grain size increased.<p>There are organic materials the can be used to make junctions similar to those in silicon. Unfortunately, these are not "simple". They are being used to build organic LED displays. These materials are rather exotic organic compounds and, since there is no large established market for them, they are not cheap. They probably could be used to make solar cells, but a square foot of display can command a much higher price than a square foot of solar cell. The higher material cost is worth it here. For solar cells, the silicon cost is lower than the organic material cost and the efficiency is better.<p>[ April 07, 2005: Message edited by: stephen ]</p>


Offline
 Profile Send private message  
 
 Post subject: Re: Solar cells down to details...
PostPosted: Sun Apr 10, 2005 8:55 am 

Joined: Sat Feb 28, 2004 1:01 am
Posts: 28
<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr> There are organic materials the can be used to make junctions similar to those in silicon. Unfortunately, these are not "simple". They are being used to build organic LED displays. These materials are rather exotic organic compounds and, since there is no large established market for them, they are not cheap. They probably could be used to make solar cells, but a square foot of display can command a much higher price than a square foot of solar cell. The higher material cost is worth it here. For solar cells, the silicon cost is lower than the organic material cost and the efficiency is better.<p> <hr></blockquote>
Nope. You are wrong. I just researched the spinach solar cell and their efficiency is the same as a flexible solar cell so they are startign to make improvements. Of course this is a really really really recent development.<p>[ April 10, 2005: Message edited by: Adam Y. ]</p>


Offline
 Profile Send private message  
 
 Post subject: Re: Solar cells down to details...
PostPosted: Sun Apr 10, 2005 9:11 am 
User avatar

Joined: Mon Feb 09, 2004 1:01 am
Posts: 2126
Location: NY
Indeed, with a 1 mm X 1 mm (.0016 sq. in.) sample research cell, it'll be awhile before that green converts sunlight to the other green ($).


Offline
 Profile Send private message  
 
 Post subject: Re: Solar cells down to details...
PostPosted: Sun Apr 10, 2005 11:27 pm 

Joined: Tue Mar 04, 2003 1:01 am
Posts: 1286
That spinach solar cell sure got a lot of publicity. Maybe they will get farther than the bacterial batteries proposed somewhere in the 1960's.<p>There seem to be two basic problems, short life and low efficiency. Three weeks is way too short to be of much use. This can probably be extended, but even lifetimes of a year or two will obviously require a great deal more development.<p>The efficiency is very low compared to silicon cells. Normally, the efficiency of a solar cell is considered to be the electrical output compared to the total radiation input. The radiation is assumed to be sunlight. The theoretical maximum efficiency of a silicon cell is put at a little over 20 percent. The infrared part of the radiation is unused and the sensitivity in the ultraviolet is reduced.<p>The spinach cell was measured with a laser beam, probably in the visible range. It was noted that a large portion of the radiation passed through the cell, and the efficiency was calculated as a fraction of the energy absorbed by the cell. The light was a single wavelength, and may have been chosen for maximum efficiency. The efficiency under these conditions was given as about 12 percent.<p>If a silicon cell were measured in the same way, I would expect an efficiency of over 50 percent.<p>Measured with sunlight, I suspect that the spinach cell would come out somewhere around 2 or 3 percent.<p>The back contact of the cell was described as an organic semiconductor. I assume that this is similar to the materials being developed for organic LEDs. It might be simpler and more efficient to make a junction between two organic semiconductors and use that as a solar cell.<p>[ April 11, 2005: Message edited by: stephen ]</p>


Offline
 Profile Send private message  
 
 Post subject: Re: Solar cells down to details...
PostPosted: Mon Apr 11, 2005 1:53 pm 

Joined: Sat Feb 28, 2004 1:01 am
Posts: 28
<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr> The spinach cell was measured with a laser beam, probably in the visible range. It was noted that a large portion of the radiation passed through the cell, and the efficiency was calculated as a fraction of the energy absorbed by the cell. The light was a single wavelength, and may have been chosen for maximum efficiency. The efficiency under these conditions was given as about 12 percent. <hr></blockquote>
Thanks. As someone isn't an engineer yet I didn't know about that bit of information.


Offline
 Profile Send private message  
 
 Post subject: Re: Solar cells down to details...
PostPosted: Mon Apr 11, 2005 2:53 pm 
User avatar

Joined: Tue Dec 04, 2001 1:01 am
Posts: 4325
Location: Bieber Ca.
Tri layer solar cells utilize both the UV and IR wave lengths, and add to the solar cell design to achieve way above the 30% level, for the same surface area. <p>Prismatic mirror designs also included in the new designs utilize more of the suns energy by focusing and filtering the sun light to its max.

Cost is only relative to market demands. <p>If the government gets off their butts and starts placing the incentives in the right area of industry, away from oil, solar costs will drop a thousand fold and be able to compete with other means of power.<p> A rough figure states that if every roof in America was covered with solar cells instead of wood shingles or petro chemical coverings, this alone would produce 50 times the current consumption of power in the US, and at the current rate of energy produced by the common solar cell of today and not what tomorrow may bring. <p>Roofs would also fare better covered in glass compared to tar or wood shingle and add to the reflective value as well to keep the home cooler.<p> We have no vision in this country except for the color of black and green, a path to no where.


Offline
 Profile  
 
 Post subject: Re: Solar cells down to details...
PostPosted: Tue Apr 12, 2005 5:13 am 
User avatar

Joined: Thu May 01, 2003 12:01 am
Posts: 436
Location: Wichita, KS
Hi Chris, That is a great sentiment. Living in the land of hail and tornadoes, I hate to think what the replacement/repair cost of my roof would be at least once each springtime when the weather goes crazy. A couple of years ago a buddy was so proud that he got his van in quickly to have all of the windows replaced after an AM hailstorm. Before he picked it up that night... a second storm hit - later that same afternoon, and took out all of the new windows.
Just my opinion... you know what they say... "People who live in glass houses..."
Dave


Offline
 Profile Send private message  
 
 Post subject: Re: Solar cells down to details...
PostPosted: Tue Apr 12, 2005 6:54 am 
User avatar

Joined: Tue Dec 04, 2001 1:01 am
Posts: 4325
Location: Bieber Ca.
But that is in the land of OZ<p>Shit happens no matter what. <p>Also fiberglass or resin replaces glass very well, [optical resins are very clear] and it even stands up to hail. <p>But the tornadoes will have to be taught to behave.<p>Also dont forget, bullet proof glass, a little more in cost, but a huge saving in the long run. <p>I hear that windmills take a beating in Kansas too?


Offline
 Profile  
 
 Post subject: Re: Solar cells down to details...
PostPosted: Tue Apr 12, 2005 4:43 pm 
User avatar

Joined: Mon Feb 09, 2004 1:01 am
Posts: 2126
Location: NY
The idea of home power generation, and receiving a check from the electric utility for a change, simply overwhelms the petty nuisance of an occasional outage.
Sorry, not to demean the devastation that nature can cause, but there are things you can do to prevent damage to a collector, as there are ways to protect your other assets.
Imagine sending your electric company a letter saying, "Thank you for your payment"! :D
Here in New York State, the installation costs you about half of the retail cost due to rebates from feds and the state, plus tax breaks.


Offline
 Profile Send private message  
 
 Post subject: Re: Solar cells down to details...
PostPosted: Tue Apr 12, 2005 6:35 pm 
User avatar

Joined: Tue Dec 04, 2001 1:01 am
Posts: 4325
Location: Bieber Ca.
Los Angeles started many small programs in some cities to ensure that 100% of new homes be fitted with Solar power. <p>They feed back into the grid by DAY, to off set their consumers power usage at work, and then by night, the customer utilizes the grid which can be mostly hydro electric and not emergency power from the consumption of hydrocarbon based generators like it is during the day, at present. <p>Peak power is almost always exclusivly petro chemical/ natural gas based generators at present. Solar energy in these cities helps to reduce this amount of consumption. <p>Once the over all cost of implementing the solar cells has been amortized, a net gain is had by all.<p> And this is a tiny project that has shown that it can be done.<p> Once the country wakes up to this possibility and purchases massive quantities of solar panels, the price will drop to a fraction of the cost today, to the point that our oil consumption from foreign countries will no longer be necessary, and thus false wars for oil also will be not necessary, which at today’s rate or facade is over 1500 lives from the milatary alone. <p> If we over produce enough cells, we can even begin with the next stage of hydrogen production from water and not the absurd proposition given to us by “Zero knowledge politicians”, of extracting hydrogen from oil.


Offline
 Profile  
 
 Post subject: Re: Solar cells down to details...
PostPosted: Wed Apr 13, 2005 2:03 am 

Joined: Tue Mar 04, 2003 1:01 am
Posts: 1286
Traditional silicon solar cells may be a loser from an energy standpoint. Melting silicon is a high temperature process using electric heating of some form (either radiation or induction). Generating that electricity is not very efficient, possibly in the 35 percent range. Diffusion furnaces are also electrically heated. The time required to recover the energy needed to produce a silicon cell may be unreasonably long.<p>The organic semiconductor approach might be better, since high temperature processes are not required. The material composition would determine whether it was N or P type, so diffusion would not be required. The fabrication steps would probably involve deposition of dissolved material form a solvent, which would not require high temperatures. Synthesizing the starting materials might require heat, but this can probably be supplied by direct combustion rather than electricity. This is a fairly efficient process and could possibly be done with waste heat from some other synthesis process.<p>The flies in the ointment here would include low efficiency and possible limited life with exposure to ultraviolet. Many organic materials degrade on exposure to sunlight, some faster than others. Ultraviolet filters might require energy to produce, since they might have to be glass, which is another energy intensive material. The lower energy required to make an organic solar cell might be offset by a short lifetime. Possibly the energy required to make the glass could be alleviated by reusing the glass to make new cells when the old ones degrade.<p>[ April 13, 2005: Message edited by: stephen ]</p>


Offline
 Profile Send private message  
 
Display posts from previous:  Sort by  
 Page 1 of 10 [ 142 posts ]  Go to page 1, 2, 3, 4, 5 ... 10  Next

All times are UTC - 8 hours


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to: