Talk:Solar cell/Archive 3

Another cleaning is called for
To all PV scientists reading this wiki. Please go over the Solar Cell site and remove poor grammar, uncited claims, and corporate "plugs". There is some degeneration of the Solar Cell information with time and a maintainance check is now necessary. Thank you for your efforts and your help. Nanomech 06:32, 23 October 2006 (UTC)

Solar panel energy payback
I am not sure that the calculation of energy payback of solar cells are practical in the way that they never include the energy cost of extracting, concentrating, distributing all the materials used in the fabrication of solar cells, plus, no mention of the energy cost to build the machines that are used to fabricate the solar cells ... and the energy cost for the people to come and work to the manufacturing plant.

The references used in the articles mentioned in "Solar cells and energy payback" are using a lot of rule of thumb to assess a quick payback. Therefore I think this part should be either removed or implemented with a practical calculation as I illustrated above.

By the way, I wish that kind of practical calculation be done for every products made.

http://www.csudh.edu/oliver/smt310-handouts/solarpan/pvpayback.htm

is currently used to support the sentence:

"Whether solar cells generate positive net energy is disputed by some researchers who object that such analysis doesn't take into account waste, inefficiency, and related energy costs that would come with a real-world solar cell."

But the source actually says exactly the opposite. It says the that they definitely *do* generate positive net energy, and their analysis includes the cost of extracting, concentrating, and delivering solar grade silicon, contrary to the talk point above. Zilles 00:38, 23 May 2007 (UTC)

Since cells are not used in isolation, the pertinent calculation is that of the system (module, inverter, etc.) This article should focus on cells.--Oldboltonian 01:14, 17 June 2007 (UTC)

p-n junction description unclear
I believe the last sentence of this quote out of section "The p-n junction" may have things reversed, or is worded ambiguously. The electric field which is established points from the n-type to the p-type layer, and so a current can flow only in that direction, i.e. electrons may only pass from the p-type side to the n-type side, and holes may only pass from the n-type to the p-type side; whereas the following quote implies the opposite. Perhaps I misunderstand the wording of this sentence.

"If a piece of p-type silicon is placed in intimate contact with a piece of n-type silicon, then a diffusion of electrons occurs from the region of high electron concentration (the n-type side of the junction) into the region of low electron concentration (p-type side of the junction) ... an electric field [...] is created by the imbalance of charge immediately either side of the junction which this diffusion creates. The electric field established across the p-n junction creates a diode that promotes current to flow in only one direction across the junction. Electrons may pass from the n-type side into the p-type side, and holes may pass from the p-type side to the n-type side."

References: http://science.howstuffworks.com/solar-cell1.htm http://www.dur.ac.uk/~dph0www5/solar.html http://solardat.uoregon.edu/download/Lessons/PVLessonPlan1SolarCells.pdf

Detritus 03:50, 5 December 2006 (UTC)

New 40% efficiency solar cells
Superefficient, Cost-Effective Solar Cell Breaks Conversion Records

That article has a new graph that can be used to upgrade from the one currently in this article. Seen [here].

Solar cell converts 40.7% of sun into electricity By Stan Beer Friday, 08 December 2006 ''A subsidiary of Boeing, has set a new world record in converting sunlight into electricity with a new type of land-based solar cell. The new photovoltaic cells, which are currently being tested in the Australian desert, can convert 40.7% of the sun's energy into electricity, smashing the previous highest performance mark of 33%.'' [Link]

More on [Google News]

Just wanted to point that news out in case it hasn't already been brought up. --Steele the Wolf 22:59, 13 December 2006 (UTC)

Wanted to add an article on this subject : http://www.worldwatch.org/node/4803 --YoavD 12:41, 11 January 2007 (UTC)

solar fiber
I heard that information on solar fiber technology was moved from the solar power article to the solar cell article. But today the solar cell article doesn't even mention the word "fiber". Has something gone horribly wrong? --68.0.120.35 06:05, 6 January 2007 (UTC)

Question
Don't the solar cell works like a greenhouse?, but instead of heating generating electricy. Sow it will also be a problem with the global heating and the Greenhouse_effect? --25 january 2007 (GMT+1

Function of a solar cell
It traps heat and convert it in to electrcity

"Manufacturers" list
This list was added to the article a few minutes ago:

Manufacturers
Wikipedia generally avoids lists like this, so it has been removed. Thoughts? --Ckatz chat spy  18:34, 29 January 2007 (UTC)


 * For anyone trying to learn about this subject this is important information. I think we should leave it in the article and make sure the list is complete and up to date. Afterall Wikipedia is about maintaining and distributing high quality information. Frank van Mierlo 21:44, 29 January 2007 (UTC)


 * Information, yes, but not information for the sake of information. The article is about solar cells, and how they work - not a business directory of who is manufacturing them. You might wish to check out WP:NOT, specifically the section Wikipedia is not a directory. --Ckatz chat spy  22:24, 29 January 2007 (UTC)
 * Sure however I believe we also have break all rules in our charter. In this case it is a rapidly developing industry that has a real impact on our lives and this list helps readers to grasp what is going on. By the way I have no financial interest in any of these companies nor any other affiliation with them. I just genuinely believe this is good information. It is often in industry that the real progress is being made. Frank van Mierlo 22:42, 29 January 2007 (UTC)

PLASMON-ASSISTED SOLAR CELLS
Hi, I think you could add something about this new discovery that improves efficiency around 19-33%: http://newton.ex.ac.uk/aip/physnews.819.html#2

212.0.126.98 07:35, 16 April 2007 (UTC)

How plants do it: quantum computation
http://www.sciam.com/article.cfm?articleID=ED1D1446-E7F2-99DF-3CBF8B2F66C0C5D4&chanID=sa003 —The preceding unsigned comment was added by 212.0.126.98 (talk) 08:06, 16 April 2007 (UTC). Moved to http://www.sciam.com/article.cfm?id=when-it-comes-to-photosynthesis-plants-perform-quantum-computation . --68.0.124.33 (talk) 01:15, 4 July 2008 (UTC)

Euro usage - "Comparison of energy conversion efficiencies"
As Ireland's the only official Euro user with an English official language, I think it's appropriate to use US currency (or British currency) as the primary referent in almost any en.wiki page, and have thus altered it here. &^@@#%&!!!!! chauvinistic or experimentalist editors who force others to act as )&&$^(@ conservative pedants. ;) 69.243.168.118 13:37, 22 April 2007 (UTC) Formerly the IP-Address 24.22.227.53 (egh. I think I'm too tired to properly grammar check this paragraph)

p-n explanation correct?
From the article:
 * When the electrons diffuse across the p-n junction, they recombine with holes on the p-type side. The diffusion of carriers does not happen indefinitely however, because of an electric field which is created by the imbalance of charge immediately either side of the junction which this diffusion creates. The electric field established across the p-n junction creates a diode that promotes current to flow in only one direction across the junction. Electrons may pass from the n-type side into the p-type side, and holes may pass from the p-type side to the n-type side. [...] Ohmic metal-semiconductor contacts are made to both the n-type and p-type sides of the solar cell, and the electrodes connected to an external load. Electrons that are created on the n-type side, or have been "collected" by the junction and swept onto the n-type side, may travel through the wire

It seems to me as if this paragraph contains an internal contradiction. If we have a p-n junction, electrons will diffuse from n to p until the emerging electrical field stops them. Then the junction acts as a diode, allowing electrons to flow from n to p. But later it says that electrons created on the n side go through the wire rather than directly to p. Why would they do that? I would assume electrons freed on n simply go through the diode over to p. My conjecture is that the above sentence should read Electrons may pass from the p-type side into the n-type side. Is that correct? AxelBoldt 00:26, 28 April 2007 (UTC)

I think this comment above makes the same point. AxelBoldt 16:23, 29 April 2007 (UTC)


 * Meh.. The text isn't at all clear.  This paragraph is actually talking about what happens when a p-n junction is initially formed and its free carrier concentration profile in equilibrium.  The later text is referring to non-equilibrium conditions (photoexcitation, which produces additional electron-hole pairs).  The p-n junction in thermodynamic equilibrium has a space charge (depletion) region which is devoid of free carriers due to the balancing of forces from diffusion and the built-in electric field caused by the charge separation at the junction.


 * Under photoexcitation, electron-hole pairs are generated by photon absorption. It's desired that these EHPs are generated in the depletion region or within a diffusion length (the average length a minority carrier travels before recombining) of the junction because it's the electric field of the junction that separates the EHPs (electrons to one side, holes to the other).  If the EHPs are not separated, they contribute nothing to the net current.  The build up of excess (separated) minority carriers on both sides of the junction is what leads to the photocurrent.  When the excess carriers recombine with majority carriers, more majority carriers must flow in to keep the system in equilibrium.  If the p-n junction is connected to an external circuit, these additional majority carriers largely come from the circuit; holes flowing into the p-side and electrons into the n-side (they also come from thermal generation, which doesn't contribute to external current and is a big part of the reason many sensitive long-wavelength detectors are operated at cryogenic temperatures).  These equilibrium-restoring majority carrier current components are what you observe to be the external current caused by a solar cell under illumination.


 * I'll add this page to my watchlist and perhaps work on it when I get the chance. It needs some serious refactoring to clarify things. -- mattb 16:54, 29 April 2007 (UTC)

I'm still struggling here. If an electron is freed by light in the depletion region, shouldn't it be pulled towards the n side of the junction (which after all is positively charged in equilibrium)? So after your explanation I would expect these electrons to collect on the n side and eventually flow out through the wire (or equivalently combine with holes that flow from the wire into the n side). So my conjecture right now is that if I measure the voltage across an isolated p-n junction in equilibrium, then p is negatively charged with respect to n, but if I shine light on it, then n is negatively charged with respect to p. Is that correct? AxelBoldt 18:57, 30 April 2007 (UTC)


 * Sorry, I typed my explanation too fast and botched it. Your first statement is correct; I reversed the flow of majority carriers.  Holes will flow into the n-side and electrons into the p-side, meaning that the photocurrent is actually in the reverse bias direction (a forward-biased pn junction injects holes to the n-side and electrons to the p-side).  What's interesting is that when you hook this up to a load resistance, the photocurrent causes a voltage drop in the load which adds forward biases the pn junction, though the net current flow is still in the reverse bias direction.


 * Most of the excess carriers never themselves make it to the contacts before recombining, but it is this recombination that causes more majority carriers to flow in.


 * If you measure the voltage drop across a lone dark pn junction in equilibrium, there will be none. Charges will rearrange themselves to balance all the forces out again, and without energy input (in this case a battery or light), there will be no sustained current flow.  The "built in" voltage of diodes can be observed under high forward bias.  Under illumination, the pn junction will be reverse biased, and you will see close to the maximum voltage possible for that light level since there is little current flowing through your voltmeter.  If you attach an ammeter you'll see close to the maximum external current that the cell can deliver at that light level.  There's an optimal point of operation (load resistance) that balances the voltage and current to deliver the most power, and that's typically where systems try to operate solar cells.-- mattb 19:26, 30 April 2007 (UTC)

Possible factual error - could someone with a proper EE-background please check "Maximum-power point" ?
The article says: - The quickest way to determine the optimal load for a given constant light condition (i.e. a stable quiescent point) is to measure the Thevenin equivalent Voltage (i.e. open circuit), then using a potentiometer as a load, monitor the voltage across it as the pot is dialed. When the load voltage is exactly half of the Thevenin equivalent Voltage, disconnect the potentiometer and measure its resistance on an ohmmeter. By the maximum power theorem, the potentiometer resistance will be the optimal value of the load for maximum power transfer (due to the equal voltage division between internal Thevenin equivalent Resistance and the load). -- I think this method is wrong for the Equivalent circuit of a solar cell. It only applies for a constant voltage source with a fixed output resistance Rs.

A Solar Cell is basically a constant current, not voltage, source. However, the parallel p-n-Junction of the photodiode clamps the open-circuit Voltage of the Cell at a point that is determined by its forward Voltage at the output current of the cell under the incident light. For an ideal p-n-junction, the forward current halves app. every 25mV. Therefore, increasing the load voltage by 25mV would lead to doubling the parasitic forward current through the p-n-junction.

If, for example, at some operating point the open-circuit voltage is 475mV at 1A forward current, and the output resistance is 0.1R, then increasing the current drawn from the cell from 0.0A to 0.875A would reduce the forward current through the p-n-junction from 1A to 0.125A, by a factor of 8. The Voltage across the p-n-Junction would then be 0.475V-(3*25mV) = 0.400V. Rs would drop another 87.5mV, so the terminal voltage would be 0.3125V. Power is 0.3125V * 0.875A = 273mW.

If we reduce the load resistor Rl any further, and even optimistically assume that p-n-current drops to 0, then we get half the open circuit voltage of 0.475V at Rl=0.233R, and only get an output power of 233 mW.

Therefore, the only way to determine the optimum load is to measure the actual output current I and Voltage V at the terminals as you dial the pot and then calculate the output power P=I*V at each point and maximise it. The optimum load is then Rl = V/I;

The problem here is that this optimum load point does not only vary with incident light, but also with temperature, which influences the p-n-forward voltage at app. -2mV/K.

Please note that I do not have actual experience working with solar cells, so maybe someone knowledgeable could check this.

If this is correct, then I would just remove the paragraph "The quickest way..".


 * It may be the "quickest", but it's not correct. The PV cell is neither constant current nor constant voltage, but more importantly, the current is not a linear function of the voltage, especially in the open-circuit condition.  The open-circuit voltage is determined by the forward I-V curve of the diode, which is completely nonlinear.  I had removed that paragraph a while back, with a comment to that effect, but I hadn't noticed the uncommented anonymous undo that followed and put it back.  So, I just now took it out again.  Whoever thinks there's something to it should comment here. Dicklyon 17:26, 2 June 2007 (UTC)


 * I'm currently futzing around with some solar cell stuff while not teaching. I don't know enough (yet) to say its right, but it doesn't seem 100% wrong, either.  Likely it is some sort of approximation.  I'll see what I can dig up, but my own work will be a priority, so don't hold your breath too long. At a glance, it doesn't upset me too much as far as approximations go.  A Thevenin equivalent requires the network in question to be both linear and bilateral, but the rule can sometimes be bent a bit if you are describing it at some specific operating point (which the contentious bit seemed to imply).  I don't know if it applies here, but like I said, I'll look into it. Until then, Dicklyon makes some good points. Burtonmackenzie 19:48, 6 June 2007 (UTC)


 * I'd be OK with it as an approximation, but still it should come with a source, if it is indeed a method in use. Here is a ref I used (#16 in Photovoltaics) that says manufacturers provide short circuit current, open circuit voltage, and peak power point; they wouldn't need all three of those if it were a linear circuit, so to me that implies that the method is not what's used. Dicklyon 02:47, 17 June 2007 (UTC)


 * Here's a PDF ref that discusses the use of a Thevenin equivalent model for a solar cell. But they get the voltage from the peak-power point, which gives a pretty good model anywhere near that point.  Getting it from the open-circuit voltage would give a very different and not usefully accurate result, in my estimation.  Dicklyon 02:52, 17 June 2007 (UTC)


 * And Here's a book that shows the kind of empirical expression actually used. It's not so simple. Dicklyon 03:09, 17 June 2007 (UTC)


 * This is the first time I've commented on a Wikipedia page, so apologies if I manage to screw up the formatting (or anything else for that matter). At any rate, Dicklyon is correct -- the Thevenin equivalent as described at the start of this entry is incorrect. The maximum power point voltage is typically somewhere in the neighborhood of 85-90% of the open-circuit voltage, and the maximum power point current is typically around 80-90% of the short-circuit current. Keep in mind that the equivalent circuit of a solar cell is a constant current source in parallel with an ideal diode and a shunt resistor, all of that in series with a series resistor. The relationship between output current and output voltage looks something like this:


 * $$I = I_{L} - I_{0} \left\{\exp\left[\frac{q(V + I R_{S})}{kT}\right] - 1\right\} - \frac{V + I R_{S}}{R_{SH}}$$


 * where $$I_{L}$$ is the current from the current source (proportional to the intensity of the incident light), $$I_{0}$$ is the dark saturation current of the diode, $$R_{S}$$ is the series resistance, and $$R_{SH}$$ is the shunt resistance. $$I$$ and $$V$$ are the output current and voltage, and the other variables should be recognizable as the usual physical constants. The product of $$I$$ and $$V$$ is the power output of the cell, and the solution of the equation that maximizes that product yields the voltage and current at the maximum power point. There's a chart on this site labeled "Basic Solar Cell Current and Power Output" that shows what the resulting I-V and P-V (power-voltage) curves look like. There's also an interactive page at the University of Delaware that allows one to manipulate a simpler version of this model.


 * The book that Dicklyon referenced includes this equation, or at least one very similar. Other books that could be used as references include The Physics of Solar Cells, Crystalline Silicon Solar Cells, and a number of others.
 * --Squirmymcphee 02:38, 28 June 2007 (UTC)
 * Thanks for your comment of support and further info. Dicklyon 03:45, 28 June 2007 (UTC)

Clarification or Merge needed
Wikipedia has an article "Solar cell" and an article "Photovoltaics", which cover pretty overlapping ground; plus an article Photovoltaic array which covers related ground from a different perspective. "Solar cell" and "photovoltaics" should be either merged, or else rewritten so that the difference between the two subjects is clear. Geoffrey.landis (talk) 20:42, 27 November 2007 (UTC)

I agree, I think a good structure is to reserve the "photovoltaics" page for the science of photovoltaics (ie, bandgap theory, materials, etc), "Solar cells" for the commercial product (ie, solar cell types, history, etc) and "Photovoltaic array" for system issues (ie, Watts Peak, Peak Sun Hours, Inverters, etc). At present there is no discernible difference between any of these pages. GG (talk) 20:28, 20 June 2008 (UTC)

It's been suggested before see 'Split, & create Solar cell (physics)' below. The topic is huge and a difficult one to tackle, but has been overlapped several times and is loosing context. See: GG (talk) 21:22, 20 June 2008 (UTC)
 * Solar panel
 * Photovoltaic module
 * Photovoltaics
 * Photovoltaic system
 * Photovoltaic array
 * List of photovoltaics companies
 * Maximum Power Point Tracker
 * Solar Power Satellite
 * Thin film
 * Photovoltaic power station
 * Renewable energy commercialization
 * Building Integrated Photovoltaics
 * Photovoltaics in transport
 * Solar vehicle

Could someone explain why solar cells are blue?
Is it the boron or a common opical coating or what?


 * Silicon has a high index of refraction, higher at short wavelengths than at long; so it has a significant reflection, esp. of shorter wavelengths. I'm not sure about coatings; there may be an SiO2 layer of a thickness that helps with anti-reflection, and if so that can also influence the color.  Anyone know more? Dicklyon 07:21, 28 June 2007 (UTC)
 * This book says it's the residual reflection of the AR coating. Seems likely, since bare silicon is more reflective, a lighter blue-gray. Dicklyon 07:32, 28 June 2007 (UTC)


 * Bare silicon reflects about 35% of incident sunlight on average (weighted to reflect the spectral content of sunlight), so antireflection coatings are a necessity. The coatings are optimized to maximize the number of photons coupled through the coating and into the silicon. However, the index of refraction of silicon spikes in the UV/dark blue part of the solar spectrum, and no other materials match this spike. As a result, antireflection coatings on silicon solar cells reflect much more light in the UV/dark blue than they do in other parts of the spectrum, giving them the dark blue appearance. Sunlight is not particularly strong in that part of the spectrum, so in terms of solar cell performance it is not a big deal.


 * As for the coatings themselves, silicon dioxide is a poor choice because its index of refraction is very close to that of glass and the other encapsulation materials used in making a PV module -- once encapsulated, an SiO2 antireflection coating would have little effect. The materials typically used for solar cell antireflection coatings have indices of refraction between about 1.9 and 2.4, solidly in the middle of the indices of refraction for silicon (about 3.8) and glass (about 1.5).


 * Silicon Solar Cells: Advanced Principles and Practice by Martin Green contains a pretty good short history of solar cell antireflection coating development. A quick summary, updated by me to reflect current trends: Early solar cells used silicon monoxide (SiO). However, SiO itself absorbs light, so it wasn't a terribly satisfactory coating. Several substitutes were found, the most popular being titanium dioxide (TiO2), which became a sort de facto standard AR coating for the PV industry from the '70s through the end of the '90s. In recent years it has been supplanted by silicon nitride, whose index of refraction can be controlled by the ratio of silicon atoms to nitrogen atoms; for this reason, it is often abbreviated SiNx. It is generally deposited using plasma-enhanced chemical vapor deposition (PECVD), which allows for easy control of the silicon/nitrogen ratio. These coatings have the added advantage that they can passivate the surfaces of the solar cell nearly as well as a high-quality silicon dioxide coating, and because of this it has become a key enabling technology in the drive to make crystalline silicon solar cells thinner.--Squirmymcphee 17:02, 28 June 2007 (UTC)

Business-side info
I had previously added some business information on solar cell manufacturers, as well as a link to a global directory of solar cell manufacturers (http://www.enf.cn/database/cells.html). The information was taken down by someone who hadn't actually reviewed the validity of the information but was deleting based on the fact that I posted up several links to ENF.

I will be reposting the information shortly, and would like to hear from any business-experts from the PV industry who feel the links do not add value to readers of the article.

Kit Temple 13:43, 2 July 2007 (UTC)


 * As I mentioned in my response to you on my talk page, the removal was not about the content, but about the fact that all your wikipedia contributions are external links to enf.cn, and that therefore you are presumed to be a spammer. If you want these links back, the best strategy is to propose them on the these talk pages, and let some other editor, not known as a spammer, decide if they are worth adding to the article.  And please do tell us what relationship you have with the enf.cn site.  Dicklyon 15:10, 2 July 2007 (UTC)

Hi Dicklyon. I did indeed take your advice and post messages on the talk pages.

I will be upfront and say that I have a direct relationship with the site in question, but have made strong efforts to include valuable information that is relevant to the pages as well as putting up some relevant links. The PV database in question has taken about 10 man-years of work to put together of the last two years (eg. many people working on it over the period) - it is also completely free of charge for companies to appear and for people to use (so people using the resource do not generate income). I have waited until the site is a clear best-in-class before adding the information to Wikipedia. I would like to add a clear note that the database has not generated net profit, and is done for the benefit of the industry (with other areas of the company supporting it).

In regards to waiting for others to repost - well since some of the pages are rarely visited, and the talk comment I have added has been the first talk comment ever added for those pages (eg. solar trackers), then it would be better to resubmit the info if few people throw up objections to it over the next few days. Most people submitting appear to be technically focused people (judging from the content added) - and I am looking to add business-focused information. Readers of Wikipedia are interested in both aspects.

I will try your suggested way first, but if there is complete silence from some of the more specialsied pages (such as solar trackers, dye cells etc.) because no people with a business focus ever bother to look at the discussion page, then I would like to resubmit the information/links and wait for people to spot it on the main page an initiate a discussion on the value.


 * If there is complete silence, that means you haven't convinced anyone. See WP:COI before re-posting links to your organization. Dicklyon 18:03, 2 July 2007 (UTC)

For the more visited pages, I will cross my fingers that some people who are familiar with the business aspects will spend the time to evaluate the quality of the content. Kit Temple 16:48, 2 July 2007 (UTC)


 * Maybe I misunderstand what it is you wish to add to the article, but based on what you're describing here it seems to me that the policies outlined in What_Wikipedia_is_not suggest that for the most part it is not appropriate. Seems to me that general business-focused information -- such as the manufacturing cost of solar cells, the total volume shipped industry-wide, etc. -- is appropriate. The sort of thing that might appear on a news service or in a consultant's report -- Company A signed a silicon feedstock supply contract with Company B -- is not. A directory of manufacturers is pretty specifically prohibited by Wikipedia policy (see "Wikipedia is not a directory" in the aforementioned link).--Squirmymcphee 20:10, 3 July 2007 (UTC)

Hi Squirmy. I accept your point below that the brand article link below can be seen as Spam, the relevance to a Wiki article about brand strength from market research reports (in the case of the information with the link deleted for example) is beyond my experience so I won't comment on that. However, I have read the link you point to where it mentions "Wikipedia is not the yellow pages." The article seems to be strongly suggesting not to turn Wikipedia directly into a directory (eg. don't put long lists of companies within the article), it doesn't seem to be against linking to directories as a useful resource of information. If someone is looking into the subject of solar cells, isn't it useful to have a link to a complete unbiased list of which manufacturers make cells? Kit Temple 10:11, 7 July 2007 (UTC)


 * I personally don't see a problem with adding a link to the front page of your site to the External Links section. There is already one such link there, though, and given the number of PV directories on the internet I don't think it is practical or desirable to list every last one of them. On the plus side, your directory includes information on manufacturing volumes; on the negative side, it is a commercial web site that arguably uses outdated figures to entice interested parties to purchase more detailed and possibly more up-to-date information (2006 figures have been available from multiple sources for at least four months now, albeit not for free). I haven't been around Wikipedia long enough to know what to do here, so it's probably best to see if others have any opinions on the matter. --Squirmymcphee 21:42, 8 July 2007 (UTC)

Actually, the use of 'outdated figures' is not deliberate. Collecting new numbers takes a huge amount of work. We have recently finished collecting the latest numbers from China and there are now 215 panel manufacturers and 40 cell manufacturers - imagine the time it takes to call up every single one of those companies and talk to the appropriate directors! (because the information can't be found on their websites). Unfortunately if we update the Chinese numbers now to 2006, then we will wipe out the European 2005 numbers due to the database system having to show the same information, so it will have to wait another 6 weeks or so until we have finished collecting all the European numbers and can update both sets. Kit Temple 13:07, 11 July 2007 (UTC)

Content evaluation request
On the suggestion of one of the more experienced Wikipedians, I am submitting suggested comments/links here in the hope that other editors not linked to the ENF site will evaluate the relevance and resubmit it to the main page:

Solar cell brands and manufacturers
Because solar cells can be of varying quality, they can impact the quality of the solar panel (module). A survey by photovoltaic research company ENF among photovoltaic installation companies around the world found that 49% of them found the brand of the solar cell used in the panel to be important. The most commonly named cell brands that installation companies thought were high quality were Sharp, Q-Cells and BP Solar.

Links:


 * Directory of Solar Cell Manufacturers
 * Directory of Solar Cell Manufacturing Equipment Suppliers


 * This seems to be a pretty clear-cut case of spam to me. Aside from the fact that brand preferences don't belong in an encyclopedia entry, the link goes directly to an advertisement for a very expensive report.--Squirmymcphee 20:28, 3 July 2007 (UTC)