Talk:Photovoltaic array/Archive 2

Properties of Solar Panels: A question.
––Do Solar panels, by absorbing light energy and converting it to electrical energy reduce ambient temperature? Or do they, in the process of attempting to absorb more energy end up giving off more heat energy throughout the day.

My question stems from a notion a friend had that a large array of solar panels in use over flat roofed houses in desert nations would not only serve as a electrical power source but would reduce the need for air conditioning or other temperature controls or just outright reduce ambient temperature. I mean, aren't efficient arrays starting to absorb about 30% of light energy? Normally the roof of a house gets heated up during the day when Sun rays falls on the roof. Thechosenone021 01:26, 20 July 2006 (UTC)


 * Interesting question. I'm no expert, but here's one thought: it must also depend upon what use the generated electricity is put to.  If it is used locally to drive any kind of appliances (including fridges!), then almost all of it will finally be converted into local heat (out of light energy). But if it were run into (efficient) batteries, or run by wires off to some other location, there may be some local cooling.  But don't forget that they convert light into electricity, not heat - although that light energy would otherwise be absorbed by something else and heat it too.  It's still counter-intuitive because, having been around solar panels, I know how hot they get in direct sunlight too! --Nigelj 17:45, 20 July 2006 (UTC)
 * Right, I was aware that that might be the case given that the panels are usually a dark color to absorb more light energy that would usually be reflected so they heat up. Of course that reflected light would go somewhere else eventually. I guess any study would need to be large enough to account for all that. Thanks though, I hope maybe someone has seen some sort of study on this topic? Thechosenone021 01:28, 21 July 2006 (UTC)


 * Actually, heat is bad for them, and it lowers their efficiency. Many have a metal backing, so that they radiate away that heat. In fact, you might do well to solder a solar hot water collector to their bottom, to cool them off. linas 21:36, 22 July 2006 (UTC)


 * A researcher at BP Solar (British Petroleum) gave me these figures:

Of every 100W of light falling on a typical module, 50W reflected, 17W converted to electricity, 33W absorbed as heat. This was a while ago and I doubt if they are any more than a rough indication, but it is clear that a) there can be a heat build-up and b) this reduces the efficiency of the PV conversion. There are various ways to use the heat in a building. I believe there are some modules that incorporate solar water heating panels as Linas said, but DIY enthusiasts should think twice before putting water in close proximity to DC electricity. Another way is to draw the heat into the building as part of the mechanical or passive ventilation system, and then it can be dumped to a thermal store of some kind, e.g. it can be turned into hot water with an air-to-water heat pump. There are some references around for some of these solutions. Itsmejudith 21:42, 28 July 2006 (UTC)

Right, but the original question is pertaining to Solar Panels effect on ambient temp. If a tree's photosynthetic process reduces temperature in the shaded areas, couldn't a photo array have a similar effect? Thechosenone021 17:34, 29 July 2006 (UTC)


 * Ah, but trees are famous for transpiration and also deep roots. Sucking up cool underground water and causing all that evaporation (latent heat) is bound to have a cooling effect.  Unlike a hot, dry, black silicon panel in the direct sun. I just dunno.  --Nigelj 20:53, 29 July 2006 (UTC)

Now the Solar panel fixed acts like a shield between the roof and Sun rays; and hence the house roof will be cooler than earlier. Another point is that the gap left between roof and solar panel is filled with air and the air circulation helps roof to be cooler and the roof doesn't transfer heat into the house, hence the inmates feel it cooler than earlier days. Karamchetti 16:11, 7 August 2008 (UTC) nehru.karam

Contradiction?
At the beginning of the article it says:

"At high noon on a cloudless day at the equator, the power of the sun is about 1 kW/m², on the Earth's surface, to a plane that is perpendicular to the sun's rays. "

a bit later on the figure climbs from 1kW/m² to 83kW/m²:

"In the Sahara desert, with less cloud cover and a better solar angle, one can obtain closer to 83 kW/m²."

surely only one of these can be correct? 128.214.9.63 12:12, 12 February 2007 (UTC)

The first figure, 1 kW/m2 is correct, although you can also obtain an irradiance this high in temperate zones in the middle of the day in the spring and summer. The 83 kW/m2 is impossible. If you look at the preceding paragraph, there is the statement that for the "United States and Europe, typical insolation ranges from 4 KWh/m²/day in northern climes to 6.5 KWh/m²/day in the sunniest regions." The sentence in question should state "In the Sahara desert, with less cloud cover and a better solar angle, one can obtain closer to 8.3 kWh/m²/day." Rkwiki 03:09, 22 February 2007 (UTC) The Irradiance in USA from one region to another varies from 1 to 8 KWh/m2 /day as per the measurements made by Standard laboratories. When the Sunrays falls on a module based on its efficiency it converts Sun energy in to Electrical Energy. At present this Convesion efficiency is 19.6% as given by SUN POWER Corporation in their Data sheet (www.sunpowercorp.com). Karamchetti 16:22, 7 August 2008 (UTC)

Places where you can buy a Photovoltaic array?
If there is any place where you can buy a Photovoltaic array (from the internet) it should be listed in the links section. —The preceding unsigned comment was added by 65.24.106.106 (talk) 18:18, 15 February 2007 (UTC).

Figures?
The figures about the Sahara don't add up. 83KW/m2 times 9 million km2 = 83x103 x  9x1012 = 750x1015 = 750 petawatts, not 750 terawatts.

I need these figures for my coursework. Does anyone know what the real figures are? —The preceding unsigned comment was added by 81.111.90.8 (talk) 01:50, 17 February 2007 (UTC).

What is meant is upto 8.3 kWh/m2/day in the Sahara. Here's a link where you can look up insolation in Europe and Africa http://re.jrc.cec.eu.int/pvgis/solradframe.php?lang=en&map=africa Rkwiki 03:12, 22 February 2007 (UTC) The figures should be read like this: 8.3x103w/m2x9X106X106 = 75.7 x 1015 =75.5 petawatts (75.5 Quadrillion (USA)watts). Karamchetti 16:52, 7 August 2008 (UTC)

arrays vs. modules
hi, is it possible to separate the two lemmata? --Trickstar 14:55, 20 April 2007 (UTC)
 * Well, they're separated now, although I can't figure out why. As far as I can tell, they aren't actually separate lemmata: an array is just a group of installed modules, right? If the only difference is between the singular and plural, I don't think we need separate articles for photovoltaic module and photovoltaic array. If anyone has a good reason why they should be separate, please speak up. I've proposed a merge on the PV module page, so editors/visitors there will hopefully participate in this decision. Specifically, I've proposed that the module article be merged with this one, because it's more popular: only 15 pages link to that article, while around 60 link to this one. Also, the module article contains very little content that isn't repeated either here or in Photovoltaics. Indeterminate 04:07, 10 July 2007 (UTC)


 * I think the articles should stay separate, since there is plenty of stuff to say about arrays that doesn't belong in an article on modules. The problem now is that this article doesn't really discuss PV arrays, it's just redundant general PV info that belongs elsewhere . I'll try to fix that soon. I'll comment on the module page too. Merphant 06:48, 10 July 2007 (UTC)

Merges
Most of the content of this article needs to go into Photovoltaics. Surely an array refers specifically to a connected set of modules, the specifics of which need to be dealt with under this title--Oldboltonian 21:23, 31 May 2007 (UTC)


 * Please follow the Talk page guidelines by posting new topics at the bottom of the talk page. As far as a merge goes... well, I agree, but I think the Photovoltaics article is quite long enough as it is, and I can imagine readers wanting to simply learn about arrays/modules without wanting to read about the current state of the photovoltaics industry. That's all I wanted when I came here. :) Unfortunately, though, it's not clear to readers whether the technology itself is known as "PV arrays", "solar cells", or "photovoltaics". I think the modules article should be merged into this one, or vice versa; please see my reply to Trickstar above. Indeterminate 04:07, 10 July 2007 (UTC)


 * I oppose a merge into photovoltaics. I think this article should be merged into photovoltaic module. An array is a collection of modules, so it naturally fits into the topic of modules. Photovoltaics on the other hand has content about the photovoltaic industry, the number of modules installed, cost and financial incentives. If the entire article is not merged, I think that the "Theory and construction" and similar content should be merged because it is information that belongs in a discussion about photovoltaic modules. An article on arrays should only discuss what is relevant to multiple photovoltaic modules rather than module construction. Since there has been no activity on the merge, I will remove the tag for now. It can be replaced if there is a reply from Oldboltonian or if another editor argues in support of a merge. -- Kjkolb 08:12, 25 August 2007 (UTC)


 * To me, the ideal structure is an overarching article entitled photovoltaics, with a summary of a number of sub articles, which should include cells (exists), modules (needs more), applications and systems (needs to be created, but would include sections and subarticles. power stations, BIPV, off grid, standalone (calculators to parking meters via temporary traffic signs, transport etc.) financial aspects from system cost to finacial incentives (mostly done). Arrays would be merged into sytems and applications.--Oldboltonian 21:21, 26 September 2007 (UTC)