Talk:Solar irradiance/Archive 1

References removed
Recently this edit by Lfstevens, removed what appears highly cited papers. However the entire manual references belong inline with the content. Thus, i suggest to remove all manual references, and if possible move them to the correct content. Maybe the editor can explain why remove only a few paper studies. prokaryotes (talk) 04:46, 15 August 2015 (UTC)

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Solar potential maps
The Solar potential maps are interesting but it wasn't clear at all that the mapping between colors and irradiation amounts are not the same among them, potentially misleading readers. Suggest re-doing these maps such that the color/irradiation scale is the same. — Preceding unsigned comment added by 71.238.62.176 (talk) 03:39, 8 March 2016 (UTC)

Insolation vs Irradiance
See What is the difference between insolation and solar irradiance? http://www.researchgate.net/post/What_is_the_difference_between_insolation_and_solar_irradiance prokaryotes (talk) 19:00, 15 August 2015 (UTC)
 * I have no opinion about the answer, but perhaps we should look for something more authoritative? Lfstevens (talk) 07:04, 16 August 2015 (UTC)

This looks like a more credible source: http://www.volker-quaschning.de/articles/fundamentals1/index.php The distinction they make is "The total specific radiant power, or radiant flux, per area that reaches a Spectrum AM 0 (extraterrestrial) Spectrum AM 1.5 (terrestrial) receiver surface is called irradiance. Irradiance is measured in W/m² and has the symbol E. When integrating the irradiance over a certain time period it becomes solar irradiation. Irradiation is measured in either J/m² or Wh/m², and represented by the symbol H", so I think Irradiance is power per area, "solar irradiation" or insolation is energy per area. Chthonicdaemon (talk) 05:57, 28 September 2015 (UTC)
 * Yes, Solar Irradiance and Insolation (Solar Irradiation) are often confused and their meanings and units are conflated in this article. The name of the article needs to be changed to include both ("Solar Irradiance and Irradiation" perhaps), or there should be two articles, one on Solar Irradiance and the other on Solar Irradiation (which is now the preferred way to refer to Insolation).  Having them both in the same article might make sense because Irradiation is simply the integral of Irradiance over a given time interval.  Indeed the www.volker-quaschning.de source cited here is more credible than the www.researchgate.net source. JDHeinzmann (talk) 11:38, 30 October 2015 (UTC)
 * I would be strongly in favour of a separate article on insolation, which can depend on altitude, latitude, cloud cover, wavelength (UV insolation is considerably weaker than IR insolation), nearby reflectors, etc.
 * Solar irradiance on the other hand is independent of all of those variables except wavelength, with "total" often meaning "over all wavelengths". Nominally it is the irradiance at top of atmosphere, but since both the solar luminosity and distance of Earth from the Sun varies from day to day, different authors implicitly take it to be the mean over one or both of these factors, averaged over a specified period.  For example the several articles in Haigh et al's book "The Sun, Solar Analogs and the Climate" use "solar iradiance", "total solar irradiance", and "bolometric irradiance" without definition making it unclear how they differ.
 * A definition of solar irradiance I'd be fine with is the irradiance from the Sun at a distance of 1 AU from the Sun. (This definition is kept simple by modeling the Sun as a spherically symmetric radiator.)  Equivalently solar irradiance is the quotient of solar luminosity by the area of a sphere of radius 1 AU cocentric with the Sun.  These are to be understood as instantaneous notions; one can then speak of mean solar luminosity, and hence mean solar irradiance, averaged over a specified period of time.  (The article Solar luminosity complicates the notion with a factor of k apparently on the assumption that the notion is defined as the annual mean where distance varies according to Kepler's Second Law while luminosity is either constant or an annual average.)
 * My understanding of "total" in TSI, based on usage, is as a spectral notion, namely "integrated over all wavelengths"; thus one can say "UV solar irradiance" but not "UV total solar irradiance". Logically "total solar luminosity" would therefore also be a spectral notion, but instead "total" in that context is more often used redundantly to emphasize that luminosity is irradiance integrated over area.
 * Meanwhile there are some egregious errors in this article, such as mixing up energy and power, but I would nevertheless suggest fixing the definitions before fixing the errors since the latter depend on the former. Vaughan Pratt (talk) 17:06, 13 December 2015 (UTC)

While I can glean/infer the meanings of these terms from the discussion, I'd instead suggest that we refer to an authoritative source and go with that. Can anyone provide one? Lfstevens (talk) 07:43, 14 December 2015 (UTC)

I've reworded the first part of the article to be more in line with the concept of irradiance, and linked to Irradiance to show the analogy. However, as I was searching for the uses of insolation, I came across Direct insolation which uses the "wrong" definition of insolation (the power instead of the energy). I suggest that we take it as we can, I feel that my edits have at least removed some blatantly incorrect units and perhaps harmonized the page a little better. I think part of the problem comes from the redirect from insolation, which I suppose used to be the name of the page. We'll have to go through all the other pages referencing insolation to fix that as well. Chthonicdaemon (talk) 08:26, 14 December 2015 (UTC)

Since when does irradiance not depend on "depend on altitude, latitude, cloud cover, wavelength, nearby reflectors, etc."? Irradiance (or radiant flux) is simply the radiant energy that crosses a specified plane per unit time and unit area. Of course this depends on the entire environment, including the source of the radiation.

My understanding has been that "insolation" means the same thing as "solar irradiance," i.e., the irradiance arriving at a surface (in this case the Earth's surface) that originated at the sun. However, the term "insolation" is used primarily in the land surface and solar energy communities. In my field (atmospheric radiative transfer), "irradiance" (the current SI term) or "radiative flux" (the older, now nonstandard term) are most widely used, so I may be wrong. I fail to see why anyone would want to know an instantaneous flux (J/m2). — Preceding unsigned comment added by 140.142.113.201 (talk) 01:56, 1 June 2016 (UTC)

Proposal to add information on Global Solar Atlas
I tried to make some changes and improvements to this article, in part to update the information but also to include a reference to the Global Solar Atlas (http://globalsolaratlas.info), which is relatively new so therefore not yet well known. These edits were rolled back by another editor because they believed them to be spam, which they are not. However, I do have a potential Conflict of Interest in adding the reference because I was involved in creating the Global Solar Atlas. So I won't attempt to re-add these edits. However, I do think they are relevant, and would encourage someone else to view what I was trying to edit and add and see which of this they feel like adding themselves. Much of the information on this article could do with improving, and I'd be happy to get involved, but I'm wary now after having content deleted. Thanks. --O-Jay (talk) 18:58, 25 December 2016 (UTC)

Incorrect formulas
Recently I corrected the formula for the declination, but the formula for the average insolation over a day is also incorrect and I can't find where the mistake in the construction of the formula is. On this wiki the formula is $$\overline Q ^{day} =\frac{S_0}{\pi}\frac{R_0^2}{R_E^2}[h_0\sin(\phi)\sin(\delta)+\cos(\phi)cos(\delta)sin(h_0)] $$, but the correct formula is: $$\overline Q ^{day} =\frac{S_0}{\pi}\frac{R_0^2}{R_E^2}[\sin(\phi)\sin(\delta)+\cos(\phi)cos(\delta)sin(h_0)] $$(so without the h0) Xyfonix (talk) 08:36, 9 March 2017 (UTC)


 * The web page you cite says that it copied the formula from Wikipedia, specifically the Insolation article that was merged into this one. It is likely the author of that page made a mistake in copying. Actually doing the integration shows that the result with the h is the correct one. StarryGrandma (talk) 08:01, 10 March 2017 (UTC)
 * A good reference for the calculation of the daily insolation is StarryGrandma (talk) 16:18, 10 March 2017 (UTC)

Unit of measure "Suns"
The cited source does not refer to "Suns" as a unit of measure. This claim should be deleted or it should have a citation that clearly defines "Suns" as a COMMON unit of measure for irradiance. An internet search produced no results that refer to "Suns" as a measure of irradiance, much less as a common UOM. Furthermore, if there is such a UOM, it probably should not be capitalized. Almost all UOMs are not capitalized, even if they derive from a proper noun (e.g., watt, newton, ampere). Holy (talk) 23:16, 3 August 2017 (UTC)
 * The only use of "sun" as a unit that I can find is on a company website where it says "For Solar Simulators, it is convenient to describe the irradiance of the simulator in 'suns.' One 'sun' is equivalent to irradiance of one solar constant." The company sells solar simulators and the unit appears to refer to the equipment, not the sun itself, and is not 1000 w/m2. The original statement in the article as added in 2007 to the Insolation article before the merge is: "The insolation of the sun can also be expressed in Suns, where one Sun equals 1000 W/m2 at the point of arrival. One Sun is a unit of power, not a standard value for actual insolation." No reference was given at the time. It does not seem to be a standard unit and may have been originally be meant to be an explanation rather than an actual unit. I think the whole paragraph can be removed. StarryGrandma (talk) 17:12, 4 August 2017 (UTC)

Agreed, that there is not enough general usage of the term, either in literature or in actual discussions of the topic. The lack of a definition by any solar industry heavyweight suggests this is just a term that perhaps an equipment maker or installer used to help describe the concept. Recommend removal. WardEnerWat (talk) 23:03, 13 September 2017 (UTC)
 * I have removed it. StarryGrandma (talk) 20:51, 17 September 2017 (UTC)

Insolation and Irradiance
Irradiance is the output of a source Insolation is the received by a sink or destination Few care about what the sun puts out but an article about it could be written. Insolation is about what arrives and can be taken in by a destination sink. This may be a fine article on that topic. They are not the same.

Scottprovost (talk) 04:12, 19 November 2017 (UTC)
 * I am not sure this is the difference between irradiance and insolation. Do you have a reference? --Ita140188 (talk) 01:45, 26 November 2017 (UTC)

Missing from the article
I don't see "W m−2" defined anywhere, on its own or in relation to any other unit, despite a huge section that uses it exclusively. I also don't see what I came here for, examples of actual solar irradiance, like at noon in Panama City on Sept 22, or noon in Denver on Dec 21. That's all I wanted, some kind of number, and none of the equations come with numbers so I can't even derive them. SilverbackNet talk 06:11, 20 December 2017 (UTC)


 * good point, I modified "W m−2" to "W/m2" as defined in the section "Units". However, concerning the data, what you are looking for is not really well-defined. As the article explain in section "Types", solar irradiance can be measured in different ways with different results. Also, Wikipedia can not be a database of irradiation data. For this you should check other sources such as NOAA. With the equations given it is possible to calculate the extraterrestrial irradiation for a certain point on Earth in a certain period of time. However the effective irradiation depends on cloud cover and other atmospheric conditions specific to the place/time. --Ita140188 (talk) 06:42, 20 December 2017 (UTC)

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WARNING: ERRORS
There are numerous major misconceptions and miss-statements in this article. It needs thorough reworking by experts knowledgeable in solar science. See NASA SORCE at http://lasp.colorado.edu/home/sorce/ etc.DLH (talk) 18:15, 1 January 2015 (UTC)
 * It would be helpful to explicitly point out what are the mistakes. --Ita140188 (talk) 01:44, 26 November 2017 (UTC)

Just where is "the top of the atmosphere"?--Damorbel (talk) 08:42, 11 March 2019 (UTC)
 * The top of the atmosphere is the place just outside of Earth's atmosphere (beginning of space). This is usually defined as 100 km altitude. I imagine that any measurement over this altitude within a reasonable distance from the Earth would give a similar result for total solar irradiance. --Ita140188 (talk) 12:11, 11 March 2019 (UTC)

Provided value seems incongruent with related articles?
In this article we read: Average annual solar radiation arriving at the top of the Earth's atmosphere is roughly 1361 W/m2.[24]

However, the article on radiative forcing includes a diagram from NASA, labelled "Incoming solar radiation (340 W/m2)" - and the article text reasserts this figure.

Is the 1361 figure a typo? Or does it measure something different? I can't figure out from the articles what difference in definition, if any, applies here. 70.24.7.7 (talk) 02:56, 15 April 2018 (UTC)


 * The figure of roughly 1361 W/m2 is well-established as TSI, also called the "solar constant", representing total solar energy measured on a surface facing (i.e., normal to) the sun, outside the atmosphere. NASA's 340 figure is one-quarter of the roughly 1361. NASA has neglected to explain the 4:1 discrepancy. The 340 represents the average energy incident on all points of the earth's surface in the course of a year (neglecting atmospheric absorption and reflection). One factor of two is on account of only half the earth (one hemisphere) being in daylight at any given time. The other factor of two is attenuation due to averaging over all latitudes; except at the sub-solar point, the earth's surface is tilted (at an angle) to the incoming energy. The section Solar irradiance gives background for this factor. The 4:1 ratio is explained in more mathematical terms at Radiative forcing and also at Solar constant. So, no typo is involved; the two figures are closely related, and both are correct. Perhaps we need to put an explicit explanation in this article for the seeming discrepancy. Hertz1888 (talk) 05:19, 15 April 2018 (UTC)


 * This '340' figure is truly bizarre, it means 340W/m2 as the input at the poles - even in winter! What useful predictions can be made with such a figure?--Damorbel (talk) 08:57, 11 March 2019 (UTC)


 * As it was explained in the previous comment, "The 340 represents the average energy incident on all points of the earth's surface in the course of a year (neglecting atmospheric absorption and reflection)." That is, it's an average over the total surface of the Earth. --Ita140188 (talk) 12:13, 11 March 2019 (UTC)


 * Thank you - that should have occurred to me. To be clear, then, since NASA's figure reflects average incident energy integrated over the Earth's surface, that is the one I would use for black-body calculation of planetary "effective temperature"? 70.24.7.7 (talk) 01:50, 20 April 2018 (UTC)

Sea-level spectrum
So there is a "Solar irradiance spectrum above atmosphere and at surface" graph in the article. It is pretty obvious it is with clear atmosphere and no clouds (still should be mentioned), but it doesn't say if it is just sun spectrum, or whole sky spectrum, and in any of two cases, when and where, or is it averaged over some locations and times? Is it at noon, or some other time, how high was the sun, etc. etc. 2A02:168:F609:0:D894:A6AA:493E:8587 (talk) 21:37, 23 July 2019 (UTC)

Units
The first sentence of the article says "Solar irradiance (also Insolation, from Latin insolare, to expose to the sun)[1][2] is the power per unit area produced by the Sun in the form of electromagnetic radiation" but the units stated further along are MJ/m2. There are also many ambiguous units like kWh/m2/day and such. I think the units should all be power/area as in the definition. Chthonicdaemon (talk) 04:30, 28 September 2015 (UTC)

I wonder how could be calculated 24 h/day on a single plot of land without refer to night (no sun),365 days/year also without any respect to season(winter full of cloud) it's misleading information detract logic ,also there are other attributes like longitude and latitude, altitude, efficiency of recovery system to workable load .Winghovercraft (talk) 22:05, 14 February 2020 (UTC)Winghovercraft

https://www.pveducation.org/pvcdrom/properties-of-sunlight/calculation-of-solar-insolation

https://meteoexploration.com/products/SolarCalculator.html

https://sciencing.com/calculate-solar-insolation-8435082.html

https://sciencing.com/solar-altitude-23364.html

https://sciencing.com/what-is-the-hottest-time-of-the-day-12572821.html

https://www.efficientenergysaving.co.uk/solar-irradiance-calculator.html

http://www.solarelectricityhandbook.com/

Winghovercraft (talk) 22:20, 14 February 2020 (UTC)Winghovercraft

No precise calculation especially outer space of Earth or on it's surface. Winghovercraft (talk) 22:38, 14 February 2020 (UTC)Winghovercraft