Talk:Solar power

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	To-do list for Solar power:	edit  · history  · watch  · refresh
Categorize/group better - e.g. photovoltaic and thermal methods blend too much Expand introduction beyond one paragraph Check for POV Check and polish prose Add and use more solid sources Move external links to "external links" section or use footnotes Clean up formatting and layout Add more images, especially of various solar energy collection methods Add table summarising world installed PV capacity across serveral years (as for wind power page - http://en.wikipedia.org/wiki/Wind_power) Explain the inconsistency of the 1000 W/m^2 at equator (first image) and the 400 W/m^2 at the top of the atmosphere (2nd image).

Contents 1 Amount of sunlight on the Earth 2 Solar land area Image Objection 3 Classification 4 UV or IR transmittance for warming through windows? 5 Price of non-focusing water heaters 6 Environmental Costs 7 Effective Uses 8 Cons 9 World solar power production 10 Indirect solar power section 11 question moved from the article 12 Global solar energy resources Map is not clear 13 Commercialism? 14 Solar hot water 15 Payback period? 16 does make one wonder.. 17 Photoelectrolysis of water 18 missing category 19 Moved material to relevant articles 20 Sample worldwide electric costs 21 Cleanup tag 22 Disadvantages 23 Classification section 24 Ordering of sections 25 Direct and Indirect 26 Types of Technologies 27 Concentrating vs. Non-concentrating 28 Energy from the Sun 29 Solar Heating Systems 30 Good Article Suggestions 31 Solar collector types 32 Intro Suggestion 33 Energy from the Sun paragraph 34 Para 2 of Energy from the Sun 35 Confusion with the Diagram and the Text 36 quantiy/quality 37 Quantity-quality paradox section 38 Units 39 Question about phrasing 40 This page needs protection 41 Requesting Citation 42 Possible math error in biomass comparison

[edit] Amount of sunlight on the Earth

Since I suck at math; how many Watts of sunlight hit the Earth per squaremeter, this sunlight being calculated after it has been reflected, absorbed etc etc. Also, the sunlight per day/second/hour across the globe would be very helpful. --- Hackeru

There is a factoid listed that says it is 89 petawatts (annually?) and is cited to #39, ENERGY AT THE CROSSROADS by VACLAV SMIL. However, I believe that the article states it was 122 PW in 2005 (in section 4). Somebody check me on this... vLaDsINgEr 17:33, 18 March 2007 (UTC)

[edit] Solar land area Image Objection

The image Solar land area.jpg has a very propogandist message. It would be less POV if it just showed the solar energy potential across the globe. It is not Wikipedias purpose to try to sell solar energy to anyone however comendible that is. I suggest removing the stars and just showing global solar enrgy input.

It is also unlcear whether the stated available w/sqm are

1. peak (ie hours around noon) ,
2. average of all daylight hours ,
3. average over a 24 hour period.
4. exclude or include hours of cloud cover

Lumos3 13:40, 14 March 2006 (UTC)

Hi Lumos3, I have moved the image to appear in the first section "Energy from the Sun" and added a more thorough description in the text and the image caption. I am sorry about the propaganda you see in this image, however I believe it is very important to visualize that the energy we actually consume is only a very small fraction of the incident energy from the sun. This fact should not be missing in a good encyclopedia. If you look at the discussions above, e.g. under "Potential Energy Generated" you can see that other people were not aware that a very small fraction of the globe's surface is enough to supply the current energy demand. --Mlino76 12:03, 16 March 2006 (UTC)

It looks like a propaganda image because its so unclear. What area supplies the 18twe energy you state , the area underneath the little stars or are these the centre of much larger areas of high solar input, what are they?

Is it peak time or is it the average over 24 hours , see my questions above ) any news on this? The link you give suppports none of your assertions. Lumos3 01:11, 19 March 2006 (UTC)

The area of the six little stars is enough to supply the 18TWe (when covered entirely with solar panels at 8% efficiency). I used stars for the shape of these areas because this image was sent initially as a Season's greetings card. The shape is admittedly not perfect and I will try to switch to rectangles or circles with the same area, but I need to redo the calculation which will take a while. To Lumos3: The incident solar power is the average over three years from 1991 to 1993 (24 hours a day) taking into account the cloud coverage available from weather satellites. You can find more information and sources for this data at [2]. Please let me know if this helped and/or if you have suggestions about how the image and its description can be improved. --Mlino76 10:38, 19 March 2006 (UTC)

Yes this helps but the link you give is " error 404 ". I am adding this to the images description page. Lumos3 17:24, 20 March 2006 (UTC)

Sorry, now the link is correct. --Mlino76 18:14, 20 March 2006 (UTC)

I updated some of the reflection/absoption numbers and added a reference. There is a diagram on the linked page which visually explains the reflection/absorption flows. Something like this diagram would be a helpful addition to this page. I changed the peak power at sea level back to 1,020 W/m². I also blended the reflection/absorption data with the peak power data in a way that hopefully explains where the peak power number comes from. I think the blending also provides a good transition to the average power information and eliminates some redundancy in the previous version. User:Mrshaba

I think the last three paragraphs in the Energy From the Sun section can be mostly eliminated or moved to more appropriate areas. The black disc reference doesn't work in it's current version because there are no numbers involved. I agree that the relative power delivered by the sun over a given area should be compared to the power used by people but the current version is confusing. Using hard numbers like xxx square kilometers or referencing a city size on each of the continents might be a better approach. I think the global dimming/warming references should also be removed. It would be interesting to replace these paragraphs with more specifics that apply to the energy flows discussed in the first paragraph. e.g. Reference to biomass absorbing light and atmospherically absorbed sunlight driving wind and hydrologic cycles. User:Mrshaba

[edit] Classification

Each category of classification needs better explanations and a short yet diverse list of examples. I think the general classification of solar power/energy is important. Just as nuclear reactors can be classified by fuel, moderator, coolant etc, so too can solar power be classified. This section (solar power/energy) acts as the trunk of the solar tree so it should include a small part of all the branches. The classification portion of this section is an effective way to point out the branches. User:Mrshaba

The hybrid ligthing example doesn't quite fit into the single transformation scheme of direct solar. Transformation might not be the correct word but I can't think of a more accurate term. Conversion? Process? A more expansive term than transformation might be required. User:Mrshaba

Removed the light mill from the direct solar list. Light mills move because sunlight heats the gas around the vanes rather than being driven directly by photons (as with the solar sail example) thus the effect is indirect. I did not transfer the light mill into the indirect section because it seemed like a miscellaneous case covered under the atmospheric phenomena umbrella. User:Mrshaba

Reworked the Active and Passive solar explanations with good results. I bulleted and expanded the examples of passive solar. User:Mrshaba

Worked on the Concentrating and Non-concentrating classifications with mixed results. The current version is choppy but I will continue streamlining and add sources when time permits. User:Mrshaba

This is my first wikipedia editing foray. Still learning how to communicate via wikipedia formatting. I'm picking up new tricks all the time but still at a loss on how to communicate with the other editors. How do editors communicate with each other directly? User:Mrshaba

Hello Mrshaba. We communicate directly through our user talk pages as well as on article talk pages. You can find me at User talk:Itsmejudith. If you set up a talk page for yourself than I can leave messages for you there. I'm fairly new myself so I know it can be confusing. Itsmejudith 18:14, 4 August 2006 (UTC)

[edit] UV or IR transmittance for warming through windows?

This sounds unlikely to me:-

"South-facing (for the Northern Hemisphere) or north-facing (for the Southern Hemisphere) windows with insulated glazing that has high ultraviolet transmittance."

Is there a reference or detailed reason? Midgley 17:35, 24 March 2006 (UTC)

If anything, you want NO glazing on your heating windows. And yeah I think they meant IR -- we care about heat loss moving out after gaining heat from sunlight. 82.93.133.130 09:32, 30 November 2006 (UTC)

[edit] Price of non-focusing water heaters

I removed the following sentence by User:68.126.200.157 "Costs about 8-12,000 dollars for a solar system to bre installed" Ignoring obvious grammar issues, I felt like this comment was not specific enough so it might be a little misleading. A solar water heater was installed recently in my home of the non-focusing type (passive collection type) and it cost much less than that. While we might not be talking about the same system at all, I think the sentence should identify what specific kind of non-focusing water heater system it quotes the price for. Second and more importantly, I think this type of information would be extremely useful to the article, especially if it were referenced with a price quote. If User:68.126.200.157 or someone else would like to look up the info for the various types of water heaters, this would enhance the article significantly. Sifaka 04:54, 30 March 2006 (UTC)

[edit] Environmental Costs

At this time, solar power is described as having "some" environmental costs. Unless these can be quantified, the word will be changed to "minor".

Actually, the other way would be more logical. Minor, compared to what? That needs quantification, unlike 'some', which is the proper neutral description .Jens Nielsen 15:04, 31 July 2006 (UTC)

"Some" can be interpreted as a little or a lot, which is far too broad. Minor is more NPOV, unless you can provide evidence to the contrary. --Skyemoor 17:45, 31 July 2006 (UTC)

I assume we mean their costs come from manufacturing process (esp PV cells, all that water, heavy metals and silicone sawdust waste). If we can find a manufacturing page, we'd probably get better info. I'm looking... 82.93.133.130 09:35, 30 November 2006 (UTC)

[edit] Effective Uses

Solar is cost effective even in grid areas, such as is exemplified by their inclusion in illuminated roadside signs around the US and Europe.

Fair enough, but the sentence starts with 'In situations where connection to the electricity grid is' (problematic). The road signs don't bear on that situation, so put it somewhere else please. It's a very minor market (cf. rooftop panels), so I don't see much need to include it on its own here I must say.Jens Nielsen 15:04, 31 July 2006 (UTC)

[edit] Cons

For backup power, there is a tremendous difference in bringing a coal plant online versus a natural gas generator, the latter being considered dispatchable. Trying to lump them together is misleading and suggests POV.

Can you suggest a source for this please?Jens Nielsen 15:04, 31 July 2006 (UTC)

Certainly. [3] --Skyemoor 15:37, 31 July 2006 (UTC)

Solar panels at high latitudes actually benefit from lower temperatures and therefore tend to produce slightly more power.

That's highly misleading at best. Insolation is much lower at high latitudes, and it's no coincidence that you see little PV in Norway or Greenland, even in off-grid areas. It's not even close to compensated by lower temperatures.Jens Nielsen 15:04, 31 July 2006 (UTC)

My mistake, I was thinking high altitudes.--Skyemoor 15:37, 31 July 2006 (UTC)

Converting to another form of power is exactly what coal and nuclear must do through the steam cycle, rejecting about 70% of the original energy. Since electric vehicles are making a resurgence, there is no reason to attempt to hide the disadvantages of traditional energy sources while only portraying those of solar; it makes for a POV comparison.

True, but I wonder if it is not taking it too far to discuss the limitations of other technologies here. The fact remains that solar power is of limited use for transport purposes. It happens to share that limitation with coal and nuclear, but not with oil or liquid biofuels. The section is meant to be a brief overview, not an exhaustive discussion of all contingencies.Jens Nielsen 15:04, 31 July 2006 (UTC)

Since energy for transportation is being discussed, and solar is listed as having a disadvantage in this area, it only makes sense to provide context about what is being compared.--Skyemoor 15:37, 31 July 2006 (UTC)

I cleaned up the last disadvantage. DC to AC inverter losses of 5-10% is the relevant disadvantage here. User:Mrshaba

I cleaned up the last disadvantage again. There is some contention here. Disadvantages and advantages should be separated. I am the editor that inserted the transmission/distribution losses avoidance point under advantages so I recognize that advantages and disadvantages can cancel each other out but that's not the point here. If we used DC appliances and lighting systems we wouldn't need inverters but we don't use DC yet so we need inverters. The disadvantage should stand without being watered down. User:Mrshaba

And even using DC has losses anyways. Esp if the power source is far from the load. You also need quite a lot of copper : ) 82.93.133.130 09:38, 30 November 2006 (UTC)

[edit] World solar power production

Something is seriously wrong in this section: compare the numbers in the first sentence to those in the table. Probably one of them is off by a factor of 1000. DonSiano 04:52, 11 April 2006 (UTC)

Adding up the numbers in the table, I came up with a total installed capacity of roughly 2600 GW for those countries in the list. Assuming the rest of the world has about half of the installed capacity, this is consistent with the units for the table being mislabeled as MW instead of kW. Perhaps when someone finds a citation for the table they can confirm this. Iamlucky13 21:40, 5 May 2006 (UTC)

The table probably comes from http://www.oja-services.nl/iea-pvps/isr/22.htm http://www.oja-services.nl/iea-pvps/isr/index.htm My reconstruction of where it came from is 13:18, 25 March 2006 Messedrocker ("World solar power production" section moved from Solar panel) Going back to Solar panel leads to a refernce to the above mentioned site. Which is .nl, which means that they adhere to continental conventions, which means that they put comma's where Americans put periods, and periods where Americans have comma's. Problem solved. :-) JdH 21:10, 5 May 2006 (UTC)

Just found this

The largest number of companies are in the solar PV industry, which is becoming one of the world’s fastest-growing, increasingly profitable industries. Global production increased from 1150 MW in 2004 to over 1700 MW in 2005 (see Maycock article this issue).

It comes from a link from Renewable Energy World. This wiki article says 1700 Mw installed PV, but according to the article this is commercial production. I found a better number for installed amounts in 2005, which was more like 5300 Mw— all the sites I found mentioning this number seemed to come from a source used by Home Power (but the bigger problem is that the sites, when clicked on, sit for a moment on the page before redirecting you to porn >:( So I'm going hunting through old HP's and hope I find a fairly new number, and also change in price per watt in dollars. Gaviidae 09:27, 28 November 2006 (UTC)

[edit] Indirect solar power section

Doesn't seem to fit with the rest of the article. Most people don't mean any of the power sources listed in this section when talking about solar power. A more approative article for this section would be renewable energy sources. Joncnunn 15:52, 21 April 2006 (UTC)

Wikipedia is not paper [4]. It can afford to give a full encyclopedic description of all energy sources that originate from the sun not just the narrow definition used by some.Lumos3 09:11, 27 April 2006 (UTC)

[edit] question moved from the article

the system in the Mojave desert is said to be the world largest below, which one is bigger? -- 69.203.102.77 (moved by CyrilB 09:23, 1 May 2006 (UTC))

[edit] Global solar energy resources Map is not clear

This image commentry says the map has "taken into account the cloud coverage available from weather satellites." Does this mean:-

• values have been marked down to levels which would be recieved taking into account the average cloud cover,

• or does it mean values have been marked up to levels they would attain if cloud cover had not been present?

Lumos3 19:56, 12 May 2006 (UTC)

It says "also taking into account the cloud coverage reported from weather satellites" meaning the amount of solar energy minus the amount of cloud cover. So, values have been marked down to levels which would be recieved taking into account the average cloud cover, you can tell if you read the sentence more closely.--LF2 17:40, 13 May 2006 (UTC)

"take into account" could mean marking up or down. Ichanged the text to applying. Lumos3 09:24, 14 May 2006 (UTC)

[edit] Commercialism?

One thing became clear after I put those external references in a list: there are quite a few references that may be viewed as commercialism. E.g. what I noted is several references to Stirling Energy Systems, in what appears to be blatant commercialism, but there are links to several other companies as well. I guess that's OK if those links it provide unbiased information, but it is not OK as it talks about "the largest" in apparent commercialism. Can somebody plow through all of this and clean it up? JdH 12:19, 14 May 2006 (UTC)

[edit] Solar hot water

There are a number of references in this article, from several sections, to Solar hot water. I suggest that the information on Solar hot water be moved to that article, with a brief description and link from here. That will also help cut down this article and improve layout and clarity.

Any objections? --Singkong2005 06:41, 5 June 2006 (UTC)

[edit] Payback period?

What is the energy payback period for solar power installations -- how long does it take to generate an amount of energy equal to that used to make/install the equipment? And what is the typical life of such installations -- what is the total ratio of energy to create to total energy produced? 69.87.202.5 23:30, 8 June 2006 (UTC)

I remember seeing data about this in the World Energy Assessment. I think it is between five and fifteen years at the moment, and declining. Jens Nielsen 15:15, 14 July 2006 (UTC)

Bull. Depends on your local electricity prices. In Austin TX, its currently about 50 years, and that's if you do the installation labour yourself. See calculations. If you think you've found an error in these calcs, let me know on my talk page. linas 05:05, 22 July 2006 (UTC)

Don't confuse energy payback with economic payback. Energy payback for PV depends upon the type of panel under consideration and the location. Home Power did an analysis a few years back and determined the average time was 1.8 to 3.3 years.

Exactly. As for typical life-- depends. Pv panels are often warrentied for 25 years, but last much longer (we'll need to Wait And See how long). Turbines can last generations (see the old Jacob's turbines from the 30's) but need regular mechanical maintanence. Solar thermal units can use relatively low amounts of energy to manufacture, but their lifespan is dependent on your seals and hose material. This is all home numbers-- I have no cluer for commercial installations, except that they certainly cost more to build. 82.93.133.130 09:43, 30 November 2006 (UTC)

I've added a link to an external wiki article that discusses payback.

FWIW this page discusses a major issue with payback analysis:

http://www.greendoug.com/viewtopic.php?t=2 Tabby 06:05, 4 April 2007 (UTC)

[edit] does make one wonder..

If DC was indeed the right choice for power distribution. Everything I CAN USE around me works on DC. Ofcourse the things I cannot use. like the govt grid which goes off and on every 2 days works on AC :-)

You mean if AC was the right choice? You can't distribute power with DC. You lose way too much of it. If you're making your own power at home, though, you have the possibility of using DC. Review the War of the Currents (Tesla/Westinghouse vs Edison). 82.93.133.130 09:45, 30 November 2006 (UTC)

Yes AC is able to be stepped up and down in voltage to suit our needs. It is much more efficent to have high voltage in the lines that take electricity long distances. But if we have high voltage in the home it is too dangerous to use. AC allows us to have both through the power of induction. 192.53.187.183 18:30, 21 March 2007 (UTC)

[edit] Photoelectrolysis of water

Photoelectrolysis of water has been researched off and on starting with Honda and his coworkers, and work continues today with Graetzel and many, many more. I have added some information under solar chemical in an attempt to fill this hole in the article. Perhaps others would like to add more along this line? Rhelmich 06:47, 21 June 2006 (UTC)

I think you are the expert here, so it is up to you to research the subject and put in some more information. JdH 08:11, 21 June 2006 (UTC)

[edit] missing category

I remember that, in the early 70s, there was an engineering feasibility study of satellite solar collection with microwave broadcast to antenna arrays on the Earth's surface (see solar power satellite). This was a formal study which found that there were no engineering blocks to such a system (eg, microwave beams so intense as to kill birds or crash planes that wandered through the beam, or sterilize the flora and fauna in and around the antenna array, and that economically feasible antenna elements could be made such that expected rates of failure would not reduce performance sufficiently to make the system desing impracticable. The question of funding, and adverse interest pressure, was not a part of the engineering study. I note that this article not only doesn't mention this as a possibility, concentrating on earth based collection, but doesn't note this serious study of the problem. I suggest that someone who is familiar with this contribute some coverage of it to this article. ww 00:51, 25 June 2006 (UTC)

I don't know about technical feasibility, but I have the feeling that this is economically way out in the middle of nowhere. Let's start with putting solar panels on all rooftops, and Concentrated Solar Power (CSP) Plants in the deserts here on earth. And build wind turbines on all windy places we can find down here, including offshore. And if all of those resources have been utilized we can always expand into the oceans; even that will be a lot cheaper than putting things out in space. JdH 03:17, 25 June 2006 (UTC)

That may be sensible, but is skew to my comment. This is a serious study and, I think, required for a full appreciation of the topic of solar power. The economic feasiblity (or not) is a point which should probably be referenced in any account of it, as indeed it is in the SPS article. The significance of this proposal is that it has been carefully study from the perspective of engineering easilibity. That's considerably different than many proposals. Very different. ww 19:21, 25 June 2006 (UTC)

The "solar power" article now has a link in the "See also" section to solar power satellite. What else should we say about it in this article?

[edit] Moved material to relevant articles

I moved a lot of material to the relevant articles, e.g. Solar hot water, and linked to there from here with a Main article: Solar hot water etc. If there's disagreement about where the material should be, I'm open to discuss it, but the important thing was to collect the material on each topic in one place, and create proper links.

Re the Photovoltaic cells section - I wanted to move most of this to the Solar cell article, but that article is quite long, and technical about the electronic aspect; Solar panel doesn't seem suitable either, as it's not just about photovoltaic systems. How should we handle this? I suggest we split Solar cell, so that Solar cell (physics) focuses on the underlying physics, going into technical details. The Solar cell article would just give a basic explanation, with more focus on applications, and achievements to date (e.g. highest % conversions achieved, leaving extended technical explanations to Solar cell (physics)). I'll post this suggestion at Talk:Solar cell. Comments? --Singkong2005 ^{(t - c - WPID)} 11:33, 25 June 2006 (UTC)

I'd like to help with the process of restructing and moving. I'm not a scientist but a domestic PV user and would like to see the article more accessible to people who know nothing about the topic. My first impression is that the classification of solar power early in the article may be scientifically accurate, but for many users it would be more helpful to adopt one dimension of classification and use that for the sub-headings in the article. Any comments? Itsmejudith 12:35, 1 July 2006 (UTC)

Having read more, a suggestion about how we could proceed. I don't think we can sort this article without careful consideration of how it relates to other articles. Singkong's suggestion was a good one. How about if we end up with this:

• Solar power – very holistic, should mention the purpose and relevance to the environment, list all the technologies under headings "direct" and "indirect", and the advantages and disadvantages
• Solar cell – title of the article should be photovoltaic cell and “solar cell” should redirect to it – just science of the PV cell
• Solar panel –classified as “good article” but use for thermal only. Apart from a brief mention for clarification purposes, take out all PV stuff that would then go into the new PV applications article (see below).
• Active solar – short but helpful article, no need to revise
• Photovoltaic applications - a new article that would carry everything about PV that is too detailed for the solar power article but not directly related to the science of the PV cell. Including building integration, on-off grid distinction, PV power stations, price drops, statistics.

Any comments, because I have drafted a "photovoltaic applications" article on this basis and could create it and remove redundant material from other articles, but don't want to upset those who have already put in a lot of work. Itsmejudith 23:02, 6 July 2006 (UTC)

I have copied some chunks into Photovoltaics. It would be very nice if people could check that article out and see if the material makes sense in there. Also there are things to do there like making the style of referencing consistent. If there are no major objections, then I will delete the copied material from this article and move some more bits over.Itsmejudith 16:56, 20 July 2006 (UTC)

[edit] Sample worldwide electric costs

I'd be curious to compare my electric costs with the rest of the world's. FWIW, I'm in Austin TX and am paying 9.5 US cents per KWh. At this price, I cannot amortize a photovoltaic system in less than 50 years (see here), and so am curious to see what the rest of the world is payig for grid electricity. linas 05:12, 22 July 2006 (UTC)

In the UK 11.9 pence (22.34 US cents) per KwH decreasing to 8.24 pence (15.35 US cents) after the first 168 KwHs in each quarter-year. But our insolation is much less than yours. And with no net metering it is worth trying to use all the self-generated power in the house rather than exporting it to the grid. And considering how to use the heat absorbed into the panels. Itsmejudith 22:42, 28 July 2006 (UTC)

Have you included subsidies (also tax breaks and the like) in those costs? If so, that makes it hard to compare at any rate.Jens Nielsen 07:15, 29 July 2006 (UTC)

There's more to the price of your electricity than the average price per kWh. This link should help.

http://www.eia.doe.gov/cneaf/electricity/epm/table5_6_a.html

A recent report out of Hawaii determined that unsubsidized solar can compete with the grid. At an average of 23.25 cents/kwh it makes sense. An important thing to consider is time of use has an effect on prices as well as gross usage. This rate schedule for Central to Northern California shows peak summer rates at 29 cents/kWh up to 51 cents if you go 300% over your baseline. A coworker's electricity bill was $750 last month thanks to a couple of heat storms so it's easier to go over baseline than one might think. I'm sure everyones gone over their cell phone minutes. It's the same deal.

http://www.pge.com/tariffs/pdf/E-7.pdf

Here are some averaged international rates but again it's important to remember that the prices vary within these countries. The high cost of electricity in Japan (21 cent/kWh) explains how solar is competing with the grid there.

http://www.solarbuzz.com/StatsCosts.htm User:Mrshaba

Writers to Home Power from California have listed daytime rates at 52 cents per kwh. IN Michigan, it depends on your utility-- Consumers' is 7.9 cents and Great Lakes' is 9.something cents. But unlike CA, MI doens't have net metering (very important to payback calcs) nor time-of-use (only for commercial/industrial customers). Those two things need to be considered before doing any more calculations. That aside, TX seems to have pretty cheap power, and if you want to go off-grid, consider that you're paying for a life-time's worth of power all up front. In this case, you do solar for hippie or black-helicopters reasons :) 82.93.133.130 09:51, 30 November 2006 (UTC)

[edit] Cleanup tag

I would on balance prefer the cleanup tag to remain in place until all the items on the to-do list have been addressed. There is rewriting currently in progress. Thanks.Itsmejudith 19:57, 24 July 2006 (UTC)

[edit] Disadvantages

No mention of limited lifetime of solar panels or effect on the local environment of large installations? — Omegatron 03:25, 4 August 2006 (UTC)

Do you want to add these points, with sources for them? Thanks.Itsmejudith 07:21, 4 August 2006 (UTC)

"average irradiation power density is only 1 kW/m2 usable by 8-15% efficient solar panels, yielding about 30-50W/m2 overally day-night average, or about 3.5 MJ/m2=1 kWh (5 cents)/m2=75 gram gasoline/m2 worth daily". This is a highly convoluted paragraph, with odd assumptions about energy conversion equivalents. Since we are talking about electricity in this paragraph, comparison to the high cost of gasoline is meaningless, especially as gas prices rise. Is anyone concerned about removing this conversion?Skyemoor 11:59, 20 August 2006 (UTC)

[edit] Classification section

I don't feel that this is an accessible section at the beginning of the article. The list of different technologies is in fact a de facto classification. So I propose moving the text currently in Classification to different sections. A section on Concentration would be appropriate, but Concentrating PV belongs in the Photovoltaics article. Any dissensions?Itsmejudith 11:43, 4 August 2006 (UTC)

[edit] Ordering of sections

I'm still not quite convinced by Mrshaba's arguments about the value of a classification section. (Although I very much hope this user stays and carries on making these helpful contributions to the article.) I would prefer to see the Active/Passive classification dimension merged with the Solar design in Architecture section. Concentration should be a section on its own. Direct vs indirect is a crucial distinction in my view and should be near the top of the article or could head the Types of Technologies section.

I suggest that Deployment of Solar Power to grids is almost entirely about PV and should be moved to the Photovoltaics article. The exception is the solar furnace in France, which I don't think does relate to PV (I may be wrong), so that and the image could go into a section here on Concentration.

I was also wondering whether Advantages and Disadvantages could go later, after the technologies have been described. But I don't have a strong view on it. Itsmejudith 21:42, 6 August 2006 (UTC)

I'm in total agreement Itsmejudith. Sometimes I miss the forrest for the trees. Active and Passive would go well with the architecture section. I can also see saving some of the indirect and direct info by blending it in with the intro. I mentioned doing this in a previous post. I think it would be interesting because it would reinforce the idea that the sun is powering the weather cycle. I was also thinking concentration really belongs in a concentrating section within solar thermal and PV topics respectively. I can see this article jumping straight into a Technologies secion with a indirect/direct primer at the top. Mrshaba 22:26, 6 August 2006

This article should be an overview and survey of the whole field. Individual specialist approaches should be enlarged upon in their own articles. It should include all technologies which tap solar power not just those which are practical today. Categorisation is therefore an important part of this article. It should not try to sell Solar power as a technology. Lumos3 09:29, 7 August 2006 (UTC)

Thanks Lumos 3. I take your points and very much agree that all technologies should be in there and that it should not try to sell solar power. But does there have to be a Categorisation section? It just seems to me to be rather complicated for a casual user to have to understand that there are different ways of categorising the technologies before going onto the details of the different techologies. The individual technologies are either very simple, e.g. solar cooker, or refer to other articles. I am bearing in mind the issues in the To Do list, which complained of the muddling of different technologies. If there is a Categorisation section, what should it include? Itsmejudith 12:41, 7 August 2006 (UTC)

I have moved 2 section lower down the article. I think this looks better to a new reader. I think the Deployment of solar power section should really be spun of to their own article with a brief paragraph here. Lumos3 13:47, 7 August 2006 (UTC)

Agree that this looks better. I'll move the Deployment to Photovoltaics, except for the Solar Furnace and its image, which I think belongs in the Concentrating section here. Itsmejudith 16:28, 7 August 2006 (UTC)

[edit] Direct and Indirect

Lumos3... Good catch on the biomass vs. vegetation distinction. Bad edit on my part. The lightmill example is not a direct conversion though. Photons don't move the vanes. Photons heat gases which move the vanes while trying to find a low pressure zone. This is an indirect phenomenon. The light mill article explains this. I'll admit that the light mill is an interesting device but I don't think it belongs in either the direct or indirect examples of solar power or solar energy.Mrshaba

You could use the same desconstruction to argue that any device is not actually catching solar energy , eg they just move electrons around, make molecules vibrate etc. The fact is that although the light mill is just a toy (today) it represents a visible and dramatic demonstration of solar power. The article should not just be limited to those technologies which are practical but should give the reader a view of the whole field. Lumos3 09:02, 8 August 2006 (UTC)

I disagree Lumos3. Indirect energy transformations involve an intermediate heat transfer fluid or chain of events. Direct energy transformations do not. All our other direct solar examples show this (with the possible exception of the hybrid lighting example). If the light mill worked in a vacuum i'd agree it's direct but it doesn't. I think the distinction is worthy and similar to the distintions between conduction, convection and radiation. The light mill works for the same reason that the solar chimney works. Hot gases want to cool themselves by expanding. As a compromise we could put it in the indirect section and group it with the solar chimney. User:Mrshaba

The classifications direct and indirect are human defined ones. All those defined as indirect follow a tortuous path of energy conversion and storage in intermediate forms. Both the light mill and solar tower convert energy in real time and so are direct devices. Your analysis depends on detailed knowledge of the micro processes involved and cannot easily be applied except by phyics experts. To say the Crookes radiometer is indirect but the Nichols radiometer is direct adds nothing to anyones understanding of the subject. They are both real time energy converters and both are direct. Lumos3 22:26, 9 August 2006 (UTC)

I think most people would call the lightmill "solar powered" and should at least stay mentioned here. If you're going to keep solar water heating with glycol and a heat exchanger, why not the mill? My 2 cents 82.93.133.130 10:04, 30 November 2006 (UTC)

[edit] Types of Technologies

The solar fiber technology is a sub-category of PV (thin film/dye). Can we move it over to PV?

I think we should also move the concentrating PV technology into the PV section. Opinions? I can see the PV section isn't broken down into sub categories but it should be eventually to cover the various ideas out there. We've already moved a lot of material into other sections. I think this material should be moved too. I'll wait a few days and then make an attempt at sliding things around.

As I see it, solar technologies break down basically into PV, thermal, chemical and lighting. I will be working on grouping/tiering the technologies along these lines. User:Mrshaba

Sound reasonable to me. Skyemoor 21:11, 22 August 2006 (UTC)

The solar fiber sub-category was covered in the solar cell article and the material was more up to date so I removed the solar fiber section from this article.Mrshaba

[edit] Concentrating vs. Non-concentrating

Moved CPV to Solar Cell article. I'd like to link to this material in the Concentrating/Non-concentration section. User:Mrshaba

Reworked the Concentrating vs. Non-concentrating material. Took some of the former choppiness out(maybe not). The material (tracking types, solar thermal) was better covered under the individual sections so I replaced the redundant material with pointers to these sections. Is there a way to put in a pointer to a specific section within an article? The solar thermal wiki article mentions a stagnation temperature of 220 C but 200 C is the number I keep finding so I used it. I know the highest temperature possible for concentrating solar is the temperature of the sun's surface but I haven't been able to find what temperatures the concentrating power plants typically run at.Mrshaba

Example: [[Talk:Solar power#Concentrating vs. Non-concentrating]] links to this section as in this example. (I think you can eliminate the part to the left of # for in-article links) - Leonard G. 02:07, 24 August 2006 (UTC)

[edit] Energy from the Sun

It would be helful to explain the difference between diffused and direct sunlight. I looked around for a Wiki-topic that explained the distinction between the two but Sunlight didn't cover this subject. This could be an area for confusion considering direct/indirect solar technologies. I think an expanding description of sunlight as it relates to solar power could be helpful at the beginning of this article. This link has a helpful image explaining reflection and absorption of sunlight by clouds and the atmosphere. Reflection and absorption would tie in well with an explanation of diffused/direct sunlight. http://marine.rutgers.edu/mrs/education/class/yuri/erb.html

Direct sunlight comes in a straight path from the sun. Diffuse sunlight can be reflected off of clouds, landscape features, etc, as well as ultraviolet radiation that follows a scattered path to Earth's surface (that's why the sky appears blue). Some solar panels exceed their direct sunlight ratings (mostly due to reflections off clouds) and can overwhelm or damage a DC/AC inverter that is sized to the array's sticker rating. Diffuse_sky_radiation Skyemoor 22:47, 24 August 2006 (UTC)

This NASA image isn't perfect but it would help. The problem is we seem to have a log-jam of images in this section. Any ideas? I don't want to hijack this page.Mrshaba

[edit] Solar Heating Systems

I wrote this section a while back while the article was undergoing a consolidation process. After reviewing this link I decided I did not do a good job with my classifications.

http://www.eere.energy.gov/RE/solar_hotwater.html

The classification of solar water heaters is involved and I think it belongs within the solar hot water article. I think we should use a few solar hot water representative examples but not present the material as if it is a classification of all the solar hot water technologies. Mrshaba 05:45, 31 August 2006 (UTC)

[edit] Good Article Suggestions

If you're reading this, you're probably aware that Solar power is a GA nominee. I've read it through and think it should be put on hold until the following concerns are addressed:

• The lead section really needs to be at least two or three paragraphs in length for a topic this wide and diverse. At the moment the lead alone is enough for it not to be considered 'compelling prose', since it's brevity in comparison to other good articles is enough to put you off reading the undoubtedly detailed rest of the article.
• In addition to this point, there are a lot of one line sub-sections in the middle of the article; whilst only summaries of larger, separate articles, these could still use being more substantial paragraphs in my opinion.
• Overall I think your sourcing is pretty good, striking a balance between readability and reliability. However, it may be stating the obvious, but wherever it says ^{[citation needed]} in this article you do need a source.
• My only other comment on the sources it that I'd like to see them formatted using Template:Cite web.
• There is a picture in the midst of the article captioned, "Pictured: Solar Cooker". This wants making a little more Wikipedish and perhaps more detailed as well.
• Finally, the layout of the article looks really quite messy in places because of pictures that upset the layout of the text. I found this very off-putting.

Sort out the above points and I reckon the article will be GA worthy, and with a minor tidy-up thereafter FA worthy, so give yourselves a pat on the back.

Regards, CountdownCrispy ^{( ?} 08:59, 4 September 2006 (UTC)

Well it's been about a week since I made the above suggestions, so in true X Factor style I'm here to decide whether or not this article has made enough progress over the past week to be considered a good article. I'll consider each point in turn:

• The lead section really needs to be at least two or three paragraphs in length for a topic this wide and diverse. At the moment the lead alone is enough for it not to be considered 'compelling prose', since it's brevity in comparison to other good articles is enough to put you off reading the undoubtedly detailed rest of the article.

• I still don't think the lead is detailed enough given the breadth of the article which it introduces.

• There are a lot of one line sub-sections in the middle of the article; whilst only summaries of larger, separate articles, these could still use being more substantial paragraphs in my opinion.

• Solar thermal electric power plants, Steam engine and Stirling engine are still too short as summaries in my opinion.

• Overall I think your sourcing is pretty good, striking a balance between readability and reliability. However, it may be stating the obvious, but wherever it says ^{[citation needed]} in this article you do need a source.

• To my eyes this has been sorted out very well, so well done.

• My only other comment on the sources it that I'd like to see them formatted using Template:Cite web.

• This is obviously a very large task and not enough to single-handedly cause you to fail the GA, but once you've sorted the article out and are going for an FA then standardising the references really wants doing.

• There is a picture in the midst of the article captioned, "Pictured: Solar Cooker". This wants making a little more Wikipedish and perhaps more detailed as well.

• Sorted out nicely.

• The layout of the article looks really quite messy in places because of pictures that upset the layout of the text. I found this very off-putting.

• The photovoltaic cell is still stretching the text a bit and I'd be very very critical if you were going for an FA but for now the layout is OK.

The article seems much improved to me since I last read it through but that lead is still very off-putting. I'll leave it on hold for now but, given that the suggested week for improvements has passed, if the lead hasn't been expanded and improved by this evening I'm afraid I'll have to fail the GA. If anyone makes improvements and wants me to have a look drop me a line on my talk page and I'll check it out.

Regards, CountdownCrispy ^{( ?} 12:13, 11 September 2006 (UTC)

Thanks for taking the time to go through the article and provide suggestions. I've only now become aware of the GA nomination and I hope I'll be able to do some work on this article. Regards, Jens Nielsen 19:01, 11 September 2006 (UTC)

Hi Jens, I'm afraid to say that I've had to fail the article simply due it's on hold status having run its course. My suggestion would be to use what myself and others have said to get the article up to FA candidate status, since once that lead is sorted it's, in my opinion, only a minor-cleanup away from reaching this status. Please drop me a line if it's nominated for an FA, since I'd be delighted to see it fully sorted and reaching deserved status.

Bye for now, CountdownCrispy ^{( ?} 20:43, 11 September 2006 (UTC)

[edit] Solar collector types

The addition of line and point focus collectors is very good, though it seems it should belong in the solar collectors article so that we can reference it here. Thoughts? Skyemoor 00:20, 12 September 2006 (UTC)

I'm for moving this material. We could briefly list the three representative technologies: power tower, trough and dish/engine and leave it at that. We should do the same thing with the solar water heating material. i.e. List some representative technologies and leave it at that. Mrshaba 01:45, 16 September 2006 (UTC)

[edit] Intro Suggestion

I've been trying to think up a structure to fit a good solar energy intro on and I think solar power's history would do well. I've stolen the idea from Perlin whose book From Space to Earth begins with a historical framework. We could go into the history of solar architecture, solar thermal and PV with a paragraph or two on each. i.e. As a result of wood shortages, the Romans were the first to actively pursue the utilization of solar energy with their architecture. After discovering glass has a tendency to trap heat (greenhouse effect), they began positioning glass enclosed rooms (heliocamini or sun furnaces) on the south (sunfacing) side of their buildings to maximize solar gain. Additionally, I recall reading that Marcus Vitruvius Pollio detailed several energy saving solar technologies in his architectural manual although I haven't been able to plod through the text and verify. If verified this would be good info that shows solar techniques have been understood since ancient times. Solar thermal was the next technology to evolve with characters like Mouchot (inspired by percieved coal shortages), Saussure, Ericsson and Shuman all contributing to the technology. There is a wealth of interesting info regarding the evolution of solar thermal technologies in the 19th century. PV's history could mention Becquerel, Einstein, Bell Labs etc... Thoughts? I was also thinking that a key terms section might be helpful toward the beginning of this article. Insolation, active solar, passive solar, irradiance, etc. Thoughts? Mrshaba 06:12, 18 September 2006 (UTC)

The intro para should provide a very short synopsis of the article, so any history there should be 5-6 lines at most. We could have a full section on history, and here are a few more references;

http://www.southface.org/solar/solar-roadmap/solar_how-to/history-of-solar.htm

http://www.vidyaonline.net/arvindgupta/assolarpower.htm

http://www1.eere.energy.gov/solar/pdfs/solar_timeline.pdf

http://www.montanagreenpower.com/solar/curriculum/timeline.html

The Roman architect Vitruvius wrote about solar architecture in detail in The Ten Books on Architecture (before 30 BC).

I have a little solar history in the solar cooking section that could be moved, or bulletized. Skyemoor 11:20, 18 September 2006 (UTC)

I don't think a history is appropriate for a wikipedia introduction section. See Wikipedia:Lead section for guidance on what should go into an introduction. A history of solar energy section would be very welcome however. Lumos3 19:55, 19 September 2006 (UTC)

[edit] Energy from the Sun paragraph

I don't find this paragraph clear as it stands. Are the percentages given for loss through reflection and absorption meant to be cumulative? Could someone who knows about these things clarify? Itsmejudith 10:26, 17 October 2006 (UTC)

Also, in the same section, what does "primary energy demand" (in the caption to the second image) mean, and why does this become "primary energy supply" in the paragraph next to it? Itsmejudith 10:48, 17 October 2006 (UTC)

The percentages are cumulative. I'm trying to figure out if this image is open source and how to upload it. asd-www.larc.nasa.gov/erbe/components2.gif This is where I got the numbers from. You can see from the image that all the numbers add up. Also if you subtract the percentages of sunlight absorbed/reflected in the atmosphere from the solar constant (1366 - 346) you get 1020 which is the standard figure given from the peak irradiance at sea level. If we had the numbers and the image it would be a good one-two punch. I'll write Langley for permission to use the image.

In regards to your second question I don't know either and I think we might want to do away with the image altogether Mrshaba 01:14, 18 October 2006 (UTC)

Whether losses are cumulative or not can be figured out from comparing the 1020 final to 1366 W/m2 inital values, which is the bottom line, what matters. There may be other losses that are not fully cited here, so the math from the given figures may not work out, but it should be acceptable to highlight only major losses here, and do the full discussion accounting for minor losses too on the insolation page.

What "primary energy demand" means can be figured by clicking on the image itself, which takes you to the image page, that lists a fuller explanation. The full explanation you get from clicking on the link on the image page, that takes you to the author's page where he lists all the proper references. When I first saw this image it shocked me how beautiful it was, how cunning its author was to gather freely available data to generate it, and since then a copycat, 2nd image has appeared, but I feel we owe respect to the author to keep this first image on here. As far as the US only image goes, government produced documents usually fall into public domain, and are great source for enriching public domain, but seems to me there is a concerted effort these days to hunt down and piece apart the origin of all government documents hoping they were done under private contract and therefore not in public domain, but luckily on this page, the individual author's world-solar-irradiance image is of higher value than the USA only image. Most .gov sites dont' specify if something was done under private contract, and sometimes you just have to assume it was created by a government employee, otherwise the whole government created published documents falling into public domain is a nonsense statement. The government is supported by taxpayers, and there is a general intent that taxpayers, that is the public, own the government generated documents. Who else would you assign as the owner? Of course there are special cases, exceptions, such as classified documents, or you can find more examples on the work of the United States Government page, but in general there is a feel that government documents are public domain, and it's practically impossible to hunt down who owns what without a central registry described on the Public Domain Enhancement Act page, that mind you, would extend copyright another 5 years from the current 90 years, but at least you'd have a clear way to tell who owns what, otherwise everyone is forced to take the attitude "I don't know who it belongs to, therefore it must be somebody's, even if it's published on .gov pages are part of .gov agency's creations." For instance that http://asd-www.larc.nasa.gov/erbe/components2.gif page on NASA might be created by a contractor artist, and the original artist may wish to retain copyright on it, but if it was made as work for hire, and NASA financed the whole creation, then NASA should own it, .gov should own it, therefore the public own it, and the original author could not retain copyright.(other than the natural authorship credits that are required by scholarly citing principles, but not by public domain principles - public domain is "do as you want with it", including the right to post it on your website without specifying its origin, though you probably couldn't legally claim it as your own creation, you couldn't lie like that.) If the original artist created the image and then let NASA display a copy on their webpage for a fee without relinquishing its original copyright, meaning it was not work for hire, even as a contractor, then NASA should either not pay for it, and not display such things on its webpages, or if it does, for whatever stupid reason, it should sound all bells and whistle alarms in the world warning people about the copyright status. Stepping back up to the http://asd-www.larc.nasa.gov/erbe/ page doesn't show an immediately obvious link or description of the image, and I clicked on every link, neither showed anything about the image, and in fact the atmospheric sciences link on the bottom is broken. So how can you tell the copyright status? Searching google hoping to find its nasa.gov or even .gov description page, as "asd-www.larc.nasa.gov/erbe/components2.gif site:.gov" clicking not to omit repeated results, gets only a few pointer to this image, most citing that it's "at NASA", as if it were NASA's, but other than that, for instance the link hosted on a .gov site, http://edmall.gsfc.nasa.gov/aacps/unit/unit2.pdf starts out as:

Support provided by NASA Goddard Education Programs

Earth Space Systems Science

Unit 2: The Atmosphere

Earth/Space Systems Science

Unit II: The Atmosphere

October, 2002

Permission to make digital or hard copies of part or all of this work for personal or classroom use

is granted provided that copies are not made or distributed for profit or direct commercial

advantage. We ask that copies bear this notice and credit is given as follows:

Earth/Space Systems Science

Anne Arundel County Public Schools.

Support for this project provided by GSFC Education Programs.

Copyrights for components of this work owned by those other than Anne Arundel County

Public Schools must be honored.

All NASA materials contained within this document or linked to this document are freely

available for use and carry no copyright restrictions.

The Coordinator of Science, Anne Arundel County Public Schools, Maryland would appreciate

notification if you plan to use all or any of this educational product at sslutksin@aacps.org.

The Coordinator of Science, Anne Arundel County Public Schools, Maryland would appreciate

notification if you plan to use all or any of this educational product at sslutksin@aacps.org

I highly dislike reading statements that "Support provided by NASA but we retain copyright." NASA should not finance things it cannot procure the taxpayer a right to access and copy. But moving on, This implies that "All NASA materials contained within this document or linked to this document are freely available for use and carry no copyright restrictions", so the above image is linked, does linking mean contained? but it seems to imply that the image is public domain. So it's never completely certain, and even sslutksin@aacps.org or whoever created this document could always be in error when they state something is in public domain, and people going based on such statements would also be in error, there are always many possibilities that you can never have full certainty, but that would apply to all public domain things too, your references could be wrong, and would stop anyone from ever using public domain images on grounds of safety, but then what's public domain good for if you can't touch it? At some point you just have to assume a source claiming something is public domain is telling the truth, or even images hosted on .gov without proper copyright warnings (where is the page that links to this image that could tell the copyright warnings, it's a badly designed site) are public domain - in fact, I'd go as far as saying .gov sites should only link to images that are copyrighted, but never host them. I would say that image is public domain "enough" to me, and would post it to wikipedia, and let the author disagreeing with it come forth and make us take it down, even though Jimbo Wales might frown at such a statement. Sillybilly 05:46, 18 October 2006 (UTC)

This is the image: http://marine.rutgers.edu/mrs/education/class/yuri/erb.html Mrshaba 15:59, 18 October 2006 (UTC)

[edit] Para 2 of Energy from the Sun

I'm concerned that this paragraph leaps from a general discussion of insolation (which is relevant to all types of solar power) into the conversion rates of photovoltaics. This relates to a problem with the article which is now mainly cleared up: that it used to mix PV and solar thermal in a way that was confusing for the reader. Does anyone have views about whether some of the material in this paragraph could be taken out of here and into photovoltaics? Should that include the map with the black dots? Itsmejudith 15:36, 1 November 2006 (UTC)

I agree with the suggestion. We could move the material into the PV section and we could add similar conversion efficiency info to the solar heating section. That would be good. Mrshaba 23:02, 8 November 2006 (UTC)

[edit] Confusion with the Diagram and the Text

There is a contradiction between the diagram of available solar power, and what it says on the text. In the text it says more than a 1000 W/m2 reach the Earth's upper atmosphere. In the diagram, it shows 400 W/m2. Can there be some clarification?

There is 1000W/m2 reaching a flat disk facing the Sun, but at least half of this is lost due to night time, and then a whole lot is lost due to cloud reflection and atmospheric haze. If you don't get the full 400W/m2 at a location, it's because clouds are in the way casting a shadow, plus some other similar factors.Sillybilly 16:40, 13 November 2006 (UTC)

[edit] quantiy/quality

I added a section on the quantity/quality paradox of soalr energy, and an external link to a more detailed discussion. The "dimming issue ' is interesting and important, but not deserving of so much space in an overview article such as this.
KonaScout 15:23, 24 November 2006 (UTC)

[edit] Quantity-quality paradox section

Am I the only one who finds this section contentious? Perhaps the figures for conversion to biomass are accurate. But this is only a small part of the picture. In relation to consumption of energy in buildings, a basic fact is that each building receives far more solar energy per year than its heating/cooling load. So in temperate climates the problem is not so much how to heat the building as how to conserve heat. In warmer climates the problem is how to use the energy for cooling. We are awash with solar energy and sometimes it is the simplest technologies, like the solar cooker, that use it most effectively. Itsmejudith 20:38, 24 November 2006 (UTC)

The diffuse nature of solar energy means that a substantial and expensive material scaffold must often be constructed to collect, concentrate, transform solar energy, and deliver it at a sufficient rate to make it useful in industrial society. Your blanket statement "each building receives far more solar energy per year than its heating/cooling load" is not universal--it certainly is not true for larger commercial buildings and factories. KonaScout 17:53, 25 November 2006 (UTC)

[edit] Units

This article makes use of non metric/SI units such as BTU and the mile. At the very least there should be an SI equivilant listed. Since this is a science/engineering article, I think it would make sense to use SI units exclusively. Harley peters 16:00, 6 December 2006 (UTC)

I've never understood the belief in the universal superiority of one unit size over another. It is surely best practice to include figures in both the major unit systems. Tabby 05:54, 4 April 2007 (UTC)

[edit] Question about phrasing

The article says

"The potential energy in the winds that blow across the United States each year could produce..."

Isn't that kinetic energy? Molinari 08:25, 18 December 2006 (UTC)

You’re right. I believe it meant to say this is the potential if fully expoited not potential energy in a physics sense. I've removed the word as it added nothing to the sentence . Lumos3 12:15, 18 December 2006 (UTC)

Why is this on this page anyway? I moved it to Wind Power talk page so somebody could decide if they want to incorporate it or not. vLaDsINgEr 21:05, 18 March 2007 (UTC)

[edit] This page needs protection

The page became unprotected today and the graffiti has resumed. The protection was working and now that it's gone we're back to eliminating garbage from a page that needs a lot more thought put into it. Please bring back the protected status. I don't know who to send this request to so I'm putting it here. Mrshaba 01:51, 3 January 2007 (UTC)

[edit] Requesting Citation

I placed a request for citation at one point in the article. The citation that it referred to was, I believe, http://www.antandsons.com/takesalook/solarpowerenergystocks_011206/ part of which says that gasoline prices are believed to hit $3 a gallon "by the end of the year" by which they meant 2006. According to http://www.eia.doe.gov/oil_gas/petroleum/data_publications/wrgp/mogas_home_page.html gasoline prices were approximately $2.334 (depends on the state). The citation should be updated with new information. 200.121.111.113 17:07, 18 January 2007 (UTC)

[edit] Possible math error in biomass comparison

In the section "Availability of Solar Energy", it is mentioned that "Annual photosynthesis by the vegetation in the United States is 50 billion GJ" and "The land area of the lower 48 United States intercepts 50 trillion GJ per year"; meaning that the average plant coverage of the US absorbs 1/1000 of the available energy ("Plants, on average, capture 0.1% of the solar energy reaching the Earth"). However it is then stated that "the energy absorbed per unit area is 6.1 GJ per square meter per year" (close -- the math using these figures says 6.25GJ/m^2/y) and therefore "This results in potential biomass production of 6,100 GJ per square kilometer per year." This last sentence I take issue with, because it presumes that "potential biomass production" occurs at the 1/1000 (0.1%) rate previously attributed to average plant coverage (6.1GJ * 1,000,000m/km / 1000 = 6,100GJ). I am certainly no expert in biomass production but as an interested reader I would assume that any land used for biomass production would have a much higher than average plant cover. If this is not in fact a mistake then a link to a source explaining the relation between average and potential plant cover would be helpful. --66.189.113.164 15:34, 2 March 2007 (UTC)

I checked the numbers that were previously provided, converted them to the metric system and rounded them off. This paragraph is intended to give the reader a big picture and I think it does. It is inherently presumptuous but I make no apologies for the information. Biomass minutae is well beyond the scope. Biomass is an indirect and marginal form of solar energy when compared to photovoltaics or solar thermal applications which "harvest" orders of magnitude more energy per area than biomass. This link lists some of the complexities involved in projecting biomass availability: http://bioenergy.ornl.gov/resourcedata/index.html Mrshaba 06:55, 3 March 2007 (UTC)