Almot wrote: They say Lat-15 would generate better amps than flat, daily, in May. Which is 32 deg for their location. In June-July they do say that flat is better, yes.
Today is 45 days before 20 June. The same tilt angles and shoulder hours will happen 45 days after 20 June, on 4 Aug. There could well be less cloud etc in the shoulder hours later on, but that does not change the angles and what amps you get in clear blue sky during the shoulder hours with the panel at the same angles.
If it is cloudy that will just reduce the amps, but it can't make the amps better with the same clouds when flat.
Give it up. Your pals in the WA wonderworld are full of it.
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Almot wrote: BFL, you've made my day no matter what Wa pals are saying ...
To me it was important to confirm that 2 flat panels provide same output as one tracking panel. Have to keep it simple.
I can't confirm that. I did say that my tracking 130w will do almost as well as the two panels (130 plus 80) did last year when those two were both tilted up, fixed, pointing South. I never did have them both flat to the roof.
So I need to define "almost as well." At noon the 130 got 8 amps while the 80 got 5 amps, so with tracking making the 130 do say 33% better for daily AH (based on area under curves in the plot shown above) so I expect it to be like having 173w vs 210w last year
If my second panel last year had been another 130, then tracking with the single 130 would not be as close. 173 vs 260.
I think there tilt angle is to high for summer. They are using lat minus 15 which would still be like 34 degrees. This is probably ideal for a tracking angle but not for a fixed panel. You have to have a lower tilt for a fixed summer panel.
I think that 15 degrees you see all the time is a chosen average Declination they like to use. Dec goes from 0 at Equinox to 23.5 at Soltice, so for a rule of thumb I suppose 15 is sort of ok.
If you are a busy bee you can follow the change in Dec and adjust your tilt weekly if you want. 8 degrees a month is two degrees a week approx.
This is what I noticed too - Wa tables (they have it for every state, cut off the end of URL and see the list) are so averaged that sometimes it defies logic. Like same angle for the whole month of Dec of June, while in reality angle goes up and then down during those months. But this is the simplest way to arrange the data if the purpose is to make a month by month table. I would say that for most people this table is already too much, and fixed angle adjusted 2 times in summer (and 2 times in winter, if you camp in winter) is enough trouble. Especially for those who are not on seasonal sites. Imagine tilt arm with a dozen notches and ugly handwritten marks like, for example, May 12, Jun 9, Jul 17 etc etc. And a list in the cabin with those dates. And a pain to follow this schedule every time you go camping.
Re: 1 tracking or 2 flat. BFL, my conclusion that it is the same was based on your numbers, not on your words. In fact, 2 flat is more output than 1 tracking, at least in summer. Just didn't want to spoil the fun. 1 tracking is 1.33 times better than 1 fixed tilt. 1 fixed tilt is - how much better? 1.6 early in the morning in May, and less than 1.6 at noon and in June - than 1 flat. 1.6*1.33=2. So 1 tracking at the very best equals 2 flat. You have more data and may check, I don't think I'm far off. This also depends on the location (i.e. latitude). Somebody in SoCal or Baja will see less difference btw 1 tracking and 1 flat, because the noon tilt is lower.
* This post was
edited 05/07/12 12:40pm by Almot *
Yes but I don't want two panels. I used the money I got back from returning the 80w panel to pay for two more 6v batteries.
Then for less than $25 ? I built this tracking monstrosity that is worth half that 80w panel in AH, so I got half that back for free so I figure I am way ahead.
I don't really need any solar at all, but it does help a lot to have that single 130w panel based on lessons learned from last year. I sure don't need any more solar than that for how we do things, and cheap panels aren't here (yet, if ever)
Of course more solar gets you more AH than less solar, but you also have to decide where to put your bucks for the most bang in the Big Picture.
Hm, monstrosity... quite a sophisticated woodwork, I would say. No kidding.
Most fixed tilt mounts (or fixed adjustable) have no tracking option, people can only tilt it higher or lower but they can't change the azimuth. I wonder at what azimuth tilting becomes less efficient than flat, in terms of daily AH, even in winter. Say, it's pointing straight East or West. Or North-East, North-West.
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