Grrr... Daylight savings

[Volvo farmer]

Crap, I'm sore. Just shovel dug four 18" holes in rocky soil and put four 12" sonotubes in to mount my homebrew panel rack. Well, I checked the time for solar noon and lined them up with that without checking for daylight savings, so I'm pointed an hour more east than I should be. I haven't poured concrete yet but I'd really rather not re-dig three holes. I'd almost be willing to let some generating capacity go, if it's not too serious. I've fixed the panels at about 62 degrees from horizontal according to some online calculator for my latitude at 37 degrees. They're supposed to be optimized for winter and I give up about 15% in summer with them set at this angle, which is OK with me.

This is a lazy question I suppose, but I haven't asked any stupid questions here recently. Anyone have a guess as to how much power I'm leaving on the table, percentage-wise, in the middle of winter with the panels oriented an hour east of solar noon?

[ruddycrazy]

Hiya Volvo,

           Eh mate if your going to all that work why not setup a sun tracker like the redrock one's or similar that way you won't have to worry about daylight savings and your panels should be facing the sun most of the time. Mind you I'm lazy when it comes to panels I just secure them to my roof and they work ok.

Cheers Bryan

[henjulfox]

http://rredc.nrel.gov/solar/calculators/PVWATTS/

If I copied this link correctly, it's a nice little online PV calculator you can use to compute output at different panel orientations. In my part of the world, I compute 2.5% yearly loss by pointing 1 hour off from due south.

I would convince myself that I did it on purpose to maximize morning collection

-Henry

[stephent]

And it depends on your local terrain. If you have a bunch of trees to the east and none to the west--you lose a bit by being off 15 deg.

If you have trees to the west and almost none to the east--you will probably gain a bit over "proper" placement, or at least not lose much if any of the total daily wattage.

Take a look and make a decision, and tell your spouse it was on purpose if it looks like more "shading" to the west. Trees shade my PV's (little ones for now) from both directions and from straight up for the yard LED lighting ones too, but I charge them a time or two a week from a small wind genny that does 6v or so.

Or you could just say it was to help gain back a bit of the "summer"/DST loss.

The early/late hours of the day are lower power producing times anyway.

Usually here I have clearer mornings then afternoons when solar heating makes the clouds more intense.

Another thought--just shift the poles/mounts in the concrete bases (if used) a bit off center if possible.

Geee--18" sono-tube times 4--what/how big a mount are you holding up? That's big enough for one of those Diesel generators I sometimes install (20KW to 1250KW).

I know your pain with the rocky soil--I have a bit of dirt between the rocks here.

[Volvo farmer]

Hi Bryan. You're talking to a experienced user of Redrok trackers.

http://www.fieldlines.com/story/2006/3/6/12351/04204

http://www.fieldlines.com/story/2006/7/8/20847/11730

These panels are homebrew, about as heavy as a patio door, and there's four of them. Add that to about 100 lbs of steel frame and I do not feel comfortable mounting all that weight on a satellite dish mount. I've thought about it, believe me.

[stephent]

ooppps--those are 12"--still big enough..

[Volvo farmer]

Thanks for that link. The numbers disagree a little bit with the link I used to figure out my tilt.

http://www.macslab.com/optsolar.html

They say the difference in summer and winter output should be on the order of 25% at 62 degrees fixed tilt at 37 degrees latitude. The site you linked shows differences on the order of 50% However, I got very little difference in output by changing the east-west angle by as much as 20 degrees.

[henjulfox]

Volvo,

I think "my" calculator uses actual climate data for a particular area vs. "yours" is straight math. For example, here in Oregon it rains all winter so we don't get much output no matter what the tilt.

Always suprises me how little the deviation from due south matters, except for shading issues, as others have pointed out.

-Henry

[Volvo farmer]

Thanks everyone, I moved the #$%@* holes today. I just couldn't live with knowing I was so far off true south. If the Druids and the Ancestral Pueloans can line up stuff to true south, so can I.