Sun trajectory and my panel positions..

ywhic · May 2012

I've got 4 panels for my setup.. 190 w each of 24v. there going to be mounted on fence posts..

Anyway.. if I were planning on running my A/C in the 1-3 pm time frame off the battery bank (to keep it cool when its 100F)..

Where would I put my panels to charge the most?? after I deplete them?? or early AM to catch the early rays..??

Most of my spring and summer is SOUTH (I am in South TX as well)..

I've used Sun Calc and got spring, summer, and winter.. but I am trying to prefigure where to face my panels..

Winter 9am the sun is South East (like 4:30pm per se) 5pm (is like 10pm per se)
Summer 9am is North East (like 1pm per se) 5pm (is like 8:30 per se)
Spring 9am is East (like 3:30pm per se) 5pm (is like 7pm per se)

Cariboocoot · May 2012

Re: Sun trajectory and my panel positions..

For fix mounted panels used to offset the A/C usage between 1 and 3 P.M. aim them where the sun will be directly on them at 2 P.M.

But that's not going to be helpful for charging the batteries after a night's use or making sure they're full up before that.

If the batteries can handle the load for an hour on their own, you could shift the aiming to 3 P.M. to take over the load and recharge afterward, providing you get enough sun. Normally in a hot climate you try to pick up the morning sun to get full power out of the panels before their increased operating temperature is combined with high ambient resulting in significant power loss.

This is one of the problems with trying to squeeze full power out of a marginal system. A tracker would solve this dilemma, but that is more money (unless you want to make your mount movable and go adjust it manually every so often).

And if you think you've got it bad, there's a 10 hour difference between Winter and Summer up here with a panel angle change of about 46 degrees.

westbranch · May 2012

Re: Sun trajectory and my panel positions..

Coot has it right, your batteries may end up being in a deficit state quickly.
IIWM I would look at getting more PV and get the battery through Bulk, and into absorb before 13;00...
then the 4 panels pointed at 14:00 hr sun can be used to power your A/C and maybe put something into the bank.
hth

ywhic · May 2012

Re: Sun trajectory and my panel positions..

Heres what i came up with last night and before I read the post this morning..

If I turn the bottom 2 190w's more south.. I can get 877 watts (based on the 77% eff number) back into the bank by 5-5:30 pm..

Picture # 2 (just did)

The 2 190's on the EAST side would pick up the same 877 watts in the AM hours..

My angles are Spring 60', Summer 85', Winter 36'.. so yup I have almost a 50' angle change on my panels..

I wouldn't try to get A/C up and going till I got my 440ah bank put into play.. so 110 ah would be the 'draw' for 2 hours..

Cariboocoot · May 2012

Re: Sun trajectory and my panel positions..

A little semantics. Amp hours are not draws, they're a fixed amount of energy (@ Voltage = Watt hours). For off-setting loads the panels need to produce the same amount (or more) of Watts as are being used in the system at that time. You can only use stored and replace Watt hours calculations where you have averaged the usage and recharging over time. In essence you're trying to plan load-shifting in advance, rather than figuring a way to make use of any 'surplus' which might be available.

If at all possible, try to figure a way to make your panels easily movable through the daily sun arc. You might not be able to determine which direction works best for your usage in advance. In never hurts to have some flexibility in that. From the looks of your diagram, the classic "solar South" direction appears to be best for you. Oddly, that's around your 2 P.M. Summer mark. I find that coincidence suspicious. :roll:

ywhic · May 2012

Re: Sun trajectory and my panel positions..

There all proposed to be directional with clevis pins on the pole(s).. (that was a forethought on my part a few days back.).

I had the building put up using the SolarCalc before I left here in PA to go down and tell them where I wanted it..

Heres the latest drawing based on a more solar south setup.. and 1 panel hanging East for the morning rise..

Cariboocoot · May 2012

Re: Sun trajectory and my panel positions..

If you put your panels facing each in a different direction you may not have enough current to do a good, quick battery charge.

Another reason for flexibility in mounting.

ywhic · May 2012

Re: Sun trajectory and my panel positions..

Heres snap shots of my road and my cabin on the SC.. April 18th (when I was there), June 21st (summer), Dec 21st (winter)

My proposed layout E in the SUMMER.. Time with Orange is still 3:30pm..

themaxx69 · May 2012

Re: Sun trajectory and my panel positions..

I'm no expert, but why not just build a couple of trackers. There are plenty of plans and videos on the net. Ridiculously cheap to build one yourself compared to companies that sell them. That's what I decided to do from the beginning. Don't know why more people don't. I think power available for more total time is more important than more power for less time.

ywhic · May 2012

Re: Sun trajectory and my panel positions..

After reviewing some other threads and having a lightbulb go on.. :roll: I'll situate the panels to be from 11 am to 5 pm for sunlight.. then use some of the incoming wattage to offset the A/C usage.. even if I cut the AH draw from the battery bank in half I'd be happy.. better than killing the battery bank alone..

The layout plan F (below) would be it I think (again posts/mounts will be directional and angle adjustable)...

Sun trajectory and my panel positions..

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