Panel angle/ Power output

[acapulco]

hey all,

I previously mentioned that I was only able to get a maximum of 5.7amps @ 24volt from my 4 x 60w solarex panels (2 x 2panels in series).

After reading some posts here about panel temperature afffecting output I decided to fool around with the mounting arrangements with the hope of redcing panel temps in order to get the most output.

I also decided to fool around with different angles of the panels to see what effect that had on power output. I checked a few sources and the recommended angle is the equivalent of the latitude of location(in my case 25- Sunshine Coast, Australia) the previous mounting was simply a log on the roof with panels leaning on log and bottom ends on bare corrugated iron roof.(angle was approx 10-15 degrees)

After only adjusting the angle to approx 25 degrees Iwas able to get a max of 7.59amps @ 24volt!!!

(read using digital MM between + lead and battery +, no solar controller; direct connection)

Obviously the angle of panels can have a signifigant effect on output; Some sources say use angle equal to location latitude whilst others say latitude + 15 degree so my question is:

 What is the optimum angle for panels to be set at?

 tia,

Ian...

!

[zeusmorg]

 It does depend on the time of year... optimum is latitude + or -15 degrees depending on if it's early summer or late winter.. lower in summer. higher in winter.. latitude in spring and fall.

[tecker]

 20 summer 50 winter

[wpowokal]

Ian, I am quite a bit further south than you (35) and my optimum angle goes from 80 deg to horozontal. Here in the west (the sunshine state) my sun is low in the northern sky mid winter to behind (south) of me in mid summer.

I used to have them fixed at 35Deg, but since making them fully adjustable imput has leaped.

Solar panel angles depends very much on location and peak use time, sales information abounds but experience teaches.

Allan on the other side

[tecker]

It's really pretty much 15 plus you latitude winter minus 15 your latitude summer. So straight up summer 30 to 40 winter sorry . A little off the optimum is what I use .My tracker is under construction .

[acapulco]

thanks all,

I was thinking of trying to find the optimum all-year-round angle but from what everyone says it seems it is worthwhile to at least change the angle twice a year. maybe more.

Also, I am starting to think maybe the panels I have are mis-labeled or something,

Surely it can't be possible(?) to be getting more power than the rated p-max?

The panels are Solarex SX-60 or maybe it was SX-65(i'll have to get out the ladder...)

Anyways, the Pmax rating for the SX-60 is 3.56amp/16.8volt and the SX-65 is 3.77amp/17.2volt.  I have 4 of these panels configured at 24volt so I assume the pmax for the 4 panels @ 24volt is 2 x the pmax of the panel ie: 3.56amp x2 or 3.77amp x2 which makes for a pmax of 7.12amp/or/7.56amp @ 24volt.

Yesterday at about 1pm in full sun conditions I measured 7.59amp@24volt going into battery bank is this possible?  Or are the panels more likely a higher rating than I think?

These panels are nearly 10years old btw.

tia,

Ian..

!

[electronbaby]

Solarex made a good module. The key to getting closest to the max power output on any module is keeping the module cool. This is why modules perform better in a winter climate (higher instantaneous current but less sun hours per day), and why MPPT is sure to give the highest output in these circumstances. A good way to do this is to mount at a steep angle. Not too steep to take the module out of its optimal sun angle, but steep enough to allow the best convection cooling of the back side. Mounting away from the roof is the best way to do this aside from a pole mount of a tracker which would be the best.

One day when your bored, and the ambient temp is high, take a hose and spray some cool water over the modules and watch your ammeter. :-)

[scottsAI]

Acapulco,

The current / voltage rating is at the max power point.

If the voltage of the battery is lower the current can be higher.

The panels are working at a lower power point.

Find data sheet for panels, and see the curves.

Panels power is 7.59 x 24 = 182 watts, well below the 240 watts rated (4 panels).

Almost one whole panels power is missing!-(

MPPT could help, unless you DIY unlikely cost effective.

Solar tracking DIY can be fun and cost effective, several good designs out there.

Have fun,

Scott.

[tecker]

 Yes test each for full load . Dmms at high noon .

[electronbaby]

Im not sure where he is located, but his numbers sound right. I generally use a 20%-25% derating for most modules in full sun with an ambient temp or aprox 80 degrees Fahrenheit. He is getting more than that so it just seems not too far off, especially for 10 year old mods.

I would always check their ISC (short circuit current) anyway to make sure.

[wooferhound]

Panel angle information . . .

http://www.fieldlines.com/story/2008/7/20/131749/605

[GeeMac]

In Feb, you should set the panels to the angle that is the same as your latitude.

Then in May the angle should be 15 degrees less than your latitude.

The next change is done in August and should set the panels to the angle that is the same as your latitude again.

In November the angle should be 15 degrees more than your latitude.

[SteveCH]

You can, as others have said and as you know, increase your total annual harvest with fine-tuning the angle of the array(s) during the seasons. I used to, at first. Then, I did some testing and found that, for my uses, setting the angle at the worst month [January here] for solar [daylength, etc.] was fine. I no longer bother to change the angle. So, it kind of depends on how much you want to work with it. Keep some written records during the course of a year and it'll help you decide.

[DamonHD]

Exactly: I leave my tiltable off-grid panels stuck at about 70 degrees, which is good for UK winter when I'm shortest of sunshine and power.  That also means that they don't eat up too much of our very small garden space!

Rgds

Damon

[Jeff]

Making a low-cost tracking mount is definitely the way to go:

http://www.fieldlines.com/story/2008/6/1/182521/4563

Eliminates all that calculation, and if I could do it, almost anyone can!

[acapulco]

hey,

 are those dates/angles for northern hemishere? I am southern hemishere(SE Queensland, Australia)

cheers

Ian

!