season panel angles

alcatel99

Hi Guys 
I hope to be setting up my panel mount soon and hoped i can get some additional info regarding best angles for summer ,winter fall,etc
i am off grid in NE Arizona between St johns and Sanders the Latitude where my cabin is situated is 34.899 * is there a website where i can find best positions for panels in different seasons 
Thanks as always for any help .

Dave Angelini

If you are in air conditioning country, and not above 3,000 feet your main benefit to solar is going to be 2+ arrays with a an easterly azimuth and a westerly. Adjusting the seasonal angle is way down the list for cooling requirements compared to azimuth. You want solar power from dawn to dusk by virtually tracking the sun for cooling or high volume farm pumping. This will also increase your battery life or allow you to use a smaller battery.

BB.

There is a very simple calculator I use here all the time:

http://www.solarelectricityhandbook.com/solar-irradiance.html

And a  more complex calculator (that allows you to pick any location by city/lat-long), and even gives you hour by hour estimates for 365 days a year:

https://pvwatts.nrel.gov/pvwatts.php

The two are probably within 10% of each other usually. Both give long term averages (~20 years) for solar data. The PV Watts output based on "real" days (each day picked to represent the average harvest for that day). Both are based on actual measurements--So clouds/marine layer/etc. are included deratings.

I probably "trust" the PV Watts more when you start playing with East/West arrays and "non-standard" angles (SolarElectric one is very quick and limited options--Great to get a quick answer for your questions though).

I am sure there are a 100 different programs and websites out there--Just have not needed to look for more. The above seem to give accurate enough results--When accuracy is something like within 10%... And realizing that these are long term average numbers and month to month or year to year, 20% variation is normal.

This also get into looking at your loads as members of two classes... "Baseline" loads that need to run 24x7 (like refrigerators, LED lighting, and perhaps a home business--Laptop computer, networking, etc.). And "Optional" loads (washing clothes, irrigation, vacuuming, irrigation, etc.). I suggest that baseline loads should be around 50% to 65% of predicted solar output (1/0.5 = 2x array, 1/0.65 = 1.54x larger solar array).

Of course, if you are willing to run a genset more often and/or are in a very sunny/cloud free climate--Those fudge factors could be a bit on the conservative side.

Solar panels are historically cheap--And last 20-30+ years... Batteries are historically expensive and last 3-5-7 years (cheap to mid-priced lead acid, >15-20 years for "forklift"). So "over paneling" is usually a good way to help keep your batteries happy and have a long life.

Also, heat kills batteries (and pretty much everything else). A very handy engineering rule of thumb... For every 10C (18F) increase in temperature (batteries: 25C/75F is "room temperature"), the life of that "thing" goes down by 1/2. At 93F, batteries age 2x faster (1/2 life).

So, keeping your batteries cool in Arizona can be a big help too (basement, earth berm battery shed, root cellar, etc.--Watch for water/flooding in below grade installations).

-Bill

alcatel99

Thanks guys very helpfull I am at 6300 ft and and on a slightly down slope so water /flood drainage is good i am putting panels on a tilt adjustable frame so my other main concern is wind/gust proofing i will also be keeping batteries in my rv in the section used for the bed so just need to add some extra insulation and maybe a couple of computer fans .

littleharbor2

Download the "Solar Tilt" app onto your phone. Really cool and flexible. nice tilt gauge built in as well.