Direction and angle

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p_hammond
p_hammond Registered Users Posts: 5 ✭
in PV Installers Forum - NEC, Wiring, Installation #1
I have a beach house in Puerto Penasco (Rocky Point), Sonora, Mexico. The house is not used from June 15 through October 1 of each year because of the weather (hot and humid).
I need to roof mount two Kyocera 85 watt panels, about two years old. How do I determine the direction the panels should face and the angle, to the horizon, at which they should be mounted for maximum production from Oct 1 through June 15?
If any one can give me the information itself, it would be most appreciated. Thank you and reply to my email if you wish, address is p_hammond@yahoo.com.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: Direction and angle

    Direction: South if North of the equator, North if South of the equator.
    Angle: http://www.macslab.com/optsolar.html (Really good site).

    You also should consider any obstructions on site that may shade or block the panels during peak sun hours (10:00 AM to 2:00 PM or thereabouts) and in your case possibly favouring Southeast a bit so that you get the cooler, morning sun as higher temperatures will significantly reduce panel efficiency.

    Si? :D
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
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    Re: Direction and angle

    To find true South visit this section of another of my favourite web sites, Build-it Solar:

    http://www.builditsolar.com/SiteSurvey/FindingSouth.htm

    (We generally put Q's & A's in forum postings so they may help other people in similar circumstances.) :D
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
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    Re: Direction and angle

    in addition to the norm of aiming south, or somewhat toward the southeast as some may wish, you need the elevation angle. as you show a need over a variety of good and bad solar seasons meaning it may still be best to opt for the worst case months which fall in the winter. all angles start with the latitude of the site which for you would be about 31°. for you to visualize the relation to a pv it will be 0° for a pv to be laying flatly or horizontal and 90° is vertical or standing up and down. that 31° is the average angle that point on the map sees to the sun. now you would still see more production in the summer months than the winter months with the latitude angle as your pv angle so many will add up to 15 more degrees to their latitude angle to harvest more power in the winter months without cutting too much from the summer months. so now you can put the pvs at 31° or go up as far as 46°. the slightly steeper angles may also allow rain to wash off the pvs better too. if i were in your situation i'd probably go around 40°, but it may depend on your preference and is not too critical.
    why the terminology of max production if unoccupied for those months? now we all like to get as much from our pvs as possible no matter the circumstances as pvs aren't cheap power. these will be in float mode service to the batteries and should be around the area of 1-2% of the battery capacity. if these pvs give more than that percentage then the max output is not as critical. do be sure to use the proper wire gauge to minimize losses. be sure to use a controller to help prevent overcharging, which could easily happen when constantly feeding power to full batteries and would stop the nighttime discharge of the batteries through the pvs.

    edit to add:
    it's interesting that i see a small volcano to the north of that area by about 30 miles. i hope that it does not become active as that just might ruin your day.:cry::p
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  • p_hammond
    p_hammond Registered Users Posts: 5 ✭
    #5
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    Re: Direction and angle

    Thanks for the very informative answer. The cabin is not used from June 15 to Sept 30 because of weather. We get no more than 4-5 inches of rain per year. Major problem is making sure the battery water stays full, sometimes in the summer our caretaker/guard forgets to check once per month and two years ago our former batteries were dry when we got there in Oct!
    Yes, we do have a good controller rated at 30 amps so no problem there. Power is used only for fluorescent lights, occasionally a ceiling fan or two, and an iBook, every thing else runs on propane.
    The volcano you see is extinct and is in the Pinacate Mountains. 15 years ago 5 couples with 4X4 trucks took three days to circle the entire range, camping out each night. Beautiful and we saw several mountain sheep.
    Thanks again. PBH
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
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    Re: Direction and angle

    no problem.
    now i did misunderstood the times of the year for it to be vacant and i now see that it is the summer to the fall timeperiod you need for float charging and this may be left at the latitude angle of 31°. if you are using a fixed angle and use the solar power during the other times this can up the angle somewhat for better winter production. you could also opt for a mount with optional positions for various times of the year. maybe you'll even let the roof angle be more instrumental in the angle if it's in the neighborhood of the angles discussed, but mount them at least 6 inches or more above the roof to allow for better pv cooling by allowing more airflow.
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  • p_hammond
    p_hammond Registered Users Posts: 5 ✭
    #7
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    Re: Direction and angle

    All makes sense to me, think I will go with the 31 degree inclination. Last Q, I think, is how to determine true South. I can see the big dipper at night, is 180 degrees from the north star the best way to figure it, should a use a good magnetic compass but then what about deviation, or do you think I can rely on the navigation system in my car to show me true north and go from there? If I go slightly east of south, how far east, in degrees, would you think.
    thanks again for all the help, we are going down this weekend to start reroofing which will involve remounting the panels, so I want to get it right.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #8
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    Re: Direction and angle

    You can google magnetic declination and find lots of sites like this one:

    www.ngdc.noaa.gov/geomag/

    Here is a Boy Scout Troop's explination of Mag Declination:

    www.troop278.net/Scoutcraft%20Pages/declination.htm

    Phoenix declination is about +11 degrees (magnetic north is about +11 degrees to the "right of north").

    I would not count on a car GPS--They tend to "stick to roads" so they may not follow your house's orientation (plus you may have to "drive through your house" to get the GPS to show the new course (many do not list degrees--just N, NW, etc.)...

    There are many models and brands of GPS's... Hard to know how yours will behave.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
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    Re: Direction and angle

    true south can be determined by solar noon. solar noon is the highest point the sun reaches in the day. if you have an object such as a stick sitting perfectly vertical during solar noon the resulting shadow will form a line in the north south direction. (very short line during summer solstice though) it may be difficult for you to determine your solar noon if you haven't access to your local sunrise/sunset times so take a nearby city such as phoenix and determine what its solar noon is from weather.com. below the temperature where it says details it will show the sunrise/sunset times. solar noon for phoenix would be smack dab in the middle of those 2 times. now being further west the solar noon for phoenix won't be the same for puerto pinasco. this is where a map can be handy as you look up the longitude of phoenix (roughly 112° ) and that for your location (113.5° ). now each ° of longitude will represent about 4 minutes of time. assuming both places are in the same time zone then you would just add 1.5x4=6 minutes to phoenix's solar noon as sunrise, sunset, and solar noon will occur later than phoenix. if you were east of phoenix the time would be subtracted from phoenix's solar noon time.
    odds are you won't get it exact anyway and it isn't necessary to be totally exacting as a few degrees either way won't kill the system. the compass method described works too if one knows the deviation from magnetic north so you have 2 ways to get those pvs aiming south.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #10
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    Re: Direction and angle

    I mark the shadow of a stick or something about 10am, and in han hour, the tip of the shadow will have moved east several inches, I lay out a row of rocks along the line till 2 or 3 pm, and I have a true E - W line, and can derive north from it. Only needs sunlight to work!
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • p_hammond
    p_hammond Registered Users Posts: 5 ✭
    #11
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    Re: Direction and angle

    Thanks to all of you for the advice, you make is sound so slmple that I think even I can follow it. Think I will go with the 31 degree angle on the panels and about 5-10 degrees to the east of true south, considering the time of the year the cabin will be used. Thanks again to all, I really do appreciate the help.
    If anyone sees any errors in my decision, please let me know. PBH
    P.S.: If you ever find your way to Puerto Penasco, Sonora, Mexico, let me know in advance by email to p_hammond@yahoo.com and we'll have a cold Corona on the beach. This particular part of Mexico is cartel violence free, probably because there is so much cartel money in all the condo, etc., development which has occurred over the past ten years!:D:D
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #12
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    Re: Direction and angle

    glad to help and thanks for the offer, but i don't expect to be traveling down that way. have one for me as i'm not supposed to drink. do stop back with info on how well it works out for you.:D
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