Solar Trackers for PV -- Worth it ?

According to most sources you can get 30 to 40 % more out of your array if it tracks the sun

unfortunately it looks quite expensive for these and the payback seems minimal over just buying more panels

has anyone experimented with a homebrew design of a solar tracker

maybe using an off the shelf timer and a small geared motor ?

it seems as if it would be pretty straight forward and could be built for far less than the 2 to 3 thousand for such as a zomeworks

Comments

  • loreleclorelec Solar Expert Posts: 200 ✭✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?

    I think I remember seeing a thread on here last month about a home made solar tracker. Maybe someone can dig up a link to it?

    Marc
  • WindsunWindsun Solar Expert Posts: 1,164 ✭✭
    Re: Solar Trackers for PV -- Worth it ?

    Is it worth it? Well, yes and no.

    A lot depends - for a grid tie system with high time of day usage in summer it probably does if you have the room. In some areas rates can vary as much as 500%+ between off hours and max power usage hours.

    At one time it was worth it in almost all applications, because solar panels were in the $7-10 per watt range. But when panels dropped to under $5 per watt, it usually was not worth it. But lately more and more utility companies are forcing people to some kind of variable rate structure, which in some cases can be as high as 75 cents per KWH in the noonish to sundown time frame.
  • WillWinstonWillWinston Solar Expert Posts: 45
    Re: Solar Trackers for PV -- Worth it ?

    good points

    and if you look at it 'globally' it makes sense to maximize the energy that went into the production of the panel

    another point is that I am looking from an off grid perspective

    ROI for me needs to be maximized since the 401K debacle (don't get me started..)
  • Solar GuppySolar Guppy Solar Expert Posts: 1,959 ✭✭✭
    Re: Solar Trackers for PV -- Worth it ?

    More panels beats tracking in all ways except one, if you don't have the space for the extra panels then maybe a tracker might be a solution. But frankly if you have space for a tracker its hard to imagine you couldn't have more panels

    Tracking doesn't give 30-40% improvement year round, summer is best with long days and larger arc of the sun ... but that typically not when offgrid needs extra power as typically they design for worst case which in the cold, short winter months

    With panels now well under 3 bucks a watt, its cheaper, no maintenance and year round power improvement to have more panels than less with a tracker.
  • WindsunWindsun Solar Expert Posts: 1,164 ✭✭
    Re: Solar Trackers for PV -- Worth it ?

    Tracking actually makes more sense for grid tie systems than for off-grid, for just the reasons you state. But even then only if you have high rates during what would be the peak production hours.
    Tracking doesn't give 30-40% improvement year round, summer is best with long days and larger arc of the sun ... but that typically not when offgrid needs extra power as typically they design for worst case which in the cold, short winter months
  • FL SUNFL SUN Solar Expert Posts: 94 ✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?

    Tracking is great when the system works and is fascinating to watch. I have a parabolic dish that tracks for a DHW show and tell. I have had enough of the glitches that come with mechanical tracking components. It is inop now, (needs new brushes) and will be glad to take it down soon for good. Fixed panels are almost no maintenance, and a small percentage more in panels needed to account for 'fixed' is well worth it in the long run.

    It's always getting out of whack with the brushes in the linear actuators - especially the azimuth actuator, blown fuses, etc... The mechanical problems to me are not worth the gain. I'm sure if one factored in the cost for maintenance and repair, the gain in harvest would be offset by repairs and down time.
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,282 ✭✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?

    Tracking offgrid is the number one way if your location supports it to get completely away from generator use. This goal is very hard to do on a reasonable budget but a tracker is the path. I can not tell you the absolute difference other than we went from 25 days our batteries did not complete charge down to 5 per year. The other feature is you are off battery power earlier in the day and can do more with a smaller battery system. Conversely you can run cooling in summer at 7pm long after the fixed array has gone to sleep.

    There just are too many variables but I would tell you a 2KW or slightly less tracker will do for most couples what 4KW fixed would do in winter up here in the Sierra. Winter is where the design is done and since all I do is trackers now it is my business model. I do not want phone calls!!! From my experience there just are too many days when an hour of sunlight at 9 am and another hour at 2 pm happen in winter. There are other senarios of clouds and just plain weather that a tracked array is superior over fixed.

    If you like cold starting generators in the snow/ dealing with surges, doing alot more maintenance, having a big footprint of panels to deal with, a fixed array is definately for you. I do like a fixed array with a tracker so I am reasonable! I probably would agree with most of the gridtie folks here except I tried it. Definately no going back!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • BB.BB. Super Moderators, Administrators Posts: 28,645 admin
    Re: Solar Trackers for PV -- Worth it ?

    I agree that tracking systems need lots of maintenance... Anything electro-mechanical outside in the weather just does.

    4-5 years ago, when I first looked into Grid Tied Solar--I went to a famous RE Store out here (Real Goods Solar Inc). They had a whole bunch of different arrays on their property. The only ones obviously not working where the 2-axis trackers (3 of them--all weathered and probably year(s?) old). They where pointing away from the sun, an actuator hanging by one anchor point, etc. If a solar store could not bother with keeping them running--why would one of their customers try.

    But, if you are interested in a tracker, doing the back of the envelope calculations is worth the trouble.

    I don't remember if you said where you are located, but assume near Springfield Illinois. And use the PV Watts Website Program to compare various options (orientation, panel size, fixed, 1 or 2 axis tracking, etc.). The PV Watts program does include ~20 years of averaged weather too...

    Pick 1kW of solar panel, one with optimum fixed mount, the other with full 2-axis tracking. Assume 0.52 Derating (total end to end efficiency: solar panel rating to 120 VAC out the inverter, flooded cell batteries).
    [FONT=Fixedsys]Results
    1kW solar panels, fixed mount, 52% efficiency
    Month
    Solar Radiation (kWh/m2/day)
    AC Energy (kWh)
    Energy Value ($) @ [/FONT][SIZE=3]8.4 ¢/kWh[/SIZE]
    [FONT=Fixedsys]
    1      3.68          61        5.12   
    2      4.47          67        5.63   
    3      4.55          71        5.96   
    4      5.58          82        6.89   
    5      5.58          80        6.72   
    6      5.98          81        6.80   
    7      6.02          83        6.97   
    8      5.73          79        6.64   
    9      5.28          72        6.05   
    10      4.87          73        6.13   
    11      3.34          50        4.20   
    12      2.91          46        3.86   
    ========================================
    Year  4.83 hrs sun  846kWhr/yr  $71.06    
    [/FONT]
    
    Now do same with 2-axis mount:
    [FONT=Fixedsys]Results
    1kW solar panels, 2-Axis mount, 52% efficiency[/FONT]
    [FONT=Fixedsys]Month
    Solar Radiation (kWh/m2/day)
    AC Energy (kWh)
    Energy Value ($) @[/FONT][SIZE=3]8.4 ¢/kWh[/SIZE]
    [FONT=Fixedsys]
    1      4.48          76        6.38   
    2      5.58          85        7.14   
    3      5.66          91        7.64   
    4      7.33          111        9.32   
    5      8.01          120        10.08   
    6      8.76          123        10.33   
    7      8.59          123        10.33   
    8      7.96          114        9.58   
    9      6.92          97        8.15   
    10      6.05          92        7.73   
    11      4.02          61        5.12   
    12      3.50          57        4.79   
    =========================================
    Year      6.41          1149        96.52    [/FONT]
    
    Year over Year 2-axis improvement over fixed mount:

    1,149 kWhrs per year/846 kWhrs per year = 1.35x more power with 2 axis tracker

    Summer/winter peak month 2-axis/fixed mount improvement:

    123/83= 1.48x improvement for July
    57/46= 1.24x improvement for December

    The amount of fuel required to make up the difference in winter between 2-axis vs fixed mount to make up the losses from fixed mount (assume genset generates 2.5-5.0 kWhrs per gallon of fuel):

    (57-46) / 2.5 kWhrs per gallon = 4.4 gallons per month per 1kW of off-grid solar panels
    (57-46) / 5.0 kWhrs per gallon = 2.2 gallons per month per 1kW of off-grid solar panels

    So, for deep winter use in Illinois, a 1kW off-grid system will require ~2-5 gallons per December to make up for the lack of 2-axis tracking. Depending on your needs (full time living vs seasonal usage, A/C or fans for summer use, etc.)--you can look at the numbers that will reflect your lifestyle.

    There are many ways of looking at the problem--and some you may choose just because it reflects your personal choices.

    Cost wise--I would be surprised if a full off grid system (tracking or fixed mount) would be cheaper per kWhr vs paying the utility to run a drop to your home and installing a fixed Grid Tied array--possibly a hybrid system (like the Xantrex XW system) if you have lots of power interruptions (such as ice storms and it takes weeks to get power restored). Also, many of the local rebates require you to be grid tied to qualify for government funding of your installation (www.dsireusa.org).

    You can also look at what your grid costs would be. Guess that your power company wants to charge you $20,000 to run power 600' to your home. You use a minimum amount of power (efficient but full use of power) at 300 kWhrs per month. And that you will spread the payback over 20 years (no interest):

    ($20,000 + 300kWH/mn * 12 mn/yr * 20yr * $0.10 per kWH) / (300kWH/mn * 12 mn/yr * 20yr) = $0.38 per kWhr effective rate for utility power

    In the end, Grid Tied solar will cost you around $0.10-$0.30 per kWhr. And Off Grid solar will cost you around $1.00-$2.00+ per kWhr (including extra losses due to batteries and inverters, storage batteries and their replacement costs ever ~10 years). A hybrid system (Xantrex XW type) will be somewhere in between.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,282 ✭✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?
    BB. wrote: »
    I agree that tracking systems need lots of maintenance... Anything electro-mechanical outside in the weather just does.



    -Bill


    This has not been my experience. I suppose on homebrew trackers this would be true. Of coarse Bill, it is alot of work squeezing a grease gun 5 or 6 times twice a year! You do have to have the stamina! The 5 trackers up here that I hang my hat on have a combined total of 22 years without problems.

    Of coarse one of the units could fail and the worst thing about that would be it is now a fixed mount......................................
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • BB.BB. Super Moderators, Administrators Posts: 28,645 admin
    Re: Solar Trackers for PV -- Worth it ?

    Dave,

    I am very happy that yours are working well for you and your customers. Do you have a brand/model of actuators that are lasting well?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,282 ✭✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?

    24V DC motors supplied as a package from Array Technologies i.e. The Wattsun !
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • MangasMangas Solar Expert Posts: 547 ✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?

    In my Off Grid system, we evaluated manual versus tracking racks and decided it was pretty expensive given 40 panels. I was uneasy about tracking reliability/maintenance and opted for more panels.

    If I remember right my back of the enevelope calc resulted in extra panels being cheaper than setting up trackers (civil/hardware) and factoring in a couple of failures over time. If you're running fewer panels and are located in a part of the country where you need to compensate for less sun power they might make sense.

    For a number of reasons, I made the decision to accept the cost of building some charging overcapacity into the system.

    Based on actual experience with the fixed array set up, I have abandoned repositioning the array twice a year as the panel capacity is able to handle the winter charging slack in only one position with a little help from the genny once in awhile.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,282 ✭✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?

    Hey Arizona!
    Almost ended up in Arizona myself! Beautiful state. You are in on of the best places in the world for solar. Question are you running a generator for your system? The reason I ask is for me the tracked array and a fixed was the key to making the generator go to someone elses house. I have client who just unloaded 1600 watts from the roof and is amazed at how much power he has late in the day tracking during summer. I am guessing eastern Arizona?? White mountains??
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • MangasMangas Solar Expert Posts: 547 ✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?

    Yes. I would not build an Off Grid system without a top of the line low RPM propane unit.

    I decided on an industrial grade Generac SG015, 1800 RPM, 15KW Propane, with the H-100 Digital Control Panel with weathertight sound accentuated cover. It's whisper quiet.

    Engineers would not install anything else. They said the 1800 RPM units last much longer are quieter and use less fuel. It is a little larger than I needed but at higher altitudes KW output is derated.

    The only service we do are oil changes. They make the industrial units in smaller KWs' too. It only runs 60-80 hours a year including weekly tests but mandatory for peace of mind especially in remote areas like ours.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,282 ✭✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?

    Agree with your comments and I too have customers like you.
    The other side of the coin is I have customers (including myself) who do not want, need, or desire to run a generator and a tracked array is the only way to get there in my opinion. Climates like yours make it very hard to run without a generator but I believe now with the inverter based DC compressor's and high SEER's that even in your neck of the woods it could be done. The key to do this is running a smaller Btu compressor at first light (7am Tracked) and running it all day (7pm Tracked) Just about impossible for a fixed array to get decent power levels at the extremes of the solar day.

    There also is peace of mind in this approach as the only day you have to be concerned with is when the sun does not shine for 2 hours. In both our necks of the woods that happens less that 10 days a year with a tracker.

    There are always other factors and each home has it's requirements. I really love remote homes and I have them in spades. Some amazing friendships over the years and very similar to my years off cruising the tropics in a sailboat. Just Fun and a ton of work. I think it is the quietness of these special remote places that can drop the jaws of city dwellers. No need to mention the stars last night!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • dlenoxdlenox Solar Expert Posts: 42
    Re: Solar Trackers for PV -- Worth it ?

    Your figures of 30-40% are pretty close to actual output.

    One of the issues to consider is the price of the tracker, currently $2000+ is about the going price for passive or active ones.

    The way to help offset the purchase of a tracker is to make your own - recently I fabricated one and including the mounting post only have about $750 into it.

    It's really not that hard to make up a polar mount, here is how I made mine here

    Dan Lenox
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,282 ✭✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?

    Dan,
    A very nice job!!! I would expect something like this from you.......
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • dlenoxdlenox Solar Expert Posts: 42
    Re: Solar Trackers for PV -- Worth it ?

    Sparks,

    Gee you have me blushing....

    Thanks for the cudos.


    Dan
  • WillWinstonWillWinston Solar Expert Posts: 45
    Re: Solar Trackers for PV -- Worth it ?

    Really excellent work, Dan


    with your permission I would like to use your design


    The only change I might make is going with a timer programmed to start at sunrise and end at sun set instead of the sensor

    might be simpler


    Thank you very much, this is just what I was hoping to find
  • rplarryrplarry Solar Expert Posts: 203 ✭✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?

    Dan
    Nice job, well documented. I built my tracker 2 years ago and if I didn't know better I would think you copied mine. About the only thing I did differently is that I used 1.5" solid steel bar stock and pillow block bearings for the inclinattion and east west axis pivot points. The only problems I have had is with the linear actuator, the limit sw. failed so the actuator went to its stop and then tore up the internal plastic gears. I had a spare so no down time. I would love to find a deal on a good actuator like you did. I also used a second linear actuator to control the inlination angle, it also allows me to lay the panels flat with just the flip of a switch in really high winds. I also used the sensor from Redroc, could not be happier. I used to make underwater camera housings, so making a weather tite housing for the little circuit board was a no brainer.
    Anyways, thanks for sharing, it looks like you had as much fun as I did in building it.
    Larry
  • TnAndyTnAndy Solar Expert Posts: 249 ✭✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?

    Great looking job, Dan.....loved your detailed page on the build.

    I also built a pair of single axis homemade trackers.....about 600 bucks each.

    I'm using Analoguy.com for the actuator controller. One controller operates both arrays using a set of relays off the circuit board output.

    Mine consists of an "H" made of 1.5" square tubing ( black in the photo ) welded to a pc of 2" round shaft steel that runs thru 2 pillow block greasable bearings bolted to a pc of 8" channel, which is welded at laditude angle to a 6" steel pole. The panels mount to unistrut that is bolted to the square tubing. A 36" actuator operates the rack.

    7882_p125114.jpeg


    7882_p124855.jpeg
  • dlenoxdlenox Solar Expert Posts: 42
    Re: Solar Trackers for PV -- Worth it ?

    Will,

    Feel free to use what ever you want - that's one reason that I post detailed info on the build.


    RP/TN,

    Due to my altitude and severe weather that we can get I did not want to use any pillow blocks, and by using delrin - never need to have to grease them!!

    The polar mount is certainly nothing new and easy to build. By using the round collars over the post I did not have to take care in how the post (and any predrilling) was positioned in the concrete. This way all can be done after the post is set into the concrete.

    Dan Lenox
  • MangasMangas Solar Expert Posts: 547 ✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?

    Thanks Dave,

    Understand your preference for tracked arrays. They seem to be the most efficient way to go. Dan's set up sure looks well done.

    My location is not for everyone. Most people go silent when out here and are in a little awe of the rugged beauty and solitude.

    They always ask do you ever miss civilization. I tell them you don't miss the services and all that goes with them but, then most people aren't willing to work this hard to live this way.

    The big solar plant makes it comfortable. You understand that sense of independance.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
  • WillWinstonWillWinston Solar Expert Posts: 45
    Re: Solar Trackers for PV -- Worth it ?

    I found it !!!

    Leave it to the Germans

    Forget all the complicated circuitry to keep the panels pointed at the sun either one or 2 axis


    This timer has an 'Astro' mode -- that means it can be programmed to turn on and off according to sun rise and sun set each day of the year-- even can compensate for latitude and longitude

    one or 2 electrical outputs

    AND it is only $115.71 from Allied

    turn the tracker drive on at sunrise turn it off at sunset
    set the second timer to return the panels to east after sunset for the next morning

    and the timer will turn on the tracker motor on at sunrise again and do it all over

    Change the angle manually 4 or 5 times over the year

    viola !!! a tracking system joe average can make on a budget


    http://www.hugo-mueller.de/faq/faq,t,en,,.html

    R0453912-01.jpg




    Ok, before one of you sharp people call me on this

    you would have to change the speed of the tracker relative to the number of hours of sun per day

    I have 2 ideas ---

    one: the timer has a programable pulse mode that might work

    two: might have to change the gearing of the motor a few times a year

    ok three Ideas

    three: a variable speed motor (there goes the simplicity again)


    ok now tell me where I screwed up :D






    edit typo
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,282 ✭✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?

    Will,

    I guess I am missing something. This sounds much like the Intermatic ST01 which is a sun timer. You still have to input something to drive the motor and you need feedback to know that it is where it is suppose to be. Most of the motors are 24VDC so are you saying you would just program it for every 15 minutes of the day?

    I did not see a rating for contact voltages. The Intermatic has a 35vdc rating and I use it for exterior lighting. How would you control 2 axis?

    I am pulling for you on this one! There was a company last year that was going to do this for portable and RV but the recession killed it. Good luck!!!!!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • Dave AngeliniDave Angelini Solar Expert Posts: 4,282 ✭✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?
    Mangas wrote: »
    Thanks Dave,

    Understand your preference for tracked arrays. They seem to be the most efficient way to go. Dan's set up sure looks well done.

    My location is not for everyone. Most people go silent when out here and are in a little awe of the rugged beauty and solitude.

    They always ask do you ever miss civilization. I tell them you don't miss the services and all that goes with them but, then most people aren't willing to work this hard to live this way.

    The big solar plant makes it comfortable. You understand that sense of independance.

    Definately understand it, do it, and make a living off it! Arizona is my second home and all my sailing mates ended up in Tucson. I miss the desert weather in winter!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • WillWinstonWillWinston Solar Expert Posts: 45
    Re: Solar Trackers for PV -- Worth it ?

    Dave:

    I guess I am missing something. This sounds much like the Intermatic ST01 which is a sun timer. You still have to input something to drive the motor and you need feedback to know that it is where it is suppose to be. Most of the motors are 24VDC so are you saying you would just program it for every 15 minutes of the day?


    Not sure if the intermatic is quite the same as the Muller. The Muller can be programmed for different locations and is a 365 day timer (it knows the sunrise and sunset for each day of the year at a particular spot on the earth)

    but my idea is to start the motor drive at sunrise then stop it at sun set

    The tricky bit, as I see it, is to have the tracking time match the hours of sunlight (about 9 hours Dec 21 to about 15 hours June 21 up here in da north)
    I think I can do this by varying the speed of the drive (maybe with a manual change a few times a year) or if using a linear actuator, connecting the driver to a longer pivot arm for longer days


    I did not see a rating for contact voltages. The Intermatic has a 35vdc rating and I use it for exterior lighting. How would you control 2 axis?

    The spec here:

    http://www.hugo-mueller.com/astro-solar-time-switches/mueller-sc-28-x4-pro-paladin-172-4x4-pro,p,en,2,108.html

    says 16 A per channel (I am assuming this is AC)


    The second axis would also be a comprimise adjusting the tilt maybe 4 times a year


    I am pulling for you on this one! There was a company last year that was going to do this for portable and RV but the recession killed it. Good luck!!!!!


    Thanks
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,282 ✭✭✭✭✭
    Re: Solar Trackers for PV -- Worth it ?
    Dave:




    Not sure if the intermatic is quite the same as the Muller. The Muller can be programmed for different locations and is a 365 day timer (it knows the sunrise and sunset for each day of the year at a particular spot on the earth)

    This how the intermatic works and it has a DC rating!!

    but my idea is to start the motor drive at sunrise then stop it at sun set

    The tricky bit, as I see it, is to have the tracking time match the hours of sunlight (about 9 hours Dec 21 to about 15 hours June 21 up here in da north)
    I think I can do this by varying the speed of the drive (maybe with a manual change a few times a year) or if using a linear actuator, connecting the driver to a longer pivot arm for longer days

    And this is the problem and always has been. A small array is alot of work to R&D but a big array 125 Sq. ft. and up is typically very robust and the gear drive motor interface is well over 125 pounds. The motor is usually just pulsed 24vdc. Google Redrock solar trackers and he will have alot of info. I have zero problems with the Wattsun trackers I have installed and use. They have some good info also. Google Array technology.


    I did not see a rating for contact voltages. The Intermatic has a 35vdc rating and I use it for exterior lighting. How would you control 2 axis?

    The spec here:

    http://www.hugo-mueller.com/astro-solar-time-switches/mueller-sc-28-x4-pro-paladin-172-4x4-pro,p,en,2,108.html

    says 16 A per channel (I am assuming this is AC)
    Yse AC ratings are assumed in most cases. DC rating are definately what you want as they are much more robust and will last longer.

    The second axis would also be a comprimise adjusting the tilt maybe 4 times a year


    I am pulling for you on this one! There was a company last year that was going to do this for portable and RV but the recession killed it. Good luck!!!!!


    Thanks

    Your welcome! Good Luck!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • kemills1kemills1 Registered Users Posts: 1
    Re: Solar Trackers for PV -- Worth it ?
    More panels beats tracking in all ways except one, if you don't have the space for the extra panels then maybe a tracker might be a solution. But frankly if you have space for a tracker its hard to imagine you couldn't have more panels

    Tracking doesn't give 30-40% improvement year round, summer is best with long days and larger arc of the sun ... but that typically not when offgrid needs extra power as typically they design for worst case which in the cold, short winter months

    With panels now well under 3 bucks a watt, its cheaper, no maintenance and year round power improvement to have more panels than less with a tracker.

    Totally agree! I've built my own tracker for a 1700w solar array (10X170W panels) and to be fair, here in Spain in the summer, I do get about 35-40% more power and the tracker cost me about the price of one panel. This made sense at the time as I paid £4.00 per watt for the panels. But now, in the UK, I can buy panels at 50 pence per watt, so the advantage is greatly reduced even if you build your own tracker and to buy one makes no financial sense at all. (tracker manufacturers take note!).

    Kev.
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