Convert stationary solar to tracking

Discussion in 'The Projects Forum' started by chergar, Jan 22, 2011.

  1. chergar

    Thread Starter New Member

    Jan 22, 2011
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    i want to build a simple horizontal tracking system. I presently have a 1/6 h.p.110 v. motor/speed reducer producing 30r.p.m.I,foolishly, thought I could use a threaded rod in the speed reducer to move the array at the speed the sun passes.I proposed to use a drum switch to reverse direction at each end of travel/day.I thought if it ran for 5 or 6 hrs. a day it would prove beneficial,say 10 a.m til 2-3 p.m.however the drum switches have a "center off" position which shuts everything down.As well the motor should come to a complete stop before changing direction [at each end]I am mechanically o.k but electronically challenged. any help would be appreciated.An afterthought,the array would remain in the 2-3p.m position until approx. 5 p.m.and then return to the 10 a.m position. Obviously a timer will also be involved
     
    Last edited: Jan 22, 2011
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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  3. wayneh

    Expert

    Sep 9, 2010
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    You DO realize that your motor is consuming over 100 watts? Your panel(s) will need to be awfully large for the incremental benefit of tracking to overcome the energy used by the motor.

    I think you could use a smaller motor (telescope clock drive?) if your panels are balanced and on bearings to allow easy rotation.
     
  4. Artfldgr

    Active Member

    Aug 15, 2008
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    An old astronomy magazine had instructions for making a simple motor and screw drive using a board, threaded rod, nuts, etc... it was back in the days when CCD photography was starting to be more common. (80s?)

    i took a quick look but couldnt find it. but it still seems that telescopes and homemade stuff is still quite alive and well, so it may be worth it to dig around.

    unless your CCD is fast, your telescope has to track the stars and i remember this design as being simple and quite clever.

    if you use two motors its pretty easy to make your own solar sensor to detect the sun and make them track it. problem is that such a thing would also need some way to not get odd with cloud interference. timing a condition? waiting till out of align a certain amount? hard part i guess would be to make a circuit that would detect the balance between photo resistors arranged as your sensor, and then turn on the motor a small amount in response.

    how much energy it takes to move the solar cells depends mostly on what kind of mount and how or if its balanced.

    the more put into the design of the mount, the less energy the system would need to move and track the sun until quite a small motor would suffice. (and enough auto junk yards for parts that can support a lot of weight if things are big)

    note that what makes it easy for a tiny motor to move also makes it easy for nature to move as well (like wind). (so if its balanced save yourself some trouble and add a brake. and so you open the brake, move the item, lock the break).

    if things are lighter than say 200lbs, then you could even splurge and get a high abec number set of roller bearings used in skating... sounds silly, but given the size of the market the bearings you get are of very high quality for as low as 10 dollars or even better in a set of 8. they can easily support the weight of large humans, and so you can use them for moderately large things, using a threaded rod, washers, and nuts to make a low friction cheap axel. (you would be surprised at the things those cheap things can be used for).

    see how they drive ferris wheels. they are moved from the outer rim so that a small motor with light power can move them at their moderate speed. yours has a VERY moderate speed, so if you balance it and drive it from the outer circle of movement you basically can get away with a surprisingly small motor (especially if you use good bearings).

    hope that all helps and isnt confusing...
     
  5. chergar

    Thread Starter New Member

    Jan 22, 2011
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    We live in Ontario, Canada and are part of a 10kw MicroFIT program. Our system consists of 48 panels (4 arrays of 12 panels each, centre-mounted on a post). Each array weighs about 800 lbs. and is approximately 200 sq.ft. I could operate the motor in stages through the day rather than continuously but my main problem is stopping at each end of travel and restarting in the opposite direction. The system is fixed at the moment but I feel we can install a bearing on the top of the post and build the tracking.
     
  6. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    The sun moves across the sky at 15 degrees per hour.

    The return speed for the next sweep shouldn't be an issue, as the arrray has all night to make that movement.

    The biggest obstacle would be balancing the panels so they turn easily, similar to loading a garage door with springs so it takes very little force to move it.

    I'm envisioning the solar panels moving like louver blinds, each panel pivoting on it's own to be perpendicular to the sun. A stepper motor running a "screw drive" shaft should be able to do this, as the rate is very slow.

    What was your attempt that failed with the threaded shaft?
     
  7. chergar

    Thread Starter New Member

    Jan 22, 2011
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    Somehow I don't seem to be expressing my problem correctly. I am using a threaded rod and have calculated how to step down the ratio so that it covers 60-70 degrees in 4-5 hours. However, I can't make it stop and reverse to the starting position for the next morning. I can make it stop but I can't make it start in the opposite direction automatically and I certainly can't go out twice every day to make it change direction. I had hoped that drum switches could be used but don't know how to overcome the "centre off" problem.
     
  8. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Do you have a different motor to use?

    DC Motors are much easier to reverse. The reason for all the other comments is simply to improve efficiency. Aligning the panels perfectly with the sun doesn't do any good if the alignment system uses all the power provided.

    You could use a smaller solar cell to control the circuit, when the voltage falls to near nothing for over 30 minutes (dark, not a cloud passing by), reverse the motor to a limit switch on the other side.

    The problem you need solved seems to be controlling the AC Motor, which isn't a good solution due to power requirements.

    How much force is needed to move the panels? Could a mid range Maxon DC motor turn the threaded rod?
     
  9. wayneh

    Expert

    Sep 9, 2010
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    Could you just turn a large disk with a pivoting arm to lever the panels? I'm picturing a piston rod on a crankshaft that goes around once each day.
     
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