 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Solar : Solar Tracking
Page 1 of 2   |
|||||
| Author | Message | ||||
| windman1000 Regular Member  Joined: 21/06/2009 Location: United StatesPosts: 91 |
Hi guys, Well my homeowners made me take down my windmill so I decided to go solar but my roof angle is way wrong for my sun direction. After reading about using car axles for gear box and stand I decided to build One. and not use DC controller, I put together a AC timing tracker that uses a sunlight eye to start it and turn it off at night, Thinking on adding a sprinkler timmer for the cloady days. This is grid tie only no batteries. This unit works well it starts up when sun is derect on my eye that is in a 6 Inch long tube, I have a nother 6 Inch tube that I can see the sun light threw it on one of the axles so I know Im pointed right at the sun. 
I only have 7 panels at this time but going to get an 8th one soon. WINDMAN1000 |
||||
| Jarbar Senior Member  Joined: 03/02/2008 Location: AustraliaPosts: 224 |
WINDMAN1000, what a fantastic construction using old car parts.Never have they been put to better use.Looking forward to your results. Anthony.  "Creativity is detirmined by the way you hold your tounge".My Father "Your generation will have to correct the problems made by mine".My Grandfather. |
||||
| brucedownunder2 Guru  Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Nice work Windman ... I like your timers and the idea behind it. I'm sort of nearly ready for something like this ,maybe we could work on that.. 
I have underground conduit containing a 12 pair multistrand cable for actuators ,Etc The steel is 70mm equal angle ,hot dipped gal, very heavy construction with solid backstays and deep foundations. Best of luck with your project. Bruce Bushboy |
||||
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Bruce I've never tried it on a large scale and I've broached the topic here before, but what do you think about using a flat-plate heliostat (mirror) and tracking the sun by bisecting the angle from it and your fixed target? Doing this would mean the only thing you'd have to move would be the flat-plate mirror and not all the electronics. It might be easier to guard against wind damage. I've tried testing the voltage output from a solar cell and it seems to be the same with a reflection as with a direct hit. I'm in the northern hemisphere, so this makes sense to me. Perhaps it's not the same where you are. If the sun's pathway is directly overhead all year long, this won't work. Just an idea. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
||||
| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Thanks Mac,, Sort of imagine what you are thinking --like the principal of those parabolic mirrow dishes with the focal point collector heating water to steam ?? I'll keep an eye on this idea.. Thanks Bruce Bushboy |
||||
| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Bruce I looked up the mean latitude of Australia and it says it's 27 degrees south. If I were building a tracker, I'd put the solar array stationary on the ground and aim it due south, then I'd use the flat mirror on a gimbal joint to bisect the angle of the sun in the northern sky (mirror facing north) and the target on the ground and track the circular movement as the Earth spins beneath. That way, all the electronics and stuff that can crack and be ruined were it bumped or shaken by wind changes, would be stationary. Only the tracking mirror would move and as it did, it would project a reflection of the sun on the surface of the PV array. I think I'd use a flat plate mirror and not try to concentrate it; keep it really simple. Since the sun's progression from the eastern sky to the western sky is circular, the only tricky part is figuring out the angle that bixects the asmith as the sun's pathway prescribes a large arc. I'm sure Glen could whip up a program that would drive the steppers. He gives me the impression he's a computer whiz. It's funny thinking about this as I'm so used to the sun's path being in my southern sky. Guess that's why you folks say you're "down under" eh? . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
||||
| windman1000 Regular Member Joined: 21/06/2009 Location: United StatesPosts: 91 |
Thanks Anthony And Bruce Bruce I dont know if this will help you but heres the electrical, Im only running one motor that turns my panels from left to right 90 degrees and up /down in steps every 20 mins then at noon it switches timers and runs in steps every 15 mins for about and hour then switches back to the 20 min steps. I raise and lower the panels with the top axle tied to bottom axle with tie rod so as the top axle turns left to right it also pivots it up to noon then back down to night. 
Windman |
||||
| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Haha, here in oZ we are all standing upside down looking at the Sun south pole upwards. Makes me dizzy just thinking about it. I have often wondered about the required motional geometry of a tracking mirror, does anyone know more about his, an internet link maybe ? If the panels themselves track the sun on an equatorial mount, it is all fairly easy, and the aiming can be quite a long way off before the output falls significantly. Just set up the rotational axis at the latitude angle (38 degrees Melbourne) modified by the season (+12 winter -12 summer 0 spring and autumn), to correct for the earths axis tilt, and make one full revolution every 24 hours, or reverse the direction every 12 hours. But with a mirror, if aiming is a few degrees off, all the sunshine may totally miss the target altogether, especially if the mirror and target are a fair distance apart. And wind shake may have a similar effect. But I would be very interested to learn more about mirror tracking. Cheers, Tony. |
||||
| neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210 |
If you mean a mirror that moves with the collectors ... ... http://www.pveducation.org/pvcdrom/properties-of-sunlight/su n-position-calculator will soon show you that while the sun's (actually, the earth's) path is circular, the aximuth and tilt angles are not regular from any point on the earth's surface. Use this calculator and compare changes in angles at 'sun up', mid-day (better still, 'sun noon' and sunset. If the mirror moves independently of the collectdors, the problems are greatly increased. What Mac says about the speed of the movemenet is true. Tilt angle changes are big at a.m. and p.m . and azimuth changes are fast at mid-day. Happy hunting! |
||||
| neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210 |
I also use a white panel fixed some convenient distance below the 'eyes' and can tell how far off alignment the sun is by the pattern on this panel. |
||||
| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Crew I don't think I'll actually be building one of these soon, but I will eventually. Instead of doing all the brainiac computer work, what I'll do is figure out maybe 12 to 24 set positions throughout the day that the mirror will travel to and lock onto. This will mean the actual pure focus point will be on target only a few minutes at each stop, but it should be good enough as what I have in mind produces something on the order of a death ray anyway, so there'll be plenty enough heat to go around. I intend using this to heat oil in a stationary, fixed-focus reflector. I intend mounting a 45* "fustrum" (mid-section of a cone) at a fixed position with a fixed focus along a pipe mounted perpendicular to its center. As the sun's rays are reflected into the mirror, those rays that are essentially parallel to the central axis will end up being concentrated on the pipe at something around 1,000 to 1 magnification. Yes, it will get screaming hot! Like I said, there'll be plenty of heat, so making sure the focus is spot on is not all that necessary. I'm thinking of 6 to 10 minute intervals per half day where the mirror will be set to bisect the angle between the sun and the focal point. This is a project for summer, so don't look for me to be doing it any time soon. As for using the tracking device on a PV array, I think it safe to say the focus would not have to be all that accurate there either, as long as the distance between the movable mirror and the focus point is not too close. Farther away will give better aiming results and small deviations won't make all that much difference. Again, with a PV array, I'd set it up to hard focus about 12 to 24 times per day and let it go at that. One thing in our favor using reflected light means (theoretically) some of the initial heat radiation will be consumed by the mirror. Since PV works on both frequency and intensity, I'm hoping using a mirror to reflect it to its final destination will mean cooler-running panels as a byproduct. I haven't actually tried this for myself yet, but in my way of thinking, it should be a keeper. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
||||
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Mac, what you seem to miss with your heliostat idea is that the mirror must be of equal size than the solar panels. We are trying to get as much sunlight as possible onto the PV modules without concentrating the heat as that would decrease the panel output. And we are talking about big mirrors here, just two of my solar panels side by side are 1.6m x 1.6m which equates to a little over 2.5 square meters. There can be a considerable wind loading over such an area but solar panel frames and their glass is pretty strong in my experience. Now, if you have a mirror as well that's another 2.5 sq m trying to resist the wind and I don't know how strong a good quality mirror glass of that size is. Me thinks that idea is over complicating solar tracking, perhaps you were not aware of the sizes involved since you seem to build things on the tiny scale 
Mirrors are useful if they are parabolic and concentrate the sun's energy onto one spot to heat water or some other medium. You can then use lots of smaller mirrors working in unison. Klaus |
||||
yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Have a look at "heliostat" on Google or "heliostat diy" or something similar. The sun wobbles about the sky quite a bit over a yearly cycle, so optical tracking is the easiest option without resorting to precise software algorithms. Although Sooty the cat may start to resemble his name if the mirror has a wander on a cloudy day. It is possible to accurately hit a very small target from quite a distance. HOT Googling tip! If you are looking for something and having no luck with different combinations of search words, try GOOGLE IMAGE (that's the next option down from EVERYTHING) works a treat, provided you are not easily distracted by pictures of shiny things!  I'm confused, no wait... maybe I'm not... |
||||
| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
While making something to directly follow the sun is not all that difficult. Getting a mirror to reflect the sun to one particular spot is a lot more complex. And getting a tracking mirror to locate both sun and target way beyond anything I can visualise. I know that this can be done, but how exactly ? What is the basic principle? Cheers, Tony. |
||||
| neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210 |
And getting a tracking mirror to locate both sun and target way beyond anything I can visualise. I know that this can be done, but how exactly ? What is the basic principle? It could be possible IF the mirror anchorage (mounting) point can be moveable (also wobble') in relation to both the collector AND the sun. Very complex mathematics and mechanical set up, I would think. |
||||
| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
optical heliostat tracking The most common method that is used today is called "target aligned tracking". Basically the axis that the mirror rotates around is pointed at the target so the mirror is always at the same ascension angle as the sun (rotating around the target). For the other axis (elevation) the angle between the sun and the target needs to be halved so a cam or gear is used, similar to a reduction drive, on the optical sensor mount, to keep the mirror at half the sensors angle. Aiming and calibration is fairly simple by adjusting the tilt and angle of the sensor. The big guys are pretty secretive about this stuff and pretend it is rocket science, I have some very detailed photo's but I may get leaned on if I post them. the best I can do without boring everybody is direct you to Heliotrack.com. This kit shows a sensor drive bisector quite well. Most other mechanical tracking techniques, like polar mounts, need seasonal declination compensation, it adds to the complexity. I'm confused, no wait... maybe I'm not... |
||||
| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I reached a similar conclusion myself, and am working on a very small scale "toy" working model of a two mirror mechanical sun heliostat. The basic idea I have come up with, is to construct a mirror rotation axis that runs parallel to the earths rotation, that rotates exactly once every 24 hours. That in itself would track the suns movement across the sky. No need to reverse the drive, it always points at the suns position, even when the earth gets in the way at night. It should follow the sun during the day, and continue to rotate at night, and be in exact position at dawn to anticipate the rising sun. A mirror is then attached to this rotating axis inclined at a fixed 45 degree angle, so sunlight is always reflected back along the exact axis of rotation. A a cheap 24 hour mains timer, the type with the rotating dial on top into which you place pins, to switch things on and off will be used as my mirror rotator. A wooden wedge cut at 45 degrees will be hot glued to the top, and the mirror hot glued to the wooden wedge. I should be able to direct the suns rays to a fixed point on the ground (due north of the mirror) by simply elevating the mirror axis of rotation to be the same as the earth's axis of rotation (as it is in this particular month) and pointing due north. Once I have my rotating mirror elevation axis and due north compass bearing sorted out, a second fixed mirror may then be able to direct the sunlight to wherever it needs to go. Cheers, Tony. |
||||
| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
That's great Tony, best way to get the brain around it is to build a working model. I'm to lazy to calculate anything by hand anymore, the axis angle here would be fixed at 57.094 degrees and today's declination is -20 degrees (added to the mirror angle). 
If you get a chance to see a solar thermal morning calibration it is spectacular. This CSIRO video doesn't do it justice. 
I'm confused, no wait... maybe I'm not... |
||||
| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Frustratingly it's been overcast/cloudy here in Melbourne nearly all day, so not much chance of really seeing anything happen. But it is set up, and sitting outside ready waiting for some sunshine. There will be two initial aiming adjustments to make. Rotating the compass heading of the whole mechanism for due north, which should have the effect of introducing a horizontal sideways error of where the beam lands throughout the day if there is any departure from true north. And setting the elevation of the rotational axis. As we have just passed Summer Solstice (Dec 21) the sun will be about 20 degrees higher in the sky than the latitude of Melbourne which is around 38 degrees. So my axis of inclination should be about 18 degrees above horizontal. If there is an error the beam landing point will move higher or lower throughout the day. I have set the 24 hour timer to read one hour slow, because of daylight saving time. My mirror should be horizontal facing up at 1pm (solar noon), and horizontal facing down at 1Am. and vertical facing the two horizons at 7Am and 7Pm. A few days of observation and some minor tweaking should, I hope, get me fairly close to having a stationary beam landing point on my target. The whole thing is a bit rough and hastily thrown together, but at this stage I just want to prove to myself that the theory is sound, and it is indeed a workable system. I am not looking for ultra precision in aiming, just something encouraging enough to maybe take it to the next stage. Cheers, Tony. |
||||
| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Or you could buy one 
Something like this 1860's stoney from Spencer and son would set you back $7000 or more. but you would have to move your home as the axis angle is fixed for one latitude, sorry. 
I'm confused, no wait... maybe I'm not... |
||||
| Page 1 of 2 |
|||||
 Print this page |
