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Forum Index : Solar : Solar Tracking
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| Joblow Regular Member  Joined: 05/01/2010 Location: AustraliaPosts: 54 |
Hi Guys, I've been told that I can get 60 - 65 percent more out of PV cell if they are on a tracking system, I recently saw one which was powered by solar (two cylinders which when heated up move the tracker to follow the sun) does anyone know of a design for something similar, I've trolled the forum pages but haven't found any. Thanks in advance  The man who never made a mistake never made anything |
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wind-pirate Senior Member  Joined: 01/02/2007 Location: CanadaPosts: 101 |
Hi Joblow I think 60-65 is quite hight. I think 30 is closer.. Trackers are quite expensive and complex. You might be better off to put up extra pannels, and not use a tracker. My neighbour used a pail of water with a hole in the bottom. fill's the pail and pull's the panels into the morning sum. as the water driped out they retured to the sunset by a spring. "He only uses this in the summer" water run's into his garden. so its not wasted. or it could drip into a good pail. Ron THE Pirate. stealing wind & solar energy is fun |
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| Joblow Regular Member Joined: 05/01/2010 Location: AustraliaPosts: 54 |
Great idea Wind Pirate, but was hoping for something a little more sophisticated 
We also get a little more sunlight than you would, just had our longest, hottest spell on record, yesterday was the first day the max temp fell below 30c here for a couple of months(Perth WA) The man who never made a mistake never made anything |
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mid north Matt Regular Member Joined: 06/01/2011 Location: AustraliaPosts: 58 |
solar panels derate in power after the panel gets to 25c Pt Wakefield Matt |
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| Joblow Regular Member Joined: 05/01/2010 Location: AustraliaPosts: 54 |
Thanks Mid North, you got me thinking so I googled 'how hot etc' and come across this: http://slashmyelectricbilltoday.com/blog/hot-water-solar-pan els/do-the-back-of-solar-panels-get-hot-if-so-how-hot-do-the y-get They say that efficiency drops with increased heat but it appears that it may not be a significant problem until 100c is reached. Also, wouldn't the cell get to maximum heat anyway in the middle of the day? There must be a crossover point somewhere between sunlight and heat when the panel is most efficient don't you think?  The man who never made a mistake never made anything |
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| mid north Matt Regular Member Joined: 06/01/2011 Location: AustraliaPosts: 58 |
hi Joblow i did a short circuit test on a old 36w bp panel on a 32c day and lost 2/5ths of total short circuit current,put the hose on the panel to cool it and got back full rated power,take the hose off the panel and watch the meter go down again quickly,do the test you will be surprized what you lose Pt Wakefield Matt |
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Tinker Guru  Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
I'm also in Perth and do have 2 x 210W panels on a 2 axis tracker (details of which are on this forum about a year and a half ago). Anyway, I get lots of solar power all day long, did not notice power drop off due to heat, perhaps by being on a tracker the panels get far more cooling airflow than if mounted against a roof. My tracker tracks on hourly intervals and consumes power only for a few seconds while the two motors run. This adds up to next to nothing power draw for the drivers, the electronic timer consumes a little more but nothing to upset the extra gain obtained from the panels pointing at the sun all day long. IMO tracking the sun constantly is not worth the complexity for a small system, doing it at hourly intervals is a good compromise. I think the guy who uses a bucket with a hole to run his tracker must be getting tired refilling the bucket every day - I would  .Klaus |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
60+ is far higher than is achievable. 30-35% is realistic though. Here's a picture (from the rear, so you can see what's happening) of one of my trackers. It's designed to be fairly straightforward to make and use, and reasonably robust. (Click for larger image) 
Mine move approximately every 20 minutes. I say "approximately", because I divide up the sun-hours into bits that I can move the panels in 2, 3 or 4 second moves. At the moment for example, I think they are moving for 4 seconds every 30 minutes. If you want to make one yourself, let me know and I'll post some construction details. |
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| neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210 |
Using a set timer is a 'reasonable(?)' approximation. (Well it is better than a fixed array, at least.) At latitude 30 deg. I find that the sun moves a 3 degree azimuth angle in two minutes at around midday, and a 3 degree move in 1/2 an hour in early morning and late afternoon which is quite a large variation. There is a reciprocal large variation in the tilt angles also. (I will be using 3 degree moves for my tracker very shortly.) To see what I mean, download a calculator from http://pvcdrom.pveducation.org/SUNLIGHT/Animations/Sun_Calcu lator.swf, (the 'old' version'). It permits the entry of your GPS co-ordinates and time zone so that you get exact data to work with. |
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| neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210 |
Down under, the commonly quoted figure seems to be 30 - 45 percent. I presume that the range is there to cater for differing degrees of tracking accuracy. |
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| neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210 |
True, but for a D-I-Y type, I have found that I can build a tracker for the cost of the extra panels (even at wholesale prices) only slightly exceeds the cost of the extra panels. I am hoping(!) to get 'near 5KW' (27 panels) production from only 20 panels. Plenty of room to move, IMO. But then, I haven't built a conventional tracker, either. |
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| Homegrow47 Newbie  Joined: 17/08/2010 Location: AustraliaPosts: 31 |
I think the improvement would always be well under 30%. For example 1kW, in Sydney 28°(optimum angle) is 1308kWh per year 2-axis tracking is 1630kWh per year Which is a 25% improvement. Using PVWatts http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/ Edit: correction for Adelaide 28% for Perth 31% So some places, give more improvement than others, due to weather and latitude. |
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RMS707 Newbie Joined: 17/11/2010 Location: AustraliaPosts: 3 |
Very interested, please post away. What size panels are on that tracker? Ian |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
I'd dispute your figures there. The *INCREMENTAL* price to go from a fixed, elevated frame, to a tracking frame (or even a seasonally-adjusted, tracking frame) is far less than the cost of an extra 30% panels. It becomes even more beneficial when you consider that (take mine for example) - 6 panels now, add 1/3 makes it another 2 panels - that makes the wind loading and dead weight higher, so the construction must be heavier (and therefore even more expensive). I used the same amount of aluminium channel to hold the thing up for fixed or tracking frame. The same vertical post. The same footings and concrete. About the only thing different was an axle, two blocks for it to turn in, a turnbuckle and an actuator. Incremental cost: I'd be surprised if it was $200. I can't buy panels for $100 each, and thats if I didn't have to up-size anything to take them. (And I have 4 tracking frames, so that'd be 8 more panels!) I made some "support/turning" blocks out of 1214 grade steel (easily machined). I made them two-up, then just cut the block in half - one for either end of the frame.    
The shaft was some 3/4" or 20mm (can't recall which I used) that I cut a thread on either end. The top arm was some RHS whose internal dimension was slightly larger than the OD of the vertical post I used. With an angle-grinder, I cut one side out to make a large U section.  
Some old gal pipe and threaded inserts made suitable mounts for the turnbuckle to attach to for seasonal adjustment, and a centre pivot pin with a couple of circlip grooves to keep it all in place.     |
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| Homegrow47 Newbie Joined: 17/08/2010 Location: AustraliaPosts: 31 |
Neil, Ross and Tinker you guys have done great jobs, well done. I find them really inspirational. I have a 1kW array in NSW and would lose the GFIT if I expand, so I have been thinking of a DIY tracker for a while. Ross I would really be interested in those construction details too (I have 6x180 monos similar to yours). For example aluminium channel dimensions and bolts sizes. |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
I'd have to go check exactly, it's been a year since I did it. Checking on some invoices though, the aluminium was 80x40x3, there was $110 worth for each array. Actuators cost me $55 each, delivered. Steel (galvanised RHS) came to $92 per array (and I still have some left over). I can't recall exactly what the posts were, I think they were 90x90x3 (ID), and the top cross arm was 100x100x5 (that should have given me 2mm "slop" either side. The axle I'm pretty sure was 20mm, because I got M20 nyloc and halfnuts to hold the frame. The bearing blocks came out of 40x40 bar stock, cut to the appropriate length. I used normal grease nipples (zerks?). Attachment for the axle-blocks was via 2 M10 x 25 bolts (I think). Turnbuckles were a largish M12 construction ($10.50 ea), but I'd probably pay the extra and get some stainless ones next time. The gal ones are pretty rough. I used M6x16 with nyloc nuts ($32/100 a set) to hold the panels to the frame, and M8x20 with nyloc nuts ($60/100 a set) to hold the frame all together, but use whatever you think is appropriate. I wouldn't go much smaller than I used - purely from a "confidence" point of view. I didn't say much about the control system - because I didn't end up having to build one. My house is all c-bus controlled, so I just wrote a few lines of code to do the tracking. (Starts tracking at sun-up, half an hour after sunset drive the panels to their mid-point for overnight parking, then half an hour before sunrise drive them fully east and the cycle repeats. Cbus has two relay outputs - "east" and "west". They drive a pair of high-current relays wired with interlocking coils so the array can't try to go both ways at the same time, and has manual operation via cantre-off toggle switch. I drive the actuators from 24V. I use the mid-point of my 48V system as "common" and drive east/west by using +48 or 0V. All remarkably simple. The actuators take 90 seconds for full travel, so thats it. 3 minutes of run time in a 24 hour period. All arrays are parallelled, so they move at the same rate. Current is from 1A to 3.5A, depending on where they are in their travel and how windy it is. Speaking of wind - not long after I put these up, we had some very nasty winds here. Gusty and screwing around from all directions. This was before I had the panels parking in their horizontal position overnight, so they were all up on one end, making more of a large sail. The panels, frames, mechanism and post all stood up to the forces fine - but clearly a 1 metre deep hole, 12" diameter, filled with concrete simply wasn't enough to hold them under these loads! The two most exposed were worst affected but all 4 needed work. I added diagonal struts and a slab under each to help keep them in place (still with a 1m deep x 300mm concrete core around each support post)   
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| Homegrow47 Newbie Joined: 17/08/2010 Location: AustraliaPosts: 31 |
Thanks Ross, that information is much appreciated. Just wondering do you manually adjust the azimuth tilt thoughout the year ? I assume it is polar axis. I guess it would make the design more complicated to keep the axis of rotation on the polar axis, and still adjust the tilt between summer and winter. So the panels are always perpendicular to the sun. Rather than just tilting the whole axis of the tracker. |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
I've re-read that several times, and must be tired. Something isn't clicking. One of the arrays is a 12-panel horizontal single axis tracker - but mounted so the axis is east-west. I use the "tracking" purely for seasonal adjustment. As for the rest: remember I used RHS for my posts? There was a reason for it. By carefully setting it out when I put them in the ground, I have the flat sides aligned (solar) N/S (or E/W if you prefer). The pin that goes through the post and top arm lock the "tilt" to that axis. Perhaps a close-up of the tilt mechanism (from the first one I made - which was probably more hard work than was justified):      |
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| Homegrow47 Newbie Joined: 17/08/2010 Location: AustraliaPosts: 31 |
Thanks for those pictures, it makes the mechanism a lot clearer. What I was trying to get at is I think a mechanism like that will only give perfect sun tracking at spring and autumn equinox. In summer and winter the panels will rotate on a different axis to the polar axis, which is what the sun rotates around. The difference in output would be negligible though. |
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| Joblow Regular Member Joined: 05/01/2010 Location: AustraliaPosts: 54 |
Magic, all I did was post a request for tracker info and have been richly rewarded with a smorgasboard of it, plus lots of different ideas to ponder. It's been suggested that NuPower (who I was thinking of getting the panels, inverter etc from), may not want to install on a custom made tracker, so waht's to stop me buying the panels on ebay, ali baba etc and doing it myself? Would I have to have an accredited installer and would I still be able to claim the RECs? The man who never made a mistake never made anything |
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