Sun tracking for solar panels

Submitted: Thursday, Feb 01, 2007 at 14:05
ThreadID: 41847 Views:5089 Replies:10 FollowUps:8
This Thread has been Archived
I have two solar panels that I would like to rig up so that they can track the sun as the day progresses. I've seen a few commercial ones that are as dear as poison. Has anybody got a plan or drawing of a simple one that I could build myself? I've got reasonable skills in fabricating.
Back Expand Un-Read 0 Moderator

Reply By: Ian from Thermoguard Instruments - Thursday, Feb 01, 2007 at 14:28

Thursday, Feb 01, 2007 at 14:28
I doubt it will be cost-effective for a couple of portable panels. The ones I've heard of are complex feedback controllers with some sort of detector to tell when it's pointed directly at the sun.

If you are right into electronics I'd suggest a PIC-based open-loop positioner. This could be programmed with a 'map' of suitable position changes each, say, 15 minutes and use a small stepper motor to move the panel frame via a suitable gear reduction. This would give about 25 positions over six hours of exposure.

If this is too complex, then just aim it North at your latitude angle +/- 10 degrees for winter/summer and, optionally, change the East/West tilt manually a couple of times a day.

AnswerID: 219003

Follow Up By: Im.away - Thursday, Feb 01, 2007 at 14:45

Thursday, Feb 01, 2007 at 14:45
Hi Ian,

you sound like just the guy to talk to. I have a background in electronics, but more on the communications side. I'm not familiar with what's available in stepper motors, who supplies them, how to select them etc. Any advice in this regard would be very helpful.

My panels are reasonably large, and heavy, being 123 Watt, glass covered, Sharp models approx 1500mm x 600mm, so I guess the panels plus the weight of any frame plus torque effects plus wind loading would all need to be considered.

We can only carry the two panels when travelling and I have installed 300 A/H of battery capacity (although our load shouldn't ever get anywhere near this), but I'd like to be able to squeeze as much charge per day in as I can. Hence the need for the tracker. Our solar regulator is excellent so there is no fear of over-charging, mainly we would be worried about undercharging.

We won't always be around to manually adjust to the sun.

I'm sure I could come up with a controller, even if it's as simple as a couple of timers and some logic, but the mechanical aspects are where I fall short.
FollowupID: 479460

Follow Up By: Ian from Thermoguard Instruments - Thursday, Feb 01, 2007 at 17:41

Thursday, Feb 01, 2007 at 17:41
I still think the tracking system will be too heavy, bulky and expensive in comparison to the benefits. Your 2 x 123W panels should put out well in excessive of 10A for 5 or 6 hours on a sunny day, without any 'tracking' (manual or automated).

However, if you want to pursue the tracking frame idea, have a look at Oatley Electronics. They have some stepper motors, several geared 12VDC motors and several stepper motor and servo driver kits. Also worth a look might be MicroZed. They are agents for the incredibly clever and easy to use PICAXE microcontrollers and also have some stepper motor and servo driver designs.

As for the mechanical design, for torque requirements, wind loads etc. that's out of my experience. But should you find a good source of information on this, please let me know, as I've got an old tracking solar hot water system I'd like to resurrect with electromechanical drive instead of the original troublesome thermo-hydraulic system.
FollowupID: 479505

Reply By: Member - Davoe (Nullagine) - Thursday, Feb 01, 2007 at 15:06

Thursday, Feb 01, 2007 at 15:06
I wouldnt have a clue but I would be thinking along the lines of the system and motors/gearing whatever they use to keep telescopes fixed on a planet. high end ametur units have them
AnswerID: 219012

Reply By: traveller2 - Thursday, Feb 01, 2007 at 15:29

Thursday, Feb 01, 2007 at 15:29
In a previous life I worked for Telstra and from memory they decided it was cheaper and easier to fit an additional panel to make up the shortfall than all the tracking stuff.
AnswerID: 219014

Follow Up By: Member - JohnR (Vic)&Moses - Thursday, Feb 01, 2007 at 20:17

Thursday, Feb 01, 2007 at 20:17
I haven't done that traveller but apparently the trackers can cost twice the price of the panels and one site I looked at suggested you should have them almost flat and use the light filted through clouds on less than optimal sunny days. Your approach sounds reasonable, just to accept less than optimal every hour and carry more capacity to cope.
FollowupID: 479529

Follow Up By: traveller2 - Friday, Feb 02, 2007 at 08:05

Friday, Feb 02, 2007 at 08:05
I move my panel a few times a day on the rare occasions I'm in a fixed camp.
FollowupID: 479655

Reply By: Kevin1243 - Thursday, Feb 01, 2007 at 17:13

Thursday, Feb 01, 2007 at 17:13
An equatorial telescope mount with a motor drive would work OK, as long as the panel weight is not too much. I have bought from Andrews Communications in the past and have always been happy. A heavy duty EQ5 mount with a motor drive will set you back about $600. The only drawback might be the weight of the mount and counterweights.

AnswerID: 219033

Follow Up By: Im.away - Thursday, Feb 01, 2007 at 17:35

Thursday, Feb 01, 2007 at 17:35
I think you're onto it Kevin. I've sent them an email requesting further details.

many thanks

FollowupID: 479504

Reply By: Member - Alastair D (NSW) - Thursday, Feb 01, 2007 at 18:44

Thursday, Feb 01, 2007 at 18:44
I think it easy to get carried away here.

If you are using solar panels that are not highly sensitive to direction then all you need is a simple motor drive that will rotate the panels by about the right amount per hour. You set the panels at the best starting point and then turn on the system. There is no need to have a highly accurate tracking systems.

A simple stepper motor of the type available from Oatley will be inexpensive, low power consumption and they have a simple driver for it. A 555 timer can be simply used to give the right pulse rate. I think to use programable devices etc is overkill.

Just my thoughts as I have often overdone things myself and then afterwards realised how much time and $ I have consumed unnecessarily.

AnswerID: 219047

Reply By: Pomgonewalkabout - Thursday, Feb 01, 2007 at 20:12

Thursday, Feb 01, 2007 at 20:12
You may get some ideas from these links as this was something that I was thinking about a while ago.

A simple timer circuit operating a relay driving a motor would do the job.

The relay would be on for a few seconds at a time maybe 15 times a day.

More complex circuits could involve heat or brightness seeking circuits but as somone has already suggested, we know where the sun rises and sets so a simple timer would suffice.

By using a relay you wouldn't even need a stepper motor but a normal DC one, the relay supplying voltage to the motor, whilst the panel moves.

Of course if all this gets too expensive then I would buy an extra solar panel.
AnswerID: 219064

Reply By: Ianw - Thursday, Feb 01, 2007 at 20:25

Thursday, Feb 01, 2007 at 20:25
Actually its quite simple to build a sun tracker. Full details were published in one of the electronics mags a few years ago (about 1990 I guess) . It will increase your output by at least 25% per day, as soon as the sun pokes up it will be charging until the sun passes below the horizon in the evening. At the time I bought a panel and did a lot of experimenting and concluded that it was worthwhile doing. The circuit used two LDRs with a shade between them and when the shade covered one LDR a motor moved the panels until both LDRs were in full sun again. Very simple. At dark, the panels were moved back to the start ready for the next morning. Motor used was a rotisserie drive from a BBQ. 3V geared motor operated from 12v for short periods required was no problem and had plenty of torque.
AnswerID: 219070

Follow Up By: Ianw - Thursday, Feb 01, 2007 at 21:00

Thursday, Feb 01, 2007 at 21:00
Just dug around in my archives and found the magazine referred to.. It is Jan 1995 Silicon Chip mag. It actually states that output will be increased by 30% or more.
FollowupID: 479542

Follow Up By: Ianw - Thursday, Feb 01, 2007 at 21:24

Thursday, Feb 01, 2007 at 21:24
If you consider that 2x123watt panels in bright sunlight should put out about 16 amps for about 5 hours unmoved, gain would be 80Amp/hours. Add a tracker and you will get another 5 hours in summer perhaps reduced to say 10Amps therefore gaining an extra 50 A/hours of charge. Note that solar panels work much more efficiently in the cool of evening or morning than they do in the heat of day. A light square tubing frame is not very heavy and if designed/built well shouldn't take up much room.
FollowupID: 479552

Reply By: techo2oz - Thursday, Feb 01, 2007 at 20:32

Thursday, Feb 01, 2007 at 20:32
Hi there,
been there done that and works out that for the extra bulk of the framework etc for the little extra that is gained was not worth it. I now have that extra little space for important things that I take. Unless you are planning on staying in the one place for more than a couple of weeks at a time I would advise simply moving them by hand at least 2 times a day. ( I move mine 3)

Whole setup including the frame and tracker was a few hundred dollars by making it all myself. The frame needs to be sturdy but adjustable to allow for azimuth adjustment but needs to be securely pegged to the ground for those sudden gusts of wind. My setup had 2 X 68 Watt Sola panels mounted side by side but connected via a swing arm. (Wish I had taken photos before breaking it all up again) The swing arm had a pivot lever which attached to a worm drive (length of booker rod) This was attached to a low current low volt motor.

The tracker is a simple device with discreet components that uses shadows to track the sun. 2 LDR's look for the light, when one falls in shadow, it applies power to the motor to move the panels (Tracker mounted on one of the frames of the panels) so both LDR are in the light. A third LDR detects dusk and drives the whole assembly east ready for the next morning. Add a few limit switches and support components and it's it is quite simple yet elegant.

I gave the board away but if I dig around I may still have the drawing here somewhere.

AnswerID: 219073

Reply By: Im.away - Friday, Feb 02, 2007 at 01:39

Friday, Feb 02, 2007 at 01:39
Thankyou all for the suggestions so far. I've certainly got a few options now. I'll be sure to post the end result. I've got 4.5 months to make it happen, so It'll end up being a last minute thing of course!
AnswerID: 219140

Reply By: Pomgonewalkabout - Friday, Feb 02, 2007 at 13:00

Friday, Feb 02, 2007 at 13:00
I'd be interested in a photocopy / scan of the Silicon chip project if possible?

I have yet to buy a Solar panel and was looking getting a Suntech freedom folding 80 watt type that come complete with a tilting stand regulator and bag or just a 85watt panel on it's own that are about $200 cheaper.

AnswerID: 219210

Follow Up By: Ianw - Friday, Feb 02, 2007 at 21:50

Friday, Feb 02, 2007 at 21:50
Can do. Need your email tho'.
FollowupID: 479882

Sponsored Links

Popular Products (1)