solar panel tracker

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mark.duyvesteyn

Member
Im am wanting to build a sun tracker for a large water solar panel. Im not too sure on the efficency gains from having it pointed it directly at the sun all the time, but i mainly want to do it cause i can, and it would be cool.

I was thing about mounting it at a fixed angle on a pivoting washing line base, and using a motor + worm drive to turn it with the sun.

now, how to track the sun. Timer based (like a clock), or light intensity based? Any other smart ways of doing it? a scanning servo and one LDR that looks for the brightest point?...


thanks
 
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Jeremy Leach

Senior Member
Well, a clever way would be to have tables of data loaded in EEPROM or the sun's path, and use stepper motors - so no searching for sun. The data you'd need must be out there somewhere, but this might be a bit ambitious ;)
 
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BeanieBots

Moderator
It's often been stated that for solar PV, it is cheaper to get extra panels than to have a tracker. If that IS true, then surely solar water heating would be even more so.
Not sure about frequent flexing of the water pipes either:eek:

Anyway, no doubt a fun project and when you publish your results here, we'll know for sure.
Personally, I'd go for two LDRs at the end of a tube. The dimensions of the tube such that both LDRs are only fully exposed to direct sun when they are pointing straight at it. Using four LDRs would give elevation as well. You can actually get quadrature sensors but they are very expensive. (~£30 last time I looked).
 
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Pekari

Senior Member
I have already done this.

It is following with time and timing will set automatically by sunshine or manually by switch (rewind/forward). It is moving with 24V AC motor, horizontally only.
To follow a sun I have 3 fototransistor, moving with panel (photovoltaic cells 2x80W/12V).

I use PICAXE 18X.

Supply: 230VAC/12VDC.
 
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manuka

Senior Member
Mark- I see you are a fellow Kiwi. Just how large is this setup? Roof mounted? Needs? Location? I've lived with diverse rigid SWH (solar water heating) setups over the decades (commercial & DIY, flat plate & tubular)) & shudder to consider the punishment your tracking setup will endure! Tracking PV systems need continual maintenance, but they have only flexing wires! As already mentioned, SWH pipe flexing alone may be a nightmare...

For my money glass evacuated tubes are now THE way to go, & of course they automatically always present a surface to the sun. Chinese kit offerings abound on TradeMe- sample below ~NZ$2300. (No- I don't have one!)
 

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papaof2

Senior Member
If you want to steer something, maybe some reflectors would be better. Not as effficient as direct sunlight, but MUCH lighter and easier to steer - plus no worries about leaks.

For input controls, use two solar cells, each about about halfway between the center and the end of the water heater, and adjust the reflector(s) for maximum output on both cells. Some of the adjustment could be preprogrammed based on season.

The reflector mechanism could be designed to lay the reflector flat in high wind conditions.

A frame of aluminum tubing could be covered with fiberglass window screen which would be the backing for a layer of aluminized Mylar. This would make a very light unit.

John
 
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moxhamj

New Member
Wind loading is a significant factor with solar tracking. You might build it on a nice calm day, but it has to withstand a gale. Roughly budget one ton of force per square metre of panel. That means big bearings and a solid frame so it doesn't vibrate. All quite possible to do, but bigger than you intuitively think. The driving mechanism needs to be strong too - with thrust bearings.

Many people have pondered over this problem for decades, and the cunning and clever answer has been the evacuated tubes that manuka has posted. No moving parts, but still able to capture light from dawn to dusk.
 
premelec

premelec

Senior Member
You might also look up 'Meinel Cusp' which is a reflector which keeps a central cyclinder always illuminated; though the effective aperture varies with sun angle.... What might be worth building is a concentrating tracking collector [for special PV cells x 20 illumination] with water cooling on their back sides... or heat pipes... getting a little off topic... :)

Perhaps the evacuated tubes will come down in price - they are very pretty - and functional.
 
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boriz

Senior Member
Timer is better. Anything relying on photosensors will get lost when it gets cloudy, but a timer will place the panel in the ideal position for a break in the clouds.
 
premelec

premelec

Senior Member
I think you can get away with rough timing with monotonic change in same direction till dark and then reset - just go for max in the same direction and then stop when light insufficient ... whatever...

http://www.heliotrack.com has a wonderful gallery of peoples efforts!
 
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