A Strong Simple Sun Tracker

Build a big array of mirrors for a solar collector and you still have one problem, it has to follow the sun as it travels across the sky. Solar trackers are expensive and complicated. Heres one that is simple, cheap and strong.

You can make it from parts found in the hardware store and garage sales.

First you need to know some navigator and sundial facts. As the Sun travels across the sky daily its astromonical position is called "right ascension"

This Sun Tracker will move the position of a solar array, heliostat or solar furnace as it makes its daily trip across the sky.


The other change your collector has to make is its altitude which changes as the season changes. This adjustment can be made on a weekly basis, and an automatic adjustment isn't usually necessary.

I will keep you up to date with the progress of my prototype equitorial mounted solar furnace with more pictures and add ons.

I felt the neccesity to publicize the Strong Simple Solar Tracker as an inspiration to anyone else that might be thinking about building a large solar furnace, but were intimidated by the tracking drive.

Now that you know you can make one cheaply and quickly, maybe you'll be tempted to take the plunge.

Step 1 Look Ma, no solder!

You can put all this stuff together without solder. Make sure to observe the correct polarity when hooking up the cord to the holes on the plug. The white wire goes on the big lug.

Comments

[zeeba]

great job :) what kind of sensor did you use ?

[shetonus]

And if a dark cloud passes?  Perhaps a second, unblocked sensor to enable the drive only during unshaded conditions.

[david williams]

You've got the letters CW at the bottom of the diagram, which suggests that the shaft rotates clockwise as seen from the bottom end. In fact, it should go the other way, clockwise as seen from the *top*. The "altitude" of the sun is its angle of "elevation". Its azimuth is essentially its compass bearing. At the equinoxes, the declination (latitude) of the sun changes by about three degrees per week. If you adjust the tracker only once a week, it will be significantly off at the end. Also, the seasonal movements of the sun are not just in the north-south dimension. There are east-west movements too. So the periodic readjustments of the machine will have to include movements in both directions. The east-west motions essentially involve moving the clock forward or back. Between early November and mid-February, it has to move back about half an hour. And "equatorial" is spelled with an "a" near the middle. Sorry to sound picky! David

[Cowboywindmillbuilder]

Thank you for your helpful comments, please feel free to correct whatever defiencies you might find. Am I correct in using a "Sundial " model of the position of the Sun? This is a work in progress, so if you see anything that might not make this work, speak up before I screw up.

[gaiatechnician]

I do not know if you are still working on it but if you are, please take a look at my latest 3 videos.  I will probably not get further than models this year but I think I have it all right.  So, jump in and complete the process!
 They are http://www.youtube.com/watch?v=uhKYvwl86pA
and http://www.youtube.com/watch?v=0-bj0guW0k0
(Just watch that one for the liquid piston tracker)
I think it just needs some simple electronics for it all to work, it is all time based (you do not need to find the sun or have any photocells ), and seasonal adjustment is manual and is marked on the side of the tracker.
Brian

[david williams]

I'm not sure what you mean by a "sundial model". Basically, your machine is okay. Apart from the little things I mentioned earlier (especially the direction of rotation!), it should work just fine. Like the gnomon of a sundial, the axis of rotation should point to the (north) celestial pole, which is very close to the Pole Star. The machine has to rotate, clockwise as seen from the north so as to compensate for the earth's anticlockwise rotation, once every 24 hours. I have a machine something like yours which just uses an old alarm-clock mechanism. An additional 2:1 gear slows the rotation down from once every 12 hours, for the hour-hand of the clock, to once every 24 hours. It works very well. As you already know, you will have to adjust your tracker in the north-south direction every few days to follow the sun's seasonal movements. You will also sometimes have to set the clock ahead or back a bit, even if it keeps perfect time. This is to compensate for a rather complex east-west movement of the sun. If you know about sundials, you will have encountered this by the name "equation of time". Relative to clocks, sundials are not good timekeepers, especially during the (northern) winter, when sundials lose about half an hour between early November and mid-February. I suspect this is why sundials are almost unknown in the southern hemisphere, where this inaccuracy happens in summertime. I was in Chile a few years ago and found that nobody knew what a sundial was! I built one, and amazed some people. I would urge you to try to think of all possible problems before you spend money on building the machine. For example, are there going to be electric wires going to the rotating part of the tracker? If so, you'll have to arrange some way to ensure that the wires don't get wound up tightly and broken after the machine has made a lot of rotations. You'll have to use "slip rings" which are tricky and expensive, or make the machine rotate in the opposite direction from time to time to unwind the wires. Have fun! David

[Tetrafish]

I seen this and thought about using 2 light sensors in a circuit. That way if a cloud gets in the way - it doesn't activate the motor to try and find the sun. But would light sensors like these actually work like toggle switches? Particularly with a 12 DC power source (as opposed to 110/220 AC Voltage)?

By toggle switch I mean like

= =>--0--<= =

the '<' are the switches (or the light sensors) and represent the 2 possible positions of each switch (ON or OFF), and the '===' would be to the positive and negative leads from the power source. '0' is the motor.

[gaiatechnician]

I put on another instructable (because i do not understand heliostats and to clarify some stuff) I think you should take a look before you go further.
http://www.instructables.com/id/Heliostat_experiment_and_finding_true_north_with_e/

[baudeagle]

I would suggest that you check out the following Instuctable. Between the two of you it sounds like you may come up with something good. I could imagine that you could use gaiatechnician's water tracking mechanism and your control (operating a solenoid valve) to come up with low voltage feasible project.

http://www.instructables.com/id/Clock-Based-solar-tracker-experiment/

Just a thought

[gaiatechnician]

The big advantage of a dripper tracker (over anything else) is that the wind will not break your control mechanism or gears (so you can use much lower quality and cheaper equipment). I actually had the clock based tracker on an equatorial mount for a while but it was too difficult to show with 2 buckets of water and 2 floats turning and restraining the reflector. As far as I am concerned 2 containers and 2 floats are necessary. So for the competition, I did it differently. Just one bucket and a counterweight. I find a digital clock a little too weak to power the raising and lowering of the little dripper pipe. If you can find something else to do that very slow motion, (it can be rotary or just up and down) even if you do it in quarter hour steps, you can make a good simple tracker. Certainly it will improve the performance of a solar panel a lot because it will be pointing at the sun a lot more of the time. You also need something to return the drip pipe to its morning position and pump the water back in the evening. You will probably have center of gravity issues as you move things up and down with the seasons. This puts more pressure on things than I expected. You may need counterweights to prevent these problems, especially if you use a parabolic dish. Brian

[offlogic]

Another great, inspirational piece.
"Vilitas, simplicitas, efficitas" should be part of every engineer's creed.
(Hey, will someone out there please nit-pick my dog-latin for "Cheapness, Simplicity, Effectiveness"?? I'm designing a family crest...).

[gmoon]

Just a couple of comments:

-- Does it work on cloudy, or partly-cloudy days?

-- This is single-direction only, right? So the mount must be manually returned to the start position at the end (or the beginning) of the day.

-- Electrical tape isn't a great solution for outdoor circuits (in fact, it's use in general is fading.) You can find other threaded sockets with wire connectors (like lamp sockets), or maybe re-use a cheap worklight--which would have a sturdy cable already attached.

[Cowboywindmillbuilder]

This is an ongoing project, with details added in the pdf file at the end. Today, I just added more info to the pdf file. Read it. I am documenting the entire design process as it evolves from start to finish. The electrical tape is for insulation, the entire tracker will fit inside a watertight housing probably made out of PVC pipe. As for retracting, I can always find a way to reverse the actuator or move it manually. Not a big deal.

[PKM]

I agree with alex, the writing in the photos doesn't add much. Did you add the words to your photos not thinking about image notes (or indeed get the images from somewhere different)? It's pretty moot anyway because your image notes explain adequately. Are you planning to build one of these? If you haven't started yet, something to consider- old/broken sewing machines are a good source of fairly strong mains-powered electric motors and usually come with an adjustable speed control (ie foot pedal), and you could fix the pedal on at a slow speed so that the motor doesn't suddenly jump when the light switch turns it on and overshoot the sun's position. Also, have you considered clouds? IDK where in the world you live so clouds might not be an issue :P but if the switch is designed to be on in direct sunlight and off otherwise, cloud cover will confuse the machine. Mind you, if you have a lot of clouds then solar furnaces aren't really worth the effort.

[Cowboywindmillbuilder]

I live in the fifth sunniest place in the United States. Check the NOAA stats for zip 89429. We are lucky to get 7 inches of rain a year. If clouds are a concern, I would think about another night light in a enclosure only the sensor would be outside and trun on in the dark, shutting down the movement. Keep on reading the plans, this is an ongoing project, I just thought the Simple tracker would help out anyone else thinking about building one.

[alex-sharetskiy]

it's hard to read the words in the pictures

[LinuxH4x0r]

Why didn't I think of this!? Great idea