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Tracking the sun! For the solar accumulating Barbecue

video Tracking the sun! For the solar accumulating Barbecue

The sun moves across the sky at 15 degrees per hour. If we could automatically follow it with our solar cookers and solar panels, they would absorb a lot more energy.
Here is an idea of how to do it that might spark your imagination.

19 comments

Mar 9, 2010. 12:48 PMgaiatechnician (author) says:

Just a note that I have a diagram http://solardesign.ning.com/photo/liquid-piston-tracker that people might find useful
and a couple of new videos about equatorial mount (one is on instructables)
Brian

Feb 27, 2008. 6:36 PMbaudeagle says:

I like your idea about using the least resources possible for controlling your cooker/panels.

Like mentioned below the sun tracker robot looks like it would do a pretty good job of this.
http://www.instructables.com/id/Robotic-Solar-Powered-Sunflower/

Although I am not an electronics expert., I maybe someone could help us out here, but I do have some thoughts on this.

You could utilize one sunflower robot with a vertical orientation. A potentiometer could be mounted to this robot and tied in to a whetstone bridge. Another leg of the whetstone bridge could then be tied to a potentiometer/float in your water.

My thoughts are this: As the robot rotates, it changes the potentiometer resistance which inturn changes the control voltage across the whetstone bridge. The potentiometer float is either adjusted up or down with the addition or subtraction of water from the tub until the voltage is equalized between on the whetstone bridge.

A small PLC or some sort of control circuit be utilized to monitor the voltage change on the whetstone bridge. The control circuit could then operate either two solenoid or proportional valves. One of the valves would let water into the tub and one would release it from the tub.

One problem that may occur is that the waves in the tank/tub would create an inconsistent signal and so the water near the float would need to be protected/isolated from this wave action. The water that is coming into or exciting the tub could be mounted below the expected waterline and at the opposite end of the location of the float. This would help to eliminate the motion of the water. A cover over the water would help to eliminate the influence of the wind or bugs dropping into the water.

I suppose that this potentiometer idea could be tied to your clock or better yet the a PLC's internal clock could control the water level directly with the feed back from the float.

If your interested you can find some inexpensive PLC controls at: http://www.aboutplcs.com/directlogic/ You may be able to set up a PID control system and thermocouple temperature sensors on this if you want to go over the top with this.

May 2, 2008. 1:12 AMgaiatechnician (author) says:

I have new water clock "dripper tracker " and clock tracker designs at <a rel="nofollow" href="http://solarcooking.wikia.com/wiki/Tracking">http://solarcooking.wikia.com/wiki/Tracking</a> I am using 2 bucket trackers currently with the outflow from one tank filling the other tank. I have found them to be very stable in windy conditions. The ideal "tracker" is still the clock or a little arm or winch that lengthens or extends (at 2 or 3 cm per hour in the case of my bucket trackers). As it extends, a plastic pipe drops and water exits from the tank, and this turns the equatorial mount with your panel or solar reflector. The exit water can fill a bottom bucket just like in my dripper tracker videos. The difference is that this one will be much more accurate and repeatable. This will definitely work and can have automated reset and restart in the morning. Photocells and so forth are overdesign in my opinion. Lets keep it simple. A cheap mechanical sprinkler timer could be adapted for this. Brian

Feb 28, 2008. 11:42 AMgaiatechnician (author) says:

I am glad someone mentioned waves in the tank. The thing that would cause the most waves will be wind acting on the reflector or panels. It will tend to pull and push the float. This is something that we will have to live with. Sizing the float and the tank properly is important here. Also important is sizing the pipe that lets the water drain out. It probably needs to be capable of taking just a little more than the per hour rate of water drainage. I also thought something to stop waves between the float and the drain pipe might be necessary but I didnt put it in. (Just wanted to get the basic concept across). Remember also that the critical thing is to turn that axis at 15 degrees per hour. If you can get a good cheap simple way to do that , adjusting your panel slightly by hand every 2 or 3 days will keep it exactly pointed at the sun all day. (and you get minimal 30% more energy). Brian I will look at your links when I get back from holidays. Thank you.

Feb 12, 2008. 2:29 AM

rimar2000 says:

I am making a concentration solar kitchen (arrangement of mirrors) that will have this feature of being able to follow in the sun. It is little the time that I can dedicate him, for that reason goes very slow. When it has it finished I will put an instructable.

Feb 13, 2008. 9:59 PMFrenchCrawler says:

Here's something that might help: Solar Tracking Bug

Feb 14, 2008. 2:30 AM

rimar2000 says:

Very interesting, well done!

Feb 12, 2008. 3:36 AMgip_mad says:

Fantastic Idea! Oh, wait- it has already been done.

Feb 12, 2008. 8:26 PMgaiatechnician (author) says:

Guess what? They have just added a tracking page at
http://solarcooking.wikia.com/wiki/Tracking
And I had nothing to do with it.

Feb 12, 2008. 8:20 PMgaiatechnician (author) says:

Ok then. Perhaps you could give the links to the video or instructable and save us all the trouble? Cheap tracking is a key part of the tracking solar accumulating barbecue project. I have read that Scheffler cookers have often had problems with tracking due to the mechanical parts. This trys to sidestep the problem.

Feb 14, 2008. 8:47 AMgip_mad says:

Guess what? here it is.
http://www.instructables.com/id/Robotic-Solar-Powered-Sunflower/
with little effort, it can be adapted to use it in 2 axis.
It's really cheap, and a local boy scout group made a similar project of a solar tracking oven.
The trick is to put photodiodes near, with a black thing between (sorry for my brutal english...), so one will be less exposed to sun then the other, and the system balances itself so they're always facing the sun.
Questions? :)

Feb 15, 2008. 3:23 AMgaiatechnician (author) says:

I am fine with it, It can be used instead of the clock in my diagram. i suspect that it can be made cheaper than the clock. In my video, the clock controlls the hieght of the water in the tank and this in turn controlls where the reflector is pointed. Parabolic reflectors are big and take massive random force from the wind. the float in a tank of water is a way of uncoupling these forces from the little clock (or sunflower) motor. The idea is to build the device as cheaply and as robustly as possible. If the sunflower was to move the big dish, then your motor would have to be quite a lot stronger and more costly. The idea is to build a device as cheap and as robust as possible.

Feb 15, 2008. 9:00 AMgip_mad says:

It's way more cheap then the clock, and it's less empirical! It will work no matter the season you're in, because it doesn't rely on timing. The motor doesn't have to be very big, since the sun is very slow it's just a matter of using a very high gear ratio! Plus, using a worm gear, you can be sure that the panel won't move in any direction unless you're moving it by the motor.

Feb 14, 2008. 8:48 AMgip_mad says:

Sorry if I have not been very nice, but it seemed such an easy task to me! But, you know, things are easy when you already know them! ;)

Mar 15, 2008. 12:41 PMgaiatechnician (author) says:

So, as it is so easy I guess you have done it?

Mar 16, 2008. 6:43 AMgip_mad says:

No, I actually don't need it, but as I've mentioned earlier a local boy scout group (guys from 12-16 years old) made a nice working solar oven with that tracking system. These things fascinates me a lot, and I'm going to build the http://www.instructables.com/id/Robotic-Solar-Powered-Sunflower/ as soon as I get some spare time.

Mar 19, 2008. 2:10 PMgaiatechnician (author) says:

Pictures of the local scout group cooker and tracking mechanism would be great. Could you obtain them please? Thanks

Mar 20, 2008. 9:33 AMgip_mad says:

I've seen it on a meeting about 6 months ago, I don't have pictures and I don't remember the group name, sorry. Anyway, I try to describe it: It was a box with aluminium foil inside,closed with a sheet of glass, mounted on a big round wood piece with bearings. the fixed motor had a smaller gear and there was a rope going around the motor gear and around the round piece of wood, as to make a high gear ratio. With a similar simple circuit as the one from the sunflower, they were moving the entire thing. Sorry for the poor english, but this is as far as I'm able to go... :(

Mar 20, 2008. 9:39 PMgaiatechnician (author) says:

Weather permitting, I will be making the mould for my (off centre) dish tomorrow. I am trying to design it so that I can reuse the mould for more dishes. Hopefully it will be light enough for a sunflower to power it. The mould will be made of cob and part of the centre of the mould will remain attached to the dish when it comes out to keep it stable. Stays may or may not be attached for more stability. The reflector will be just over a sq meter in area so hopefully in full sun we will get 500 watts focused on the accumulator. Initially tracking will be by hand. (A 24 hr circle will be attached to the axis and used to point it in the right direction) with a watch as the guide. Anyway, hope it works! It has been 6 or 7 months in the pipeline. Brian