Solar PV tracker

For a class project (PV Design, Appalachian State, Dr. Dennis Scanlin) I decided to try making a low cost PV (photovoltaic) tracker. Being able to follow the sun's path through the sky can raise your solar panel system's output considerably (30-50%), but the argon filled ones can be a bit pricey, and seem to be a bit unsteady in wind. I looked at several different designs, looked at what materials I could find, and this is how I did it.

The panel is mounted to a frame, which is attached to two bike wheels. The wheels are mounted to a larger wooden frame, and the wheels and panel are moved by a 12 volt linear actuator. The sensor is an LED model and is purchased from Redrok Energy.

The LED sensor senses the path of the sun and tells the actuator how much to move to keep the panel properly oriented. At the front of the tracker are two legs that can be adjusted to the proper altitude for seasonal changes.

I used bicycle wheels because they are durable, strong enough to handle some weight, and best of all, in my case, free!

Step 1 What do you need?

Here is what I used to make this tracker, and where obtained:

*Several treated 2x4's (Lowes)
*Two wheels from a free bicycle- free or almost free bikes are pretty easy to find from the local landfill or thrift store
*A piece angle iron with pre-punched holes (Lowes)
*A 12 volt linear actuator-(~$75?)- (Ebay)
*An LED tracking sensor- (~$40)( http://www.redrok.com/led3xassm.htm#led3xforsale )
*Various nuts, bolts, screws, cable and wire -(scrounging around my workshop)

Comments

[ensoarts]

ALL electronics has a linear actuator for 36$ but its also 36volts,  Do you think you could string 3 panels together to power the actuator. Will the redrock run on 36vs?

[redrok]

These types of actuators use permanent magnetic DC motors. Just run the 36V, or 24V, actuator on 12V. They will move slower, a good thing, with little loss in force.

Duane
Red Rock Energy
redrok.com/led3xassm.htm

[wmiles]

Will the 12v be enough to trip the relays though?

[shakespeare1212]

Great project but honestly it could be so much more better looking. Please may I suggest that you find a hippy, artist friend to carve some awesome nature scenes into the wood, faries, suns, moons, stars. etc, then stain it, and you're ready for the solar festivals.

[Xzav]

I'm new to the electronic field and sometimes it seems intimidating to me. About the Led tracker, do I need to know how it works in order to use it? I would like to know how it works. Can you explain a little on it. Thanks

[Shiftlock]

"Bicycle wheels, working tirelessly (no pun intended)"

No pun intended? Really? Because it sure looks to me like you absolutely intended to make that pun.

[Xzav]

It was still funny.

[hdb111]

Should two Linear Actuators be used for a larger array? Say Four Panels?
Thanks folks.

[brassmonkey666]

I want to add this tracker to my solar array over the next month or two. It seems the largest consideration is going to be which linear actuator to use.

Obviously if you can find a free or cheap one from someone who is junking an old satellite dish that would be great.

But if left to buy one, other than the stroke and finding one of the appropriate voltage, how much force should one be able to exert on say, 2 45W panels and still be able to operate in blowing winds? It seems like you would want to minimize this in order to draw the lowest amount of current from your battery bank so that you gain the maximum power from your tracker and invest as little power as possible into driving the thing. Thoughts?

[Gunkarik]

Very helpful, thanks for sharing!

[kd4uwk]

Thanks for sharing the photos are good

[segarza]

A nice simple and effective design. Thank you for sharing it. Isn't it funny how the minute you share your project with the public, we instantly began re-analyzing and re-designing it to death and flooding you with a million ways you could have done it better? Oh well, that's just human nature I guess. You did a great job!

[playfair1965]

You know you could have said that a better way LOL 9-)

[segarza]

Yeah, I know...I had that one coming didn't I? lol

[tbone56]

Thanks for making this. It is truly instructable.
I have a question about the movement.
How many degrees do the panels move each day?

[kosme]

great project

[jakesnake]

red rock just keeps your money

[playfair1965]

Great work.. Now I just got to get a solar panel to put on it hehe Thxz for the post.

[jolshefsky]

I really like the design where you bolted boards to bicycle wheels -- it's an elegant, strong solution that uses (as you mention) free resources. Even bent rims would work fine.

I'll have to give this some thought ... I'm working on a design for an "external Trombe wall" which I can attach to an existing window for the venting.  Of course, making it insulated, situated off an existing wall, and now pivoting, I'm getting away from the simplicity of Trombe's design.

[ktkeith]

Not to denigrate the work you did, but do you really need the photo sensor? The position of the sun can be calculated for any time of day, any day of the year. Why not just program an EPROM to store a lookup table for the correct angle, hour by hour, day by day (about 4,000 data values for the daylight hours of a single year), and use it with a simple microcontroller to adjust the angle incrementally? A bit more complicated at setup, but probably about the same total price, more accurate, and likely more reliable.

[lloydrmc]

Uh... How about because his approach is considerably easier and cheaper? And didn't you read about the brightest part in the sky not necessarily being where the sun is?

[bwitmer]

Sure, there are many ways to do it without using any sensors, this is just how I chose to take a crack at it. The reason I went with the sensor over the EPROM is that I know how to hook up the sensor, but have no idea what an EPROM is.

[doctorbigdaddy]

This is a well thought out project! I may have missed it ;but, how does the device return to the morning position after it follows the sun until sunset?Again many thanks for sharing your work!

[redrok]

Parking is built into the LED3X.

When it gets dark or with heavy storm clouds it heads toward the Eastern limit switch. If the sun comes back out it resumes tracking.

Duane
Red Rock Energy
redrok.com/led3xassm.htm

[shetonus]

I like the concept of pointing your solar panels at the sun, and have suggestions for improvement:

1. I would suggest that the wheels be mounted on an A-frame so that struts could be placed from the outside edges of the panels to points tangent to the wheel to provide bracing against strong winds. 

2. I find that sun position sensors aren't really necessary for pointing since we already know where the sun will be at any given time of the day.  Also, some sun trackers may have difficulties tracking the sun's position on overcast days and may operate erratically on partially sunny days when clouds intermittently block and reveal the sun.  A system built around small uProcessor with an on-board clock can be programmed to provide positioning information to your drives, and if you want to get fancy, the sky's the limit for adding sensors, providing web connections, what have you. 

[redrok]

For PV panels and the like the sensor method is superior to the clockwork methods because they find the brightest part of the sky. Yes this may not be where the Sun is behind the clouds.

If you measure the power from the panel this other direction will be greater.

Furthermore, the sensor is influenced by other sources of light such as reflective sand and snow adding even more power.

Duane
Red Rock Energy
redrok.com/led3xassm.htm

[shetonus]

Just a thought about item #1... Cables could be used instead of struts if the PV panel were sufficiently sturdy. 

[spicegal27]

can you please help me in buildind a similar model for ma project....plz suggest me some books

[Laral]

Looking at the finished design, I see an easy mod you can make to compensate for the sun's declination. You can mount the panel on hinges at the top with metal straps with holes at the bottom like you did for the front of the mount. You need to add enough wood at the top to allow a -23.5 degrees tilt at the bottom and a long enough metal strap to allow a +/- 23.5 degree tilt. You can add a simple scale with markings for each week or 2-week period of the year for manual adjustment, or you could theoretically add another actuator. BTW why didn't you just cut the angle of the 2x6s the same as your latitude. You're not going to be moving this around are you?

[gaiatechnician]

Good suggestion. I have something very similar on the tracking solar accumulator videos.  At this time of year and in the winter there is only a tiny adjustment in 2 weeks. Around equinox there is a large adjustment. You might adjust every week  to get maximum performance. The image has the seasonal adjustment shown as you suggest. Hopefully it is clear enough at this size.
Brian

[speedstix]

Cool! For a class project our group and I decided to make a Maximum Power Point Tracker. It did not track the sun but it did try to find a point where the panels were operating at their maximum power. I am wondering what sort of efficiencies have you achieved using this setup. Did you do any tests between stationary vs tracking power measurements? I am very curious.

[azapplewhite]

Speedtix, FYI NREL has a huge data base with measured solar radiation data that compares fixed vs. 1-axis and 2-axis trackers. It even even includes the impact of tilt (declination) and there is data for every month of the year. Very useful resource for anyone out there trying evaluate the potential benefit of various schemes for their particular location.
Go to: http://rredc.nrel.gov/solar/pubs/redbook/
I suggest going down to the middle of the page where they have individual state data. Note that for EVERY location they provide annual data for ALL the relevant mounting and tracking schemes. Your tax dollars actually at work!
Hope this satisfies your curiosity on this topic!

bwitmer: great instructable!!

[arjannugteren]

Is there and equation to calculate the inclination i need to set the panel to for any given place on the world? Or is a matter of guessing towards optimization?

[Laral]

Again, that's DEClination, and here's a simple equation to calculate it:

http://pvcdrom.pveducation.org/SUNLIGHT/DECLIN.HTM

You then need to add the result, which can be positive or negative, to your COlatitude to get the current angle that the normal to the rotational axis should be at.

[filmnuts]

I would not call that equation simple (yikes!), but it is helpful for finding the solar declination on a given day and would definitely come in handy with a PV panel that pivoted on two axes.  However, as I said below, this equation is not necessary, as long as you are dealing with a PV panel with fixed inclination.  The optimal angle will always be the same as the latitude of the PV panel.  It's a fact.

[Laral]

Well what's NOT simple about a multiplication, a subtraction, a division, and a sine? If that's not simple to you why did you even ask if there is an equation if you are not prepared to use it?

[filmnuts]

If your panel has a fixed inclination (as the one in this Instructable does), you usually want the angle to be the same as the latitude of the panel's location.  A location's latitude is very close to the mean sun height over a year.

[Laral]

That's DEClination and you need to set the normal to the axis to the COlatitude (90-latitude).

[redrok]

Some also call this Zenith Angle

[Laral]

There seems to be enough confusion without adding yet another layman's term. Why not just stick with standard astronimical terms?

http://en.wikipedia.org/wiki/Declination