Solar Tracking

[Wao nahele kane]

Long shot here-
Has anyone out here built a solar tracker and if so; did you happen to figure out the average power increase over a fixed position orientation? Is your system capable of tracking across the subsolar point crossing? Is it a photo sensor type or algorithm based system?

I'm in the midst of building an algorithm based tracking system with a 21.5' x 16' array and would like to compare notes etc.


- Armed citizens provide security of a free State.

[mac nut]

nope

[MarkP]

My roof has about a 15 degree slope and that slope faces about 20 degrees east of south, so I have spent considerable time rationalizing how Eden Roc tends to get the best sun before lunch, and when cloudy it is better to have the panels flat. In other words, no.

Now while I may be rationalizing that doesn't mean I am completely wrong. It is in fact true that the best angle for panels to be at when the sky is overcast is completely flat since the light is coming uniformly from all directions. The bottom line is that with today's prices for panels it is better to buy more panels than a tracker. This would be particularly true here in Puna where the cloud cover is so variable.

[ericlp]

http://www.youtube.com/watch?v=Rt4HZOsOwNQ Don't expect those hobby servo's to move full size panels. But the concept is there.

You'll gain 40-50% depending on if you make a dual axis tracker. Tho, I looked into it. If I could find someone to WELD a frame for me I might think about it. But it would have to be SEMI cheap... I mean I'm not sure how much it would cost to build a SOLID frame for say 4 panels but, I guess if I could find someone to do that I'd do it.

You can buy pre-assembled kits and you just stick them in a jar. I think the newer kits also have a "cloud" sensor that is necessary so that the controller doesn't think the sun went down.

If you are good at welding I could make the kit (electronics) maybe we could make a few for some test runs.

[Wao nahele kane]

For small systems... yes, buying a second set of panels is sometimes a less expensive choice but that option also hinges on other factors with regard to viability (required space for solar L.O.S., thermal reflection), etc.

A good site for technical solar information is at http://www.nrel.gov/.

Being between the tropics (referencing latitude there)vastly alters the dynamics involved and increases the requirements of a tracking machines articulation capability as well as its programming complexity and or electronics systems - if to be fully automated. Outside the tropics, the machine articulation requirements are minimized (commonly offered machines and systems) as well as the other system requirements. For that reason, the common online off the shelf systems are not fully compatible with our location 20% of the year. The subsolar point crossing of our latitude twice yearly reverses the polar orientation and common machines are not capable of such tracking requirements unless manually reoriented and or "circuit reversed" twice yearly. In a nutshell: we require "bipolar" machines at our latitude if we're after full automation.

In this build I'm using 2 slewing drives each driven by a NEMA 42 stepper motor, the microcontroller is the open source Arduino Mega.

If anyone is interested in checking out the build, etc. I can create a new thread that maybe more appropriate in the building section and post picture links as I move along throughout the build.

ericlp - I've unintentionally ended up with a near complete second drive kit (long story) it will be short one horizontal mount (azimuth) slewing drive and one stepper driver. The drive kit parts came to around $1,800 total. One of the other aspects is a custom made slip ring which adds another $100 in parts as a DIY sub-build. There's also 4 large pillow blocks adding to the cost and finally about $1500 in steel stock. Total in materials is between $3,500 and $4,000... it's less than the price of a second 4700 watt array

- Armed citizens provide security of a free State.

[Wao nahele kane]

With the average 4700 watt array coming in around $8,000 +/- source dependency plus delivery. Then considering the cost of materials to build two stationary array frames say perhaps $1,000 in metal as a DIY. A dual stationary array less the cost of the initial array itself, the total is at $9,000 but more likely far more if not a DIY project.

- Armed citizens provide security of a free State.

[MarkP]

I spent $1800 to triple my admittedly puny original 720 watt array to 2160 watts. We in puna contend with a fair amount of cloudiness that occurs at random times. Would a tracking system track where the sun is in the sky or would it somehow detect the most advantageous position given overcast, reflection from clouds on a partly cloudy day, etc? If the latter then the array would be moving all over the dang place on a typical day as the sun came and went. If the former, it would be pointed the "wrong" direction a lot of the time.

In my case I wish I could either adjust the pitch according to season or that I had fixed them at the best pitch for winter, which is about 40 degrees off of horizontal. Even with them 15 degrees off horizontal I seem to be getting enough to fully charge the batteries and am throwing some power away every day. Come summer I won't know what to do with it all. The 40 degree pitch would give me more buffer in the winter and I wouldn't miss it during the summer when longer days compensate for a less perfect angle. That being said the primary point I set out to make was that when clouds enter the picture the whole issue of aiming becomes very complicated with the only simple rule that in a uniform overcast the best angle is flat so that the panel can "see" the most sky.

[Greg]

I lived on a wooded lot about 20 years ago and had two panels mounted on a wheelbarrow frame with a hundred feet of heavy romex. I could move the panels around as needed to catch the sun. No foolin; it worked fine.

[Bullwinkle]

old school - clock drives were the rage - salvaged some small units from telescope drives.....

[Wao nahele kane]

I started by looking at this regions history regarding extended consecutive days with low insolation values and determined the 5X rule was adequate to apply here in Puna. Some areas, persons and or uses (business) may demand better than 5X and some less than. That number of days (5) multiplied by my average daily consumption determined the Battery Bank size. From there, the array size was determined by the average insolation hours in this region via 2 axis tracker and the battery bank rating.

This tracker will be controlled by algorithm and aims at where the sun should be throughout the day. Because it uses a reprogrammable microcontroller with multiple input and output pin-outs further capabilities may be introduced such as extended period cloud fringe aiming, heavy wind parking, wash parking, repositioning for area access if needed, etc.

Yes there will be days with excess power production but that's the way it is with PV. One could use the surplus energy to run a pond/pool pump, AC or produce hydrogen gas for eventual use in an electrical generator and or automobile...

- Armed citizens provide security of a free State.