Solar tracking systems

[Naptown]

From PV Watts for the Dallas-Fort Worth area for a 1 kW system

no tracking - annual kWh production projected at 1404 kWh

1 axis tracking - 1783 kWh

2 axis tracking - 1876 kWh

Or about 26% more harvest. Based on E-W tracking. Tilt angle will provide a minimal increased harvest.

[TnAndy]

Yeah, that 's what I understood about tracking ....the biggest bang for the buck was East/West, so I didn't make a provision for my first two arrays to tilt. But later, studying PV Watts and seeing I probably should have increased the tilt angle some over latitude, I decided to make this next one tilt. Wasn't all that hard, nor did it increase the cost much. It won't be auto controlled, I simply put a DPDT switch from the 24v power supply to the tilt actuator, and plan to adjust it about 4 times a year, manually. The E/W will have the standard "analogguy" controller board, and track daily.

Basically, I welded a set of 2" flange bearings to the side of the 8" pole using a pc of 8" channel as a spacer/base for the bearings. Then ran a short pc (about 18") of 2" shaft steel thru the bearings and holes in the pole.

Pic of the top of the pole ( later capped it with an 8" round plate ):



Next, I welded up a frame out of 3" square tubing, about 48" x 24" ( 18" inside, to match the shaft ). Then welded the center point of the 48" side to the shaft ends. Added a couple of "standoffs" to the ends and welded studs to them to mount the E/W pivot section later. Also welded couple pcs of flat steel with holes drilled to mount the ends of the actuator later. In this pic, a pc of scrap Unistrut is bolted in place of the actuator to keep the tilt base from flopping around right now.



Next, I welded up a base for the E/W tilt. 2" square tubing with a 50" pc of 2" shaft steel and couple of 2" pillow block bearings. The base is about 58" wide by 120" long. This gets bolted to the tilt base above on those studs.



Then drilled holes in the tubing to mount 4--200" pieces of Unistrut on the base, Unistrut being the "mounting rails" for the panels. I used UniRac S-5 mount clips on the Unistrut, the kind that are normally used for standing seam type roof ribs.....they worked fine.



Then we set the whole thing in place in the hole with a mini-ex as a crane, braced it up good and I had a guy come pump concrete in the base for me. ( same as the previous two ).



Since this mount was taller, and farther up on the hill, I built a temporary deck under it to work, and handle the panels onto the frame.

[russ]

Nice looking setup!

[defed]

one factor that would determine the cost effectiveness of a tracker is if you can build it yourself. if you had to buy everything pre-made and have it installed, yea, it would be cheaper to add more panels. if you are a DIYer, as TnAndy is, you can do it for much less. i plan to build my rack next yr and am going to try to incorporate tracking, which would only require slight modifications to the stationary rack, as Tn has pointed out.

[TnAndy]

Yep....I'd agree.....commercial made tracker would be really hard to justify, cost wise. With what panel prices have dropped to, I suspect most tracker manufacturers are gonna be out of business before long.

My situation is sort of unique for several reasons:

1. I needed to pole mount in this location, roof mount just wouldn't work.

2. I'm fairly handy about building things and scrounging for materials.....the 8" pipe in this project, for example, came fairly cheap from a local industrial scrapyard. I manage to find odd pieces of square tubing, then cut/adapt them for what I want to do, and not pay full retail for them. The 2" bearings, for example, are a fairly cheap, off brand bearing ( about 30 bucks ea ) versus a good, high speed bearing like a Browning at 120 bucks ea....my thinking being I didn't NEED a high speed bearing, since this thing only does about 1 revolution per day.

3. This location is protected from high winds by a high, western ridge that that prevailing winds are forced over the top, and leave us fairly sheltered....I'm not sure my design would work on a wide open area subject to a lot of wind....lot of sail area in those arrays.

4. There's the 'fun' factor......

Overall, in most residential situations, roof, or some type of fixed ground mount would be the most practical, and economic, way to go.....I fully admit that.....but sometimes it's just fun to do something because you can.

Take this "sky"zebo I built on the outboard end of our deck.....took 19' of foundation block just to get the floor level up to the deck....just because it was fun when done to sit in the tree tops.....ahahahaaaaaa....

[defed]

that tower is pretty neat.

i am much the same situation as you. i can fab stuff, and what i can't, my dad or brother can. i have access to material free and at cost. roof mount might be better for me, i'd just rather NOT put them on the roof.

i wanted to do single poles like you have, but i'm worried about (10) 3'x5' panels on one pole, and having several creates shading/spacing issues. i've read many threads about ppl putting 100 sq ft of panel on a 8" pole in a 10" hole 4' deep with 3 bags of sakrete. they say it will withstand a hurricane...but to me, that just doesn't seem like it will stay up! i guess alot of that depends on the type of virgin soil you have. it gets pretty dang windy here in the winter. i'm leaning towards a traxle design, which will be easy to rotate e/w, but will be a challenge to change tilt angle. i've got to get my brother to draw it on his CAD software.

[TnAndy]

I'm a seat of the pants kinda engineer, and tend to overbuild rather than under, so when it came to concrete, I put 4x4x4' bases on the first two ( and had no problems in two years ), and used a 5x5x5' on the new array.

The first two arrays are 141 sqft, and the new one is 175sqft. I did put a pair of shock absorbers on the tilt base of the N/S tilt along with the actuator, because adding that second axis also concerned me about more movement, so I hope the shocks will give it more points of support.

Shading of each other certainly CAN be an issue.....the east array of the first two gets some shading by the west array last hour of the day this time of year...I screwed up and should have put them about 10 more feet apart, so DO watch out for that !

[defed]

somewhere, i have a link to a site where you enter your coordinates, array size and position them on a grid. it goes thru the suns angles on june 21, sept 21, etc, you can track it by hr of the day and it will show the shadows at each hr.

after using it, i saw how far apart things had to be, which is why i want to get as many as possible on each rack. then again, i need to really watch my temp array closely. if it gets alot of shadowing in winter between 7 am and 10 am from surrounding trees anyway, i guess if they shaded each other at those times would be irrelevant.

[anfederman]

Commercial Solar Tracker Controller Manufacturer

Our company lauritzen.biz Manufactures the controllers for solar trackers. Our controllers will work for stand alone units to utility scale fields. Our web site has a lot of info on our products and information on what we think is important in building these systems. Of course we'd like to sell some units, but we are interested in the experience of folks rolling their own system.

The link to our web site is in my member profile, If you are interested.

Thanks

[TnAndy]

Hi, and welcome to the site.

Looked up your company, called them, and for a single control unit, you guys want over 900 bucks ? Wow.....the one I'm currently using, and works pretty darn well, ran under 150. I'm thinking you guys ain't gonna be breaking into the small guy market, huh ?

[anfederman]

@TnAndy,

Not trying to sell to you, just share info. We are commercial not residential, but we are interested in small scale commercial. Farms, ranches and orchards might be really good locations for PV. Say for example an orchard or vineyard that has some unusable land on a south facing hill. A small tracker field might make economic sense if unused capacity can be sold back to the grid. In more urban areas with lots of sunshine and high temperatures, power is most needed during late summer afternoons. This is when tracking PV is advantageous.

We've put a lot of development into making very reliable products that are remotely controllable. I don't think anyone else has iPhone compatible controllers! I am hoping that people who have built their own systems would like to know about ours. Thanks for checking us out. Our solutions page has some PDF files on linear actuators, tracker accuracy, and backtracking that you might find useful.

[Naptown]

There is a local company to us who produce a small (2 panel) tracker. It is designed for home use and mounts on a 6x6 wood post. http://www.atrsolartech.com We just installed one so the Jury is still out but hopeful.

[vinniethePVtech]

There is a local company to us who produce a small (2 panel) tracker. It is designed for home use and mounts on a 6x6 wood post. http://www.atrsolartech.com We just installed one so the Jury is still out but hopeful.

How wide of a diameter post hole base would you need for that? I would assume atleast a 3' deep hole, with a 10' diameter to handle wind shear, good substantial amount of concrete. Does that seem about right?

[Naptown]

I believe they recommend 3' deep and 24" diameter.
These do not sit very high off the ground so there is not much moment for wind.

[russ]

I believe they recommend 3' deep and 24" diameter.
These do not sit very high off the ground so there is not much moment for wind.

24'' diameter?