Interesting alternative way to do tracking...

[DamonHD]

http://www.kurzweilai.net/reducing-the-cost-of-solar-power-with-mobile-robots

"QTS utilizes a pair of autonomous robots, one primary and one back-up, to control 300 kW of solar panels with high accuracy and reliability.

The robots travel on a track and adjust each mounting system to optimally face the sun in succession. Each robot replaces hundreds of individual motors and controllers found on conventional tracking systems. "

Rgds

Damon

[Bruce S]

Interesting idea. The proof will be in the long term. There's clunky old servos still working today to day for a year at a time.
If this works out it would save weight, and complexity.
Nice article.
Bruce S

[fabricator]

There is one thin there I find to be somewhat of an obfuscation, in the last couple lines they say "typical tracking systems require thousands of pounds of concrete and steel"  What are they using to anchor their arrays? duct tape and packing peanuts?

[boB]

I saw one of these down at SPI in Orlando last week...   I took a short video of it but didn't get it doing its thing where
it gets to the base of the pole, connects up kind of like R2-D2 did to the computer wall in Star Wars, and turns a
gear thing to rotate the array.  It is pretty darn neat !

I should have gone back and recorded it again but maybe they have a video on the web site ??
boB

[snowmass]

Being that I am tracking an array consisting of 21 sharp 235 panels. A total of 4938 watts, with dimensions of 16x22 ft.
with just a 30 amp dc geared motor and atv winch as the drive. Three deer feeder timers and withstood 60 mph winds
so far. I can't find it to impressive.

[fabricator]

WOW! That's a big array, about what I want to build, you wouldn't happen to have any pics would ya?

[snowmass]

http://www.fieldlines.com/index.php/topic,146967.0.html

Here's a few. When I get back from vacation, I would like to take pics of how I did it in detail with explanation. Yesterday I installed a
pair of large shocks and is now completed. ... Thanks

http://www.youtube.com/watch?v=3bU1FcY_hGQ&feature=youtu.be

[fabricator]

That would be much appreciated.

[fabricator]

That setup is beautiful, I love the round track, in my opinion that would be better than two actuators, the load is spread out a lot more.

[ChrisOlson]

This circle track tracker had a 10 kW array on it.  $140,000 for whole setup with the tracker and concrete work, etc.. for the foundation.  It's a heavy duty unit - that track is made of 1/2" thick steel and it sat on 6 three foot diameter concrete footings that went down 6 feet .  60 mph wind and this is what was left of it.  Tore the anchor bolts right out of the footings.



--
Chris

[boB]

What the heck is that, Chris ?  Looks like a crop circle cookie cutter.

boB

[ChrisOlson]

Yeah, it wasn't good for the owner of it.  He borrowed money to put it in - never heard the outcome of the insurance on it.  That track was roughly 20 feet in diameter and it had a 2 hp gear motor on it to drive it.  It had some type of grid tie inverters on it that I'd never seen before, right on the back of the array, and there was one inverter for every four panels on it.
--
Chris

[snowmass]

Piece of crap. Should of had a wind sencing device, like are use on awnings to roll them up in high winds, to lock it down and  turn it out of the wind.
I've seen some brainy people do some stupid things. CHING CHING...

[Frank S]

hard to tell what kind of mounts were used but I would say someone did not consider their wind loading well enough

Using bonehead math; and judging the size of the array to be about 40ftx17 relative to the approximate 20ft diameter of the base figuring that the wind had at least ½ mile unobstructed flow @ 60MPH that would be about 16.6 PSF meaning a total force of 11228 LBS When spread over that much area it doesn't sound like all that much until the height gets considered creating a moment arm or fulcrum then the load on a single anchor point could be 10 to 15 times that figure.
 You didn't mention how many anchor bolts or what type
 Based on you saying they were torn out of the concrete I'm guessing that they were not cast in place or deep core epoxy. If Hilti or redhead wedge type anchor bolts were used I would think they would have used at least 6 or 8 on each footing 5/8” or ¾” and at least 6 inches deep the problem then becomes spacing as a ¾” bolt would need to be minimum of 6” on centers and not closer than 6” from the edge
 There is an IKEA sign here that I designed, and another company built because at the time we didn't have the capacity to handle a 43 meter long 1.5 meter diameter tower any way the sign is 3 sided 12 meter by 4 meter on top of a 43 meter mono pole anchored with 28 1 ½” bolts embedded 2meters deep the footing is cone shaped   6meters deep 5 meters diameter at the bottom and 3 meters diameter at the surface with 6 piles driven another 8 meters down  so far it has stood 2 years and has withstood wind gusts  in excess of 100 MPH several times 

[ChrisOlson]

I come up with 9.2 Psf @ 60 mph with a 1.0 coefficient of drag.  However, the Cd on a large solar array is higher than that - more around 1.2.

--
Chris

[Frank S]

ASCE 74 shows the  CD on a long cylinder tube would be 1.2  .8 for a short on long flat plates 2.0 and on short plates 1.4

as does the EIA-222-F
"[Force = A x P x Cd x Kz x Gh

A = the projected area of the item

P , Wind pressure (Psf), =.00256 x V^2  (V= wind speed in Mph)

Kz, Exposure Coefficient, = [z/33]^(2/7)     1.0 <= Kz <= 2.58
z = height above average ground to midpoint of the item (IE, antenna, or tower span) in feet.

Gh, Gust response factor = .65+.60/(h/33)^(1/7)    1.0 <= Gh <= 1.25
h =  overall height of a tower (used for an antenna mounted at its top) in feet.

Cd = 2.0 for long flat plates and 1.2 for long cylinders. Aspect ratios >=25
Cd = 1.4 for short flat plates and .8 for short cylinders. Aspect ratios <=7

The relationship between drag coefficients for cylinders and flat things is, 1.2/2.0 = .6 or .8/1.4 = .57, in this case less than 2/3

EIA-222-F thinks the wind speed is the "fastest mile basic wind speed" at 33 feet above the ground, not the actual peak sustained wind speed. These values are not the same as the 222-C spec, they are defined by State & County locations, rather that the older wind speed zone maps.
There are no additional site specific exposure factors cited in this spec.]"


 Like I said I just used a simple bonehead shortened quickie Frank formula But I've never gotten in trouble by over estimating
 I think it can be agreed on that someone missed the mark on their anchorage though with 6 anchor points positioned around the base @ 60 degrees to each other any 2  anchor points should have been sized to withstand the full force of a max wind load for the region with a FOS of 4 to one minimum code and 8to one California std on a 4 or less anchor point it would have been any single anchorage
 Here is a link that some may find helpful  http://www.arraysolutions.com/Products/windloads.htm

[Valalvax]

Wouldn't it be smarter and simpler to build a... not sure what the actual name of them is, but a wind fence, basically a fence to break up the wind/slow it down?

[Mary B]

My small array that is 10x10 is only sitting on 4 5/8th inch x 12 inch anchor bolts into a 12 inch dia x 4 foot deep footing. Has withstood 75mph already. I had a 45 foot tower that was self supporting tubular that sat on a 12 inch square plate with 4 1 inch dia x 3 foot long anchor bolts in a 3x3x7 foot deep footing. Had 5 square feet of antennas at the top of it. That rode out some 100mph winds more than once.

[ChrisOlson]

I think it can be agreed on that someone missed the mark on their anchorage

It was all installed within a week at the prompting of the owner because he got his grant and his loan money and wanted it in right away.  What I was told was that they drilled the footings for wedge anchors and the concrete wasn't fully cured yet.  A week later the wind storm comes along and ripped the anchor bolts right out of the green concrete.

The last I heard the insurance company was haggling over it.  I has never been replaced.  I'm guessing the insurance company refused to pay for it, the contractor refused to pay for it, the guy that owned it refused to pay for it, and the bank owns a pile of junk.
--
Chris

[fabricator]

That was stupid, each of those foundations should have had four 1" all thread rods 3" long into the foundation with a plate bolted to the bottom, then a plate the same size mounted above the concrete like you mount a light pole or monopole tower, that thing would still be working.

[Frank S]

I think it can be agreed on that someone missed the mark on their anchorage

It was all installed within a week at the prompting of the owner because he got his grant and his loan money and wanted it in right away.  What I was told was that they drilled the footings for wedge anchors and the concrete wasn't fully cured yet.  A week later the wind storm comes along and ripped the anchor bolts right out of the green concrete.

The last I heard the insurance company was haggling over it.  I has never been replaced.  I'm guessing the insurance company refused to pay for it, the contractor refused to pay for it, the guy that owned it refused to pay for it, and the bank owns a pile of junk.
--
Chris

green pour loading now where have I run into that before? I can see at least 2 parties at fault here. The owner and the contractor both should have to share the cost the Owner for being impatient, the contractor for not insisting he wait until the concrete was aged."O" liability to the ins company.

[JW]

Most of the last 6 or so posts about the anchor's are off-topic, the robot array that Damon started this topic is about,  has no anchors.

You guys need to either contain or reduce some of this constant hyjacking of threads.

I used to do it myself, so just take this with a grain of salt.

JW

[dloefffler]

Oh S.....

I am in the process of building out my array which will be 50 feet long, 7.5 from leg to leg with a 36 or so degree tilt. It is anchored with 12  12" sono tubes 4' into the ground, each tube has 4 foundation anchors welded to 4 pieces of interconnected rebar (1/2") at approximately 1'  fo the bottom of the footing. Footings are 5000 psi concrete,  Supports are 3" sched 40  pipe welded to a 8"x6" 1/4" plate with 4 holes bolted to ordinary construction anchor bolts.

We are on a windy site, excellent for wind turbines.

So, what could possibly go wrong?


Dennis