Sun hours

[bcroe]

Oft decried, but a decent beginner learning tool, the Horrible Fright kit is now updated to 100W, on
sale for $1.50 a watt including a charge controller with readout and a couple lights for the 12V
battery you must add. Bruce Roe

After a break for required seasonal duties, am contemplating a design of the last primary component: the
pivot point connecting the fixed base to the pivoting 24 panel mount. Snow has been very late this year,
but now threatened. Bruce Roe

[bcroe]

Here is the Nov progress report. Very favorable weather has allowed completion
of the tilting array foundation and construction of the fixed base. 6 ball bearings
will be mounted near the top and shimmed for good alignment. The array center
of gravity will attach to the bearings, making tilt change much easier.

PVpost shows the top of a foundation post, the L bolt was jig supported while
pouring for best accuracy of position, height, and angle. The bolt and surface
have the same 10% slope as everything else.

PVTsup shows the 6 bearing supports lined up on my 10 % grade heading
downhill to the right, north. The camera is tilted too. Surprised myself with its
accuracy; everything just bolted together no problem. The front and rear
supports are connected together by concrete and rebar at a 4 foot depth.

PVsing shows a closer view; that yellow level is set perfectly vertical, to show
how much slope there is. No earth movers or retaining walls required, the sun
doesn't care. The minimum of dirt/rock was disturbed, using lightweight
equipment. But I do need to be careful of bare spots and erosion. All the
grass not directly over concrete is intact; the rest will be tended.

The ever present black buckets serve a couple of purposes. Rocks that get
to the surface get thrown into the nearest bucket. And a bucket turned over
can be a seat for any tired retiree. Bruce Roe PVpost.JPG
PVTsup.JPG
PVsing.JPG

[bcroe]

The inclinometer says the E-W panels are up around 74 deg; the S panels are 24 deg. Google earth
shows the facing direction isn't very accurate; didn't measure the error. . Bruce Roe

[bcroe]

Hey Bruce...another quick question...I think your East/West array has a ~60* tilt. The
Fronius white paper says that a 15* tilt is the most beneficial for an East/West array. Just curious why you chose
such a sever tilt for that array?

Is it because you want to limit the clipping on your inverters?.......or do you have some other reason?

Yea, and Google says the cheese goes on the bottom of the burger. My notes indicate the frame is 74.4 deg
up from flat, but that doesn't take into account the array follows a 10% grade. I can't put my inclination gauge
on the edge of the panel; need to use a level to get it straight up when measuring the combined angle. Too
cold & dark to do just now.

I initially found my expensive inverter plant had little to do when the sky was somewhat cloudy. More panels
would help, but they would be wasted in clipping if facing S in good sun. So they are more or less facing the
rising and setting sun.

With that in mind, I needed some kind of triangle wide enough that I could work inside, and that wouldn't blow
over too easily. Thats about all the science in this model. Production measurements indicate it wasn't such
a bad guess.

Bruce Roe

[DanS26]

Hey Bruce...another quick question...I think your East/West array has a ~60* tilt. The Fronius white paper says that a 15* tilt is the most beneficial for an East/West array. Just curious why you chose such a sever tilt for that array?

Is it because you want to limit the clipping on your inverters?.......or do you have some other reason?

ps....your right that the Fronius 7.5 uni inverter is a single MPPT inverter.....their newer inverters have multiple MPPT capabilities.

[Jim Jakosh]

Thanks Littlharbor. I found a lot of them and some with a wind speed indicator that is programmed into the electronics.It must change the angle in high wind. Thank you so much. This saves me a ton of work! I'm thinking this would work for a max of 4 panels.
This gets the design work started earlier!!!!!!!!

Cheers, Jim

[littleharbor]

You can find lots of single and dual axis tracker electronics and rams on eBay. Stuff like this..
Solar tracker.jpg

[Jim Jakosh]

I have a new 6 panel array and I think I must be losing about 30-40% by not having the panels track the sun east to west. I have been taking measurements of the angle to hit the panels perpendicular north to south to figure the best time to set them at a new angle- maybe 6 times year. But I started measuring the east to weast angle too and there is a vast angle change from east to west during the day. I am now looking for a tracking system for a 4 panel array that I might build next spring.
Inetdog, do you remember who was selling the tracker for $155. I;m not a computer guy much at all and I was thinking of making a tracker for both directions with 7 to 9 presets and the unit would click to an angle based on the most energy hitting the small solar panel at that angle. I'm gong to try to get help from our high school robotics class.

[bcroe]

And did we strap a Jumping Jack soil compactor to a vertical or a Home Depot style paint shaker to the top rail? Pictures of the front are good for magazines, pictures of the backs are better for me... Also want to hear your current thinkings on large ground mount with tilt. Thanx.

The vibrator may not make this version; I have one from getting bubbles out of home panel
days. It would probably take a lot of testing to optimize, to get the axis, frequency, and perhaps
waveform right. The worry is cracking panels, or difficulty extending to multiple panels.

I will show you a rear picture of a tilting array just as soon as its together (may be impeded
by season and weather). Bruce Roe

[AzRoute66]

[... from Post #167] Assuming the snow has a place to go, there will be motorized vibrators attempting to shake it off on the next round. Bruce Roe

And did we strap a Jumping Jack soil compactor to a vertical or a Home Depot style paint shaker to the top rail? Pictures of the front are good for magazines, pictures of the backs are better for me... Also want to hear your current thinkings on large ground mount with tilt. Thanx.

[bcroe]

Bruce, Just wondering how your strings are attached to your Fronius inverters? Specifically.....do you combine strings at the arrays then send a single DC home run to each inverter? I'm just curious how the inverters handle strings of different powers. In other words if you have East and West facing strings combined then the MPPT for each string is vastly different over the course of a day, but the strings are combined. Just curious how the Fronius inverters handle that from an MPPT standpoint?

I know that the Fronius inverters that you have can each handle 6 individual strings each with a different MPPT....but when you combine strings and use a buss bar in the inverter it appears to me that differential capability gets lost. If that analysis is correct......how much is lost if any?

There is an OUTBACK PV12 dual feed combiner box at the end of the arrays closest to the
2 inverters, each 7.5KW. The combiner normally takes 6 (lower voltage) circuit breakers, or
4 (higher voltage) fuse holders, on each side. Each side has a pair of 6 gauge wires running
the 230' to an inverter. At this voltage losses hardly exceed 1%. However, by turning around
the top bus bars, 6 fuse holders may be fitted to each side, my configuration. This is no
where near any components capacity.

The Fronius inverters have 6 fuseable input positions; I buss 3 together with fuse positions
shorted for the 6 gauge feeds. I am not aware that the inverter has any multiple MPPT
capability. Every string is made up of 720 series cells, either 10 panels of 72 cells or
12 panels of 60 cells. As Sensij points out, the voltage doesn't change much for varying
sun, and the curve isn't that critical, so they seem to play nicely together.

I haven't made any cost effective claims here; terms like "mad scientist" and "science
experiment" have been heard. I've already shown that the basic standard design can
be improved on here. Still being in the experimental stage, we shall see. It will always
be more expensive to generate PV power under the clouds than in the SW desert, but
I'm not that far from breaking even. Bruce Roe

[J.P.M.]

I don't know enough to evaluate whether or not the system represents the pinnacle of cost-effectiveness. If parallel strings of east and west facing panels are the biggest problem, the design must be pretty darn good. Here is Fronius's white paper on the losses that those parallel strings might experience, relative to independent mppt. (<1% difference in annual output, by their model)

I don't know enough about Bruce's arrays either, but given his installed orientations and particularly tilts, I'd question whether his annual output for his arrays in their current configuration couldn't be matched by a single array using the same panels and equipment with the same tilt adjustable features in a more southerly orientation but with a lower surface area.

I appreciate the idea that he seems to feel spreading/shifting more output more over the day and thus getting more production earlier/later in the day is useful, and may result in some savings via smaller inverters, etc., I also sure don't know any demands/particulars his POCO or distribution equipment may make to limit his max. output at mid day, but, aside from those things, and maybe some others, if he's on some form of NEM grid tied billing arrangement, he'll get more annual production per m^2 of panels with a more equator facing orientation, and probably spend less to do it.

But, all that said, he's got a hell of a system and seems to be having fun. What's not to like ? We all have our hobbies that wind up as holes down which money disappears. Hail the freedom. I doubt his system is optimally cost effective, but neither is mine. Hang in there Bruce. Enjoy.

BTW, on panel temps. I'd SWAG that in the same orientation(s), ground mounted arrays will probably have a lower operating temp. than similarly oriented roof mounted array(s). But I'd also be pretty sure arrays in different orientations in the same environment (ground or roof) will have different panel temps., depending on orientations, as f(energy balance) and additionally tend to be somewhat f(time of day). One perhaps practical outcome/consideration of that, particularly for way off south, high tilts, would be that white backed panels at off south azimuths and high tilts would probably tend run cooler than black backed panels in the same orientation, and so be more efficient in a given orientation.

[DanS26]

I don't know enough to evaluate whether or not the system represents the pinnacle of cost-effectiveness. If parallel strings of east and west facing panels are the biggest problem, the design must be pretty darn good. Here is Fronius's white paper on the losses that those parallel strings might experience, relative to independent mppt. (<1% difference in annual output, by their model)

Thanks sensij, that white paper was most helpful.

[sensij]

Well he**, lets just point these arrays all over the place as long as they are connected in parallel.......money should be no object. Yes I'm being sarcastic.....but in reality arrays should be designed to produce the maximum power for the least cost. Bruce's experiment, although noble, does not appear cost effective to me.

I don't know enough to evaluate whether or not the system represents the pinnacle of cost-effectiveness. If parallel strings of east and west facing panels are the biggest problem, the design must be pretty darn good. Here is Fronius's white paper on the losses that those parallel strings might experience, relative to independent mppt. (<1% difference in annual output, by their model)

[DanS26]

The mpp voltage is not vastly different for the array orientation more directly receiving the sun and the one that is not, so combining the two orientations in parallel does not cause unacceptable loss. A lot of the effect is thermal... the array getting direct sun will be hotter, and have a lower mpp voltage than the cooler parallel string, but I think the effect won't be as bad for ground mounted panels as it might be on the roof. The mppt will seek whatever voltage maximizes power, so it will tend to follow the mpp voltage of the array in direct sun.

Well he**, lets just point these arrays all over the place as long as they are connected in parallel.......money should be no object. Yes I'm being sarcastic.....but in reality arrays should be designed to produce the maximum power for the least cost. Bruce's experiment, although noble, does not appear cost effective to me.

In defense of Bruce's design....it appears he is locked in on the AC side of things so he is maximizing the DC side of things without regard to payback.