25 kW Solar power project in Iowa.

[Redneck in training]

Before using some alternate to the standard rails and clamps for panel mounting, it would pay to find some install manuals on-line and read the mounting recommendations, warranty invalidation for non-approved mounting methods and so forth.

I noticed the installers used a torque wrench on every bolt in my system. I am assuming it matters.

Attaching the panels to a wood frame without the mounting rails might be a risk. The wood can warp, cup, twist, shrink, expand, etc. The aluminum frames on the panels aren't going to like any of that. There is also the chemical reaction possible with treated wood in contact with metals to think about.

Some things to consider before you decide the cost of rails and clamps isn't worth it. Just for the ease of installation, I would think those are worth quite a bit.

If you do build your own mounting frame, I would consider designing it to easily allow adjusting for three fixed panel angles -- winter/summer/fall+spring. I assume in Iowa snow depth accumulation is not much of a problem, ground mounts would be my choice for ease of install, maintenance, etc. on a large system.

I already decided to use solar mounting rails and associated hardware. I also figured that at current cost of the panels it is easier just to make the system bigger than to go to the complication with tilt adjustment.

 

[Redneck in training]

You can, but the number of cycles for the switch gear is typically less than 200 before they fail.

I had one panel where the lug terminal on the back of the panel was loose from the supplier. I failed to catch it, although I did notice that one array had slightly less voltage than the other. I put it up to the tolerances in the panels. It survived a week, and then the lug was completely vaporized, and a hole was blown through the panel.... :ashamed:

Be respectful of the power involved in these things.

What I meant is that once the panels are illuminated they produce power that is hard to turn off in example by throwing blanket over the them. I think the micro inverters is way to go even though it cost more.

 

[sawdust_maker]

So after you take $20,000. from your neighbors, friends, family and every taxpayer in the US you will still owe $33,750.00 which you will recoupe at the rate of $21. a month. At $21. a month it will take you 133 years to break even if the loan was interest free.
Am I still missing something?

Don't forget that you invest that rebate up front, and collect some interest on that sum.

Then you presume that power costs go up, generally faster than inflation. This is a good bet.

John

 

[Redneck in training]

I decided to use solar rails and when I added all the necessary hardware such as clamps, legs, grounding stuff etc. the $/W jumped quite up to about $2.34 before rebate. Hope I have all the parts in and nothing is missing now.

 

[tcartwri]

I built all my own racks, which was cheaper by quite a bit, but it was time intensive. The commercial racking is super fast to put up, and for such a large system it would be the way I would go also. 25KW is a lot of panels.....

The only thing I would have done differently, is to make it a two axis rack rather than fixed. It is a minor pain in the butt to keep the snow off of mine, at 45 deg. In the winter I would like to have been able to go up to 60 deg to shed the snow easier. In Iowa I imagine you don't get the wet sticky stuff we get here.

 

[MotorSeven]

Red, first I would do a survey an every appliance in your house and reduce consumption. Have you thought about heating with wood or pellet? Change every light bulb to LED(I just spent about $300 and have another $300 to go). Upgrade any old refer or freezer that is not efficient by today's standards. Raise the thermostat(a/c) & run more ceiling fans. Build a solar hot water heater and go to a instant HW heater....a regular HW tank sucks electricity 24/7 to provide about an hour a days worth of hot water...not efficient.

Bigtiller mentioned passive solar panels. Easy & cheap to build if your house faces the right way. There are many things you can do to reduce your electrical needs. Some are expensive, other's not so much.

I'm heating with wood and I opted for 4 ceiling fans instead of a/c...next summer will be the real test.

 

[Redneck in training]

I built all my own racks, which was cheaper by quite a bit, but it was time intensive. The commercial racking is super fast to put up, and for such a large system it would be the way I would go also. 25KW is a lot of panels.....

The only thing I would have done differently, is to make it a two axis rack rather than fixed. It is a minor pain in the butt to keep the snow off of mine, at 45 deg. In the winter I would like to have been able to go up to 60 deg to shed the snow easier. In Iowa I imagine you don't get the wet sticky stuff we get here.

Thanks for the suggestions. My idea is to make the racking out of wood bolted together by carriage bolts. Then on the top will be two solar rails for each column containing four panels each in landscape position. I found mounting rails 164" long for 41.85 plus shipping at CivicSolar. I was originally considering Unirac but it was way too expensive (10k without supporting structure). I will build it with fixed tilt and if there is an issue with snow accumulation I will redo it later to variable tilt. Based on "what if" using PV watts there is only marginal power gain changing the angle.

Edit:
I have redone the PV watt "what if" and found that the variable tilt has larger impact that I originally thought. I think I will still do it fixed for now but in two column sections so in the future each could be tilted indpendently.

 

[tcartwri]

Thanks for the suggestions. My idea is to make the racking out of wood bolted together by carriage bolts. Then on the top will be two solar rails for each column containing four panels each in landscape position.

That's pretty much what I wound up doing. My cross bracing is Architectural Al C channel. Structural C channel would be stronger, but you don't get the nice flat bolting surfaces.

 

[JeffInCO]

I totally understand your interest in microinverters... I, too, would be a bit apprehensive in dealing with the 400-500 volts that you can't turn off except by working at night or covering the array. It'll be even better if/when they come out with the panels with built-in microinverters. As you mentioned, I heard a few years ago that this is coming, but haven't seen anything so far.

In any case, good luck with your project... and keep us posted!

Jeff

 

[Redneck in training]

Red, first I would do a survey an every appliance in your house and reduce consumption. Have you thought about heating with wood or pellet? Change every light bulb to LED(I just spent about $300 and have another $300 to go). Upgrade any old refer or freezer that is not efficient by today's standards. Raise the thermostat(a/c) & run more ceiling fans. Build a solar hot water heater and go to a instant HW heater....a regular HW tank sucks electricity 24/7 to provide about an hour a days worth of hot water...not efficient.

Bigtiller mentioned passive solar panels. Easy & cheap to build if your house faces the right way. There are many things you can do to reduce your electrical needs. Some are expensive, other's not so much.

I'm heating with wood and I opted for 4 ceiling fans instead of a/c...next summer will be the real test.

I have done all that. Fridge is brand new high efficiency, washing machine and dryer are brand new also hi eff, freezer is OK, the most often used lights are LED, heating is geothermal but we still burn 40k kWh/year.