My +3.2kw portable array system... Solar Trailer

[TOU47]

If not desiring to mount Solar panels on a roof, (which I don't prefer for many reasons...especially with bifacials) racking can be one of the most expensive parts of the system. Most really don't allow much flexibility or adaptability let alone mobility...definitely not cheaply in time, labor or money.

So...I started with an old cheap but completely functional 17' single axle boat trailer for $300 as a foundation. For a financial & weight penalty one could easily substitute a tandem but I didn't feel it was needed for my application or goals. I then added a used DC Solar racking system that I picked up reasonably for about the same price as the raw steel. I could have easily built similar but this was faster & much less labor. I actually believe it was cheaper financially even DIY.

With the help of a great friend, I then attached it compete with the great but simple pillow block bearing pivoting system. I designed this to be removable with 6 large bolts but with permanent welded brackets. As it orginally had smaller, weaker & very dated 5x2=10 mono panels (previously removed), I relocated & reinforced the orginal bracket geometry in favor of 4-3.5'x7' bifacial panels on each side for a total of 8 for +3,120w. Panels sit plenty high to take advantage of their full bifacial capabilities & out of the snow & provide drainage. (Which I've clocked higher than 500w per for short periods but 450w for longer periods.) They are obviously easy to clean & maintain.

Basically, I set it up as TWO arrays that can be connected in series or parallel or individually. Even being 3.5'x7' panels, the way we mounted each side, it does NOT shadow each other no matter the time of day...so far. (Winter solstice may be slight?) Each side individually pivots 270 degrees...can be 100% horizontal but also 100% vertical for transport. (with locked double 1/2" pins on each side. It can be parked anywhere as the panels can pivot to what ever side is south etc. It also has tethering points on all 4 corners for anchoring.

Basically, it is meant to be a +3.2 KW portable power generation system based on the the old DC Solar designs intentionally sans the batteries & inverters etc. This was meant to be portable as well & interchangeable depending what components you want to use with it with the click of 2 cables...NOT onboard, although they could be added if desired. (DC Solar's HEAVY forklift batteries, though, dictated way too much to the platform & too little flexibility.) I can use a side by side to easily move this around.

Currently use is a single EG4 inverter & 4 EG4 batteries stored in an insulated & vented storage container with a 50 amp plug for our 5th Wheel & additional outlets...50' away. I.E. 2 simple 8 awg extension cables. Later it will be moved to our house for use while living in & finishing it. (Post frame) It will then eventually be replaced with a permanent array. Later again to a barn & or AirBnB cabins etc. It works for me & the cost & flexibility is right.

 

[rodrick]

Looks good ?

 

[koppted]

The front panels look lie the would block the panels behind them, unless the sun is directly overhead.

 

[TOU47]

The front panels look lie the would block the panels behind them, unless the sun is directly overhead.

No it doesn't even a little.

 

[Zwy]

The front panels look lie the would block the panels behind them, unless the sun is directly overhead.

If the trailer runs east/west, the sun would be higher in the sky at peak sun. Earlier and later in the day, the sun would be at an angle to the longitudinal length, thus not shading the rear panels.

 

[TOU47]

If the trailer runs east/west, the sun would be higher in the sky at peak sun. Earlier and later in the day, the sun would be at an angle to the longitudinal length, thus not shading the rear panels.

? correct. The trailer faces due south running east to west.

 

[TOU47]

At the request of my wife & after a thinking about it a bit, I decided to be more safe with my +3.2kw of power on this trailer. I added a DC disconnect switch with MC4 connectors which I probably should have had to begin with.

After shutting this switch off, I upright the 2 arrays, disconnect 2 cables & the 4 anchors (which I think functions as additional grounds?) & I can then move it. Total time less than 3 minutes. BTW I went with 8 awg for all cables to the inverter. I buried this in a conduit.

 

[Hedges]

After shutting this switch off, I upright the 2 arrays, disconnect 2 cables & the 4 anchors (which I think functions as additional grounds?) & I can then move it. Total time less than 3 minutes. BTW I went with 8 awg for all cables to the inverter. I buried this in a conduit.

Do you have a grounding conductor from frame of PV panels back to your inverter/SCC?
You should.

 

[Subdood]

If not desiring to mount Solar panels on a roof, (which I don't prefer for many reasons...especially with bifacials) racking can be one of the most expensive parts of the system. Most really don't allow much flexibility or adaptability let alone mobility...definitely not cheaply in time, labor or money.

So...I started with an old cheap but completely functional 17' single axle boat trailer for $300 as a foundation. For a financial & weight penalty one could easily substitute a tandem but I didn't feel it was needed for my application or goals. I then added a used DC Solar racking system that I picked up reasonably for about the same price as the raw steel. I could have easily built similar but this was faster & much less labor. I actually believe it was cheaper financially even DIY.

With the help of a great friend, I then attached it compete with the great but simple pillow block bearing pivoting system. I designed this to be removable with 6 large bolts but with permanent welded brackets. As it orginally had smaller, weaker & very dated 5x2=10 mono panels (previously removed), I relocated & reinforced the orginal bracket geometry in favor of 4-3.5'x7' bifacial panels on each side for a total of 8 for +3,120w. Panels sit plenty high to take advantage of their full bifacial capabilities & out of the snow & provide drainage. (Which I've clocked higher than 500w per for short periods but 450w for longer periods.) They are obviously easy to clean & maintain.

Basically, I set it up as TWO arrays that can be connected in series or parallel or individually. Even being 3.5'x7' panels, the way we mounted each side, it does NOT shadow each other no matter the time of day...so far. (Winter solstice may be slight?) Each side individually pivots 270 degrees...can be 100% horizontal but also 100% vertical for transport. (with locked double 1/2" pins on each side. It can be parked anywhere as the panels can pivot to what ever side is south etc. It also has tethering points on all 4 corners for anchoring.

Basically, it is meant to be a +3.2 KW portable power generation system based on the the old DC Solar designs intentionally sans the batteries & inverters etc. This was meant to be portable as well & interchangeable depending what components you want to use with it with the click of 2 cables...NOT onboard, although they could be added if desired. (DC Solar's HEAVY forklift batteries, though, dictated way too much to the platform & too little flexibility.) I can use a side by side to easily move this around.

Currently use is a single EG4 inverter & 4 EG4 batteries stored in an insulated & vented storage container with a 50 amp plug for our 5th Wheel & additional outlets...50' away. I.E. 2 simple 8 awg extension cables. Later it will be moved to our house for use while living in & finishing it. (Post frame) It will then eventually be replaced with a permanent array. Later again to a barn & or AirBnB cabins etc. It works for me & the cost & flexibility is right.

Very cool. Those panels look like my 445W Canadian Solar bifacials. Based on your total power rating and panel dimensions, I'm guessing they're the CS 390W's?

You said it can be tethered down, so how does it do in high winds?

 

[TOU47]

Do you have a grounding conductor from frame of PV panels back to your inverter/SCC?
You should.

I don't really understand this. The inverter & batteries are 70' away (grounded) with 8 awg PV lines buried in a sealed conduit.

 

[TOU47]

Very cool. Those panels look like my 445W Canadian Solar bifacials. Based on your total power rating and panel dimensions, I'm guessing they're the CS 390W's?

You said it can be tethered down, so how does it do in high winds?

Thank you. You are correct...CS BF 390W's. I bought them new for $0.42/W & couldn't turn them down at the time. (A friend & I bought 4 pallets though.)

Regarding wind, we have had 40-50 mph gust...it hasn't moved but I do hear the leaf springs squeaking a bit in heavy wind. Most wind is from the South/SouthWest which mostly just treats it like a spoiler...no lift. Just pushes it down more.

When I know there is going to be heavy wind from the North (much less common, mostly winter) I rotate the north array to face the north which seems to deflect any lift... take 2-3 minutes to flip array angles. Facing BOTH North & South, atleast this spring & probably the summer too, this doesn't seem to effect output as much as I would have thought.

BTW, one of the reasons I went this route was for portability but also to analize, duplicate & rework the design for my other permanent arrays after my house is built for 21kw.

 

[Hedges]

I don't really understand this. The inverter & batteries are 70' away (grounded) with 8 awg PV lines buried in a sealed conduit.

PV+ and PV- could have 150V maybe up to 600VDC between them, depending on your system.
At the equipment, PV- may have a path to ground (some equipment has GFCI fuse/breaker to ground. Some SCC connect negative to battery negative, which may be grounded.)

If leakage or fault exists between PV+ in the PV panel an panel frame, or if damaged wire shorts to frame/rack, the metal structure of PV array could carry up to +600VDC.
If you touch the frame while standing on earth, you complete the circuit. If frame is grounded, current flows through ground rod and earth, but you form a parallel connection. This would have current flowing through you. There will also be current flowing through the earth, and a voltage drop across it, "step potential".

If you run a wire, "equipment grounding conductor" from your equipment to PV frames, any fault current flows through that wire and everything is at the same potential (or just V = IR different, using R of copper wire.)

Additionally, some systems drive about 60Vrms AC common-mode on PV wires. Forum members have been shocked standing on metal ladder and touching PV frames on the roof. One had his RV with wires going to PV array on a cargo container. He noticed his dog didn't like to climb steps of RV. He found AC voltage between RV chassis and earth. Ground conductor between equipment and PV array eliminates this problem.

 

[Subdood]

Thank you. You are correct...CS BF 390W's. I bought them new for $0.42/W & couldn't turn them down at the time. (A friend & I bought 4 pallets though.)

Good score on the panels (~140 total?). That's about the price per watt I got from Santan Solar, but I only got 8 of them.

The angle adjustment intrigues me. Can you elaborate how you made that? I can see it's a central hub type mechanism. Since it's a central pivot point, do you have any flexing issues with the panels?

I considered making my ground mount adjustable, but couldn't justify the extra costs, and complexity for a few more kWh a month.

 

[TOU47]

Good score on the panels (~140 total?). That's about the price per watt I got from Santan Solar, but I only got 8 of them.

The angle adjustment intrigues me. Can you elaborate how you made that? I can see it's a central hub type mechanism. Since it's a central pivot point, do you have any flexing issues with the panels?

I considered making my ground mount adjustable, but couldn't justify the extra costs, and complexity for a few more kWh a month.

Yeah...I bought these 18 months ago. Panel prices per watt just keep getting better which is a good thing. I've seen them the same but rarely better to an average Joe since then. Mine are 3.5'x7'... what are your dimensions?

I may have been unclear...it actually has a DC Solar trailer's racking system that I bought used & then modified for my application (ONLY the rack). I bought it for all the reasons I stated but additionally I was paying for their R&D to reverse engineer for my later permanent arrays. The keys are the pillow block bearings bolted to 1/4" flat plate, the round plate with locking holes & the double 1/2" locking pins on each of the 2 arrays. Pretty simple.

Again these panels are bigger & heavier than the originals but of course more power. Hence it is not balanced/ counter balanced as they are mounted off center in relation to the center. I cut the old mounts off & repurposed the metal elsewhere & added stronger & longer metal positioned for MY panels. I also added/welded 1" angle steel to reduce flex which really doesn't exist as it has 2 panels afixed to each support with the exception of the end which is rigid by default. Hope that answers your questions. Here's a few more pictures that you may find useful from before I modified it slightly.

 

[Subdood]

Thanks for the detailed reply, that's very interesting. I don't think I've seen anything like that. A solar trailer, yes, but not like this.

Mine are 3.5'x7'... what are your dimensions?

Same size, and they weigh about 63lb each. I think yours and mine are the same CS platform. Mine are the CS3W-445MB-AG's.

 

[TOU47]

Thanks for the detailed reply, that's very interesting. I don't think I've seen anything like that. A solar trailer, yes, but not like this.


Same size, and they weigh about 63lb each. I think yours and mine are the same CS platform. Mine are the CS3W-445MB-AG's.

Your welcome, thx for your kind word; I'm pleased with it. Interestingly, I posted this a month ago with very little interest in it.

Is also interesting that the weight for both our CS panels are the same. I would have gone with your panels if a choice for the same money but these are what I have & they're paid for & they work well. BTW, I have pulled over 520 watts each on a sunny day with the ground covered in snow. Bifacial works really well if set up right!

Btw, it really is stupid simple design, relatively inexpensive project for what it is & very effective for its intended purpose. (High power, relatively light weight, simple, adjustable & mobile.) BTW, I've yet to weigh it, but I'm guessing the entire thing weighs less than 1,500#.

As noted I will be designing my ground arrays nearly identical. I think most are overly complicated & others are just a little too simple sometimes... all are too expensive if pre-fab IMHO.

I wish I could take the credit for the design for the rack but it was what I basically had in mind though. I bought the rack for about the same price the steel would have cost me to build it myself...it saved me a ton of time & money buying it already built.

The only changes I'd make if starting from scratch would be would be to center balance the panels & to widen the distance between the 2 arrays to help with potential shadowing in the winter with our larger panels. It's no problem right now & probably not 10 months out of the year. I'll let you know next December though. ?

 

[Subdood]

520W out of 390W panels is awesome, that's a third more power than the total panel rating. I betting being in a high altitude location like you are (CO), you get better exposure and more sun than here in Eastern KY. I don't know what mine can produce under ideal conditions, but I think I'll put some white sand or gravel under the array to enhance reflectivity. It's also hard to know what they can pull when I don't have a battery to charge. Total capability is 3.56kW, and the most I've been able to pull out of them is about 2.8kW on a sunny day. Just a small battery would help get that capability up, but for now I'll have to be content without one. Funds are kinda scarce right now, so gotta pay the bills and stuff..

Right now I'm concerned with what looks like some hot spot cells on the top side on some of my panels that are directly above the unistrut support rails. It may be nothing but I'm still investigating it. I posted a separate thread on the general discussion section.

Good luck with the bigger system, I'll be interested in seeing how it turns out. Have you got an idea about what inverters and batteries you're going to use?

 

[TOU47]

520W out of 390W panels is awesome, that's a third more power than the total panel rating. I betting being in a high altitude location like you are (CO), you get better exposure and more sun than here in Eastern KY. I don't know what mine can produce under ideal conditions, but I think I'll put some white sand or gravel under the array to enhance reflectivity. It's also hard to know what they can pull when I don't have a battery to charge. Total capability is 3.56kW, and the most I've been able to pull out of them is about 2.8kW on a sunny day. Just a small battery would help get that capability up, but for now I'll have to be content without one. Funds are kinda scarce right now, so gotta pay the bills and stuff..

Right now I'm concerned with what looks like some hot spot cells on the top side on some of my panels that are directly above the unistrut support rails. It may be nothing but I'm still investigating it. I posted a separate thread on the general discussion section.

Good luck with the bigger system, I'll be interested in seeing how it turns out. Have you got an idea about what inverters and batteries you're going to use?

That production high was basically perfect conditions & only for couple of hours. I have had 450 watt averages over an entire day though. So has my friend. I think the big draw for bifacials for me is if nothing else they actually can get their rating & do it easier even on overcast days. Half the key is that they need to be elevated atleast 3' above the ground at their lowest setting...all mine are.

I agree that maybe it's easier to achieve higher production here at higher altitude & sunshine. BTW I also previously had 2 panels producing for my 5th wheel's 4-12v batteries via an elevated array.

I'm into my systems way more than I care to admit but the intent is to maintain off grid status. It was much easier to justify when I was looking at a hook up bill of over $44k all totalled.

Right now with 3.2kw potential & 20.5 kwh storage I can't use all the power in a day so far. I am all EG4...6500EX & LIFEPOWER4 48v batteries (4). I have 2 inverters so far but am only using the 1 at the moment. I will likely add 1 more inverter for 3 total & 6 more batteries when the house is done. Best part is no bills & it is quiet power... no more generator if I can help it. (I do have a couple though just in case. All bets are off on the middle of winter. )

Strange on the hot spots, how did you notice them?

Thx again!

 

[Subdood]

$44k just to hook up power? That's insane. You must be in a remote location for a Poco to charge you that much. Sounds like you have quite a bit of battery backup already, plus you already have all those panels. So I guess you're having a house built then? Pretty cool to be off grid.

A genny would make sense, for redundancy sake. Before I went on this solar trip about a year ago, I considered getting about a 5kW inverter generator, but didn't want to deal with the noise, fuel running out, fumes, etc, so I went with an Ecoflow solar generator instead. It's just a 700W/720Wh unit, and is useful, but I wanted a more powerful system. We get frequent outages here in these hills, and we have several fridges and freezers, so I wanted some kind of backup. We also have had bad ice storms, but most of the outages are because of spring/summer storms.

I only noticed the hot spots on the panels yesterday as it was cloudy and not much glare on the array. They could've been there longer, but didn't notice. Kinda got me bummed out, I'm worried about my panels getting ruined, but maybe it's just a cosmetic thing. May have to reconsider my ground mount racking. Right now the panels are in portrait mode, and unistrut support rails run across underneath the panels. Could be a shadowing issue of the rails, but some on here don't think so. Output doesn't seem to be an issue, but that's hard to determine definitely. I'm still investigating.

 

[peakbagger]

I have a DC solar trailer and for someone south of the snow line with high year round sun angles, the panel mounting arrangement may have been fine but they were not a good fit for my use up north. One of the postings was about buying the DC Solar "engineering" I am unsure how much engineering was done as much as shade tree fabrication. A FYI is they used non UV rated wire for the home runs from the array to the electronics box and it should be USE 2 rated. I live in a windy zone and noticed that in windy conditions the separate rows of panels can flap a bit. The DC Solar panel mounting arrangement to the booms was also not great particularly the lower outside corners, the mounting strips are not longer enough and should be channel. My trailer and a few others show evidence of fatigue cracks on the lower corner aluminum panel rails. In my case one panel was obviously replaced and a stiffener was installed while the panel on the opposite end has a cracked rail right at the point of most stress, which I beefed up with aluminum flat stock (not ideal but probably good enough). The general concept of leaving such a big gap between the two rows of panels also was not a great idea in a snow zone as snow piles directly on top of the generator, batteries and fuel tank. DC was based in California and I expect many of the trailers are down south so snow may not be an issue but wind may be. Therefore, I modified mine by building new support posts and locating it so that both arrays are in one plane and connected to each other. I used hardware but probably could have set it up with hitch pins so that the panels could be rotated for travel. Snow either slides off or I can rake it off pretty quick and the generator and batteries are undercover. It has been two winters with this setup and I have had as much as two feet of snow on the panels that did not slide off with no issues. I do notice that the main beams between the pivot points show quite a bit of deflection when loaded with snow. Its probably within the elastic limits but if I left the systems unattended during the winter with the potential for more snow, I would probably build some temporary mid span supports. They used roller type pivot bearings, but that is not a great choice for roller bearing, and bronze bushing is cheaper and better suited. I could have got fancier and made it so the overall angle could be changed by making the new support posts adjustable, but it was complexity that I really did not need as the reflection off the snow somewhat compensates for a shallow winter angle (It should be 30 degrees in my near 45 degree latitude. Note the taller relocated posts are supported of the side rail and then a shorter post transfers the load to the lower rail. Once I attached the two sets of panels together, it really stiffened things up. Snow builds up from snow sliding and raking so I run my snowblower in front of the lower edge in the winter.

I have heard there may be DC Solar forum on Facebook but since I am not on it, I havent seen any non facebook alternatives.