How high is too high for mounting solar panels? - RV-Dreams Community Forum

Sushidog · RV-Dreams Family Member

How high is too high for mounting solar panels?

Alie and Jims Carrilite · RV-Dreams Family Member

Here's the smart a&& answer, as long as their under 13'6" high, no issue.
The other answer would be to consider the additional wind load. Not only moving the panels higher into the slipstream, but also the panels acting as a wing and wanting to pull upward on the roof. With the correct bracing it could be done though. Another thought is roof maintenance. If you need to replace a vent or re caulk a seam or opening somewhere, would a panel have to be removed to do it. Just thoughts.

Sushidog · RV-Dreams Family Member

Thanks for the reply, Alie and Jim. Since I will only go at most an inch higher than the roof mounted AC unit (maybe 11' 6") it will still be a much lower than a typical fifth wheel. Good idea about vent cover replacement, caulking or AC servicing. Yes, more than likely a panel will have to be removed to do so - 8 bolts to be removed and reinstalled/panel, as I would leave the brackets attached to the roof.

I think the best idea is probably a compromise - to mount the panels about 4" off the roof, to clear the plumbing and shower vents (which usually rise about 3") this would allow more compact panel placement, while still allowing for plenty of cooling air underneath. It would also reduce (though not eliminate) the length of shadows thrown by the AC and vents, allowing closer placement to these items. Life is full of compromises. If I do this, I don't think I will have a problem finding room for 5 panels, (which, according to my plans is what I feel I need), but 6 would be a challenge. I'm just trying to think 20+ yrs. down the road when the panels are only producing 80% of their rated output. Of course by then, solar panels will have a much higher efficiency and I'm sure the price will drop too, making removing the old units and upgrading them with then current technology a better choice than overbuying now (saving about $350 and 60 lbs. too.)

Chip

A-S Travelers · RV-Dreams Family Member

How many watts of solar and how many amp hours of battery are you planning for? With 5 or 6 large solar panels and the required batteries, will that overload the max weight of of the travel trailer?

Sushidog · RV-Dreams Family Member

Good questions, A-S Travelers.

I'm planning on around 2,000 watts of solar panels. If I use 5 of these high-efficiency 435 watt panels: sunelec.com/solar-panels/sun-435w-modules-grade-b.html at 56 lbs each, this equals 280lbs. or around 310lbs. or so on my roof with brackets and wires. I will use 8 - GC-2 type golf cart batteries, wired in series for 48 volts, (which is what my high efficiency HSAC-12H/C heat pump will require www.geinnovations.net/Specifications.html ) According to the literature, this amount of solar and batteries should be sufficient to run the AC for 8-9 hrs. at night (I'll have about 110 usable AH at 48v) and about 16-18 hrs/day total from the solar panels - though I don't plan to run the AC anywhere near that much leaving sufficient power available for other 12v uses. These batteries weigh about 66lb each for a total of 528 lbs. When the weight of the heat pump (99lbs), charge controller (10lbs), inverter charger (38lbs) and cabling, fuses, junction boxes, monitor, 48v-12v DC converter, etc. (65lbs) are added this gives a total system weight of around 1,050 lbs.

So for planning purposes, I'm budgeting for around 1,100 lbs. added weight. This means I'm looking for a TT or toy hauler with at least 4,000 lbs. CCC, (5,000 lbs. would be ideal) like this one: www.forestriverinc.com/ToyHaulerTravelTrailers/WorkandPlay/default.aspx
Another option is to find a TT with around 3,000lbs CCC (like a Sprinter 331RLS) and swap out the 5,000 lb. axles/15" wheels with a pair of 6,000 lb. ones with 16" wheels. I plan or locating the batteries (the heaviest part of the system) directly over the axles, or at least as close as possible to minimize frame stress. If choosing a front bedroom model TT I will mount the AC on the tongue. If A rear bedroom model is selected I will move the spare tire to offset at least some of the 99lbs added to the rear of the TT.

A system like this will be expensive, (about $6k) but its payback should be at around 2 years of use (12 months at $500/mo.) in monthly CG/RV park fees + electricity savings, not to mention the main benefit of being totally grid/CG independent (not being crammed, awning-to-awning and slide-to-slide into RV parks and CGs). Assuming I get around 550, 50% cycles from my batteries (What Arizona Wind and Sun suggests is a typical golf cart battery's average life) and I use them daily for an average of 6 months/yr. this means they will last around 3 years before needing replacement. I may then switch to 8 Rolls/Surrette S-550 batteries (depending on my finances) which have twice the capacity (and thrice the life) with a 456lb additional weight penalty (though at a premium price), allowing me to run my back-up EU2000 generator less on low sun days. These will capture more of the energy my panels produce too, thus matching with them better (but will add another $1,900 to the system price.) Plus, I've been told to buy a cheap set of batteries to learn on before getting your good ones, to avoid making costly mistakes which may ruin them prematurely.

Chip

-- Edited by Sushidog on Monday 29th of December 2014 01:16:15 PM

Technomadia · RV-Dreams Family Member

That will be quite the impressive setup!

We're running for our first extended off-grid time with our new 1400w setup (800w on the roof and 600w on the ground) paired with our 500AH 12v lithium battery setup.

We're on day 12 with shorter winter days, and finding we have more energy than we know what to do with during most days. We're all electric (fridge, cooking, etc.) and even with running both our big computer monitors all day long and doing outdoor movie nights off our projector - it's quite abundant. So 2000w with your ample batteries will give you a lot of leeway to not worry about things like tilting or getting through cloudy days or temperature variations... should be really sweet!

As far as the mounting and panels, one word of potential caution AMSolar gave us in regards to larger panels is the potential for more flex in them while in motion.. and it potentially harming the panels over time. They've found the smaller panels (100w and 160w) tend to do better over time for in motion RV use. Don't think they have anything in writing that I can direct you to, but might be a potential point of consideration in your design.

- Cherie

Sushidog · RV-Dreams Family Member

Thanks for the info, Cherie. I guess I'll have to make sure they are well supported at multiple points, as I can't see putting 20+ smaller panels on my roof. I think the brackets, wiring an added weight, not to mention the sq footage of roof space required would be undoable. A typical 100 watt panel weighs around 21lbs each. Add the weight of all the wire, connection boxes, etc. and the equivalent wattage to what I'm considering would weigh in around 500 lbs and take up about 175 sq. ft. of roof space to make 2,100 watts. The panels I referenced only take up 115 sq ft of roof and make 2,175 watts. It's a good thing Sun panels come with a 10 yr product warranty and a 25 yr power output warranty. If flexing during travel does damage them I'm sure it will do so during the first 10 years of use. Here's the specs on these fine panels: sunelec.com/datasheet-library/download/sun/ds-e20-series-435-solar-panel-datasheet(2).pdf

Those lithium batteries sure are sweet and would resolve the weight issue, but I'm afraid to ask how much those lithiums set you back. Plus I would probably need 2 banks that size to match the usable capacity of the low-tech (I prefer "mature technology") Surrettes. Your wonderful videos and informative Blog has inspired my solar ambitions. Thanks or your fine work.

Chip

The Junkman · RV-Dreams Family Member

Boondocking sounds like a cost effective way to go.. and while I don't mind paying for the electric.. I would love some extra space..

Just curious.. Where could I boondock in the fort myers .. or ft myers beach.. or Naples area?

Is there a website for sites?

BiggarView · RV-Dreams Family Member

Chip, just a thought... If you fashioned some kind of fairing that attached at the front of the trailer to help guide airflow around the panels that might mitigate the tendency for the panels to act like a wing.

2k watts on a TT... interesting engineering challenge. confuse smile

TRAILERKING · RV-Dreams Family Member

You're going to put all that on your Little 2006 Aliner XLE???

Technomadia · RV-Dreams Family Member

Lithium isn't as expensive as you might think and can have a lower lifetime cost for those who anticipate lots of cycles .. especially if you're willing to build your own bank from cells (like we did.. we paid around $3k for our 500AH, which is safely usable to 20% or lower DoD and doesn't suffer Puekert's Loss). There are other options on the market too... we right now have Balqon Energy on our radar, which offers built banks too, and in larger sizes.

Our full series on lithium at http://www.technomadia.com/lithium

Oh, and the GS100 panels like we installed on our roof weigh only 14.5lbs at 18.3% efficiency. AMSolar also offers the GO160 (160w w at 25.5 lbs).

-- Edited by Technomadia on Monday 29th of December 2014 11:01:33 PM

-- Edited by Technomadia on Monday 29th of December 2014 11:05:06 PM

Sushidog · RV-Dreams Family Member

TRAILERKING wrote:
You're going to put all that on your Little 2006 Aliner XLE???

You're a funny guy, Trailerking!

I recently bought my tow truck (cause I found one for a great deal - $11k for a 6.4l F-250 in great shape) but haven't decided on my TT just yet, as I still have about 3 1/2 years to go before I retire and outfit my rig to go FT.

As to the fairing idea, Biggaview, I plan on building a tall truck topper (to carry a couple of small motorbikes with us) and extending foldable aerodynamic wind diverters on the sides and top of the topper to direct air around the TT. I will be making these wind deflectors out of lightweight Coroplast with air tabs on the edges to help ease the air stream over and around the camper. I also plan on adding a tail cone made from Coroplast, similar to what's seen on some big rigs these days to also reduce drag. I may well add a small Coroplast diverter to the leading edge of the solar panels on a 45 degree angle, or quarter a plastic pipe longitudinally to present a rounded surface, both front and back as an air dam to further reducing drag.

Junkman there are many sources of boondocking sites available. Unfortunately most are available out west.

Here's a good site: https://www.boondockerswelcome.com/ and a search listing of 3 boondocking locations in the Ft. Myers/Naples area offered by members: https://www.boondockerswelcome.com//SearchLocationResults/26.14204%2C-81.79481_100/20%2B25%2B30%2B35%2B40%2B100/all/all/all/all Pay close attention to length restrictions as the one by Punta Gorda, FL is the only one that will fit your rig.

There are a couple of boondocking sites in the Osceola National Forest USFS - near Lake City, FL. Check them out here: http://www.boondocking.org/poi/search.aspx

Here's an article with a bunk of great links: http://roadtreking.com/apps-websites-help-find-perfect-boondocking-spot/

BTW, I found someone that has a small trailer that they are FTing in with a rack mounting their panels above their 2 rooftop vents (about the height of a rooftop ac unit). It's AKA Bob from the Vandweller's forum.

Here's a pic to give you an idea what I'm talking about: And a link to a good boondocking article there with a couple more shots of his solar set-up: http://www.cheaprvliving.com/blog/finding-boondocking-sites-part-1/

Great ideas guys, keep 'em coming!

The Junkman · RV-Dreams Family Member

Thanks for the links.. Yea, I knew you can park about anywhere in the desert.. I've seen them in very remote places as I was gold prospecting out there.. Kinda cool , for a bit.

Right side of the country .. looks like you need a very small rig.. to travel and boondock regularly.

Looks like I'll save the boondocking for the left coast. Will check out those sites though.. if they can fit, and are remote enough while still in reach of cities, Maybe I'll check one out.

thanks

Sushidog · RV-Dreams Family Member

Thanks for the info on the Lithiums, Cherie and Chris. So 400 usable AH (at 12v) costs $3k, that equals a 100ah 48v battery bank. Of course comparing them to a $700 bank of 8, GC-2 golf cart batteries yielding the same usable 100AH is meaningless, as they have entirely different properties and a much longer life. However comparing them to a $2,600 bank of 8 of the more expensive, yet longer lived and deeper cycling Rolls/Surrette S-550s might be a little closer, as they are not as affected by Peukert as a "normal" RV deep cycle battery (they are essentially repurposed fork lift batteries). If I only cycle them down 50% for longer life of 1500 cycles, a 428ah (at 48v) battery bank will yield 214ah (up to 300ah if occasionally brought down to 30% charge - for a 1000 cycle life, according to their literature.) So 200 usable AH (at 48v) in LiFpo4 will cost $6k and 300ah will be $9k. I'm sure the lithiums will last even longer than 1,500 cycles, but one still has to get over the hump of affordability. Besides, it's going to be a tough sell to convince my DW (even if I could come up with that much scratch all at once) that my solar ac/heat boondocking system will cost almost as much as the travel trailer it's going on. Now if the price drops by 1/2 over the next 7 years, (a distinct possibility) when I'm ready to upgrade from my first set of GC-2s to the S-550s they will definitely be on my radar (though I realize they will not be just a drop in mod.)

Thanks for the info on the smaller 18%+ efficiency solar panels. Thirteen 160 watt panels will get me 2080 watts for only 331 lbs, under 400 lbs when the mounting hardware, wires and junction boxes are taken into account. Plus I have the added price of those items, the added panel price and the added roof area they will occupy. Plus the price of those GO160s from AM Solar are as much as the Sun 435 watt panels from Sun Electric (If I buy them in a pallet of 20)! $300 for a 160 watt panel is a little pricy. Here's some great panel prices that change weekly: sunelec.com/ Of course I'll need to share the purchase with others, (as I only need 5) say at a solar install rally. Or I could buy a few leftovers from a residential roof install (sometimes you can get a great deal on remnants, as the solar contractor just wants to get out from under them, as he makes his money on installs, not individual panel sales. I'm sure that by the time I'm ready to buy, the prices will drop even more, as they seem to be falling almost monthly with their efficiency going up as well. I'd love it if 3d solar technology is ever developed as it will be perfect for flat panel mounting, capturing sun for more hours a day, driving real world output through the roof. www.solar3d.com/technology.php

Chip

Jack Mayer · RV-Dreams Family Member

Chip, I did not study all the details in the above thread, so I'm sorry if I cover something you already considered or was in the details above....My opinions are below. They are simply MY opinions, and should be taken as such.

You can rack above roof vents and most skylights without issue, or you can change out the vents to low profiled ones. I'd consider long and hard before racking above AC units. That is awfully high and wind load and tree branches are going to be SERIOUS issues to address. I'm not saying it is not possible, but it sure does complicate stuff. Also, Flex of the racking system is a serious consideration. As is attachment to the roof. I'd be inclined to attach at the roof edges and build a superstucture based on edge connect only....But that assumes you have enough structure in the roof to do it. MOST RV ROOFS DO NOT. I cannot stress this enough. MOST roofs will not allow a good superstructure above it without serious attachment consideration. On my NH I can go edge to edge with just a passive support in the middle. But the construction of a NH is totally different than most RV roofs.

The price of LFP or similar "lithium" batteries now seems to be about the same as AGM. In your scenario I'd be looking at the Lithium.....Take a look at what Starlight Solar sells to start with. The performance characteristics of lithium on a system as large and sophisticated and pricey as what you are building is where I would want to start in the design process. If I HAD TO, I'd back off to AGM. But I would not consider flooded cell unless forced to. I would not start there.

I'll be interested in where you end up with the completed system. It will be interesting. There are not many mobile systems that large. I know of one that has 3000 watts on a large trailer....but nothing I know of is any larger.....They are running a 24 volt system of AGM batteries...because the 48/12 volt converters were not available when they built and they did not want to build a custom setup. And they did not want to tap the bank for the voltage reduction....that is a BAD idea.

I'm currently running 1220 watts on a 12 volt system with 1200 AH of AGMs. That is about as large as I'd go on a 12 volt system. For various technical reasons you likely appreciate. My next system will likely be 48 volts. BTW, what DC/DC converter are you using for 12 volts? Custom?

Sushidog · RV-Dreams Family Member

Thanks for the reply, Jack.

There will be enough roof space without going over the AC as I'm planning on getting a trailer with a single roof mounted AC unit and will be utilizing a mini-split for my off-grid AC which does not require roof mounting. The structural integrity of the roof will be a major factor in selecting my travel trailer. This is one of the reasons that I am considering a work & play series toy hauler with a one piece aluminum roof, like the 30WRS model. Removing and reinstalling such a large solar system every 10 years when the rubber roof needs to be redone sounds like a PITA that I would like to avoid too. Forest River just announced a couple new, larger Work and Play models, but the specs are not out yet and I'm afraid they will be too heavy for my F-250.

I went to the Starlite Solar website, but they don't give any prices on their products. I still have a few years before I will be buying and a lot could happen to battery prices in the meantime that would make lithiums more affordable. I would need 8 of those 200ah, 12v battery banks to roughly equal the output of a $2,600 bank of 8, S-550 Rolls batteries. Sure they are only 40% the weight and may last twice as long, but I still need to be able to afford them. If I delay buying my permanent bank for 7 years, the question is how much more affordable will they be? Will they start to approach the price of the S-550s? Or will another, more affordable technology be available by then? Time will tell.

As far as 48v-12v DC converters, I was thinking of using something like this on low wattage circuits, like LED lights, fans, water pump and fridge, as they are cheap and over 90% efficient. www.ebay.com/itm/DC-DC-Converter-Voltage-Reducer-Regulator-48V-Step-Down-to-12V-10A-120W-DC-to-DC-/110773551304 and using something like this for heavy current draw: www.ebay.com/itm/DC-48V-to-12V-20A-240W-STEP-DOWN-DC-DC-Power-Converter-Regulator-NEW-/330844607241 It is less efficient, but supports 20 amps for heater blower motor and slide-out circuits. If one had an unusually heavy power draw requirement, a couple of these cheap 20 amp converters could be used in parallel. Sure there are better, more efficient units, but they are not worth the added expense for at best a 1-2% gain in efficiency. Probably over 90% of the power I will be drawing from my batteries both from my power hungry heat pump and inverter will run on 48v DC, so straining for that last percentage of efficiency on low current draw items is expensive and futile. IMHO

Chip

Jack Mayer · RV-Dreams Family Member

The DC converters you list may work for your applications. But be sure that your current draw is coverered. Some leveler leg and slide motors draw far more than the power listed there.

If you are looking 7 years from now,then all bets are off and I would not evne bother researching battery technology at the present time. It will all be different then.

Sushidog · RV-Dreams Family Member

Thanks, Jack.

Yes I will be getting my trailer and solar system in 3-3 1/2 years with a set of cheap "learner" GC-2 batteries with my "permanent" replacements to come perhaps 3 years later when the first ones expire. I can't afford everything all at once. I'll be stretching as it is. This research may be a little early, but my selection of trailer, its CCC, roof construction, etc. (my major expense) depends on the size and configuration of my "off road energy system" as I want to integrate the entire concept into my ultimate FT boondocking TT rather than just piecemealing everything together, hoping things work out for the best. My DW thinks I'm a little anally retentive when it comes to major purchases. It took me over 2 years to research my last new car, however 6 years later with 300,000 miles on the clock with nary a bit of trouble it is still going strong. I hope I'll have the same "luck" with my FTing rig.

At one point I even considered integrating about 400 watts of solar panels into the roof of the custom truck topper I am building, (so I could move the truck and orient it to capture more sun - especially if my TT is parked under a shade), but I discarded the idea as unnecessary and cumbersome, as there would be times when the truck is separated from the trailer (containing the house batteries), usually in daylight hours, so no charging could be accomplished. The obvious solution is just not to park my TT in the shade unless I have hook-ups (or am willing to burn some fuel in my little generator - which I'm sure will be unavoidable from time to time.) I have a small genny now that I use to run the little AC and charge the battery in my Aliner, but will be purchasing a better EU2000 Honda as a back-up when I FT. Interestingly its 1,600 watt output will run the 12,000 BTU heat pump (in both cooling and heating mode) and still charge the batteries (much like my little 1,200/1,500 watt cheapo genny does for my Aliner now.) The specs of my planned AC says it only uses 560 watts in cooling mode and 600 watts in heating mode, so even after suffering the inefficiencies of an inverter charger, an EU2000 would still be able to put 17+ amps into my 48v battery bank when the sun doesn't shine and the heat pump is running, giving me a little over an hour of night time cooling or heating for each hour of genny runtime, even with the AC/heat running during the day - at least on paper. Well see how well this works when put in practice - unless someone here beats me to it. ;)

Chip

HighwayRanger · RV-Dreams Family Member

This thread is timed perfectly, as I'm wondering what the solar mounting situation might be on the currently popular diesel pusher motorhomes that use the Girard awning "rail" above each side of the coach, full length. See my avatar for a picture. With these awning rails (in which there is a dummy duplicate look rail along the driver side) you cannot see the A/C shrouds from the ground. These rails would seem to create a large and continuous shade problem for people with solar panels on normal mounts. I would think that you would need to use taller than normal mounting brackets to get the panels up higher, near the height of the awning rails. Any thoughts? Jack?

Thanks,

Roy

-- Edited by HighwayRanger on Wednesday 20th of May 2015 07:23:10 PM

-- Edited by HighwayRanger on Wednesday 20th of May 2015 07:23:34 PM

LarryW21 · RV-Dreams Family Member

All the miles I had driven along so many routes and not once spotted a "blown off" solar panel. All my fellow RVers with solar that I've talked with and not a one ever said they had a panel blow off...glued, screwed or glued and screwed.

I'm not "sold" on your TT being cooler by mounting the panels at four or six inches above the roof rather than 2 inches. Any studies on this?

-- Edited by LarryW21 on Friday 7th of September 2018 11:57:54 AM

Howard · Host

Thread is being closed. It was started and ended in 2015. It was revived today by a spammer who has since been deleted and banned.