Solar Panel Height Above Roof

[gypsydan]

I aprreciate all the comments, especially about branches. And height is only an issue if the panels are not securely attached [ground effect?], BUT is there an issue with panel placement in relation to the front or side of the RV?

The thought:  Is there an optimal distance for panel placeement at the front of the roof, or next to the roof side edge? In other words, could there be any ground effect with panels placed too close to the front of the roof (the added turbulance of wind rolling over the roof edge and creating additional pressure under the panel), or of gusts catching the panel if it too close to the RV side?

[Jack Mayer]

Printers and some other electronic components like sine wave power. Not all of them, but some of them. I'd always put in sine wave if I could afford it, but to just run a few components it is a judgment issue. For example, in our truck systems we generally put in modified sine wave systems since we just do casual use of a microwave and coffee pot.  

As to height from the sides, the biggest concern would be limbs under the panels. Any effect of aerodynamics would be so specific to the situation that it would be hard to predict. I've never seen an adverse effect from aerodynamics on raised panels....but that does not mean it could not happen.

[oldjohnt]

Dan, as  noted before regarding roof placement and tilting and wind factors, I prefer the front to be somewhat lower then the rear so wind while driving down the road is pushing more downward (plus improves drainage when parked) versus lifting the panels if the front was higher,  and I prefer the front be close to the roof as much as possible to avoid wind flow under the panels.

As far as Pure Sine Wave (PSW) versus the cheaper Modified Sine Wave (MSW closer to a square wave), I've NEVER heard a person complain their PSW wasn't operating all their devices properly while I HAVE HEARD of a MSW causing problems. Sure it costs a bit more, but its my opinion and choice in an RV with an assortment of sensitive electronics as well as general usage, PSW is the best way to go. YOUR MONEY YOUR RV YOUR CHOICE.

As far as MPPT versus the cheaper PWM solar charge controllers, I view PWM as more of a start up (how I started), often lower power, and lower voltage method versus MPPT which has advantages. 

As always a persons budget constraints are relevant and its HIS free choice, not ours

Best wishes, go for it

John T    Currently "Back home again in Indiana" but still full time in the RV having sold our farm last fall  

[gypsydan]

On 4/17/2018 at 10:41 AM, bigbillsd said:

Dan,  I put these panels on my amazon wishlist a while back so I can find them when I am ready to pull the trigger.  Two of them get you 316 watts, 12 volt allowing a PWM controller.    Unless you are powering your computer directly from the pwm controller the power will either come from the battery or an inverter.  Most folks would either be plugging their laptop into a 12v power connector or 120v outlet.   If you have the PSW interter then you are already golden without the expensive MPPT controller.  I personally power my computers  (SageTV server and a couple laptops in the MH) from 120v PSW power (or shore power if available)   I am currently dry camping on the Beach north of San Diego.    Based on this second week of dry camping I'm confident I understand how much power I use from my batteries based on info gleaned from my Trimetric Battery Monitor so I can size my own solar installation.    Just the part of figuring out how much I will get from panels lying at a slight angle on my roof.   That data is difficult to pinpoint due to so many variables,  it will be mostly trial and error.  Probably buy two of those 158 watt panels and what the actually produce then adding more if need be or just run the genny to make up the charge during the evening. 

2  each 158 watt 12v panels for around $365

Bill, Thank you for the comment. I had not seen the DMSOLAR panels. I can easily put 4 along the driver side roof, but in the beginning will only go with 2, as I don't know how long I will be keeping this coach. And, I can now use the PWM controller.

 

On 4/10/2018 at 9:37 PM, Zulu said:

You might use a variation on my PV panel install. First, I screwed down 2" wide aluminum strips to my roof. Then I attached 2" L brackets to these strips and my PV panels. 

My panels are only about 2" from the roof, but if I wanted to jack them up to 5" I'd probably just use wider L brackets.

So with my system, if you get a strong enough wind or an errant tree branch, then a good section of the roof would come off with the panels.

Thank you for this design suggestion. I like it.  I had planned on using angle iron from Home Depot with predrilled holes in them. That way I could bolt to the roof frame and easily then attach panel supports from the upright portion of angle iron. I have to study your design more closely to see how I would attach the risers to lift the panels. 

Thanks to everyone.  This is what this forum is all about.

 

[Yarome]

If my comment was taken as my personal concern over stress on your mounts or roof, my apologies. If it's a concern for you... an angle iron will certainly solidify the install.

My main intended point was using a 2 part mount and L bracket to allow for easy relocation of the risers... making it easy to play around with various heights, angles and greatly simplifies roof maintainence. IOW... you don't have to be committed to a set "plan" out of the gate.

[bigbillsd]

BTW,  I just found these Mono panels on Amazon 175 watt solar panel for $199 each.   Pretty reasonable price for a larger mono 12/18volt panel.   I also found a grape solar 180 watt for $220 from home depot.  Usually can't  get this close to $1 watt with higher wattage 12v panels.  I prefer to have fewer panels on the roof of a moving vehicle.. 🙄

-Bill  

[jcussen]

Try your local craigslist.  https://houston.craigslist.org/ele/d/355-watt-new-mono-solar/6577682498.html

[Chad Heiser]

11 hours ago, bigbillsd said:

BTW,  I just found these Mono panels on Amazon 175 watt solar panel for $199 each.   Pretty reasonable price for a larger mono 12/18volt panel.   I also found a grape solar 180 watt for $220 from home depot.  Usually can't  get this close to $1 watt with higher wattage 12v panels.  I prefer to have fewer panels on the roof of a moving vehicle.. 🙄

-Bill  

If you are paying over a $1 a watt on panels in today's market, you are paying too much.  There are lots of deals out there for good panels.  You may have to hunt a little for them, but they are there.  A year and a half ago, I bought 235 watt Canadian Solar panels for way less than $1 a watt through a liquidator.

[Yarome]

56 minutes ago, Chad Heiser said:

If you are paying over a $1 a watt on panels in today's market, you are paying too much. 

I would have to agree to disagree. Panels are not created equal and much like everything else in this world... you get what you pay for. Considering that panels are the backbone of any solar system and the very limited amount of real estate on an RV we generally have to work with... skimping on panels isn't where I would choose to save money at the expense of performance and/or durability.

Deals can be had, and a $3/watt panel doesn't necessarily mean they are worth their price tag, but the comparison of panels shouldn't stop at poly vs. mono.  

From bigbillsd's post... of those two I would take the grape solar's. Those are their "budget line" imports but rank much higher than their counterparts.

[Chad Heiser]

10 hours ago, Yarome said:

I would have to agree to disagree. Panels are not created equal and much like everything else in this world... you get what you pay for. Considering that panels are the backbone of any solar system and the very limited amount of real estate on an RV we generally have to work with... skimping on panels isn't where I would choose to save money at the expense of performance and/or durability.

Deals can be had, and a $3/watt panel doesn't necessarily mean they are worth their price tag, but the comparison of panels shouldn't stop at poly vs. mono.  

From bigbillsd's post... of those two I would take the grape solar's. Those are their "budget line" imports but rank much higher than their counterparts.

I agree that you should not skimp on the quality of the panels installed in an RV, but quality panels can be had for around $1 a watt without too much effort.  You just have to hunt around to find the best deal.  Like I said in my other post, I bought some nice Canadian Solar panels for well less than $1 a watt over a year ago and prices continue to come down (as typical with all technology) over time.  My panels were bought in bulk and I split the order with 3 other people, which was why I was able to get such a good price.  This isn't typical with most RVers trying to purchase panels, but it worked for me and allowed me to get an amazing deal.  Sometimes you just have to be creative and think outside the box when you are hunting for deals, but even buying them in small quantities can be done in the $1 a watt range.  What kills the price from most wholesalers is shipping.  Look around and find a wholesaler you can go to in your area or in your travels to avoid shipping costs and the price becomes much nicer.

[jcussen]

Agree with Chad. Link to Craigslist I posted above is for a Grid-tie system installer. He buys pallets of panels at time and usually the brand and quality the buyer wants to pay for. Any left over from an install, he sells through his ad. Last year bought some Suniva 320 watt panels off him for about 70 cents a watt. While these are not the best 21% efficiency panels, they are US made and good quality. Just need to keep your eyes open. I do remember the days when even the cheapest panels were $3 a watt.

Added bonus was that after I installed the mounting brackets on the coach,  I took it to his shop and he used a forklift to put them on the roof for me. I fastened them down and drove home and did rest of wiring necessary. 

 

[GlennWest]

24 minutes ago, jcussen said:

Agree with Chad. Link to Craigslist I posted above is for a Grid-tie system installer. He buys pallets of panels at time and usually the brand and quality the buyer wants to pay for. Any left over from an install, he sells through his ad. Last year bought some Suniva 320 watt panels off him for about 70 cents a watt. While these are not the best 21% efficiency panels, they are US made and good quality. Just need to keep your eyes open. I do remember the days when even the cheapest panels were $3 a watt.

Added bonus was that after I installed the mounting brackets on the coach,  I took it to his shop and he used a forklift to put them on the roof for me. I fastened them down and drove home and did rest of wiring necessary. 

 

Does he carry any higher voltage panels. When I go this route I will be on 48V instead of 12v

[jcussen]

9 minutes ago, GlennWest said:

Does he carry any higher voltage panels. When I go this route I will be on 48V instead of 12v

I have bought about ten 300+ watt panels off him in the last 5 years or so. They have all had VOC of at least 40 to 48 volts. If you need to charge a 48 volt battery, just run two 40 volt panels in series [80 volts] through a solar controller that has an input of at least 100 and a 48 volt output.

[GlennWest]

I may contact him then. I am not 40 miles away.

[DesertMiner]

 Not all RV roofs can handle the larger sized panels. For some only the smaller non grid tie lower  voltage panels will  fit.  Your guys make it seem  that  the larger sized panels is the only way to go solar.  Each solar panel install on a RV is its own individual installation along with its selection of panels and associated equipment including the wiring. It’s great that some folks can use the larger sized grid tie panels and get a better price per watt. Folks new to the solar experience  need to be be aware that different sized panels are available and the price per watt will vary. Most folks can’t buy a pallet of panels to get the best price. 

 

 

 

[GlennWest]

True, but I have removed front ac and patched hole. Also wide body. Soon the skylight going bye also. Be wide open up front

[jcussen]

38 minutes ago, DesertMiner said:

 Not all RV roofs can handle the larger sized panels. For some only the smaller non grid tie lower  voltage panels will  fit.  Your guys make it seem  that  the larger sized panels is the only way to go solar.  Each solar panel install on a RV is its own individual installation along with its selection of panels and associated equipment including the wiring. It’s great that some folks can use the larger sized grid tie panels and get a better price per watt. Folks new to the solar experience  need to be be aware that different sized panels are available and the price per watt will vary. Most folks can’t buy a pallet of panels to get the best price. 

Yes it is self evident that every RV will not use the same setup. When I had a truck camper, I used three 100 watt panels because that is all that would fit. If you look at the Craigslist listing I posted, you will see he is selling single 150 watt panels for $120.

Grid tie just means that panels are used to produce electricity to sell back to the power company, has nothing to do with voltage or size. The reason big panels are used on grid tie system is simplicity. For a 5000 watt system, lot easier to run wiring and mount twenty 250 watt panels than fifty 100 watt panels. The higher voltage of the big panels,[more cells] also makes it easier to use smaller wiring, You can run panels in series as long as 600 volt max is not exceeded.

http://energyinformative.org/grid-tied-off-grid-and-hybrid-solar-systems/

 

[bigbillsd]

I'm guessing everyone missed the critical words in my post. "Usually can't  get this close to $1 watt with higher wattage 12v panels."

I was not referring to cheap grid tie panels everyone else is discussing as then I would need to use a triple the cost MPPT controller to be able to use some of that higher voltage to charge my batteries.    -Bill

[jcussen]

1 hour ago, bigbillsd said:

I'm guessing everyone missed the critical words in my post. "Usually can't  get this close to $1 watt with higher wattage 12v panels."

I was not referring to cheap grid tie panels everyone else is discussing as then I would need to use a triple the cost MPPT controller to be able to use some of that higher voltage to charge my batteries.    -Bill

Bill, perhaps they exist, but have never seen a 12 volt [18 actual] panel bigger than 180 watts.  Not sure what you mean by cheap grid tie panels, but as I explained, you can use 50, or 100 watt 12 volt panels in a grid tie system if you want. The panel referenced in the Craigslist ad was 150 watt 12 volt and can be used with a PWM controller, and cost $120, so yes, less than $1 per watt. Quality can of course vary, no matter what wattage and voltage your panel is. Couple of years ago bought some Renogy flexible 100 watt panels, $240 a panel, in less than a year they had turned yellow and the plastic film on top of the panel was peeling off. Here is a bigger 12 volt panel.

https://www.youtube.com/watch?v=lD5RbvGl_M8

 

[DesertMiner]

200 watt 12 volt (18 volt) are available but it’s the upper limit. I have 175’s and 200’s   and they are working out great. I have space limitations which prevented the use of the larger panels. I still think the OP would surly benefit by going to an MPPT controller but that’s not my call. 

http://stores.ebay.com/480v-solar?_trksid=p2047675.l2563

[Yarome]

Extraordinary deals do happen, but for the "average Joe"... if I were looking to buy panels today... smallest form factor (production/sq. ft.), lightweight, durable frame, treated glass, highest efficiency and component ratings... to outfit a modestly sized rig with limited real estate... I would expect to be paying somewhere in the $1.90-$2.50/watt range.

Compromising a step down from those type... I'm still in the $1.50-$1.75/watt range.

Can you find panels for under $1/watt? Absolutely!

Where I disagreed was the statement that if you're paying more than $1/watt are you paying too much. I say "hogwash!" 🤣

IMO, long term production per square foot should be the main focus... with considerations for weight and durability playing into the equation... and lastly, how much is it going to cost you to get there (a.k.a. "compromise").

Not often considered into $/watt figures is the mounting costs. Brackets, wiring, larger c-boxes, etc... they aren't free.

A "for example", for illustration purposes: You have 1-160watt $2.25/watt panel. It's capable of higher levels of production in lower light levels and a higher overall efficiency rating. Over the course of the day It can match and likely outproduce 2-100watt $1/watt panels. So... you've basically taken up 60% more of your real estate for the same amount of production, spent 2x$1/watt for basically $2/watt to do it, and with the additional spent on another set of brackets and wiring (not to mention the additional weight and holes in your roof) are you really "ahead"?

You can certainly boast you only paid $1/watt, and that you're packing 1000watts of solar. Meanwhile, the guy next to you is only packing 640watts (for the same cost, lower weight and fewer holes in his roof), doesn't have any shading issues because he didn't have to use "marginal" areas of real estate and outproducing your 1000watts. I don't call that a "win".

Before anyone jumps down my throat... that is a general example and isn't saying anything in particular about anyone's arrays. However, I've certainly seen it first hand and only intended to spark a different train of thought when planning your solar install.

I fully realize that goes against the, "blanket every square inch you can as inexpensively as possible"... seemingly... majority school of thought. Sometimes... less is more.

I'm also not saying that it isn't worthwhile to have whatever and at whatever price point of solar on your roof. In whatever shape, size, or price point ANY solar is good solar and more than worthwhile doing.

[jcussen]

56 minutes ago, Yarome said:

Extraordinary deals do happen, but for the "average Joe"... if I were looking to buy panels today... smallest form factor (production/sq. ft.), lightweight, durable frame, treated glass, highest efficiency and component ratings... to outfit a modestly sized rig with limited real estate... I would expect to be paying somewhere in the $1.90-$2.50/watt range.

Compromising a step down from those type... I'm still in the $1.50-$1.75/watt range.

Can you find panels for under $1/watt? Absolutely!

Where I disagreed was the statement that if you're paying more than $1/watt are you paying too much. I say "hogwash!" 🤣

IMO, long term production per square foot should be the main focus... with considerations for weight and durability playing into the equation... and lastly, how much is it going to cost you to get there (a.k.a. "compromise").

Not often considered into $/watt figures is the mounting costs. Brackets, wiring, larger c-boxes, etc... they aren't free.

A "for example", for illustration purposes: You have 1-160watt $2.25/watt panel. It's capable of higher levels of production in lower light levels and a higher overall efficiency rating. Over the course of the day It can match and likely outproduce 2-100watt $1/watt panels. So... you've basically taken up 60% more of your real estate for the same amount of production, spent 2x$1/watt for basically $2/watt to do it, and with the additional spent on another set of brackets and wiring (not to mention the additional weight and holes in your roof) are you really "ahead"?

You can certainly boast you only paid $1/watt, and that you're packing 1000watts of solar. Meanwhile, the guy next to you is only packing 640watts (for the same cost, lower weight and fewer holes in his roof), doesn't have any shading issues because he didn't have to use "marginal" areas of real estate and outproducing your 1000watts. I don't call that a "win".

Before anyone jumps down my throat... that is a general example and isn't saying anything in particular about anyone's arrays. However, I've certainly seen it first hand and only intended to spark a different train of thought when planning your solar install.

I fully realize that goes against the, "blanket every square inch you can as inexpensively as possible"... seemingly... majority school of thought. Sometimes... less is more.

I'm also not saying that it isn't worthwhile to have whatever and at whatever price point of solar on your roof. In whatever shape, size, or price point ANY solar is good solar and more than worthwhile doing.

All very good points about panels, but I think the point that several of us are trying to make, is what you actually pay for a panel.  Couple of years ago was looking at  Solarworld panels. From the big panel suppliers a 250 watt panel was $450+. Did a search nationally on Craigslist, and found EXACTLY the same panel in St Louis for $275, cash and and carry. I would not presume to tell anybody that they would have to spend a certain amount to get a quality system and would not assume that a $2 per watt panel is necessarily better than a $1 per watt panel just because it cost more.

 

[Jim Gell]

I installed four 265 watt panels of the size you are planning to use.  I also needed to clear a sewer vent.  I raised mine maybe 4 inches above roof and removed the cap over the vent pipe and inserted a little copper wool to keep animals out.  I was surprised how much cooler the bedroom under our panels stays even in bright AZ sun. 

I was worried about tree limbs and wires being caught under mine, so I made a aluminum diamond plate deflector for the front edge. 

My trailer has a strong roof but I went ahead and attached my panel hardware through the roof into the rafters.  I was able to mark the location of the aluminum rafters looking at the condensation on the roof on a cool morning.  On the downside, if anything does take my panels off, the damage could be worse to the trailer. 

I designed to be able to tilt my panel, but after 3 years of use I have never needed to tilt them.  Advice from Jack Mayer, and I agree with, is that when the wind comes up to the point you should lower the panels, you are NOT going to want to go up on your roof to do it. 

Mine are not quite flat, maybe an inch lower at one end lengthwise.  It is not enough to keep the lip around my Grape panels from collecting water which can turn into little mud puddles.  I sweep dust off when I sweep off my slide roofs before we move, maybe 20X a year, and also take a wet rag and bucket and clean them well maybe 5X a year.  

 

[gypsydan]

On 5/7/2018 at 5:16 PM, Jim Gell said:

I was worried about tree limbs and wires being caught under mine, so I made a aluminum diamond plate deflector for the front edge. 

Could you send a picture of what your diamond plate looks like when attached to roof.  I would like to do the same. You had attached a picture, but it never get posted, so don't know if it was of the plate.

Thanks. 

[Darryl&Rita]

It was there, now it's gone. Jim's aero dam was similar in appearance to what you'd see on the leading edge of a roof top luggage basket. Made out of Diamond Plate, but I don't know the thickness. Probably either 1/8" or 1/4". I  should have paid more attention, when I was up there.