Solar Panels - Residential vs RV

[1bigmess]

There are smartphone apps to help find the proper tilt for panels from day to day if you really want to get precise, and some will use the accelerometers in the phone to help you set the angle for your panels. I use one called Solar Tilt on Android.

https://play.google.com/store/apps/d...rtilt&hl=en_US

[vsheetz]

Originally Posted by Sbrownstein

Well, they are from the government and here to help you. Go to :https://pvwatts.nrel.gov/ You can build your system and get power on a month to month basis including temperatures, irradiance, angle and average weather.

Today, few tilt panels, but then most of them are on home roofs that are already tilted. It ain't worth it.

Excellent tool.

I used to size and design my residential ststem. Use it in a ongoing basis to ensure the system is working properly and meeting expectations.

I also used to model differing senarions for my RV system to assist with the design desicians. Panel tilting, time of year, etc.

[Smitty77]

Always interesting to read the different views and approach to panels. We ended up oversizing our total watts, so we would not need to tilt.

Another item to consider when determining which way to go with a panel, is the efficiency ratings, and also (And I'll get the proper term incorrect, and too lazy to refresh my memory on what the proper lingo is!), the angle of the sun to the panels. Some can start producing power at much lower angles then others. Temperatures, and the impact to a panel power production, also fit into the broader term of 'efficiency ratings'.

We went, now 7-8 years ago with House Panels from Panasonic, 48V with great overall specs. Back then, 250W was the top dawg for power output from Panasonic in that line. We mounted X's 4 to a residential racking system Spanning over our bathrooms solar dome, so an added benefit of shading for hot seasons, and less sound transfer during hail!), and X's 1 panel flat mounted to the roof. The X's 4 have zero shading from any of the coach roofing items. The X's 1 will occasionally have some shading from the Winegard Traveler. We have one other open good site on the roof, where another panel could be flat roof mounted if we ever want to. Our MidNite Classic 150 MPPT is already yielding plenty of power, and has capacity to handle another few hundred watts. (1250W total now.)

We too did Alaska, and worse then those road conditions. We travel nasty highways of California going and coming multiple times a year. Roadways bad enough that a pot hole impact caused enough damage that we had to replace two robust Michelin XZE*'s tires... So so far, zero problems with Residential vs Non Residential panels...

Best to all,
Smitty

[TajMahal]

Keep it on topic about small vs large panels like OP asked, drop the tilting issue thing!

[rarebear.nm]

Originally Posted by 757driver

For those that are interested in tilting 30 degrees in the winter in the southern USA is not quite correct. Santa Fe in the winter would be about 50 degrees (latitude (35 degrees) +15 degrees =50). Summer is your latitude -15 degrees.

We both failed to state if we measuring degrees from the horizontal or vertical. My 30 degree reference is from the vertical. I suspect you were measuring from the horizontal. In which we both about the same depending on the week in the winter. If you want to get picky about angles, it should be adjusted by about 1.5 degrees per week to adjust for changing sun angles.

Just over configure the panels and don't even think about tilt angles.

[jcussen]

Agree with many. Just put as many watts as possible on the roof. I run about 90 volts from 320 watt+ panels for over 10 years. I use unistrut with no tilting ability to secure them to coach roof. You cannot have too much solar.

[Reed Cundiff]

Wow, 2750 W of solar. That is quite enough to run an air conditioner without depleting battery suite. I am jealous.

Both solar contractor son and wife think we have quite enough solar and my protests for more panels fall on deaf and engineering exact calculations. They both note we go to high elevations in Rocky Mountains for summer.
Reed and Elaine

[757driver]

Originally Posted by rarebear.nm

We both failed to state if we measuring degrees from the horizontal or vertical. My 30 degree reference is from the vertical. I suspect you were measuring from the horizontal. In which we both about the same depending on the week in the winter. If you want to get picky about angles, it should be adjusted by about 1.5 degrees per week to adjust for changing sun angles.

Just over configure the panels and don't even think about tilt angles.

Since we are talking RV solar of course panels start out flat and horizontal and tilt from there, not vertical. Hard to get clearance on the underpasses when panels start vertical. Adjusting RV solar 1.5 degrees a week would be a chore and rather futile. Of all the tilting of panels I have seen in the desert (Yuma and Quartzsite) in the winter very few are tilted properly but every bit helps. If one is going to tilt at all might as well be close to optimum, doesn’t cost any more. With AC’s and other obstacles on my roof if I did not tilt in the winter I would not be energy self sufficient. With 1100W I regularly see 6.5kw per day energy production. One size certainly does not fit all.

[R.Wold]

I have five 315w LG residential panels on my 30’ Bay Star, flat mounted. Had six on my last coach but this one has more roof penetrations so only 5 would fit. Never any issues with mounting but you have to pay attention to your roof construction.

As mentioned earlier, with residential panels comes residential equipment, and one thing to consider is that not all inverters do well in mobile applications. Im using a Victron 24/3000 and 2 MPPT 150/35 controllers and 2/3 of a Nissan Leaf battery. And while sufficiently rugged, it is also a fairly complex and expensive system.

Your decision should be based on what you are trying to accomplish. I wanted to run my air conditioning off my solar so I went big. If you are just keeping batteries up, or even running a microwave and coffee maker, you don't need nearly as much power and could get away with a decent battery bank and 12v panels to keep them charged.

[R.Wold]

Originally Posted by CountryFit

Residential solar panels have advantages for their high capacity/high voltages/high efficiency/low costs in genenral terms. I installed 11 Sunpower 250w 42v panels on our coach in 2014, they have been working great.

Wow! Got a pic of that roof? Im working with 30’ so a lot more limited. What are you using for a battery bank and inverter?

[Searching_Ut]

I wouldn't worry about the roof. With the Be it multiple smaller panels, or one larger panel you should be able to easily distribute the weigh/wind forces on the roof adequately.



The only argument I've seen against using larger panels that made any real sense to me was that you might get a little more flexing which could result in micro fractures in the silicone cells. I would think that would be very design dependent on the individual cell, and not something your could use as a general rule. I also don't recall seeing many folks complaining about solar panel failures on the RV's.



I'd just go with what fits best configuration wise with your individual RV, budget, and how you intend to use them.

[rarebear.nm]

I've been using large commercial panels from Silfab with no problems. I agree depending on your energy needs, go for what ever will give you the most watts for the size and layout of your roof.

I would go with any of the better panel makes that provide what you are looking for. All of these large panels are designed for high wind loads already, to me that's a total non-issue if you mount them well. Flexing issues, maybe but never heard of it at least with the better makes. Flexing issues will involve the panels, how they're mounted, structure of your roof and the body as well as the frame and suspension system. Basically everything from the tires to the individual cells.

I was going to be able to use 3 large panels (350+ watts each) or 4 smaller panels for much lower wattage based on my roof's layout.

[RVGlen]

Thank you! I'm going to try to go with residential panels. I ordered a book to read up on. I did review some panels and may go with LG or Panasonic.

[CountryFit]

Originally Posted by R.Wold

Wow! Got a pic of that roof? Im working with 30’ so a lot more limited. What are you using for a battery bank and inverter?

Here you go...
2750w Solar Panels, I Made It... - iRV2 Forums

My battery is a 1200ah Lifepo4 pack, and inverter is a Magnum MS2812.