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Old 02-04-2017, 06:33 AM   #1
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Hartsburg , Missouri
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Angle of fixed solar panels

To optimize performance, should fixed solar panels be installed as level as possible or should they follow the contour of the roof on each side of the trailer with the idea that at least one side will have a more optimum angle for the sun? --Frank
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Old 02-04-2017, 08:01 AM   #2
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The slight difference in angle you are describing in your two alternatives will be immaterial in terms of increasing your solar gain. In summer, panels that are more or less flat on the roof are nearly optimally positioned. In winter, you need to start thinking about tilting the panels at about a 45 degree angle towards the sun (i.e., south) to maximize your solar gain.
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Old 02-04-2017, 11:47 AM   #3
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IMHO you will never get optimum exposure unless you continually reposition to "follow" the sun which is why I simply followed the roof line with mine. My landing pad at the house is shaded so I haven't been able to see how much PV my 500 Watts will produce, but even with the shade I have observed 2 AMPS on the remote.

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Old 02-04-2017, 02:56 PM   #4
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In a home system, the optimal position is mounted on a South Facing roof with a slope equal to that of the location's Latitude. Here in FL, my location of nearly 30 degrees latitude matches well my roof's 30 degree slope. This assumes the system is used year round (which may not be the case for a trailer), and is done so in order to maximize the capture as the angle of the sun changes through the seasons. It is easily verified by checking the azimuth of the sun angle through any popular astronomy site. On the Vernal and Autumnal equinoxes, the azimuth of the sun at solar noon is exactly 60 degrees above the horizon which results in a direct 90 degree perpendicular attack. Earlier and later in the day, this angle changes both from rising and setting and east to west movement of the sun. In the winter, when the sun is lowest it is well below perpendicular and it is also when the sun is higher in the sky during the summer solstice. So to sum it up, it varies! lol.

A horizontal array might work out well in the summer when the azimuth at the Solar noon is 90 degrees or more (here is FL it is greater than 90 degrees at high noon), but when trying to optimize with different angles and directional orientation is likely to be less optimal. Also consider that when camping, you are more likely to get direct sun overhead when under a canopy of trees or even in the proximity of trees.

I would go with a more aerodynamic approach if possible as the impact to your overall energy efficiency measured by carbon footprint, is probably going to depend on your mileage when towing. I suspect horizontal panels may be better, but have no evidence to prove it.

I personally opt for solar on my house, and none on my trailer, but to each their own. If I do go that route for the sake of boondocking where generators are limited, I would go with a couple of 250W panels mounted above my tonneau cover of my truck possibly with an adjustable rack to optimize when parked (directional orientation is a breeze with a truck) , coupled to Enphase microinverters (which I also use on my house), a Tesla powerwall ( ) storage unit also mounted in the truck which contains it own inverter to produce 120V output, and simply run to the trailer via the standard shore power cable. I might carry a genny to also charge the Powerwall when the sun is nonexistent. But that's just me. Rewiring the entire trailer and trying to optimize panels on a roof of a trailer which I would prefer to park in the shade, seems silly. Barking up the wrong tree. Bring your shore power with you. I can always charge the Powerwall initially from my home system for pennies.

In short, think different, and use off the shelf parts and keep it simple.
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Old 02-04-2017, 03:15 PM   #5
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One last comment, in any home solar system planning, it is generally recognized that Solar thermal gets you the most bang for the buck. A solar thermal hot water system easily pays for itself in a matter of a few years, as opposed to several for solar PV. This assumes the alternative is electric heating of hot water. The panels themselves are compact compared to the expanse of a PV system. It also requires storage and in colder climates a drainback heat exchanger. That said, I can see where Solar thermal can save significant energy in providing hot water and even heating to a trailer, and I have seen such systems for larger rigs, but often wonder why AS folks don't explore this option. I'd save my roof space for that eventuality if I really thought I wanted to go that route.
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Old 02-04-2017, 06:20 PM   #6
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I have looked at the Tesla powerwall but there seems to be a supply problem. I would like to add a powerwall to my grid tied system here in the panhandle. Do you have a source that has an inventory?

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Old 02-04-2017, 09:51 PM   #7
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Tesla power wall is grossly overpriced. Better buying battery bank, lead Acid, or AGM. Do Rea search on google for power wall and you will see the issues.
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Old 02-05-2017, 06:42 AM   #8
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Not really wanting to hijack this thread. Let's start another one for Tesla Powerwall. BTW this is the 2nd generation Powerwall 2 and the cost is significantly lower than that originally advertised (try the configurator). But to answer the q's above, you can now order directly from Tesla on their site (they are taking deposits as of today and claim installations begin this month.) What I like about them is the off the shelf natureincluding the temp management system and I am willing to pay a premium for that. Will it work in a mobile application, and will there be licensed installers willing to do that sort of install, those are topics for the other thread. I'd also like to discuss going all electric and ditch the propane bottles. This sort of weight reduction can make carrying around a couple of Powerwalls in the truck more acceptable load wise. I did notice the Tesla X Airstream Sport demo unit had done just that, but its not a camper in the true sense of the word. But now we are getting way off topic. Cheers!
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Old 02-05-2017, 07:14 AM   #9
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Wow, this thread moved away from the OP question! IMHO, the little bit of difference in how you mount fixed panels will not matter when you try to factor in seasonal, campsite and foliage variations. Where you camp and how you park is going to make a much bigger difference. Some of us are now using a combination of fixed and portable panels to get more amp-hours than fixed arrays can provide. Access to other roof mounted equipment and/or maximizing the number of roof panels may be a more important factor than flat or slightly angled.

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Old 02-05-2017, 01:34 PM   #10
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Summer Time Solar

In the USA in the summerime the sun is almost directly overhead for 8 hours or more. Therefore you really don't need to set your solar panels at an angle. In the winter, however, try to get them to face south.
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Old 02-05-2017, 02:05 PM   #11
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Regarding the use of Tesla's Powerwall for RV use:

I have been asked that question several times and here is my take on the topic:

The power wall was created for specific use IN A RESIDENTIAL OR COMMERCIAL APPLICATION. This implies that they ARE NOT constructed for the rigors of the road....namely vibration, repeated bouncing and jarring from being toted around.

They are a completely different design than the Tesla vehicle power pack and must not only be placed in a specific orientation (vertical against a wall) but must also be used with Tesla-specific peripherals.

Voltage does not match RV specifications either, which then necessitates either DC to DC converters or an inverter to create 120VAC, then a converter to produce the 12VDC. Lots of line loss and inefficiencies there.


Will it work...........perhaps for a while

If you have the available funds to all means go for it!

Just don't be disappointed by the eventual failure when you use a residential product in a mobile environment. Happens all the time........
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Old 02-05-2017, 04:48 PM   #12
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flat mounting vs angled.

I have both flat (horizontal) and angled panels on my Argosy. I mounted the first pair horizontal in the center of the roof with the idea that I would receive sun from either side. The second pair is either side of the roof vent so further outboard and looked better angled so I installed that way.

Horizontal gets sun from both sides but reduced due to sun angles. Angled gets better sun from one side and little from the other. Probably a wash from output standpoint. What I have really noticed is that when I clean them, the flat panels are always very dirty since the water stands on them while the angled panels stay much cleaner since the rain runs off and takes the dirt with it.

I am planning to change the first pair to angled at some point in the future.
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Old 02-05-2017, 05:50 PM   #13
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Although my system is quite different from most, I installed the roof panel with tilting ability on both sides. The tilting bars are marked by degrees calibrated from the roof mount. That way, you can use the solar chart for latitude based on where you are at the time though having one side of the trailer being southern is best. The portable panels are a non-issue.
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Old 02-05-2017, 06:44 PM   #14
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Yes, panels mounted flat will tent to collect surface water and dry with all that dust that has collected. They need to be washed regularly to keep producing. In northern climates, the water freezes and if it gets between the frame and the solar panel it can continue to expand that joint.
I mount my panels on a bit of an angle, just so they drain sitting water off them.

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Old 02-06-2017, 06:53 AM   #15
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Has anyone used a solar tracking system on a portable unit?
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Old 02-06-2017, 09:32 AM   #16
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To learn some of the basics about the powerwall, I found a DIY powerwall video (obviously not for an RV). I can see how the "economy of scale" has made Elon so rich! Doubt that I would construct one, but entertaining, nonetheless.
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Old 02-07-2017, 11:48 AM   #17
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That guy is pretty cool. He must be really good with a soldering iron to connect all those re cycled batteries together but $300 beats the heck out of $3,000.

He has some LifPo 85 amp hour packs for sale at $45 for those of you in Southern CA who can go to his place and pick them up. He won't ship. 😒😡

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