Landscape or portrait

fatheadl · December 2006

Hi all,
Is there any difference in performance when panels installed landscape or portrait?

Thanks in advance

mike95490 · December 2006

Re: Landscape or portrait

however the sludge runs off the best , or what fits your roof the best.

The panels dont care - wait I see someone selling AM panels and PM panels....

Just keep them sunny side up

BB. · December 2006

Re: Landscape or portrait

Might be a difference if you have shadows (like a drain pipe or chimney nearby)... Otherwise, it is mostly how easy to install and looks (I have panels installed both ways because of the obstructions on my roof).

If you are tilting the panels above a flat roof (or using adjustable racks), "portrait" will probably catch the wind more--so the mounts have to be stronger/bolted down better.

-Bill

Roderick · December 2006

Re: Landscape or portrait

There are two considerations I can think of. My apologies if I'm stating the obvious.

1) If one orientation allows you to avoid a shadow at some time of day, or maybe even a shadow at dawn or dusk, then that would be advantageous.

2) If using racks, the most economical mounting would seem to be a long rack, or racks, horizontally oriented. A portrait orientation for the panels would possibly allow more panels to fit on a given rack, saving a little money.

I personally would not be concerned about which orientation of panels was a stronger mounting, but maybe someone else can relate an anecdote in this area.

System2 · December 2006

Re: Landscape or portrait

I made my own pole mount rack and due to the way the panels were predrilled, I was able to save some rack weight by placing them portrait. Basically placing them portrait allowed for 4 horizontal runners while placing them landscape required 8. I also eliminated some of the length (weight) in the main cross bar that is attached to the vertical pipe. I suppose this might vary depending on if you are using angle, C-channel, or something else as the rack frame.

System2 · December 2006

Re: Landscape or portrait

One thing I've found, is that if you live in a snow area, most are better in the landscape position. That's because of the way the cells are wired in series. If mounted in portrait, the snow slides down but any remaining at the bottom, will block cells from both strings, but if in landscape, the lower side is all one string, thus the upper string still produces power.
Wayne

BB. · December 2006

Re: Landscape or portrait

Wayne,

Would that be (roughly) at 1/2 voltage and full current (two bypass diodes per panel)?

-Bill

mike95490 · December 2006

Re: Landscape or portrait

Wayne from NS Cana wrote:

One thing I've found, is that if you live in a snow area, most are better in the landscape position.

Good point.

System2 · December 2006

Re: Landscape or portrait

No, the panels I have, are 12 volts, but each has two parallel strings that run lengthwise. If one string is shaded by snow, the other still puts out full voltage, but only half the current that would be produced given no shading. Half is better than none at all while waiting for the snow to melt.
You can test yours by shading half a panel with a blanket and see how yours react.
Cheers
Wayne

Test edit

aj164 · March 2009

Re: Landscape or portrait

I have a question that relates to this old thread.

Can you mount modules with the rails running parallel to the longest dimension (landscape) of the module?

If the rails are parallel to the _short_ side, then you have 2.5 ft of module between the clamps.

If the rails are parallel to the long side, then that's about 5ft of module between clamps. I got to thinking this might not be enough strength. Anyone have modules mounted this way (landscape)?

Landscape:
-
|= (rail)
|
|= (rail)
-

Portrait
-
|
|= (rail)
|
|
|= (rail)
|
-

vtgoingsolar · December 2011

Re: Landscape or portrait

Old Thread - but seeing the first sunny after snowy days on my panels.. and poking around I discovered what everyone confirms.. Portrait panels with 3 strings of 20 cells each.. arranged in 6 long columns.. get hosed when the snow melts and gets all the way to the bottom of panel.. exposing 90% of the panel.. Still.. i get 0 watts from it (solaredge power optimizers so I can monitor them individually and see the affect exactly ).

The snow hangs up on the bottom edge of the top row of panels as well as the bottom row.. and its not anything on the roof that is stopping it as we only had a couple of inches. The edges just catch the snow as its melting.

I know winter is not the best month for power.. especially with me at 44 degree latitude and my 6 on 12 roof angle (26 degrees I believe ) .. but on a sunny day w/o snow recently I still made 15 kwh (18x240W solarworld with solaredge ) .. With snow.. and sun.. zilch.. Mounting them landscape.. would get me 2/3 power from the same panels I think at these times.. but perhaps complicates the install a bit.. not sure.. If that made it cost more $$, perhaps would never pay for itself.. Not a cloud in the sky right now.. literally a dusting the other day (but its about 20 F out and was 5F this morning so not much melting from ambient temp.. but panels in sun are melting now )

I don't even own a ladder so can't get up there to brush anything off and risk my life for $3 / day its making on the best of days now.. 30 kwh was my best day in the summer..

Just preaching to the choir here..

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Cariboocoot · December 2011

Re: Landscape or portrait

At 44 Lat your panels ought to be at 64 degrees relative to the horizon for Winter. Snow wouldn't stick to that.
This does point out the twin problem of A). mounting panels parallel with the roof regardless of angle/latitude and

. not being able to change panel angle for varying seasonal insolation.

Sometimes another word for compromise is "mistake".

Windsun · December 2011

Re: Landscape or portrait

Cariboocoot wrote: »

At 44 Lat your panels ought to be at 64 degrees relative to the horizon for Winter. Snow wouldn't stick to that.
This does point out the twin problem of A). mounting panels parallel with the roof regardless of angle/latitude and . not being able to change panel angle for varying seasonal insolation.

Sometimes another word for compromise is "mistake".

While that is true, not always so easy to change the panel angle with roof mounts

. With the price of panels being a lot lower, and the price of the mounting hardware being much higher than it was a few years ago in some cases it is now more cost efficient to go with more panels and fixed flat mounts.

Something I have noticed is that even when installed landscape, some installers will butt the panel edges with no gap between the top and bottom rows, which means that when the snow melts the upper panels drain onto the lower ones...

Cariboocoot · December 2011

Re: Landscape or portrait

Well that's another kind of mistake; obviously there needs to be some gap between upper and lower panels otherwise you run the risk of forming a secondary "panel roof". Got to be able to get rid of he snow to somewhere, no matter what orientation/angle the panels are at!

vtgoingsolar · December 2011

Re: Landscape or portrait

So Around here.. I have NEVER seen anyone mount any racks to change the angle of their panels with respect to the roof. In the summer how far off would I be with my 6 on 12 pitch roof ? I bet not very.. and since i make much more power then.. seemed like a good plan. We are also in a high wind area and I would think elevating them on racks would create quite a wing. Perhaps with the right hardware that is a non issue. If I wanted perfection, I would have gone with a tracker I suppose. I would be curious how much more harvest would be expected in a year by taking the 60+ degree angle you advise in the winter (and then spacing my panels further apart so i don't get shadows) along with some other fixed angle in the summer.

So what is the going opinion on how far apart my 2 portrait rows should be from each other ? . There is a small gap.. enough for water to run down for sure.. but not more than an inch i bet.

Back to the question.. DO many people mount them landscape to help with the snow melt and configuration of the strings in each module ? My installer never mentioned this as a consideration and has not returned my emails from more than a week ago at this point to just agree with my observation.. which there is no debate about.. blocking them across a short direction is a killer.

Cariboocoot · December 2011

Re: Landscape or portrait

You might want to look at Mac's Lab panel orientation page here: http://www.macslab.com/optsolar.html
Good explanation of angles and their effect on power through the year for different latitudes.

Way up here in the Great White North tilting the panels seasonally is almost a necessity, as the sun angle changes drastically between Summer and Winter.

Just my opinion, but the landscape/portrait difference is a matter of what fits the panels best to the roof. Shedding snow is more a question of angle and having enough gap between rows so that when it slides off the upper ones it doesn't 'bridge' the gap and end up covering the lower ones.

One of Icarus's time-honoured solutions is a bit of heat tape on the panels in just the right place to make sure everything keeps sliding until it's gone.

vtgoingsolar · December 2011

Re: Landscape or portrait

Well.. at this point I have what I have... There is a small gap between rows.. and a larger , irrelevant perhaps , gap between the modules left / right.

Could be an illusion but appears the bottom edge of the top row is slightly elevated.. on purpose perhaps ?

My angle, just like any roof mounted panels I have ever seen on a house, is whatever the roof is. 26.5 I believe. PVWatts for my situation says 4952.. If I put 36 degrees.. close to the one angle best compromise I get a whopping 4998. $10 of electricty. Net.. I think my #s are a reasonable compromise w/o going crazy.

I did see that web page recently when trying to find info on landscape vs portrait.. Good reading..

The heat tape thing.. Given the proximity of my panels to each other.. would a method of that work for me ? Where would the tape go in an ideal world ? Do I want it to melt from the bottom edge of the top row and drip down (and then freeze solid on the roof underneath in the shade ? )

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techntrek · December 2011

Re: Landscape or portrait

vtgoingsolar - I love the side-by-side photos above showing your panel snow coverage vs. their output. That is going to be a must-link-to post when I tell people (usually on other forums) how just a little shading will kill the whole panel... and they don't believe me.

I'm looking forward to real-world input on the heat tape, but my personal 2 cents would be to apply it on the lower edge of each panel. In the close-up pic above, the one that is peeking up above the panel just below it. That would put it as close as possible to the snow that is hung up on the lower lip so more of the heat would hit its target.

Cariboocoot · December 2011

Re: Landscape or portrait

I've never used the heat tape myself, but here's what Tony/icarus says about using it (quoted from another thread on keeping panels clear):

"As an alternative project, consider a semi conductor heat tape, t-stat controlled, with a timer and a photo cell. During daylight hours, if the photo cell goes dark, being covered with snow, and the t-stat says it it below freezing, the heat tape heats. A simple regimen of tape around the lower edges and perhaps the sides will quickly heat enough for the snow to slide off."

vtgoingsolar · December 2011

Re: Landscape or portrait

Thanks folks.. Its amazing how little I really knew when starting this endeavor and everyone was all smiles and sales pitches.. but the details that a good engineer would ask for, I just was lulled into complacency and did not ask .. Of course, what would I have done differently ? If I was given a choice about portrait vs landscape and told I'd get more out of them based on the way the cells are strung together.. and i could get 2/3 output with 1/3 covered.. I would have gone for it for sure I think.. I think installers just tend to be very in the box .. by the numbers.. and are not trying to be too fancy.. It's as if they are trying to pitch solar but not how to get the most out of the solar they install.

And .. all these observations are after a few dustings of snow.. Imagine if we get 3 feet as we can get.. portrait / landscape is not going to save me then.. I have no way to get up there and not sure I would want to risk the avalanche coming my way , knocking me off the ladder.. We have had an incredibly snowless winter so far so its been a non issue. It could be covered for 3 weeks and that will make me very sad.

As to heat tape.. I would think I would just make it something I turn on / off as needed, keeping it simple.. I doubt i'll do anything at this point.

techntrek · December 2011

Re: Landscape or portrait

vtgoingsolar wrote: »

As to heat tape.. I would think I would just make it something I turn on / off as needed, keeping it simple.. I doubt i'll do anything at this point.

That's what I would do. At the very least I would make the switch one of those 20-minute bathroom heat lamp timers so I could trigger it and then forget it. Would really suck to forget about a few hundred watts of heat tape for a day, or two...

vtgoingsolar · December 2011

Re: Landscape or portrait

What is the product that folks recommend for heat tape ?

rumleyfips · April 2012

Re: Landscape or portrait

I just tried one of my new panels ( Honeybee Solar, Toronto). We are in Nova Scotia and got snow 5 o5 6 times this winter. Most times it melted within 3 days.

I charged 2 batteries and one 245watt, 36voc panel ran them up from 24.6 to 30 volts at 8+ amps real quich.

Shading dropped the output to 0 amps, whether all six rows across the bottom in portrait, 2 rows along either side in landscape oe diagonally across one corner. The cheapest , easiest way seems reasonable if orientation makes no difference.

Now to decide how much space to leave between rows. Some say not much and others say leave some room to shed snow.

vtgoingsolar · April 2012

Re: Landscape or portrait

While I have not gotten up there to see if blocking along the long direction does what I think it does.. the solar panel manufacturer agreed that it would still produce power from the other strings if one string of 10 or 20 cells were blocked along that long direction.. Yet.. when blocking along the short direction.. even 2 cells of the 60 blocked at the bottom.. will knock out the entire panel due to the protect diodes. Perhaps it varies from manufacturer to manufacturer. We only got snow a few times here in Vermont (pathetic) and when we got it.. it was often around freezing so it melted quickly.. but there were a few times when a pile built up below the bottom row on the roof, leaving no where for the snow to shed as it just ran into that pile on the roof.. blocking just a little of the bottom of my portait panels and voila.. no power.. heart breaking and with no ladder or safe rake.. i could just watch it. If we had lots of snow, I would for sure get up there I guess.. I hate to let power go to waste.

I do see that many of the trackers I see around are arranged in landscape orientationso wonder why they do it that way.. .. perhaps just a better shape.

I have seen some info on panels with integrated solar hot water system integrated into the panel.. to pull head from the panels to increase output in the summer (cooling panels) and that can be circulated with warm fluid in the winter to melt the panels.. nifty idea if you ask me.. but.. i'm told that if you did all your panels this way.. you would make TOO much hot water and have no where to dump it unless you had a large use of hot water.. So perhaps only doing 6 panels would be needed for a typical home with modest usage.

An interesting idea anyway ..

BB. · April 2012

Re: Landscape or portrait

I probably would only care about landscape if you have snow that collects on the bottom of the panel and/or some sort of shading (panels blocked by panels in front/vent pipes/etc. during winter with low sun angle). Otherwise, whatever mounts best for you (my roof 1/2 are landscape and the other 1/2 are portrait just based on roof area).

-Bill

solarvic · April 2012

Re: Landscape or portrait

Now to decide how much space to leave between rows. Some say not much and others say leave some room to shed snow.[/QUOTE]
For me I kept my panels as close as I could get them. Two of the poletop racks I have were designed for 2 rows of 4 panels. So I left about 1/2 inch between each panel. If I would have left more space between them I would have only got 2 rows of 3 panels. solarvic

Windsun · April 2012

Re: Landscape or portrait

Spacing can be anywhere from 1/8" up to whatever you want. You need at least 1/8th" to 1/4" to allow for expansion and contraction. Aside from that, if the spacing is too narrow, ice can build up between the panels. On most rail mount systems, you get automatic spacing from the mounting clips. I don't recommend heat tape at all, far too difficult to get even coverage without spending as much on the tape as the panels cost.

There is no easy answer for snow - or actually the ice you get from snow melt. Usually the panels themselves heat up enough to melt it, but you have to have someplace for it to go - some horizontal mounting can create an ice dam if not installed correctly.

ggunn · April 2012

Re: Landscape or portrait

vtgoingsolar wrote: »

What is the product that folks recommend for heat tape ?

Resistance heating is pretty inefficient. Would the benefits of heat tape be enough to offset the expense of powering it?

vtmaps · April 2012

Re: Landscape or portrait

ggunn wrote: »

Resistance heating is pretty inefficient. Would the benefits of heat tape be enough to offset the expense of powering it?

I think so, if used judiciously. Over at the Midnite Solar forum there is some talk of a controller that can backfeed the panels to heat them up and melt snow. My top of pole mount does not go all the way vertical :-( and I have been home on blindingly sunny days with no solar gain (until I brush off my panels). Personally, I wouldn't heat my panels because I can brush them off. Those with inaccessible roof mount panels might gain the most from such a system.
--vtMaps

vtgoingsolar · April 2012

Re: Landscape or portrait

ggunn wrote: »

Resistance heating is pretty inefficient. Would the benefits of heat tape be enough to offset the expense of powering it?

Ive lost full days of production for a tiny bit of snow on my panels so unless heating them up is going to use say 15-10 kwh, it would be worth it.. I sure doubt it would take that amount of energy.. Heat tape on the edges might not do enough... no idea.. i doubt ill try it.. but i can't stand to see days go with no production on an otherwise sunny winter day.. A ladder and rake are in order as long as I (a) don't kill myself and (b) don't damage a panel.

jagec · April 2012

Re: Landscape or portrait

ggunn wrote: »

Resistance heating is pretty inefficient. Would the benefits of heat tape be enough to offset the expense of powering it?

Actually, resistance heating is 100% efficient.

But you're squandering a very high-value form of energy whenever you use electricity to make heat.

Landscape or portrait

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