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diy solar

Snow on my panels is killing me

hammick

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Sep 19, 2020
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Last winter and now this winter so far have been crazy for snow. I'm on day three of generator charging because my panels are covered with crusty icy snow. The roof is too slick to get up there and even if I had a roof rake I think it's too crunchy to remove. It's too cold to spray them with water. My 9 roof mounted panels work great year round when there is no snow.

So I'm think of installing three or six panels vertical on the wall of my building. One wall faces due South and another wall due East. Maybe three of the panels on the East wall to catch the morning, winter sun. The Hughesnet satellite dish is going away in a couple weeks so I should have plenty of room for 3 or 6 panels.

Anyone ever install vertical panels for winter charging?

South facing wall: (the two 100w panels are for trickle charging vehicles, toys, tractors, etc. and work very well for that).

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East facing wall:

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WOW -- beautiful location -=- and totally awesome barn thingy ... just curious on why with so much land you did not GROUND mount these - especially with any snow issues ...

It was 87 here today so not really any help on snow removal questions ...
Vacation place in Montana that hopefully will be our retirement home. 2,400 sq ft Monitor style barn but only 800 sq. ft. is living quarters. If it becomes our permanent retirement place we will build a small house and the current living quarter will be a guest home.

In hindsight I wish we had ground mounted the panels. Last winter was the only time in five years since we built that the panels were covered in snow for a long stretch of time. But last year was the first year we kept the inverter on when the place was vacant. So they could have been covered before that and I wouldn't have really known. When I started leaving the inverter on when vacant I also configured my Schneider Conext equipment for remote monitoring.

I am installing a 16s 280ah LifePO4 battery in December so I'm thinking I could probably get away with 900 watts of panels facing South to keep the batteries charged when we aren't there and the panels get covered.

Even with a ground mount if I'm not there I would have to have somebody come by and clear the panels.

So installing panels on the South wall is the best and cheapest solution I think. Last time I had my installer add 900 watts of panels it was $1,200 Might be a little cheaper for a wall mount. Actually I could do it myself but I can take the 26% tax credit for his labor and he does a good job.

Some better shots showing why living off grid is worth it:

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DJI_0189.JPG
 
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Geez, you certainly have the space for any project you want to take on there... Great Spot !

Honestly, the gain you would get with an adjustable Ground Mount would pay you back Very Quickly. I am not talking about a tracking system as that get's mighty steep but just a rack that can be set for spring/summer/fall/winter for angle. There are many good commercial ones at fairly reasonable prices and not hard to install either.

Now I will toss an idea at you.... Assuming the Wall in Question is straight south facing (remember to orient your future house to make use of the sun (so East-West orientation) you could mount a "powered" Awning with solar panels on the building side to allow you to adjust angles. It would not be that hard provided the building structure can handle it (more than likely it can).
 
Vertical is less ideal even for winter, so some slope will help.
No need for more inverters or SCC. Just make string of same voltage as existing ones and connect in parallel.
(Assuming MPPT. For PWM, you have to stay under max current limit)
You only lose a few percent for power leaking back into the off-angle or snow-covered ones.
Peak power from the multiple string of different orientations is, to the first order, whatever the area facing sun represents.
panels at 90 degrees to each other would peak at 0.7 times what same orientation gives.
So yes, that could clip production on highest days unless you increased SCC capacity 50%. But for your winter days with snow cover, nothing lost.

Panels can be had for $0.15 to $0.50 per watt, plus shipping.
I've paid about $200 to $400 shipping for one to four pallets delivered to a freight yard; I go there with my pickup truck.
 
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Now I will toss an idea at you.... Assuming the Wall in Question is straight south facing (remember to orient your future house to make use of the sun (so East-West orientation) you could mount a "powered" Awning with solar panels on the building side to allow you to adjust angles. It would not be that hard provided the building structure can handle it (more than likely it can).

Steve I'm intrigued by the "powered" awning idea. Out building is 2x6 on slab. Built to withstand our high winds up here. 3/4" OSB on 2x6 followed by metal siding.

My panel installer doesn't like adjustable mounts because of our wind potential. However I suspect a lot of that is because he installs what he know and doesn't have an competition up here.

With a powered mount I could leave the panels vertical when we aren't here. I could also put them vertical after the sun goes down in case the winds pick up over night. We have concrete walkways on all sides of the building and like to walk the perimiter in the evening scoping for wildlife and watching the sun set. The ability to put the panels to vertical easily would be nice.

So do you have a powered mount that you recommend or is this a custom DIY thing?

Thanks.
 
How many hundred miles you live from civilization and how much do they charge per Mile to come to you?
You can get 6600W of panels installed with a 5Kw inverter for $3000 here all day long.

What about trying to find some used panels and putting them on the wall? The roof mounted panels have the warmer periods covered, wall mounting would take care of the cold months.... and add some extra Kw to the summer generation.
Put them in pairs by screwing the frames directly together then Hinge them on the wall and make a stay or prop so you can lift them when the snow has passed so you can get efficient generation in summer.

I'd definitely go for the south and east split. Making max Kwh is not about the highest peak output, it's about the best output for the longest time. For battery charging especially, getting the longest duration current is much better than the max peak current.
Solar is not very popular up here except for the off grid people that have no choice. Really only one installer in our area and he is always swamped and not quick to get back to you. He doesn't teach people how to use their systems. He sets it up and leaves basically. My neighbors who had him do their entire systems go through batteries every two or three years because they don't know how their systems work or anything about battery maintenance.

I bought all my panels from him and he did the install. He does a good job. But I wanted Schneider equipment and he only does Outback off grid. I'm glad I learned a lot about solar because I designed and installed my entire 5kw system except for the panel install. I paid about 1/3 of what he wanted for a similar Outback Radian system. I have the ability to remote monitor/configure as well as remote generator start.

Watching the sun this morning I'm not sure putting three panels East and three South makes sense. Three panels won't put out a lot of amps for charging. Six East and Six South would make sense but I don't want to drop that amount of cash until we figure out if we will build a house up here. So I think six panels facing South makes the most sense. Either at a 20 degree tilt or on an adjustable mount. But definitely on the South facing wall.

Since I will soon have a LifePO4 bank getting fully charged will no longer be an issue. My main concern is when the place is vacant. If my roof panels get covered for a month at a time six South facing panels should be able to keep the LifePO4 bank where a want it and still take care of the small loads when the place is vacant.
 
Vertical is less ideal even for winter, so some slope will help.
No need for more inverters or SCC. Just make string of same voltage as existing ones and connect in parallel.
(Assuming MPPT. For PWM, you have to stay under max current limit)
You only lose a few percent for power leaking back into the off-angle or snow-covered ones.
Peak power from the multiple string of different orientations is, to the first order, whatever the area facing sun represents.
panels at 90 degrees to each other would peak at 0.7 times what same orientation gives.
So yes, that could clip production on highest days unless you increased SCC capacity 50%. But for your winter days with snow cover, nothing lost.

Panels can be had for $0.15 to $0.50 per watt, plus shipping.
I've paid about $200 to $400 shipping for one to four pallets delivered to a freight yard; I go there with my pickup truck.
Hedges my panels are in series strings of three and then paralleled into my combiner box. The additional vertical panels would be the same. Six more panels for a total of 15 would be right at my MPPT CC max.

I'd love to know where I can get panels anywhere close to .15 per watt. That would be $135 for 900 watts. Sounds too good to be true even with shipping costs.
 
You can probably get half a dozen 300W panels from Santan solar for $1000 or less, delivered. A dozen for $1500 or less. Depending on your preference and selection.

I got four pallets, 110 SunPower 327W for about $0.35/w including delivery.

"Six more panels for a total of 15 would be right at my MPPT CC max."
Not if half of them are covered in snow!
Have you computed that considering different angles?
What is the max output current of the MPPT and what voltage battery? What spec panels?

Because MPPT generally limit output current to something they are comfortable with, can be over-paneled to the point of clipping on best days.
With 90 degree orientation between strings, e.g. 10:00 AM and 4:00 PM, 50% over-paneling won't clip at all. Seasonal angle difference isn't as large, of course.
 
You can probably get half a dozen 300W panels from Santan solar for $1000 or less, delivered. A dozen for $1500 or less. Depending on your preference and selection.

I got four pallets, 110 SunPower 327W for about $0.35/w including delivery.

"Six more panels for a total of 15 would be right at my MPPT CC max."
Not if half of them are covered in snow!
Have you computed that considering different angles?
What is the max output current of the MPPT and what voltage battery? What spec panels?

Because MPPT generally limit output current to something they are comfortable with, can be over-paneled to the point of clipping on best days.
With 90 degree orientation between strings, e.g. 10:00 AM and 4:00 PM, 50% over-paneling won't clip at all. Seasonal angle difference isn't as large, of course.
I will check out Santan Solar. Thanks!

Here are my CC and panels specs:

CC:

Maximum PV Array Voltage (Operating) 140 VDC
Maximum PV Array Open Circuit Voltage 150 VDC
Array Short Circuit Current 60 ADC maximum
Nominal Battery Voltage 12, 24, 36, 48, 60 VDC
Battery Voltage Range (Operating) 10 VDC to 80 VDC
Maximum Output Current 60 A (for all battery voltages except 60 V)
Maximum Output Power 3500 W
Auxiliary Output 5–13 V, up to 200 mA Tare Loss/Night-time Power Consumption 2.5 W Charger Regulation Method Three-stage (bulk, absorption, float) Two-stage (bulk, absorption)

Panels:

Solarworld SW285 x6
  • STC Power Rating 285W
  • PTC Power Rating 259.1W 1
  • STC Power per unit of area 15.8W/ft2 (170.0W/m2)
  • Peak Efficiency 17%
  • Power Tolerances 0%/+2%
  • Number of Cells 60
  • Nominal Voltage not applicable
  • Imp 9.2A
  • Vmp 31.3V
  • Isc 9.84A
  • Voc 39.7V
  • NOCT 46°C
  • Temp. Coefficient of Isc 0.04%/K
  • Temp. Coefficient of Power -0.41%/K
  • Temp. Coefficient of Voltage -0.119V/K
  • Series Fuse Rating 25A
  • Maximum System Voltage 1000V
Hanwha Q-cell x3

Model NumberQ.PEAK G4.1 300 BFR
STC Rating300.0 Watts
PTC Rating274.5
Open Circuit Voltage (Voc)39.76 Volts
Short Circuit Current (Isc)9.77 Amps
Frame ColorBlack
OriginKorea
Power Tolerance-3 / +3%
Module Efficiency18.0%
Area17.67 ft²
Weight41.45 lbs.
Length64.57 in.
Width39.40 in.
Height1.26 in.
 
Steve I'm intrigued by the "powered" awning idea. Out building is 2x6 on slab. Built to withstand our high winds up here. 3/4" OSB on 2x6 followed by metal siding.

My panel installer doesn't like adjustable mounts because of our wind potential. However I suspect a lot of that is because he installs what he know and doesn't have an competition up here.

With a powered mount I could leave the panels vertical when we aren't here. I could also put them vertical after the sun goes down in case the winds pick up over night. We have concrete walkways on all sides of the building and like to walk the perimiter in the evening scoping for wildlife and watching the sun set. The ability to put the panels to vertical easily would be nice.

So do you have a powered mount that you recommend or is this a custom DIY thing?

Thanks.
Your local installer is mind set & locked, while also not teaching his customers how to use & maintain their system is just Bad JuJu all around and does no one any favours. Bad Business IMO.

Your structure could likely handle something like a pair of smaller awning systems (6 panels) but you may have to add sistered studs for added support for the hinges. The concrete footing will make sure nothing goes anywhere.... I have seen DIY awning systems using motorised scissors but no commercial offerings as such. There are some which are mounted on the sides of Trailers that I have seen advertised, I imagine they would be similar.

Adjustable Racking is built just as durable as non-adjustable as well as the advanced tracking systems, they can withstand hurricanes & tornados (not all of them, granted). If you are getting that bad storms, the panels themselves would likely break before the racking, seriously.

Now I am gonna be quite plain about this. These days solar panels are CHEAP, especially for what you can get in the states.... Over Panelling is something we do in my area (Algonquin Park Canada area) for compensation purposes. To setup a rack or two with combiners that include breakers, and even an extra SCC for them, they can pick up the slack.

Santansolar has amazing deals but there are others across the states that have similar. New, New Old Stock, Used and even Grade-B (which is often blemished and not worse issues). https://store.santansolar.com/product-category/solar-panels/
 
I really don't understand why you didn't at least install the panels between the two roof levels with more slope!
At Great Falls, the optimum slope is 40°, you seem to be far from that.
That would have solved a good part of the snow problems as well.

Maybe a crazy idea, but if you catch a day when it is not that cold and back power the panels to their nominal power for an hour or two, you could get them warm enough to melt the ice?
It is perfectly safe to inject in a solar panel the same current it would produce at full load, you cannot do anything wrong.
It implies you have a DC-power supply that can provide the amps at constant current.
That might be the problem in the middle of nowhere...
 
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Maybe a crazy idea, but if you catch a day when it is not that cold and back power the panels to their nominal power for an hour or two you could get them warm enough to melt the ice?
It is perfectly safe to inject in a solar panel the same current it would produce at full load, you cannot do anything wrong.
It implies you have a power supply that can provide the amps at constant current.
That might be the problem...
Well I just purchased a 10a power supply so I can top balance my LifePO4 batteries when they arrive. It is the one Will recommends and has a constant current mode. It only goes to 30 volts so not sure if it would work.

My panels are three strings of three. Do you back power all 9 at once, each string separately or each panel separately? Can you do this when the sun is shining. Once the snow starts to melt off they will start producing. Thanks.
 
Well I just purchased a 10a power supply so I can top balance my LifePO4 batteries when they arrive. It is the one Will recommends and has a constant current mode. It only goes to 30 volts so not sure if it would work.

My panels are three strings of three. Do you back power all 9 at once, each string separately or each panel separately? Can you do this when the sun is shining. Once the snow starts to melt off they will start producing. Thanks.
Normally the battery voltage is lower than the panel voltage. So you can't put a lot of energy back to your panels from the battery alone. But if you put your (CC CV adjustable) 10 amp power supply in series with the full charged battery, you might get to the point where you can backfeed the panels with enough current/voltage to warm them up.
As said, as long as you do not exceed the rated voltage/current it's safe.
I would backfeed a string until the snow slides, then the other one...
Of course the warmer it is and the more sunshine you have, the earlier you will melt the ice.
 
Normally the battery voltage is lower than the panel voltage. So you can't put a lot of energy back to your panels from the battery alone. But if you put your (CC CV adjustable) 10 amp power supply in series with the full charged battery, you might get to the point where you can backfeed the panels with enough current/voltage to warm them up.
As said, as long as you do not exceed the rated voltage/current it's safe.
I would backfeed a string until the snow slides, then the other one...
I just came up with the same idea this morning.
If you apply Voc or Vmp to the PV string (will take Isc to do that), it will dissipate it's wattage rating, around 200 W/m^2. Maybe that will do the job. Turn off SCC first so it doesn't suck down your power.
 
I just came up with the same idea this morning.
If you apply Voc or Vmp to the PV string (will take Isc to do that), it will dissipate it's wattage rating, around 200 W/m^2. Maybe that will do the job. Turn off SCC first so it doesn't suck down your power.
You will probably need Voc+15% due to the low temperature. Watch the current to be <Imax., that is what matters.
 
You have it done industrially as well, so it should work:
Hains snow removal

With enough electrical skills, you could even build a half-automatic system based on those:
1200W buck boost module. (choose the 1200W module)
You need a double inverter powerful switch to:
a) switch the panel off from the SCC onto the output of that module
b) switch the module onto the battery.

Upon commissioning, carefully trim the CC limit to a max of 80% of your panel max current.

But before doing all that, you should increase the slope of your roof modules to 40°, which is the optimum for your latitude anyway.
 
Oh man! Is your personal hate against me blinding you at that point?
Which "inbuilt diode" are you speaking about that would prevent a back-feeding?

The almost always built-in bypass diode does not prevent a back-feeding, they prevent only a reverse voltage.
The blocking diodes are to my knowledge never built in and would have been in the OP's installation a design mistake.
Amy's tutorial about the subject...

So what?
 
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You have it done industrially as well, so it should work:
Hains snow removal
I got a better way.

Connect in parallel an identical string of PV panels. Hang them where they won't get covered in snow (e.g. the side of your "barn)
When the sun shines on them, they will rise to Vmp and MPPT SCC charges batteries.
When batteries get full, SCC stops drawing current and voltage rises to Voc. At that point, they are leaking Isc back through their own PV cells.
Except, they are in parallel with an identical set of panels. So, half of Isc leaks back through the cells, and half through the snow covered ones.
Well, not exactly 50/50 split, because different temperature. Semiconductors work by thermally excited electrons escaping the atom and then being swept along by E-field.
But some of the current will backfeed the snow covered panels.

But before doing all that, you should increase the slope of your roof modules to 40°, which is the optimum for your latitude anyway.
At present tilt, not much tendency to slide.
At 40 degree tilt, if bottom edge on roof rather than being ground-mounted well above snow, will slide until it piles up, won't clear panel.
Snow coming off the roof acts like stalactite/stalagmites. once snow closes the gap this self-clearing won't progress very well.

1603633789572.png
 
Can someone link to a vid or creditable paper of batteries being linked to normal Household type panels discharging back into them via direct connection?
I do not believe it can happen unless the panels are some cheap junk without inbuilt diodes or there is some sort of controller that gets around the Diodes by using an AC wave form to work on the half wave or a higher frequency than their typical clamping time.

I would really like to see a demonstration of a quality panel Rather than some 100W ebay crap) direct linked to a battery(s) backfeeding it before I'd believe it.
A PV panel sized to charge battery won't get backfed except at a very low current. That would accelerate draining battery.
If you connect a nominally 12V (approximately 20 Voc) panel to a 12V battery, when sitting at 13.6V or whatever fully charged battery shows, that is way down from Voc.
Backfeed would be (at most) the difference between Isc of panel, and current at 13.6V on the IV curve.

If you connected the same 20 Voc panel to a 24V battery it would backfeed well in excess of Isc. The photodiode's exponential curve would go to a massive current, so resistance would be the limiting factor.

A photocell isn't a reverse-biased diode. It is a forward-biased diode.

On this IV curve:


Note how much lower output current is at 13.6V than at zero volts. The difference is an upper limit on what backfeed current I would expect. But most of that voltage difference is probably from series resistance, not from the photodiode. So actual backfeed will be much less. (Use that resistance to calculate how much current a 24V battery would backfeed into a 12V panel.)
 
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