Snow on my panels is killing me

[100kwh-hunter]

You could adapt this to a pressure tank to apply de-icing fluid!

24' Telescoping Wand

Would RV antifreeze work as a de-icer?

Why a pressure tank? go to a car scrap yard and you will find all the parts needed, incl tank electronic pumps hoses and nozzles even a good lead acid cell if wanted/needed...sorry did not mean to be rude

 

[hammick]

OP here. We were doing fine until about two weeks ago. I've been remotely staring my generator for over 10 days to keep the batteries above 60%. I spent all my time during the 45 days were were up over XMAS installing my LifePO4 bank. Didn't have time to address my panel/snow problem. Yesterday my neighbor spend about 2 hours in -17 degree weather clearing my panels. She got five of them partially cleared. Yesterday I was getting 4 -5 amps of charging and was happy. Well the wind covered them overnight and I'm not going to have her do any more clearing. I'll ask her to switch out my aux diesel tank so I can keep charging with the Genset.

So I have to get this figured out and will head up in March to install some South facing panels.

When we aren't there I can get by with between 7 - 10 charging amps for now. What size panels do I need to get that assuming they are completely vertical?

Or if I am willing to spend hundreds more could I install two of these Panasonic 340w panels in parallel to get approx 9 amps of charging?

Panasonic 340W Solar Panel 96 cell VBHN340SA17 Monocrystalline White - A1 Solar Store

Panasonic 340W VBHN340SA17 Solar Panel 96-cell combines great aesthetics and efficiency with proven reliability | Reviews, pictures - A1 Solar Store

a1solarstore.com

Can I skip using a combiner box for now and just put the sting on a breaker in my Midnight Solar box. The combiner box for my roof panels is not at all ideally located for wiring in the wall mounted string. I'd put in a nice service loop so I can install an additional combiner box this summer when it's warm and I have the time.

Thanks and let's please keep my thread about vertical panels instead of ideas on how to melt the snow. I appreciate all the ideas to melt but I don't think any are practical when I am 1,200 miles away. Hell a snow rake isn't proving to be very practical.

 

[Hedges]

Or if I am willing to spend hundreds more could I install two of these Panasonic 340w panels in parallel to get approx 9 amps of charging?

Panasonic 340W Solar Panel 96 cell VBHN340SA17 Monocrystalline White - A1 Solar Store

Panasonic 340W VBHN340SA17 Solar Panel 96-cell combines great aesthetics and efficiency with proven reliability | Reviews, pictures - A1 Solar Store

a1solarstore.com

No reason to spend $1/watt. For the $730 you'd pay for two of those panels, you could get several times the wattage from SanTan, truck shipping of a pallet to freight terminal included. Or, locate panels within driving distance. You could probably get 2500W of panels from Santan, delivered.

 

[hammick]

No reason to spend $1/watt. For the $730 you'd pay for two of those panels, you could get several times the wattage from SanTan, truck shipping of a pallet to freight terminal included. Or, locate panels within driving distance. You could probably get 2500W of panels from Santan, delivered.

Thanks Hedges. Any guess what charging amps 750 watts of the cheap Santan Panels would give me. I'm guessing around 5 amps. Assume vertical mount and full low southern sun. I'm trying to put a bandaid on this problem until summer.

Thanks.

 

[Hedges]

I forget what your voltage is.
In cool weather, probably get 90% of STC watts so close to 700 watts from 750W (STC) of panels.
What does insolation chart show, maybe 2 hours effective?
So 1400 Wh, which would be 100 Ah into a "12V" battery at 14V, 50 Ah into 24V battery, 25 Ah into 48V battery.
Assuming MPPT charger.

With SanTan panels $50 each for 250W, and shipping a pallet $100 to $200, probably get more than just 3 panels. You can get an extra MPPT charge controller too if needed.

 

[hammick]

I forget what your voltage is.
In cool weather, probably get 90% of STC watts so close to 700 watts from 750W (STC) of panels.
What does insolation chart show, maybe 2 hours effective?
So 1400 Wh, which would be 100 Ah into a "12V" battery at 14V, 50 Ah into 24V battery, 25 Ah into 48V battery.
Assuming MPPT charger.

With SanTan panels $50 each for 250W, and shipping a pallet $100 to $200, probably get more than just 3 panels. You can get an extra MPPT charge controller too if needed.

I'm 48 volts 16s 280ah Lishen bank. Sometimes my eyes glaze over trying to size solar panels. I found the midnight solar string sizing calculator. I was overthinking this. Charging amps is as simple as total watts divided by charging volts I guess. So 750/55 = 13.6 amps Obviously this is best case scenario which I will not see with vertical panels.

I need to measure but maybe I will do three of the 350 watt panels which are $100 each. 19 amps charging. Claim to be installed but never powered. No manufactures warranty (just 1 year Santan warranty) but I'm guessing those warranties are useless anyway.

 

[MisterSandals]

I need to measure but maybe I will do three of the 350 watt panels which are $100 each. 19 amps charging.

What is there to measure? The specs for the panel should be on the back of the panel.
What do you mean "19 amps charging"? Are you referring to the panel amperage? That too is on the panel label.

 

[hammick]

What is there to measure? The specs for the panel should be on the back of the panel.
What do you mean "19 amps charging"? Are you referring to the panel amperage? That too is on the panel label.

19 amps is what I have calculated will going to my batteries with three 350 watt panels in series. Obviously I will see less since my inverter is powering light loads when I'm not there and the panels won't be at the ideal angle.

I can't just add the maximum power current of each panel, right? That would be 27 amps.

My math for charging amps is 1050 watts (three panels) divided by 55.4 volts (my bulk charging voltage) = 19.3 amps

 

[MisterSandals]

19 amps is what the Midnight Solar calculator says

Okay.

(350w x 3) / 55v = 19a

 

[GregE]

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:

View attachment 25747

View attachment 25748

Just Beautiful

 

[Deej]

hammick,
I am curious as to what you decided to doing relating to this topic.

I have a similar situation. I am planning to install panels in parallel on my SE wall and also on SW wall of my house. I am not planning to not tilt them due to the potential for high winds.

 

[nonoceb]

Hi, for heating solar panel i suggest to see this video for the principe of physics

I think you can supply a solar panel with the normal current flow with a negative supply (and current regulation to not damage cell) it's will emit infrared light perfect to heat.
the main issue is bypass diodes, dam!

"The diodes’ main task is to protect the solar cells from overheating when partial shading occurs." ?

Checking bypass diodes on solar panels: Part 1 - pvBuero

Almost all solar panels include integrated bypass diodes. Crystalline panels generally have three of them, which are located in the junction box and can each bypass a third of the panel when necessary. The diodes’ main task is to protect the solar cells from overheating when partial shading...

photovoltaikbuero.de

 

[rin67630]

Hi, for heating solar panel i suggest to see this video for the principe of physics

I think you can supply a solar panel with the normal current flow with a negative supply (and current regulation to not damage cell) it's will emit infrared light perfect to heat.
the main issue is bypass diodes, dam!

"The diodes’ main task is to protect the solar cells from overheating when partial shading occurs." ?

This is full of wrong information:
to get your panel heating, you must supply a FORWARD current to the panel. This current will only flow to a usable value if you exceed Voc by some percent. (e.g. for a 40Voc Panel inject 43v or more limited in current.
The bypass diodes are not interfering since they a not fed forward.

"The bypass diodes’ main task is to protect the solar cells from overheating when partial shading occurs."
Yes, but not like you think.
When a panel is partially shaded a half string gets a reverse polarity. Cells are not designed to cope with a reverse polarity of more than 20V and will begin to avalanche like a Zener.
That is the very reason why bypass diodes are there to prevent this reverse voltage.

So to heat a panel, feed it forward with more than Voc. The bypass diodes will not prevent that.

 

[Hedges]

So to heat a panel, feed it forward with more than Voc. The bypass diodes will not prevent that.

Doesn't need to be more than Voc.

At Voc (and panel at 25 degrees C), it will conduct Isc, dissipating power W = Voc x Isc which is greater than nameplate wattage.
At Vmp, it will conduct (Isc - Imp), which is considerably less than nameplate wattage.

At cold temperatures, current will be lower for a given voltage.

If you have two PV strings in parallel, one on the roof covered with snow and the other in a protected location such as under the eaves exposed to sun, then if SCC isn't drawing power from the array it will warm the covered panels. Difference in temperature will affect how much current/power is dissipated in each string.

Having the strings on separate MPPT charge controllers wouldn't help, but if paralleled on one it could.

 

[nonoceb]

So to heat a panel, feed it forward with more than Voc. The bypass diodes will not prevent that.

In the link : For 24 cells, the “breaking point” voltage is about 336 volts"
this is a lot of high voltage to feed a 76cell panel!

edit : i just made a real test on small 150w panel voc = 20V, isc = 9A
At 21V with the solar panel under sun i was able to inject > 1A (current limited mode)
At 20V, injection is 0A

 

[rin67630]

Doesn't need to be more than Voc.

In fact it does not matter: feed it with constant current ~Isc (here it runs at 105% of Voc.)
There are a bench of good boost converters able to do that even from battery voltage.

 

[nonoceb]

Yes it's very clear now, shaded cell see negative voltage and positive current and when we inject power cell voltage is positive, function of iradiance and current is negative.

 

[Deej]

Having the solar panels being able to de-ice themselves is very interesting clever idea. However, I don't believe that I am comfortable enough to try this myself until I have had a chance learned more about it.

At this point I am planning to install some panels (since I already have the extra panels) wired in parallel on my SW and SE walls. Does anyone have any pointers regarding installing panels on a wall in a windy area. I am planning to have them parallel to the wall a few inches off. I am far enough north that the angle is not as much a concern (compared to the wind). Any suggestions are appreciated.

thanks

 

[pollenface]

Where I'm located. It's best to have panels tilted around 50-60 degrees during the winter months (although it doesn't snow here).

I'm sure vertical panels facing the right direction would give you more output than you are receiving currently. Worth a try!

 

[willh]

Any updates on this system? Have you wall mounted a few panels for winter charging? Would be interested to know what you have determined to work or not work.

 

[Tomthumb62]

Panels can be had for $0.15 to $0.50 per watt, plus shipping.

Where do you buy your used panels from? And what age starts becoming too old to buy them used to justify shipping expense?

 

[Hedges]

Santan solar is a vendor many are happy with.
There are other liquidators like them.
You'll also find local vendors on Craigslist and eBay.

Good panels should have lots of life left even when 20 years old.
Some panels, and some environments, have rapid degradation.
I would look up the brand and year/model in test reports.

Is there a reliable resource to compare panel makes/models

SanTan treats you right. I did a quick visual inspection as I unloaded each panel. Where I saw damage, he took care of that. I had bought extra, so had spares, and nothing had to be shipped to resolve the problem. He turns over a huge quantity. If you assembled an array and they all/most fell...

diysolarforum.com

I think used panels can be a better deal, more kWh/$ over lifetime than new.
Relatively new panels (past 5 to 8 years?) are likely to have 50% greater efficiency, 50% more kW/m^2, than panels from 20 years ago.

 

[fromport]

Santan solar is a vendor many are happy with.
There are other liquidators like them.
You'll also find local vendors on Craigslist and eBay.

Good panels should have lots of life left even when 20 years old.
Some panels, and some environments, have rapid degradation.
I would look up the brand and year/model in test reports.

Is there a reliable resource to compare panel makes/models

SanTan treats you right. I did a quick visual inspection as I unloaded each panel. Where I saw damage, he took care of that. I had bought extra, so had spares, and nothing had to be shipped to resolve the problem. He turns over a huge quantity. If you assembled an array and they all/most fell...

diysolarforum.com

I think used panels can be a better deal, more kWh/$ over lifetime than new.
Relatively new panels (past 5 to 8 years?) are likely to have 50% greater efficiency, 50% more kW/m^2, than panels from 20 years ago.

I just looked at santan and would you advise anyone to buy these?

Blemished SanTan 250W Solar Panel | SanTan Solar

www.santansolar.com

“These panels have developed cell-side vinyl cracking, which is cracking in the vinyl layering beneath the cells. This has allowed for water intrusion, which has caused discoloration on the vinyl and busbars. They may contain other blemishes such as snail trails or minor surface scratches. Please see pictures for more details. The panels still output approx. 75% of the listed specifications.”

bargain at $0.14/watt ?!
WCPGW, right?

[/sarcasm] I would want those even if they would give me money. imo pure chemical waste

 

[Hedges]

I wouldn't advise that, but some people here have bought because they're cheap (the people, also the panels) and are happy.
Given the labor, shipping, support components, I've decided to stick with relatively premium parts.
I happen to be well paid and in an expensive market. For those on a shoestring budget, and living where property taxes are $50/year not $12,000/year, prices are looked at differently.

Santan has something for everybody, new and used (but large stocks only of used.)

 

[hammick]

OP here. Guys I apologize that I have been absent from this thread for so long. Things have changed for us. On June 15th, 2021 we had a massive forest fire that completely burned our 40 acres and the entire area. All the trees are gone ? (Robertson Draw fire outside Red Lodge, MT). Our building was spared because we had a good perimeter. Others weren't so lucky. We didn't get out in time (stupidly trying to save vehicles) and rode it out with the Hotshot crew. They saved our lives and are unsung heroes to us.

Then on November 16th, 2021 we had category 4 winds that did a ton of damage to our place. These winds lasted for over two hours. Our insurance claim is more than it cost to build our place. These are the kind of winds that completely destroyed some structures and vehicles.

Three of our panels were shattered and the rest all sandblasted. Insurance has paid us for the panels so we are installing 12 260w Q-cell panels on an Iron Ridge Ground mount. This mount will have the proper angle for our area and should solve our issue with snow covering the panels. The damaged array on the roof is operating at about 70% and will not be replaced when we get the new roof.

Putting the panels on the roof was a mistake that we will not repeat.

Thanks for all the advice and help on this.