diy solar

diy solar

Snow on my panels is killing me

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.

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I remember that fire, you are about 150 miles from me. My opinion, bi-facial is what I use over here in Miles City MT. Miles City MT might be my mailing address but I am closer to Colstrip MT as the bird flies. Making it easy access to sweep off helps too and with 40 acres I am sure you can find a spot on the ground.
 
I remember that fire, you are about 150 miles from me. My opinion, bi-facial is what I use over here in Miles City MT. Miles City MT might be my mailing address but I am closer to Colstrip MT as the bird flies. Making it easy access to sweep off helps too and with 40 acres I am sure you can find a spot on the ground.
Glad to hear you and family got out ok, and the damages are insured.
The building, with two levels of roof line,( especially if the ridge run 90-degrees to the prevailing wind), is a snow drift machine. PV on that lower level roof at low pitch is inviting snow to drift over them. Perhaps a lesson well learned for everyone that has been following this post: putting PV on a roof in locations likely to accumulate snow, where access is limited (for any reason) to remove that snow, is not ideal.
Hope you are able to get your new PV set up soon, and post a follow up to show it.
 
Bifacial panels on ground mount will get power from the reflection on the backside especially with snow cover. That’s how I’d do it.
 
I won't tell anyone else what to do, don't know their skill level or circumstances...

Personally, I put in north/south posts, broke out the hole saw and went to town using a string to more or less line the holes up.

My posts are tall enough so livestock, wildlife, lawnmowers and kids don't crash into the panels.

A pipe through the holes, panels on the pipe. Rotate pipe and panels sun track east/west.

I've done ring gear, screw gear, jack screw to rotate the panels. I use a simple timer and $1 stop switches and move panels to relative positions, the sun does not need to be continously tracked.

I also have an extra stop switch so I can turn the panels face down, edge to the wind in storms. With 1/2 inch screen on the backs they bounce hail, and the rodents can't attack the wiring.

Depends if you have batteries or not... I'm off grid with batteries. I disconnect panels from charge controller (switch) and apply power to my panels from batteries. This works best before daylight.

A panel that's NOT producing is a great big electrical resistor. Electrical resistance heating is 100% efficient. 1 Watt makes 3.41 BTUs directly into the glass. This makes a water layer between glass and ice/snow.

To regulate how much power you throw at the panels, a DC Pulse Width Modulator (PWM) makes a cheap power controller. (All over ebay and Amazon)

Manually, switch to disconnect panels from charge controller, switch to connect PWM to panels. The PWM will have an 'Off' switch, but a lock out switch is safer so you don't get the PWM trying to feed the charge controller.

With some isolation diodes you can skip some of the switches. I use a timer on the PWM, push the button or crank the knob and have a second cup of coffee while the panels clean themselves, but my panels start almost vertical facing east in the mornings, a shallow roof mount will take quite a bit longer.

As for the big diode/backfeed debate...

Bypass diodes are NOt back feed diodes. Bypass diodes are on the panels, they simply let production from other panels bypass shaded or damaged zones on panels.

Back feed diodes are usually in the combiner box (series/parallel) or in the charge controller (small series only).

If you bought into the micro-inverters behind each panel, then you are screwed all the way around, your only option is heat tape on the backs of the panels and an AC power grid connection to run them off of...
These little gimmics are mostly for the "Look At ME!" Grid tied only systems where inverter losses aren't as important as saying you have solar and having the 'Connectivity' on your phone to show off with... Good luck with that...
 
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Depends if you have batteries or not... I'm off grid with batteries. I disconnect panels from charge controller (switch) and apply power to my panels from batteries. This works best before daylight.

A panel that's NOT producing is a great big electrical resistor. Electrical resistance heating is 100% efficient. 1 Watt makes 3.41 BTUs directly into the glass. This makes a water layer between glass and ice/snow.

What battery voltage, and what panel Voc? How much current?


I expected a panel to conduct Isc if driven externally to Voc, but that was not the case. I ended up using 2s of panels in the sun to get 79 Voc, 41 V(load) applied to a single dark panel which carried 2A (about 0.4x Isc).



This works best before daylight.

I can believe you get the most current when no light falls on the panels, but I'm not convinced the most heating.

In the sun, 20% of energy gets converted to electricity, and open-circuit all that gets burned up in the panel. In addition, 80% is either converted to heat or reflected.

Backfeeding to Voc of one panel, I get Voc x 0.4x Isc ~= 0.5x STC wattage dissipated or just 10% of what sun would do.

Seems to me that your being able to rotate panel so sun falls on backside without reflective snow could do a better job.
Maybe paint backsheet black and use a sheet of clear plastic as "glazing" to make it a solar oven. (think the increased absorption is more important than improved insulation, given low temperatures involved, unless there is wind.)
 
Should we set up a snow/ice melting test and just try it out?
I have a 440 CSI just sitting in the shop...it is spare due to shipping damage and was replaced with brand new, so if we "cook it" I am not out anything.
What would the ideal feed-in current and voltage be for a single panel? VOC 46vDC ISC 9.26A Delta is -0.27v/C
 
Serious
Anyone ever install vertical panels for winter charging?
Going back to page 1 of 5: Yes.

You overpanel in northern latitudes anyways, and the ideal tilt is not too far off from vertical in winter, so whatever you ‘lose’ by being vertical in the summer- at my house anyways- doesn’t even matter.

Lots of great reading in the thread but it’s gotten complicated when the side of the building is just there begging to be used.
 
Just got 3 FEET of snow from 2 storms. Not a flake of snow on my panels and NO ice either.
Panels worked the next morning without me having to fuss over them.

How is that possible?

Stand the panels straight up i the winter. No snow, No ice, no problems. Never put panels on roof in snow areas. Ground mount on poles that allow vertical tilt.
 
I would build a catwalk with steps leading to it. Then have a long handled module brush stowed on the catwalk to pull the snow off from the walkway. (4) 4x4 posts, stair stringers, a few 2x6's for catwalk joists and walk boards and 2x4's for hand rails. Or heat them.
 
Just got 3 FEET of snow from 2 storms. Not a flake of snow on my panels and NO ice either.
Panels worked the next morning without me having to fuss over them.

How is that possible?

Stand the panels straight up i the winter. No snow, No ice, no problems. Never put panels on roof in snow areas. Ground mount on poles that allow vertical tilt.
Mine have been at 60 degrees since first snow. No snow on my array and it has snowed several times and has been around 0F for temps. MT Solar mount.jpg
 
I use a SE facing vertically mounted set of panels. Here is what I am getting from them. There will be 6 more panels mounted beside this array for battery charging only. I would go all the way up with 8 panels, but I can't find anyone to help me get the job done.

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You could rent a lift, I just use my off road forklift with a scaffolding platform on it.

Either that or put a sign out front that says "Free Beer".
 
Block and tackle?

Or just climb a ladder, then pull panel straight up with rope?
I tried the ladder method. I need to connect the wires and hold the panel at the same time. I could probably use the chain hoist if I had somewhere to attach it that was a good clip above

I will probably end up renting a telehandler and suspending it from the forks to get everything done properly. I am very risk adverse to falling glass and sharp things. It's on the list, but not a super big priority at the moment. I have an office that needs to be rebuilt from a flood and to finish off my system to power the house first.
 
OP here. Ended up doing it right and installing 4.3kw of panels on an Iron Ridge ground mount. It's rock solid and the winter charging is insane. I may never run my generator again. I still have the 1.7kw array on the roof as well.

Pic's please
 
You could rent a lift, I just use my off road forklift with a scaffolding platform on it.

Either that or put a sign out front that says "Free Beer".
Go to a local school or college sporting event, talk to a few people about what you want to get done, offer some beer and money, Done.
 
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