Snow on my panels is killing me

rin67630

Solar Enthusiast
When you are not there, do the batteries get warm enough in the winter to charge? (over 32 degrees F)?
They are supposed to be charged and only need a tiny float charge at 13,8V. Cold batteries under 0°C will charge slower, but also self-discharge slower, so it just compensates.
 

JoeHam

Photon Sorcerer
@george65 it sounds like you have a monster PV panel setup.

At what voltage do you pull all that power to the SCC and what SCC’s do you use?

Just curious.
 

george65

Solar Enthusiast
@george65 it sounds like you have a monster PV panel setup.
Yes. I had around 25Kw of panels before taking some down and selling them off to make way for new, larger panels.
I think I'll end up with 26-28 Kw Of panels depending what I keep and what I can fit.

I have a large house in an area that gerts very cold in winter and is entirely electric. People often comment on my power usage but don't take into account their gas consumption or heating with fire wood. Because we are electric only we can also have monster power consumption and this is what I'm trying to offset.

At what voltage do you pull all that power to the SCC and what SCC’s do you use?
I am Grid tie. I have set my arrays up at generally strings of 8 panels which depending on what they are, can be around 280 to a bit over 400V.
I have 4 grid tie inverters presently of varying size and brand ( some bought new, some used). They add up to about 16Kw atm.
There are 19 kw of new panels I have to put up and I'll keep some of the smaller ones as well but I won't change the inverter capacity much.
I make far more power than I can use in summer and the inverters I have will rarely max out in winter even over clocked when I most need the power so little reason to add any more inverter capacity.

Just curious.

Not a problem.
I like to see what other people have as well just to judge how much I have lost the plot and what the sane people are doing. :0)
 

Hedges

Photon Sorcerer
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.

"Six more panels for a total of 15 would be right at my MPPT CC max."

You can generally get away with making more watts available, because CC should limit its output current to what is wants. It would be possible for an MPPT CC to not protect itself, so you could check with manufacturer. PWM CC can't protect themselves that way.

The most important limit is Voc, and it looks like you have plenty of margin for cold weather.
ISC is 60A, so 6 strings all oriented the same would be below that. (different angles would reduce actual current produced.)

So you have Solarworld 3s2p + Hanwa 3s1p,
119 Voc at ambient (plenty of room for cold weather without exceeding 150 Voc. One panel -0.119V/K, other not listed)
29.5A Isc (limit is 60A)
2378W PTC
49.5A into 48V (SCC should self-limit to 60A)
39.6A into 60V

Looks to me like you could over-panel to double the panels, all oriented the same, and be just below 60A Isc
Of could power would be limited part of the day by 60A max to battery.

Putting 9 similar size panels on the wall, angle is different so area facing sun and peak wattage available is reduced, but charge controller will still clip to 60A some seasons. Winter with snow on the roof, the wall mount panels will make a big difference.
 

rin67630

Solar Enthusiast
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.
By the way, rake-removing the white loose part of the snow, just before a predicted sunny day, is always effective!
Without it, the sun can reach the dark panel through the transparent ice crust and frequently warm it enough to provoke a slide.
 

george65

Solar Enthusiast
Winter with snow on the roof, the wall mount panels will make a big difference.
Do you know of any tables or calculators for vertical mounted panels in full snow Conditions.? I imagine on a sunny day facing the optimal direction, the efficiency of the output would be very high, maybe 80% or more.
 

hammick

Solar Enthusiast
"Six more panels for a total of 15 would be right at my MPPT CC max."

You can generally get away with making more watts available, because CC should limit its output current to what is wants. It would be possible for an MPPT CC to not protect itself, so you could check with manufacturer. PWM CC can't protect themselves that way.

The most important limit is Voc, and it looks like you have plenty of margin for cold weather.
ISC is 60A, so 6 strings all oriented the same would be below that. (different angles would reduce actual current produced.)

So you have Solarworld 3s2p + Hanwa 3s1p,
119 Voc at ambient (plenty of room for cold weather without exceeding 150 Voc. One panel -0.119V/K, other not listed)
29.5A Isc (limit is 60A)
2378W PTC
49.5A into 48V (SCC should self-limit to 60A)
39.6A into 60V

Looks to me like you could over-panel to double the panels, all oriented the same, and be just below 60A Isc
Of could power would be limited part of the day by 60A max to battery.

Putting 9 similar size panels on the wall, angle is different so area facing sun and peak wattage available is reduced, but charge controller will still clip to 60A some seasons. Winter with snow on the roof, the wall mount panels will make a big difference.
Thanks Hedges. Since the used panels are so cheap I'm inclined to buy another CC to take full advantage of the additional power. I can get another one for under $500 shipped. It's worth it to me to get another Conext CC because I can remote configure/monitor all my Conext equipment. And the Orian BMS I will be using with my new LifePO4 bank has the ability to shut down down and turn back on the Conext CC and Inverter (so I'm told).
 

Red Squirrel

Solar Enthusiast
I know the struggle, same issue with my shed panels. I gave up on trying to keep the snow off but would sure be nice to get free power year round. We get too much of the crappy stuff now days. The wet/icy snow, instead of just the normal snow that is easy to brush off. I even see stop signs caked with snow every time it snows now, so I feel even vertical panels would have trouble. But I think vertical ground mount might be the best bet still, at least they are easier to reach with a scraper.
 

george65

Solar Enthusiast
Just being pedantic by pointing out a curiosity- In Brisbane,27.4S, for the last few weeks the southern facing walls are first to greet the sun!
Yes, My house is about 50o off facing Due east and I have been noticing the same thing.
Unfortunately I have the Biggest tree in the District in my front yard which makes the front roof a total wash and another tree on the south side of the shed which takes it out as well. I was going to do an east/ South east facing ground array for a test to see how much power I can get out of a 5 Kw Inverter in a day. With the 3rd orentation, I think I'll have no trouble getting 50 Kwh or a 10X rating factor.

In any case, I switched all my solar off 6 weeks ago and I'm still trying to burn off all the power I racked up before the next meter read which is getting close so no point in trying to make more EXCEPT in winter when there is never enough. ( although I'm getting close!)

Unfortunately the south is then useless when you could use it the most so again, Not going to gain much unfortunately.
 

MurphyGuy

Solar Enthusiast
I live in Michigan, here is the only advice I can give you:

1) If part of the panel is clean, it will warm up a bit and melt the rest of the panel. When we get snow, I usually brush off the heavy stuff and let the sun do the rest for me. Once a small amount of black is showing, the sun's light heats the panel up a bit and melts the rest. The process is obviously dependent on how deep the snow is, but generally speaking, and inch of icy snow will be gone in two or three hours.

2) May I suggest some kind of pipe-heating cable be installed under the panels and in contact with the back-face? I've never actually tried this, but if you were to attach about 15 feet of that anti-freeze gutter or pipe heater cable to the underside of each panel, it would probably only take about 20 minutes for it to melt most of the ice away.

3) I bought a Makita 36v leaf blower and I now blow the loose snow off my panels. We normally use a push broom at the end of a 16 foot extension pole to pull the snow off the panels. But I discovered that sometimes the snow is that super light and fluffy type that just needs a good gust of wind.
The leaf blower takes me about 5 minutes to blow off my 14 x 56 foot array (ground mount). We bought a battery unit so we don't have issues starting a gas unit in the cold temps.

4) If the inside of that barn is heated, you could pipe some of that warm air to the underside of those panels. A small automotive style blower fan connected to some 2" pvc pipe would probably deliver enough warm air to melt the snow and ice away. Some skirting on the outside edge of the panels to keep the warm air constrained a bit might also help.

5) Move the entire array to the ground and put it on a single axis tracking system. Your array is small and could easily be supported by a couple of 6 x 6 pressure treated lumber posts. Tilt it vertical when it snows. This would also increase your power generation from season to season since the array would no longer be slaved to the angle of the roof.
 

rhino

Solar Enthusiast
A note about expecting the sun to melt snow off.. depending on where you live and the ambient air temperature the black framed panels work much better for fully getting snow and ice off. I have both black framed and silver framed panels on same array and the silver framed ones has ice that forms from the snow melting off the actual panel surface. The black frames ones warm up enough in the sun to prevent the melt water from refreezing on them.
 
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