Question about snow coverage ...

[oldryder]

1st winter for me with a 12KW ground mount array. 2 strings per 6000w. grid tie inverter. No optimizers or microinverters. Exceptionally heavy snow this year with lots of drifting. Snow was heavy enough to drift up to bottom of the panels and then pile up on the actual panels. Some panels are partially covered, some even completely covered. Is it safe to leave everything energized. I thought from reading that a partially covered (i.e. shaded) panel in a string was a real problem. At this point I'm wondering if an optimizer or micro inverter per panel is necessary in an area where snow is common. I already know I will add snow fence before next winter. (I already do that for part of my driveway). for this year do I have to shut it down until the panels are clear of snow? Thx to anyone taking the time to offer advice.

[bcroe]

I have a sticky here on snow tolerant ground mounts. The
first step is mounting panels high enough to be clear of any
ground snow. Bruce Roe

Array20Rear1.JPG

[oldryder]

THx for reply. In a normal year they'd be high enough. Even the commercial arrays I can see from the Interstate have the same problem this year. I still need to know if the partially covered panels are a reason to keep the array shut down until they're cleared. If yes, does the partially blocked panel(s) cease being a potential problem, excluding the lost output, if DC to DC optimizers or microinverters are used?

[littleharbor2]

Can you get a snow blower out to the array?

[peakbagger]

A snowblower is my fix, as long as the chute is pointed away from the panels. The next array will be higher. and on a slope to reduce the issue but I still leave room for snowblower to make a pass.

[Mike 134]

To answer your question there are bypass diodes in the solar panels for just your type of situation. You'll need to do some searching through your manufacturer's documentation how they are wired in I.E., 1/3 or 1/2 of the panel and do they work better with landscape or portrait orientation.

[oldryder]

Thx for replies. Yes to snowblower, that was always the plan. Just kinda got overwhelmed this year by much more snow than usual. Mike 134; thx for info on bypass details. I will look into that.

[bcroe]

Here panels have 6 rows of cells the long way. The junction box connects
to a row along at edge, which is wired in series to the other row end, then
wired back in series in the next row to the junction box. This section can
be handled by one bypass diode. The other pairs of rows do the same.
To try and get some output with partial snow, the panel might be mounted
landscape so the top rows, complete sections handled by a diode, are
snow free and functional. The lower panels with snow would be bypassed.

With the panel mounted portrait, snow on the lower area will kill all the
sections.

Perhaps the qustion here is, what if the wiring is snow covered? My combiner
box was never intended to be waterproof. If snow/water can find its way to
any conductor, you could blow a ground fault fuse, maybe worse. The
panels might be OK, but I might open the 2 pole DC disconnect switch
in that extreme condition.

I go down the array above with the snow blower hitting the top panels.
Any snow on the array usually slides off without manual labor.
Bruce Roe

[peakbagger]

An interesting article about solar panel failures related to snow in Japan and a pretty interesting picture

Snow damaged 30 MW of PV systems in Japan in 2018-21 period – pv magazine International (pv-magazine.com)

My guess is with large solar fields, the installation design and details are optimized for the lowest cost and unusual weather conditions on occasion do not line up with design assumptions. I used to drive by a few large arrays in Mass that on rare occasions would get buried with snow as they mounted too low to the ground. I wonder if this type of failure is significant enough for the loss underwriters to charge a premium ? I find a lot of developers will take the risk to make a bit more profit and let the insurance company deal with it as the developer usually cashes out long before it is an issue.

As an aside, I used to work in a facility in a cold location. The ASHRAE 99% design low temp was -21 F. We did see temps as low as -35 F overnight on rare occasions. I generally included a -35 F design temp in design requirements. Folks forget that 99% design means there could still be 3.65 days that exceed the numbers in a 365 day year I have seen steam air coil preheaters freeze solid on air intakes unless they were designed for that type of service.

[Calsun]

The problems in Japan were the result of incompetence or corruption or both. They had panels at less than 1 degee of slant despite being at 36 degrees of latitude. The installers went cheap on the framing for the panels and the owners paid the price. It comes down to not having blind faith in contractors but in always doing your own fact checking.

Always much more expensive to fix problems then to have done the job right the first time. I never rely on contractors to do the design or product sourcing for anything important.