What mounting angle for bifacial panels at 47.8N?

[LordGarak]

In my research so far I've gotten many different answers. From 45 degrees to 18 degrees from vertical and everywhere in between.

We currently have 1200watts of panels roof mounted at something like 20 degrees which meets our needs in the summer as it was designed for. But now my parents have been enjoying the winter there, they have to run the generator every evening. The current system has already paid for itself in generator gas savings. So we are ready to reinvest in a much larger system. The current system is 12v and doesn't really have any room to grow. So I'm building a whole new 48v system to run in parallel. The existing system will continue to run the 12v fridge, water pump and lights. The new system will take over all the 120v loads(Starlink, TV, small kitchen appliances, etc..) and be able to charge the 12v system as needed. I've got a line on 8x545watt bifacial panels for 4360watts which is over 3 times what we have now. I'm planning on a EG4 3000watt inverter/charge controller(3000EHV-48) and 2 EG4 rack mount batteries(~10kWh of storage).

I'm not really concerned about summer production at all. We already have enough in the existing system. The biggest constant draw on this system will be Starlink. It's the short grey days of winter I'm concerned about collecting enough power. We will expect to occasionally have to run a generator if we have a few days of very grey skys.

Snow is somewhat minimal and doesn't seem to stick around any more. But we can still get snow from December through April.

We are leaning more towards having this array mounted on a shed rather than ground mounted. Which will diminish the advantage of bifacial panels somewhat, but they are actually slightly cheaper than regular panels through my supplier. We get very high winds on our property(200km/h). We need to build a shed anyway and know how to build a shed to handle the wind. We would build the roof so that one side is at this optimum angle, clad in white metal and the panels mount something like 4ft off the ground to keep them well above the snow which typically can drift 2-3'.

I would really like to see some data from a similar latitude testing different angles and showing production on grey winter days.

 

[Brucey]

So you may want to angle for the shortest day of the year when the sun is at its lowest angle. That will be a challenge with 200 mph winds. I think @shadowmaker is running his at 80 degrees so just off vertical.

 

[hwy17]

Yes, angling for best production at the worst time of winter is a good strategy for off grid or self consumption production.

Does pvwatts work for your location? I would use that, and then dial the angle up and down, and look at the winter hourly data.

You can then look particularly particularly for information about what the worse cloudy weeks could look like, and the ideal cloudy angle could be different than the ideal sunny angle. The weather model is consistent between runs, so you can find the same bad weeks and compare angles.

 

[Supervstech]

There are websites that calculate based on your location. Best to search for them, and gear the Nile for winter production.
But you are likely going to need 10 times the current setup to offset generator use entirely.

 

[Steve_S]

I'm in North Eastern Ontario Canada - close to Algonquin Park.
Optimal Angle for "Annual Generation" is 45 Degrees for me and yes that works and I see my production peaks in March & September as expected from that fixed mounting BUT for usage optimization it isn't good.

Simply put, in spring/summer/fall the longer daylight hours provides boat loads of solar generation.... heck on average I am in float mode by 11:00am from march to end of Sept. BUT after September it all goes to crap ! When you go from 12 hours daylight to 5 you REALLY gotta tweak! Winter of course is the worst, because snow covers panels, clouds and shade + crappy angle cuts generation terribly.

After a few years of "things" I am finalizing the systems and changing the arrays around to optimize solar generation in Winter because I have little issues in summer and even with "winter optimized" angles I will still generate far more than my daily consumption. As a result I am reinstalling my arrays @ 30/33 degrees as the Best Compromise, to produce more power during low sun hours. See example below:

Far too many people focus on summer production optimization and don't appreciate that summer generation is so much easier.

 

[shadowmaker]

I live quite a bit north from you, so optimizing for winter/snow is even more important. 19 hours of summer sun doesn't need much effort to get enough solar energy. Like Brucey already said, my panels are 80-85 tilt and fixed. Angle is close to optimal for winter, but most importantly there's no snow on my panels ever. My array has survived 100km/h winds so far, but I really doubt it could stay in one piece in 200km/h storm. Luckily we don't get that kind of winds here.

This is how I'd do it (and probably will in near future): Shed wall facing 180 azimuth (south) painted ultra white. Panels in front of that wall (not on the wall) with concrete footing. Aluminum custom welded framing (really easy DIY and quite cheap for me) high enough for snow. UV-protected windshield glue to make it extra rigid (link in my signature to see how I did it, first two pages). Support from top of the panels to shed wall. No support needed behind panels if done this way to avoid backside shadows. Also panels installed "loosely" (spacing between every panel) and white pebbles or similar on the ground to maximize backside irradiation. Done this way you don't loose any production because of "bad" tilt even summer and harvest every possible foton in winter even when snowing. Shed enables vertical tilt (or close to vertical) even with such high winds. Little "wings" added to shed could accommodate even bigger array than shed if needed. Some angle to those wings and you could direct even more sunlight behind panels.