The panels still don't generate any electricity at night of course, but other than that the output is an almost perfect inverse of the conventional equator-facing angled mounted panel output.
Just search for "bifacial solar panels graph".
We currently have:
- summer optimised array: almost flat, 15 degree, optimised for maximum power on sunny summer days, mostly runs our cooling
- winter/morning array. Points SSE, 65 degree incline. Gets great energy in the mornings, and on winter mornings. Performs surprisingly well in overcast conditions. Generates about the same power in midwinter and midsummer.
- winter/afternoon array. Same as the above, but SSW.
18kW total faceplate capacity, in reality we peak at around 5kW, but have that for about six hours of the day for 9 months of the year. Also means I can run three arrays on two MPPTs as the two tilted arrays are basically mutually exclusive as to when they make power.
The other reason for leaning towards vertical panels is cleaning. The flat panels accumulate a crust of crap (pollen, soot, dust) that cements on there fast, and requires vigorous scrubbing to remove. Kills 20% of the capacity unless I get up there with a broom every six weeks. The 65 degree ones I have not had to clean once, as stuff just slides off them.
That, and a pallet of bifacials is now cheaper than a pallet of monofacials.
But shading is also a factor. If you want to get unobstructed sun across the whole day, you need to be built on a nice curve of a hill? Or build just a straight line of panels?