Hi guys I have just been offered 600W JA Bifacial solar panels for the same price quote for 550W JA conventional. I don't have any experience with the Bifacial tech and from internet search seems they are good for steep angle in high latitudes but aren't likely to be that great for latitudes in the tropics unless you put a reflective surface underneath. Anyone with thoughts or experience please?

I just had new panels installed. The quote was for 550s. I didn't specify more than the wattage. Installer arrives with 585s, says that it's the best deal he could get. They were bi-facial.

I don't see that you can lose anything if you put them on a roof, and you're not going to lose financially.

I actually thought of getting a reflective surface under them, but I don't know what to use and I am really not keen on having to get up on the roof, unmount the panels, lay the reflective stuff and so on.

I have 9 x 550 JA bi-facials and 9 x 545 Trina mono's installed on a flat roof which is painted white (6 bi-facials in series, 6 mono's in series and the 3rd bank is 3 of each, all in series). Installed on different MPPTs, so I can monitor the generation of each bank, and as they are facing the same direction (North) and all at the same angle, the results are interesting. In summer, early morning ( from 5 to 8am) and late afternoon (3pm to 5pm), the bi-facials are generating more power, and peak daylight (9am - 3pm) the mono's are generating more. The mixed bank is generating exactly halfway what the other banks are doing at that exact time, but on overcast days, the mixed bank is generating more. This bank is also generating all day (no high or low times), like the other 2 banks do during certain times of the day. Will be monitoring them during this winter, so the see if the result will be different. I'm based in PE, so summers aren't too hot and winters aren't too cold.

I suspect Bi-facial's will do better on a flat roof (pref. white or silver painted) and mounted with suitable frames to give them a tilt around 45 Deg from horizontal.

Alternative would be a ground mount system, but then one would need to "engineer" something reflective around the structure.

Would be good to know if my simple examples would generate more than Mono's.

On 2025/04/19 at 11:20 AM, Sidewinder said:

around 45 Deg from horizontal.

I am all for more space and reflective surfaces behind the bifacials but why would one go to 45 degrees?

On a north facing roof, it is a reasonable compromise on production between summer and winter. In summer, the sun is almost at 85 Deg above the horizon around noon, whereas in winter, it will be close to 30 Deg. Unless you have an adjustable setup.

It you tend to use much more energy during winter, then a higher angle is preferred, and visa versa.

5 hours ago, Sidewinder said:

It you tend to use much more energy during winter, then a higher angle is preferred, and visa versa

GeyserWise says not to go higher than 37 degrees:

10 hours ago, Sidewinder said:

On a north facing roof, it is a reasonable compromise on production between summer and winter. In summer, the sun is almost at 85 Deg above the horizon around noon, whereas in winter, it will be close to 30 Deg. Unless you have an adjustable setup.

It you tend to use much more energy during winter, then a higher angle is preferred, and visa versa.

A reasonable compromise for year-round production is to set the tilt angle approximately equal to the latitude of your location (e.g., ~30°–35° for much of South Africa. This balances summer and winter output reasonably well.