7.3 kW Bi Facial Rooftop Panels: ~7 year ROI: Fact OR fiction?

Hexane

Screwdriva wrote: »

After some measurements of the roof

Now I understand why you are keen to reduce potential sea level rises! Nice house, hope all goes well with the install.

Screwdriva

Hexane wrote: »

Now I understand why you are keen to reduce potential sea level rises!

It's actually a Lakehouse in Zone 2 but the point stands

ABrass

Why have a partially shaded south facing panel? If you still have the solar edge then that's not a big deal but another east or west facing panel seems to make more sense

Martyn1981

Screwdriva wrote: »

The panels are transparent, so the solar reflective paint is clearly visible through them. If its visible, it will reflect to the rear of the panel, which will lead to added generation.

That's really interesting (damn I'm a right nerd!). It'll also be interesting to see how generation varies depending on the location of the panel to the sun ..... stick with me here, this is going to get painful ...... but with Solaredge you'll be able to not only see generation for each panel, but also power through the day, so will, for example all panels on the same face generate roughly the same power in the morning, or will the panel(s) to the east of the group generate more due to some direct sunlight 'sneaking' under the east edge and bouncing up, and a similar result when the sun is 'sneaking' in from the west. Taking it further, will upper panels see a boost in the summer (when the sun is high in the sky), and vice versa in the winter.

I'll stop now, I'm even boring myself.

michaels

Screwdriva wrote: »

LG400N2T Panels & P505 SE optimizers have arrived. They're massive! After some measurements of the roof, we've arrived at the following:

6 panels on the South facing roof with 1 panel expected to partially shade thanks to the chimney (see pic)
2 Panels each on the West and East facing roof to extend generation for the longest duration.

The panels are transparent, so the solar reflective paint is clearly visible through them. If its visible, it will reflect to the rear of the panel, which will lead to added generation.

I'd look at the time of day pricing from the octopus agile thread and possibly conclude that 4 West facing panels might work better than the E/W split - although the invertor cap might play in to your calculations too. Do you need to worry about string voltage or does the optimizers mean that isn't an issue?

Exiled_Tyke

michaels wrote: »

I'd look at the time of day pricing from the octopus agile thread and possibly conclude that 4 West facing panels might work better than the E/W split - although the invertor cap might play in to your calculations too. Do you need to worry about string voltage or does the optimizers mean that isn't an issue?

The Optimisers will look after the differences in panel generation.

I also agree with Michaels on the split because the W is slightly SW and the E slightly NE so the W side should do better. Also as the W faces the water I'm guessing that it will do better during hours of low sun (above the horizon) than the E side.

Hexane

Exiled_Tyke wrote: »

the W is slightly SW and the E slightly NE so the W side should do better. Also as the W faces the water I'm guessing that it will do better during hours of low sun (above the horizon) than the E side.

This is going to be awesome.... some of the reflection off the water will end up generating extra power by hitting the panels from the underneath, and some from sideways/above? It's like sunbathing next to a pool (or the sea) getting a tan faster than sunbathing nowhere near a body of water (or so I was told)

Screwdriva

Wow, you took it to a whole new level with reflection off the water adding to generation. And here I was wondering if the solar reflective paint was worth the cost. Installation is due to complete tomorrow, assuming the paint has a chance to dry.

We had to have 2 panels on the East side, which only left 2 panels for the West. 2 on either side of the Chimney and 2 above it.

Martyn1981

Screwdriva wrote: »

Wow, you took it to a whole new level with reflection off the water adding to generation. And here I was wondering if the solar reflective paint was worth the cost. Installation is due to complete tomorrow, assuming the paint has a chance to dry.

We had to have 2 panels on the East side, which only left 2 panels for the West. 2 on either side of the Chimney and 2 above it.

I'm just relieved that I'm not the only crazee one on here that finds this so interesting.

Regarding the paint, I'd say that that seems like a 'have too' for such an install. Without side by side comparisons you may never know the benefits, but had you not done it, you'd spend the next 30yrs driving yourself mad wondering if you should have ..... or is that just me.

Screwdriva

Martyn1981 wrote: »

Regarding the paint, I'd say that that seems like a 'have too' for such an install.

Knowing my need to maximize spec, I'd have done it anyway. That said, LG documentation states that maximum bifacial gains of 20+% are when the roofing behind the panel is white. Pretty obvious stuff if you ask me. A side by side comparison of standard white paint vs. reflective paint vs. dark roof tile would be one I'd be interested in