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

Screwdriva

ispookie666 said:

@Screwdriva the modelled generation for a west facing seems to be high, but we all know that most of our systems regularly beat the predicted numbers. 

Based on our past years performance, the modeling is conservative for our roof. I've included an image of the first 5.5 months of our West (technically 230 degrees WSW) aspect generation for 2023 ( the worst year on record solar generation wise). Limits gone. Clipping is also not expected to be an issue given our existing generation curve's peak at ~12:30 pm. (This is highlighted at around the 12 min mark here)


P.S. @Martyn1981-  Note the 17% difference between the two existing West facing panels. Panel 1.1.7 has no obstruction to it's left (South) whereas 1.1.6 is obstructed by 1.1.7. I have no other way to explain the outperformance relative to the other bifacial panels (which are all outperforming the standard monocrystaline panels on the roof to their right).

Screwdriva

New all time high for the month of June! 

Screwdriva

Interesting breakdown of the month of August for a PV only system on Flux. In effect, import cost per kWh of ~25.9p vs. an export rate of 21.7p, which highlights how lucrative the tariff can be for net exporting households despite the lack of storage.

Screwdriva

BEFORE: 

AFTER: 6 X 550W additional SHARP Bifacial Panels. These were the closest aesthetic bi-facial panel available from a quality brand.

Martyn1981

Just a thought about PV, not really a suggestion for this case, but it seems that the planning permission(s) for PV have loosened.

Two things I've noticed (but no idea how long ago it changed) are firstly - PV on flat roofs used to require PP if they were at a different slope (not mounted flat). But now they can be upto 1m higher than the roof surface.

Secondly, wall mounted PV (like roof mounted), is now 'likely to be considered permitted development', subject to conditions. Previously, I'd swear, wall mounted PV required planning permission. The main condition for wall mounted is that they don't protrude/project more than 200mm from the wall (or roof) surface.

So ........ and finally getting to my point ...... in that photo, I'd have thought 4 panels (2x2 portrait format) on either side of the main opening/balcony, could look quite nice. Some properties have wood panelling sections for decorative additions, and well positioned black PV panels could look just as good.

As I say, not suggesting it necessarily in this case, but more a general point that wall mounted PV could become a 'feature'.


Edit - Here's a pic I've grabbed, showing how wall mounted PV can be used as a feature:-

Screwdriva

Looks like the Heatable team are seeing 15+ % incremental gains with their REA bi-facial rooftop panel installs.

https://www.youtube.com/watch?v=mj6ZmIZP4hw

Screwdriva

Things are looking up!

Just one sunny day shy of the all time high (May 2020 lockdown anomaly) despite a pretty mediocre April. Generation continues to hover around 3-3.6kW during the 4-7pm Flux export window (26.5p per kWh), which has dramatically improved export earnings. 

Martyn1981

What do you put the change down to, v's previous years (+20% to +60%?), given that Apr 2024 was one of the worst?

Screwdriva

Martyn1981 said:

What do you put the change down to, v's previous years (+20% to +60%?), given that Apr 2024 was one of the worst?

The 6 X 550W bifacial panels installed late last year on the WSW aspect as well as the 2 X 400W bifacial panels moved to the ENE aspect have effectively increased early morning and late afternoon generation (with minimal clipping during the 11-2pm generation peak). Harder to quantify any albedo aka bifacial gains but effectively, the curve has been raised entirely, with a stronger lift pre-11am and post 2pm.

Screwdriva

And that's a wrap for May '24 (one of the weakest Mays on record). Despite this, the previous monthly all time record (set 4 years ago just after the Covid lockdown) was obliterated with a new monthly all time high of 720kWh. The % of export during the lucrative 4-7pm window has risen to 23.5%, leading to a 18p per kWh blended export rate. This should increase a bit more in June. 

This despite some clipping during the clearer, sunnier days. I expect this to be new norm for peak generation months.