camelot-forum.co.uk

I'm a bit out of the loop with solar now

Fresh install, on a new (to be built) workshop roof

I think ON roof will be much easier to diy than IN roof (I can use insulated metal clad roof panels for the roof)

I'm struggling to find any real world numbers of mono vs bifacial panels

being a new roof, I could use white roof sheets for maximum reflection

I'm off setting oil heating so in about the best cost/payback position their is I think?

535watt mono panels
https://www.cityplumbing.co.uk/p/longi- ... m/p/104460

500watt bifacial
https://www.cityplumbing.co.uk/p/dmegc- ... b/p/120105

where would my money be better spent? - I'm not buying just yet, but will be in the coming months

Biracial are only useful if you’re ground mounting and can put some marble chippings below the panels. Otherwise zero benefit.

I often think that a more useful comparison would be comparing the kWp per sq m with the price.

+1 for bifacial being pointless on a roof.

I have decided to to with a white roof for the upcoming shed build, and have also decided to go for bifacials.

The panels wont be far enough off of the backer to make a huge difference, but the thinking being is the mono panels with white backing would basically do the same job as a white roof 20cm away so you wont get worse output, for the same as a mono, only the same or better.
And the price between the two for the size i am ordering is literally negligible, so may as well take a punt.

Ive got a purchase order in for 20 panels with the battery group.
They have got bifacials for £55 upwards inclusive of VAT, but are waiting for more stock currently.

I would go with best W/£ TBH.

I had this choice a few years back and decided to get some bifacials as the the price was about the same, and they were to go on the barn roof (white fibre cement) with a high angle as the roof slopes down to the north.

In theory, on an overcast day they should benefit from diffuse light hitting their backs, but it's not obviously significant. I could if I were bored cover the back of one panel and compare outputs, but as they're in a daisy chain to a GTI, measuring the individual outputs is more faff than I have time for.

Just a thought, does the Wp rating of a bifacial panel assume that it gets some irradiation on the back face. Thus if it gets minimal/none because it is near the roof surface, it will actually get less power than an equally rated mono panel.


PS my comment on power per square metre is mainly relevant to those with smaller roofs where output is limited because of the roof size.

John_S wrote: ↑Sun Mar 02, 2025 11:10 pm Just a thought, does the Wp rating of a bifacial panel assume that it gets some irradiation on the back face. Thus if it gets minimal/none because it is near the roof surface, it will actually get less power than an equally rated mono panel.


PS my comment on power per square metre is mainly relevant to those with smaller roofs where output is limited because of the roof size.

The Wp rating is based on the STC like every other panels, i.e. cell temp 25 degrees, solar irradiance of 1000W/m2 and an air mass of 1.5.

Its too difficult to calculate the extra because every installation is different, some do say up to an extra x% depending on the installation conditions.

John_S wrote: ↑Sun Mar 02, 2025 11:10 pm Just a thought, does the Wp rating of a bifacial panel assume that it gets some irradiation on the back face. Thus if it gets minimal/none because it is near the roof surface, it will actually get less power than an equally rated mono panel.


PS my comment on power per square metre is mainly relevant to those with smaller roofs where output is limited because of the roof size.

Yes!

The headline Wp figure usually includes a rear/front irradiation ratio of zero. The documentation usually includes a higher rating with a 10% rear front irradiation ratio.


EG: https://cdn.shopify.com/s/files/1/0257/ ... 1715681572

thanks everyone

sounds like I might as well stick with mon panels then :-)

trying to ge my ducks in a row and design the roof to fit as many panels as possible!