Help choosing Panels

woolgar.c

We're looking to get a solar PV & battery install. We're getting some further quotes for the whole system & have had some useful advice already on a range of quotes. 

We want to understand the kit a bit better to help our decision making. We're hoping to make a final decision soon & be done with the research! I've done a similar post to focus on batteries. 

As for the panels themselves we've been advised by some that there are all fairly similar with long warranties & by some to avoid those made in China. 

Are bifacial / dual glass panels newer / better tech? It's been suggested they are more durable & more effective (and hence would be working closer to their max more often?)

I presume the highest W possible would be best? e.g. aiming for 455W beyond 430W. Would this be more important to output than the actual make of the panel?

Our roof is 40 degrees pitch, South facing, no shade. So based on this we feel microinverters aren't needed. We're not sure whether to add optimisers so if some become dirty or faulty it wouldn't reduce the output of the whole system / string. 

The panels that have come up in different quotes have been:

Aiko 455W
Longi LR5 430W
DMEGC 440W
Sharp Bi-facial 435W
JA Solar 440W
Vertex S+ Dual Glass N-Type Solar Cells 440W

Thanks!

ka7e

I actually have 505W panels, my independent supplier managed to get 5 on my roof after other quotes were for 4 x 430W. I understand they may be heavier, but I had a roof survey which said it was OK to use them.

woolgar.c

ka7e said:

I actually have 505W panels, my independent supplier managed to get 5 on my roof after other quotes were for 4 x 430W. I understand they may be heavier, but I had a roof survey which said it was OK to use them.

Did you get the survey due to the weight of the 505W panels or were you planning to have one anyway?

nologo

The panels selected depend on the size of your roof, it's usually suggested the maximum amount of generation you can afford/willing to spend should be fitted,so if you have a small roof that faces south maybe the bifacial panels would suit as they may exceed their nominated generation, also panels come in various sizes so more maybe fitted as they can get two rows on instead of one row of larger panels, if you have a large roof then maybe more standard panels will give better value?

My own systems have both sharp and trina panels, they generate about the same they have a similar warranty they look the same.
regards.  Nologo

Solarchaser

If you have a huge roof, then I'd advise to go with smaller wattage panels as they are significantly cheaper.
However if you have a small roof, then its probably worth paying the premium for the larger panels.

Your reality will probably be somewhere in between.

If you have no shading issues I'd personally skip the expense of optimisers,  however they are quite a polarising debate.
Generally those who have them really think they are useful, and those without can't justify the extra expense. 
Many modern panels do what REC panels have done which is make the panel two half's, so that if something is causing an issue on one half, the who panel isn't down.

The comparisons I've seen with bifacial panels on a normal roof, rather than a rotating or vertical ground mount etc, show they are pretty much comparable with normal panels, so imo not worth the extra cost.
If it was a standing ground mount or something which could take the sun from different angles, I think you could justify bifacial. 

I've been messing with solar for around 8 years and have been involved with a good few solar projects, so I've been around a bit. I don't know everything,  no-one does, so my advise is take multiple opinions and decide yourself.

The big problem with solar and batteries right now is it's still plagued with fly by night sales people, and many self proclaimed experts, so take your time and way up as many opinions and options as you can.

Screwdriva

When it comes to bifacial panel performance, I prefer to rely on numbers rather than anecdotes. These are my 3 top sources of evidence, across geographies:

1) Side by Side test in the US.

2) Side by side panel comparison by Heatable (a UK installer) 

3) Side by side data from an end user's roof in Cambridge, highlighting a ~13% average increase in efficiency vs. a mono facial panel. (It is always recommended the invisible area behind the bifacial panels is painted white for maximum albedo gains). 

From the above, safe to say you can expect > 10% increase in generation on most days (#3 above highlights that much higher outperformance is possible. The one exception are sunny, hot days, which is when bifacial panels struggle to outperform standard panels).

Given that the quote you have shared with bifacial panels is in fact substantially lower than all other quotes, I see bifacial panels as a "no brainer" choice of technology. Sadly, real world awareness of these panel's performance on roof installations is severely lacking, which is why the above links should prove enlightening. 

One last thing since this is a Green & Ethical forum - bifacial panels use glass (vs. a plastic rear sheet) and are more environmentally friendly. 

Reed_Richards

Maybe first paint your roof white if you are getting the bifacial panels?

Magnitio

Reed_Richards said:

Maybe first paint your roof white if you are getting the bifacial panels?

Or maybe fit mirror tiles on the roof:)

ka7e

woolgar.c said:

ka7e said:

I actually have 505W panels, my independent supplier managed to get 5 on my roof after other quotes were for 4 x 430W. I understand they may be heavier, but I had a roof survey which said it was OK to use them.

Did you get the survey due to the weight of the 505W panels or were you planning to have one anyway?

Internal and external roof survey was done by the installer before we decided on the array.