Solar Panel Guide Discussion

Martyn1981

tunnel wrote: »

You def don't want the 4 linking to one from the other aspect, absolute no no.


There is an alternative, the benQ330W panel, 12 of these is 3.96kWp but again comes at a premium. Not sure if you could use 4 of these on one string and then make up the other string with different panels up to the 4kWp max. Speak to the installers about this as it may be possible.

Just looked and those 330 or 315's are fine, just a shame the 285's aren't high voltage, as they're a nice price.

Another option is the Solis 3.6kW dual MPPT inverter. It's very (very) cheap, good efficiency, and has an MPPT range of only 100V+.

Mart.

michaels

Thanks for all the input

So would the solis inverter be ok with 4x 250w approx 30v panels or would it still be best to go for the 285w panels? Any other dual string inverters with low volts?

Martyn1981

michaels wrote: »

Thanks for all the input

So would the solis inverter be ok with 4x 250w approx 30v panels or would it still be best to go for the 285w panels? Any other dual string inverters with low volts?

I think the Solis would be ok, but I'm always a bit worried when saying what something is in theory, rather than the installers or electricians, who actually understand all of this.

If you go to the Swithenbanks shop (see my link in last post) you can have a look at inverters, but I'm struggling to find more with such a low MPPT point.

You can also have a look at the panels, and read the spec sheets, but again, most are ~30V. Remember it's not really about the Wp, it's just about getting the volts high enough. For my original ESE I had to have 2 inverters, but have since found several decent dual MPPT inverters that could cope with the lower voltage on my smaller string.

Another option still, is SolarEdge, I've got that on my WNW (T has it on 1 system too). It's excellent, but there's always the issue of having extra bits of kit, up on the roof and hard to get at if they fail. Here's some background on SolarEdge.

Mart.

michaels

Thanks

A solarEdge was mentioned as a possibility but it was £600 extra and I wasn't sure it could possibly pay for itself.

Martyn1981

michaels wrote: »

Thanks

A solarEdge was mentioned as a possibility but it was £600 extra and I wasn't sure it could possibly pay for itself.

No probs.

SolarEdge is excellent, especially in tricky situations like this. The PO's cost about £30 each, so that could add £500. The inverter is reasonable, and it's very efficient, 12yr standard warranty, and cheap to extend to 20yrs. But access has to be considered even with 25yr warranties on the POs.

Found another option, been struggling to find more 72 cell panels, but the Seraphim range are 72's, and have high voltages of about 50V. They are quite cheap, and do a 285Wp. The only thing to note is that they are a tiny bit wider by 64mm than most panels. It's not much, but you mentioned that the space for the 4 panels is tight, so trying to highlight anything I spot.

See, lots of options, slowly, and you can pretend to the installers that you know what you're talking about, or at least, keep a mental check on what they suggest.

Mart.

Martyn1981

There's also the Upsolar panels with built in SolarEdge, and only cost about £10 to £15 more each.

Mart.

pinnks

My small system is exactly half the size of the larger one. Both have the same panels and SMA inverters. I appreciate that a SMA 1600TL will have different characteristics to the 4000TL but it is interesting in the mornings that the large system with 14 panels (west-facing) is up and running while the 7 panel system (south-facing) is still "asleep". It is not until the bigger system is generating about 80W that the smaller system wakes itself up. Once it gets going it quickly overtakes the larger one as it is of course facing the morning sun.


Not scientific but supports Mart's concerns about small numbers of panels on a string. It is also something my installer mentioned when planning my system as I was considering putting 4 panels on a somewhat shaded east-facing roof to complete my roof-decoration. His "I wouldn't bother" was drive more by low switching voltage from only 3 panels than by the shading issues.


Gary

tunnel

Solaredge shouldn't cost £600 more than a SMA inverter...period. Hell, even micro inverters don't cost that much

michaels

tunnel wrote: »

Solaredge shouldn't cost £600 more than a SMA inverter...period. Hell, even micro inverters don't cost that much

I don't know 16 x £30 = 480 plus markup plus does it take longer to install?

tunnel

michaels wrote: »

I don't know 16 x £30 = 480 plus markup plus does it take longer to install?

Less the £250 inverter price?