Do I need optimizers?

[boulter]

I'm already pretty sold on optimizers vs microinverters, but one installer gave me two quotes. One was without optimizers and 2 SunPower 5002m string inverters instead. He said I may not need optimizers given minimal shading on my roof. What do you all think? The biggest shade producer is the large tree on the right.

IMG_2425.jpg

This photo was taken at 5 pm.

[radareclipse]

How about a picture in the morning and one more towards the evening?

[ButchDeal]

I'm already pretty sold on optimizers vs microinverters, but one installer gave me two quotes. One was without optimizers and 2 SunPower 5002m string inverters instead. He said I may not need optimizers given minimal shading on my roof. What do you all think? The biggest shade producer is the large tree on the right.

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This photo was taken at 5 pm.

You can see shadows already for evening and the east trees will cause morning shadows not to mention the roof itself ( dormer ) will cause more shadows. Get SolarEdge and also gets single inverter instead of two.

[radareclipse]

SolarEdge + Optimizers = More performance and able to deal with shading issues

[ButchDeal]

SolarEdge + Optimizers = More performance and able to deal with shading issues

Maybe you know this but for those that don't; SolarEdge inverters will not work without SolarEdge MPPT power optimizers, it is a fully integrated system and you can not use the solaredge inverter without the optimizers.

[radareclipse]

Don't you just love when that happens….complete system design.

[boulter]

Thanks for the replies.

Here's a photo at 8 am. IMG_2502.jpg

The SunPower panels from the proposal would go mostly on the roof of the main house with fewer above the garage where there is shading from the tree.

Here's some detail from the proposal:

Please watch this 3 minute video which explains the function of the cells' "bypass diodes": https://www.youtube.com/watch?v=nwWnZgbeRfU .. At an average solar availability rating of 90% between the two surfaces anyway, your roof has very little shade in the first place. What shade it does have is concentrated in the early mornings and late afternoons where optimizers will be of little benefit -- typically they perform best in "irregular" shade. By using standard inverters (two medium sized ones technically, since they cap out at 8kw each), you could save $6,000 on the projects sticker cost while losing essentially zero performance, but most importantly protect yourself from potential future failure rates of 31 electronic boxes on your roof.

[radareclipse]

Correct me if I'm wrong, but if you are using conventional inverters, a partial shade situation would knock out that whole string that the shaded panel(s) is connected to. Correct?

[sensij]

Correct me if I'm wrong, but if you are using conventional inverters, a partial shade situation would knock out that whole string that the shaded panel(s) is connected to. Correct?

If the shade drops the string voltage below the inverter's minimum input voltage, yes, the entire string can be wiped out. Otherwise, the effect is more complicated. The shade should cause the bypass diodes to be utilized, which would allow the unshaded string current to be maintained. That limits the loss to only the bypassed (shaded) 1/3rd's of the affected panels, which aren't going to produce much even when optimized.

However, if you have strings in parallel that are combined, which must fundamentally always be operating at the same voltage, if one string is partially shaded (and with some panel sections bypassed), it will pull down the voltage of the other string away from its maximum power point.

[ButchDeal]

Here's some detail from the proposal:

Please watch this 3 minute video which explains the function of the cells' "bypass diodes": https://www.youtube.com/watch?v=nwWnZgbeRfU .. At an average solar availability rating of 90% between the two surfaces anyway, your roof has very little shade in the first place. What shade it does have is concentrated in the early mornings and late afternoons where optimizers will be of little benefit -- typically they perform best in "irregular" shade. By using standard inverters (two medium sized ones technically, since they cap out at 8kw each), you could save $6,000 on the projects sticker cost while losing essentially zero performance, but most importantly protect yourself from potential future failure rates of 31 electronic boxes on your roof.

That is some BS to get you to go with what they proposed. Those are small inverters, that brand caps out at 8kw but others do not. Optimizers help with any shade, doesn't matter how "regular" the shade is.

[boulter]

I would think it was BS too except they also gave me a quote for a SolarEdge 10k inverter with SolarEdge P400 optimizers as well. Same SunPower panels. They didn't seem to care which proposal I chose (they actually said the margin was the same), but the one without optimizers came out at $4.53/w vs $5.10 with optimizers.

[boulter]

Now I've got a quote for $4.33/w for 31 SP 335s and 2 5002 inverters which is pretty attractive. Does this sound legit?

The bypass diodes within the SunPower cells are designed to work as well as panel-level optimization, which is basically the trump card on its own. Here's the overview vid again (3 min) https://www.youtube.com/watch?v=nwWnZgbeRfU

There's no denying that the house isn't in the middle of the desert, but I suppose compared to average other houses we come across every day, it is relatively shade-free. Between that and its due-south azimuth, you're easily in the top 10% of the sort of solar-house-feasibility roulette wheel. Maybe not perfect, but in very good shape.

Those photos are helpful and illuminative, but are also basically at the worst possible times as far as shade effects (great for demonstrating the concerns, but a bit skewed to the extremes / not fully indicative of rest of the day). The bulk of the solar production is during the "peak sun exposure" times of about 10am-3pm. This is when the sun is most directly overhead, and has the most perpendicular exposure to the panels. Easily 80%+ of the power for the day is made during this time, even if that time is only 50% of the daylight hours, in which the tree, dormers, and ridge are of minimal effect. There's surely some morning shade from the one tree in the early morning, and some dramatic shade in the afternoon from the ridge and dormers, but these are already relatively marginal production times that in the scheme of things, are not as big of a deal. And again, you do have the bypass diodes, so the shade issue is not all-or-nothing -- it should still be quite good even in the morning and afternoon.

For the inverters, its just that they cap out at 6kW each, so we'd use two medium sized ones instead of one large one. They are priced per-watt, so it costs no more than if there was an option of a 10kW one in the first place.

[sensij]

Have you gotten any competitive non-Sunpower quotes? Like you, I find Sunpower's engineering fascinating, but I am unaware of any real world data that suggests you will get any more power from their panels over another less expensive brand. Real world data showing panels are pretty much interchangeable are much easier to come by.

[J.P.M.]

Now I've got a quote for $4.33/w for 31 SP 335s and 2 5002 inverters which is pretty attractive. Does this sound legit?

The bypass diodes within the SunPower cells are designed to work as well as panel-level optimization, which is basically the trump card on its own. Here's the overview vid again (3 min) https://www.youtube.com/watch?v=nwWnZgbeRfU

There's no denying that the house isn't in the middle of the desert, but I suppose compared to average other houses we come across every day, it is relatively shade-free. Between that and its due-south azimuth, you're easily in the top 10% of the sort of solar-house-feasibility roulette wheel. Maybe not perfect, but in very good shape.

Those photos are helpful and illuminative, but are also basically at the worst possible times as far as shade effects (great for demonstrating the concerns, but a bit skewed to the extremes / not fully indicative of rest of the day). The bulk of the solar production is during the "peak sun exposure" times of about 10am-3pm. This is when the sun is most directly overhead, and has the most perpendicular exposure to the panels. Easily 80%+ of the power for the day is made during this time, even if that time is only 50% of the daylight hours, in which the tree, dormers, and ridge are of minimal effect. There's surely some morning shade from the one tree in the early morning, and some dramatic shade in the afternoon from the ridge and dormers, but these are already relatively marginal production times that in the scheme of things, are not as big of a deal. And again, you do have the bypass diodes, so the shade issue is not all-or-nothing -- it should still be quite good even in the morning and afternoon.

For the inverters, its just that they cap out at 6kW each, so we'd use two medium sized ones instead of one large one. They are priced per-watt, so it costs no more than if there was an option of a 10kW one in the first place.

As others note, you can get similar performance for a lot less than S.P.

[boulter]

I'm somewhat limited in roof space because of the dormers, so the higher-wattage SunPower panels seem like the only ones that can get me to 100% of usage. Plus, they're the only true all-black panels.

See my other quotes at http://www.solarpaneltalk.com/showth...time-in-Boston