SunPower Equinox system

[infinity]

I was wandering around a home show and the salesman was touting that these are the best systems due to their best in the industry efficiency. Has anyone installed these systems? I'm currently not in the market for a PV system just wondering if anyone has heard of them.

https://sunnymacsolar.com/our-technology

 

[GoldDigger]

I was wandering around a home show and the salesman was touting that these are the best systems due to their best in the industry efficiency. Has anyone installed these systems? I'm currently not in the market for a PV system just wondering if anyone has heard of them.

https://sunnymacsolar.com/our-technology

The general feeling is that the added benefits in terms of efficiency and warranty on the panels does not make up for the high cost premium over other panels.
The added efficiency shows up in watts/m² of panel area, not in watts per dollar or watts per panel. If you have a relatively unusual situation where your installation space is strictly limited and you absolutely have to maximize the output power that may be a good reason to specify SunPower.
I also do not think it is possible to buy the SunPower panels except from an installer/dealer. (Except maybe for factory seconds.)

 

[infinity]

The general feeling is that the added benefits in terms of efficiency and warranty on the panels does not make up for the high cost premium over other panels.
T

It's funny that you should say that when I asked about price he didn't say anything specific beyond the higher efficiency makes up for the higher cost. The 25 year warranty is nice though. Is a micro-inverter system better than a combiner/single inverter system?

 

[jaggedben]

It's funny that you should say that when I asked about price he didn't say anything specific beyond the higher efficiency makes up for the higher cost.

Total sales BS. The installed cost per watt is the installed cost per watt. Panel efficiency is already baked into that. Same as Golddigger said, unless you have space restrictions and using higher efficiency panels allows you to recoup a bigger investment in the same roof space, there's simply no truth to his statement as you related it.

The 25 year warranty is nice though. Is a micro-inverter system better than a combiner/single inverter system?

Micro-inverters have their advantages and disadvantages, although on balance I tend to lean towards them (I installed them on my house), especially for smaller systems. With rapid shutdown requirements these days it is harder to save money using other types, compared to before.

LG has beefed up their panel warranty and is more or less a direct comparison to Sunpower at a better price. Also one might think LG probably has a better chance of still being around in 25 years. Almost all solar panels now come with a 25 year 'performance guarantee' although that is not always a solid warranty against all kinds of defects. The LG and Sunpower warranties are more solid in that respect.

 

[ron]

Is a micro-inverter system better than a combiner/single inverter system?

If the install will be with odd shading conditions, or a single string with panels in different orientations, the micro-inverter may produce more power because if its individual ability for MPPT https://en.wikipedia.org/wiki/Maximum_power_point_tracking
whereas a single inverter would be affected by a single panel being shaded or different light intensity of one panel than other panels on the string.

 

[infinity]

If the install will be with odd shading conditions, or a single string with panels in different orientations, the micro-inverter may produce more power because if its individual ability for MPPT https://en.wikipedia.org/wiki/Maximum_power_point_tracking
whereas a single inverter would be affected by a single panel being shaded or different light intensity of one panel than other panels on the string.

This was another point that the salesman mentioned during his sales pitch.

 

[GoldDigger]

If the install will be with odd shading conditions, or a single string with panels in different orientations, the micro-inverter may produce more power because if its individual ability for MPPT https://en.wikipedia.org/wiki/Maximum_power_point_tracking
whereas a single inverter would be affected by a single panel being shaded or different light intensity of one panel than other panels on the string.

If a single panel was partially or completely shaded, the most power you would lose with a single inverter would be the output of that panel. All that a micro or optimizer would gain you would be the addition of whatever limited power that single panel could produce. If you have partially shaded strings in parallel or losing the Vmp of one or more panels would drop you below the operating voltage of a string inverter, then you could have a real problem, needing a solution.

 

[jaggedben]

If a single panel was partially or completely shaded, the most power you would lose with a single inverter would be the output of that panel. All that a micro or optimizer would gain you would be the addition of whatever limited power that single panel could produce. If you have partially shaded strings in parallel or losing the Vmp of one or more panels would drop you below the operating voltage of a string inverter, then you could have a real problem, needing a solution.

That goes against what I was always taught about shade or mismatch on panels in a string affecting the current throughput of the entire string.

 

[ron]

If a single panel was partially or completely shaded, the most power you would lose with a single inverter would be the output of that panel. All that a micro or optimizer would gain you would be the addition of whatever limited power that single panel could produce. If you have partially shaded strings in parallel or losing the Vmp of one or more panels would drop you below the operating voltage of a string inverter, then you could have a real problem, needing a solution.

In a single string, if a panel was shaded, I believe the string becomes open circuited and the voltage goes to 0.

 

[ggunn]

If a single panel was partially or completely shaded, the most power you would lose with a single inverter would be the output of that panel. All that a micro or optimizer would gain you would be the addition of whatever limited power that single panel could produce. If you have partially shaded strings in parallel or losing the Vmp of one or more panels would drop you below the operating voltage of a string inverter, then you could have a real problem, needing a solution.

If I understand correctly what you are saying, you are mistaken. With a regular string inverter if a module is completely shaded the whole string is cut off.

 

[GoldDigger]

If I understand correctly what you are saying, you are mistaken. With a regular string inverter if a module is completely shaded the whole string is cut off.

I beg to differ. If the string is in parallel with another equal length string to one MPPT input, that string may or may not contribute, depending on the details of the MPPT algorithm.
But if the string has its own MPPT input it should still work, giving the Vmp of the remaining panels minus two or three diode drops from the bypass diodes. If the dark panel has defective bypass diodes or is ancient enough not to have any, then you will lose the whole string.

 

[ggunn]

I beg to differ. If the string is in parallel with another equal length string to one MPPT input, that string may or may not contribute, depending on the details of the MPPT algorithm.
But if the string has its own MPPT input it should still work, giving the Vmp of the remaining panels minus two or three diode drops from the bypass diodes. If the dark panel has defective bypass diodes or is ancient enough not to have any, then you will lose the whole string.

I don't think that's correct, but I'll check and get back to you.

 

[GoldDigger]

I don't think that's correct, but I'll check and get back to you.

By all means do your due diligence.
If it were not the case, there would be no point in making panels with bypass diodes in them.
Now if the panels were single panels in parallel to an MPPT Charge Controller, any shaded panel would certainly not contribute. The voltage loss would be too great relative to the other panels.

 

[ggunn]

By all means do your due diligence.
If it were not the case, there would be no point in making panels with bypass diodes in them.
Now if the panels were single panels in parallel to an MPPT Charge Controller, any shaded panel would certainly not contribute. The voltage loss would be too great relative to the other panels.

I hear you, but by the same token, if a shaded module would only take itself out there would be no reason to sell optimizers. I don't think it's a simple answer. When irradiance goes down, module current goes down but voltage doesn't (much). I've thought about it a lot but I have yet to pencil whip it.

 

[Zee]

measured half the amps in a string due to two being in shade.

Details:
20 Suntech Power STP185S-24/Adb+ modules and 1 SMA America SB4000US
Installed 2011.
2 strings of 10 each combined to the one input on inverter.
One string had a telephone pole shading no more than 10% of 2 panels in a string of 10.
That took the whole string down to less than half the output of other one.

 

[GoldDigger]

measured half the amps in a string due to two being in shade.

Details:
20 Suntech Power STP185S-24/Adb+ modules and 1 SMA America SB4000US
Installed 2011.
2 strings of 10 each combined to the one input on inverter.
One string had a telephone pole shading no more than 10% of 2 panels in a string of 10.
That took the whole string down to less than half the output of other one.

I specifically noted that my argument did not apply to parallel strings to a single MPPT input when only one was shaded.

 

[GoldDigger]

I hear you, but by the same token, if a shaded module would only take itself out there would be no reason to sell optimizers. I don't think it's a simple answer. When irradiance goes down, module current goes down but voltage doesn't (much). I've thought about it a lot but I have yet to pencil whip it.

Look at the entire IV curve of the cells, not just one quadrant. You can try to force more current through them above the PV current for that insolation, but that will drive the cell voltage negative and possibly damage the cells. And as soon as the applied negative voltage exceeds the forward diode drop of the bypass diode(s) they will conduct, effectively taking those cells out of the series string.

One way of looking at it which might help is this: Start with the string operating momentarily at just the Imax of the shaded panel section. At this point the voltage across the cell terminals is zero. That is the definition of Imax. As the MPPT algorithm tries to reduce its load voltage even more, the current from the unshaded panels will increase and the shaded panel will move into the negative voltage quadrant. The bypass diodes keep it from going very far into that quadrant by going into forward conduction.