New to Grid Tied Home Solar...

[ultrarunner]

It has been a few months now of producing power...

The 6 kW array has been averaging about 26kW per sunny day read from the Invertor.

The peak production seems to be no more than 4.6kW which happens noon to 1 pm daily...

I was hoping it would be a little closer to 6 so a little disappointed...

Panels are 12 years old and it got me thinking maybe I could replace a few of the 160W panels with 300W panels but maybe it is not as simple as a straight swap?

Daily production is limited by shade late in the day which impacts total output as the sun is still strong but the panels are in the shade...

As a side note... PGE is trying to revamp rate structure to offset massive losses/claims from the fires... some are predicting kW rates in the 30-40 cent range.

 

[techman]

Rule of thumb number on panels is that they lose 1%/year due to aging and UV exposure. Replacing a few panels with new 300w is not a good idea. Panels in a string (wired in series) should all be of the same type and rating. Since a panel is fundamentally a current source (not a voltage source) the higher output panels will be capable of higher current output, but in series with a lower power panel the current will be restricted to the lowest current in the string. If you replace them, do them all.

paul

 

[ultrarunner]

Houston... I might have a problem as the 6 kW array is made up of 30 165W panels and 6 170W panels totaling 5970 Watts.

Did not know all panels should be the same in a String system...

Replacing 36 panels with 300W would put me at 10,800 Watts.

The panels are subject to some shading late in the day...

Another question... can I simply wash the panels with soap and water? Pollen is blanketing the panels.

Maybe Micro Invertors would be best when the day comes?

 

[deezler]

I'm at 1.5 yrs in on my 5.5kW array (16x 345 watt panels) here in "cloudy" Michigan. I can get about 5.1 to 5.2 kW peak production, mid day around this time of year. Best single day total output is 38 kw-hrs, but an average sunny day is typically more like anywhere from 25-32 kWh. Sometimes what looks to the eye like a pure, sunny day, still has a layer of overcast, haze, fog, occasional clouds, etc that will diminish system output.

My panels are on individual micro-inverters, so not in a string. If one panel gets hit by partial shade, the other ones don't care one bit. This really helps maximize daily production in certain partial-shadier hours of the day.

I have only cleaned my panels off one time, last May when I noticed diminished sunny-day output, and climbed up on the roof to see they were covered in a layer of pollen. I washed them off with a mild dish soap solution and microfiber towels, no problem.

 

[techman]

The 165w vs 170w is a small difference which would not have much of a negative effect on the system, but the 170's are limited to 165 in all likelihood. Based on a total of 36 panels, you most likely will have 2 strings (2 x 18 in series)

As for washing them, water perhaps with some soap is fine. Do not use a pressure washer which could force water through edge seals and cause problems with the panels.

Your shading issue could be a factor is only a few panels are shaded. In that case the string associated with the shaded panels will be effected. If the shading affects the larger array, then you don't have many options. If the shading is confined to a few, then micro inverters will help by allowing all of the unshaded to still produce at a higher level. You would need to weigh the change against the cost of the micro inverters and a bunch of rewiring versus the payback of the additional power gains. If the shading occurs early or later in the day, when output is significantly reduced, then the benefit is likely not worth the investment in any case.

paul

 

[Redneck in training]

Houston... I might have a problem as the 6 kW array is made up of 30 165W panels and 6 170W panels totaling 5970 Watts.

Did not know all panels should be the same in a String system...

Replacing 36 panels with 300W would put me at 10,800 Watts.

The panels are subject to some shading late in the day...

Another question... can I simply wash the panels with soap and water? Pollen is blanketing the panels.

Maybe Micro Invertors would be best when the day comes?

If you decide to install 300W panels check if the racking will accommodate them. The 300 W are larger.

 

[ultrarunner]

The panels appear to be in good shape but I know a tree limb put a slight bend in one of the panels... it must have caught the leading top edge of the middle panel... that panel has slight bend to it.

The bend is not apparent in the attached picture...

The panels are ground mount in 3 arrays...

Picture late on a January Day...

 

[ultrarunner]

Soon it will be 12 months and time to settle up with my Utility...

I have a "Retail" surplus of about $650 from net metering.

Utility pays 3 cents per kW for excess power which is the wholesale cost.

Options are to roll forward or get a check.

During the year the City took over generation??? still have to use power company infrastructure which means the 3 cent per kW would not be coming from the Utility since we buy through the Aggregator...

My simple 2 page gas and electric bill is now 8 or 9 pages...

Still on the learning curve as the year closes out in January.

As a side note... my 10 year old panels stop producing when it gets gray and cloudy... neighbors new 300 W panels were still producing about 500 W long after mine stopped... with both have 6kW systems.

 

[coldsteelva]

Good to see an update. That's interesting to hear about the lower sensitivity of the PV cells after 10 years. I knew that over time PV cells reduced output, but I didn't think they would lose sensitivity to actual solar energy. Knowing all that you know now about solar and metering, would you still consider installing solar based on the expected return on investment? I realize in this instance, you took over an existing system. Do you have other considerations, such as an ineffectual power company?

 

[aczlan]

Good to see an update. That's interesting to hear about the lower sensitivity of the PV cells after 10 years. I knew that over time PV cells reduced output, but I didn't think they would lose sensitivity to actual solar energy. Knowing all that you know now about solar and metering, would you still consider installing solar based on the expected return on investment? I realize in this instance, you took over an existing system. Do you have other considerations, such as an ineffectual power company?

Could also be that the neighbor's newer panels are more efficient than the older panels that ultrarunner has.

Aaron Z