Is there a difference between grid tie or non grid tie panels?

[John Simmons]

I have two nearly 10 year old Kyocera KD250GX-LFB2 > 250 Watt Solar Panels, for a total of 500 watts. They still work great, but technology has moved on, efficiency has gone up etc.

I have seen newer panels that claim to be able to provide 400 Watts of total power instead of 250 Watts out of the SAME footprint. When I first bought the Kyocera panels they were labeled for off grid use. I am currently in Mexico and the panels I am looking at are labeled for “Grid Tie”.

My question is, if I replace the Kyocera panels with the new higher output same footprint panel (assuming the MPPT controller will work with the panel) is there really a difference between a panel labeled for grid tie vs one labeled for non Grid tie? Being able to increase efficiency by harvesting 800 watts vs 500 watts out of the same space is extremely tempting.

So, is there a difference or not? Is it just marketing?

Thanks for any help.

John.

 

[chrisski]

Not just marketing. Some not for grid tie panels have had labels removed for whatever reason so they’re not UL compatible. I think some grid tie panels have mini inverters in them and won’t function unless connected to a grid tie system. A lot of panels don’t have these restrictions and would be fine. Not sure where you’re at, but Arizona has a lot of used panels for sale on Craigslist.

 

[John Simmons]

I am in Mexico, so there is also a bit of a language barrier going on. I do not want the microinverter type panels, or anything like that. I was going to place them in parallel for my 12 V system. I was assuming that the rating voltages would be too high etc. I really need to go back and look the proposed panels up on line but the salesman seemed pretty disappointed when I said I wanted non grid tie. He truly believed there to be a difference.

 

[Hedges]

Used to be people used PWM charge controllers, so Vmp around 17V was ideal.
Grid tie systems have typically been high voltage series strings, up to around 600V or 1000V max open circuit. So any voltage works, just connect suitable number in series.
Lots of economical big panels, from 250W to 500W.

Used be be panels were connected to ground on the negative side, and positive side was higher voltage than ground. And then grid tie was the same. Today, grid tie is often with a transformerless inverter, and half the panels are zero to +300V or -500V, while the other half of panels in a string are zero to -300V or -500V. And some panels started degrading rapidly, due to what is called PID, Potential Induced Degradation. Some panels have more of a problem with that than others.

If your system is off-grid, any grid-tie, off-grid or label removed panel will work. First thing is make sure Voc, adjusted for record cold temperature, doesn't exceed charge controller rating.

Panels these days can put out 200W/m^2, vs. 130W/m^2 some years ago. So yes, 50% more power in same footprint.
If your system is negative ground, maybe "p-type" silicon, immune to PID when positive relative to earth, is best.
SunPower is n-type. They are supposed to degrade slower from sunlight. Once upon a time, they had a PID problem when negative grounded. Data sheet for the E20 panels I bought say they have very low PID degradation, but I'm going to switch them to a positive-ground inverter.

I am in Mexico, so there is also a bit of a language barrier going on. I do not want the microinverter type panels, or anything like that. I was going to place them in parallel for my 12 V system. I was assuming that the rating voltages would be too high etc. I really need to go back and look the proposed panels up on line but the salesman seemed pretty disappointed when I said I wanted non grid tie. He truly believed there to be a difference.

What are the specifications for your charge controller? That will determine if a given panel can be used, or if multiple panels could be in series.

 

[John Simmons]

I have a Morningstar Tristar 45 amp MPPT controlller. It is set up for 12 V output but can take a maximum solar input of 125V. The Kyocera 250W panels are wired in parallel for 500 Watts and are specified at 30V open circuit.

From what I am hearing, as long as I remain below the maximum voltage input rating of the Tristar MPPT which is 125V, I can upgrade the panels with no problem. The new panels would also be placed in parallel rather than series. I plan on keeping negative ground as I am not comfortable mixing grounds in different parts of different pieces of equipment. Aluminum masts, aluminum exhaust manifolds, stainless propellor shafts, bronze heat exchanger, bronze propeller, bronze through hulls, steel engine, there are already so many competing dissimilar metals all protected by a few sacrificial pieces of zinc that my comfort level in changing to positive ground in the MPPT controller (even if it lets me) is too low for my peace of mind. I also just bought a brand new samlex evo 3000 12 V inverter, not getting rid of that thing!

I need to go back to the store and get the manufacturer and model of the panel I looked at.

Again, thanks for everyones help.

 

[John Simmons]

I had earlier contacted Morningstar about upgrading a 45 amp MPPT controller to 800 watts at 12 V. I asked if it was going to self destruct and their answer was that it would just limit itself to the 45 amps, but nothing bad would ever happen. So for maybe a bit of time during the sunniest part of the day, I don’t get the full output, but to be honest, I have NEVER seen my 500 watt system output 500 watts. Even with a HUGE 1200 Ah lithium bank running a 1 hp refrigerator holding plate, I MIGHT get 30 amps During peak load time. So I look forward to seeing if 800 watts really will put out 800 watts because I NEVER got 500 watts out of my 500 Watt panels.

john

 

[snoobler]

I have a Morningstar Tristar 45 amp MPPT controlller. It is set up for 12 V output but can take a maximum solar input of 125V. The Kyocera 250W panels are wired in parallel for 500 Watts and are specified at 30V open circuit.

From what I am hearing, as long as I remain below the maximum voltage input rating of the Tristar MPPT which is 125V, I can upgrade the panels with no problem. The new panels would also be placed in parallel rather than series. I plan on keeping negative ground as I am not comfortable mixing grounds in different parts of different pieces of equipment. Aluminum masts, aluminum exhaust manifolds, stainless propellor shafts, bronze heat exchanger, bronze propeller, bronze through hulls, steel engine, there are already so many competing dissimilar metals all protected by a few sacrificial pieces of zinc that my comfort level in changing to positive ground in the MPPT controller (even if it lets me) is too low for my peace of mind. I also just bought a brand new samlex evo 3000 12 V inverter, not getting rid of that thing!

I need to go back to the store and get the manufacturer and model of the panel I looked at.

Again, thanks for everyones help.

If you're mixing and matching panels of different brands/models, here are some guidelines:

For parallel:
Select panels with the same number of cells or nominal votlage.
Each parallel string must have similar Vmp/Voc values for the panels.

For series:
All panels in the string should be very similar in Isc/Imp. All panels in the string will be limited to the LOWEST current of all panels in the string.

Voc = 30V is atypical. If 30V is Vmp, they're likely 60 cell panels.

EDIT: They are 60 cell panels. Vmp = 29.8V

https://www.solarelectricsupply.com/fileuploader/download/download/?d=0&file=custom%2Fupload%2FKyocera-KD200-60-Series.pdf