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96-cell module vs 60-cell module what difference?

Discussion in 'Energy, Environment, and Policy' started by brucet999, May 27, 2017.

  1. brucet999

    brucet999 Active Member

    Joined:
    Mar 12, 2015
    Messages:
    1,955
    Location:
    Huntington Beach, CA
    I have had two different proposals for rooftop solar. One is 4.8kW with 16 LG Mono-X 60-cell 300W modules; the other 4.62kW with 14 Panasonic HIT 96-cell 330W modules; both with SolarEdge optimizers and inverter. Net cost difference after tax credit is $1055 in favor of the LG system. Panasonic PTC rating is 311.3W x 14 = 4.36kW vs LG PTC rating 271W x 16 = 4.34kW, so despite the higher nameplate rating of the LG array, actual production would be almost identical for my house. Average ambient high temp here is 68ºF and we get regular afternoon off-shore breezes of 4 to 5 mph - in other words PTC conditions.

    I asked Panasonic what might make the more expensive Panasonic modules worth the difference and was told that:
    -LID for Panasonic is only 0.5% (type n cells) vs LG's claimed 2%, so Panasonic's system = 4.34kW vs LG = 4.25kW
    -Panasonic degradation rate is 0.26% annually vs LG 0.55%
    -Panasonic temperature coefficient is 0.258%/ºC vs LG 0.41%/ºC. Pretty much taken care of in PTC, I guess.
    -Panasonic's 96 cells produce higher voltage (max 69.7V) for any given irradiance than LG's 60-cells (max 38.9), so it will reach the 8V threshold level of the optimizers earlier and stay producing later in the day, thus producing more power.

    So how can I quantify all that? Can the Panasonic system overcome its $1055 initial cost deficit?
    PV Watts is not specific enough to help much. I guess I could enter the PTC ratings corrected for LID instead of STC.
    Degradation rate difference is very small, 0.29% annually. I guess I could average it; 1.5% over 10 years, 2.9% over 20.

    The most interesting point is the voltage threshold effect. How can one calculate how much difference that would make? Longer active time in the afternoons would mean selling more power to SCE at higher peak TOU rate.

    How does one even arrive at PV productive hours, anyway?
     
  2. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

    Joined:
    Mar 8, 2012
    Messages:
    13,237
    Location:
    Texas
    Not answering your question, but my experience with LG is that you had better hope you never have a problem. LG service on the few LG products I've purchased is not good.
     
  3. Sharkbait

    Sharkbait Member

    Joined:
    Apr 5, 2016
    Messages:
    464
    Location:
    Los Angeles
    I'll comment on the 60-cell, LG Mono X (monocrystalline) panels I have on my system. I had two failures during the first year (out of 24 panels). My installer replaced them both under my warranty. No problems. In fact, he also replaced both optimizers (just in case). So was it panel failure or optimizer - who knows? I never found out. As a side-note, each failure was on a different string.

    My system will be three years old in a month. I've noticed no performance degradation during 35 months of operation. Amazing but true. My panel performance is very, very close to PTC. Two days ago, my 24-275w panels produced 48.257 kWh of power, the highest amount of power generated in one day for my system. It's very rare to have morning low cloud conditions where I'm located, about 100 miles east, northeast of you, so I was producing the same amount of power three hours before peak and three hours after peak (peak power is currently reached around 12:45 PM) this month. My panels are facing very close to 180º azimuth.

    The 96-cell panels will, of course, have a different footprint. If you're mounting them on the roof, make sure the configuration has the proper fit and finish with perimeter access for fire department if your municipal codes require. I have plenty of property, so my system is on the ground, about 90' from the inverter. Also as a side-note, I have my panels professionally cleaned twice a year and rinsed with DI water for $70 for each visit. It's worth it to me to have the panels producing peak power and cheaper to have them cleaned if on the ground than on the roof.

    The differences described are really 'mouse nuts' compared to after-sales support, company strength, warranties, insurance and more. Even when you do the homework on your installer, even the big companies go belly-up. If your installer goes out of business, it might be good to know who would support your system and at what price, perhaps by the visit and/or hourly rate. The installer doesn't provide equipment warranty. The manufacturer does. Who has more distributors of panels, inverters, and optimizers in your area - LG or Panasonic? In the end, I think a defective panel can be delivered to the manufacturer through a local distributor but don't quote me on that. Ask your installer. Better yet, ask the equipment manufacturer.
     
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  4. Ampster

    Ampster Member

    Joined:
    Oct 5, 2012
    Messages:
    827
    I will take a stab at answering that question. PV Watts uses Capacity Factor which displays at the bottom of their final screen. That number is derived from weather patterns, your location and the specifics of your installation, It is expressed as a percentage of ideal generation. For example, 24 hours a day, 365 days a year would theoretically yield 8760 hours of solation. At my latitude and with a 10% tilt facing south the Capacity Factor is about 17%. I prefer to translate that into a multiplier that I can use much easier to derive expected annual output of a system (Capacity Factor divided by 8760). That multplier is about 1500. Using that multiplier, one could expect from the 4.8kW system above, installed at my location to yield 7,200 kWhrs of energy a year.

    Remember the factor is specific to averages of weather at that location, latitude and mounting characteristics.
     
  5. miimura

    miimura Active Member

    Joined:
    Aug 21, 2013
    Messages:
    1,883
    Location:
    Los Altos, CA
    Another way to look at this is how many equivalent ideal hours of generation do you get per day. 17% * 24 hours is 4.08 hours of ideal generation per day. 4.8kW * 4.08 * 365 = 7148 kWh / year
     
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