Higher efficiency means more energy?

kings914
kings914 Registered Users Posts: 1 ✭
edited July 2017 in Solar Product Reviews & Opinions #1
Solar sales been telling people higher efficiency means more energy produced. But solar system price calculate by cost per watt. So when compare apple to apple, a same 10kw system , 1 with 19% efficiency rate, another one with 22%, will the one with higher efficiency produce more? If so with 19%and 22%, how much approx will generate?
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    No, not likely.

    If you are talking the panel rating of the array, you might check what the panels produce under load at temperature.

    There are 2 ways to look at this the PTC (PVUSA?) which lists the output of panels under a more realistic set of variables. and the Normal Operating Cell Temperature (NOCT) value. Which is often published in the panels literature.

    If you are doing a grid tied system, the different types of inverters might be important. If you have partial shade, Micro inverters would increase effective harvest.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Horsefly
    Horsefly Registered Users Posts: 476 ✭✭✭✭
    #3
    You are comparing apples and oranges. The cost per watt is simply the cost of a PV panel divided by the nameplate rating in Watts. So that is really your outlay cost.

    The efficiency of a panel is really saying how much electrical energy you will get for the area you are exposing. Most panels from a given manufacturer have varying efficiencies within a particular line. That's why a given panel family may have 275W, 280W, 285W, and 290W panels. They all will look the same, and have the same dimensions. It's just that when tested the 290W panels have a higher average efficiency than the 280W panels.  A typical 60-cell panel will have dimensions somewhere around 65" x 40". That works out to be 1.677 square meters. The standard test condition (STC) are 1,000W of energy hitting one square meter. So for a 1.677 square meter panel, under STC 1,677W are striking the surface of the panel. If the panel is rated 280W, the panel efficiency is the 280W divided by 1,677W, or 16.7%. 

    So the bottom line:
    1. The cost per watt is one of the measures of how much you will be spending in your initial install. Of course the other measures are the other components, such as inverter, charge controller, battery, and that pesky wire.
    2. The efficiency of a panel is just how much power it will produce for a given surface area. Not very important in most cases, unless you are somehow really pressed for space to put your panels.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 8S (25.6V), 230Ah Eve LiFePO4 battery in a custom insulated and heated case.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #4
    A 10kw pv array should produce 10kw under the conditions under which it's sold, typically STC as horsefly says. Except in a lab, conditions are never STC, so we have to look at factors like panel temperature coefficients to estimate what real world production will be.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Solray
    Solray Registered Users Posts: 246 ✭✭✭
    #5
    Higher efficiency means the same amount of work is being done for less energy input into the system. For PV it means the same amount of power for fewer photons striking the panel. For wire, it means less energy is used to heat the wire so more is transmitted through it.
    Higher efficiency means different things to different applications.
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  • Horsefly
    Horsefly Registered Users Posts: 476 ✭✭✭✭
    #6
    Solray said:
    Higher efficiency means the same amount of work is being done for less energy input into the system. For PV it means the same amount of power for fewer photons striking the panel. For wire, it means less energy is used to heat the wire so more is transmitted through it.
    Higher efficiency means different things to different applications.
    My point was that for PV panels (which seems to be what the OP is talking about, given the efficiencies he quoted), it's not a particularly meaningful consideration.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 8S (25.6V), 230Ah Eve LiFePO4 battery in a custom insulated and heated case.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited July 2017 #7
    The efficiency is usually directly proportional to the price more efficient more expensive, so if one was selling power the cost versus increased production would have to be calculated to guestimate the time needed to recoup the added expenditure .See cost vs value in the link
    below. 

    http://news.energysage.com/what-are-the-most-efficient-solar-panels-on-the-market/
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Solray
    Solray Registered Users Posts: 246 ✭✭✭
    #8
    They don't mention the LG NeOn 2 panels there. They have 21.5% efficiency which puts them with Panasonic and Sun Power.
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  • aminaelis
    aminaelis Registered Users Posts: 14 ✭✭
    #9
    The efficiency of solar panels means the efficiency of the energy conversion from the energy of sun light hitting the panel to direct current. Or am I mistaken?   
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,101 ✭✭✭✭✭
    #10
    Panel efficiency is based on output vs. overall size of the panel. CELL efficiency is based on conversion efficiency vs. cell size. Solar panels have areas which aren't covered with cells so  will have lower efficiency than the individual cells within. You can usually find these numbers in the Mfg. info. sheets

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #11
    aminaelis said:
    The efficiency of solar panels means the efficiency of the energy conversion from the energy of sun light hitting the panel to direct current. Or am I mistaken?   


    Basically the difference is related to the size, a panel of a given size at 20% efficiency, versus an equally sized panel of 17% efficiency would produce 3% more energy, theoretically . So for example a 100W 20% efficient produces 100 Watts, the 17% panel using the same amount of area would be 97 watts, factor in the price difference as a percentage, if the 20% version is 3% more expensive then all is equal, but if the price is 20%more, then not such a good deal. If area is the motivating factor is area, perhaps it is worth buying the more efficient panels, who knows, but if the difference in production was > 20% then that would be a significant amount worth considering. Personally a few percentage points is not a motivating factor fo me because the margin is too small.
    Personal opinion, others may differ.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,886 ✭✭✭✭✭✭
    #12
    Adding on to the good info...When one starts tracking an array,  the size of the panel (or efficiency) can allow more power from a spec that limits square footage for wind and snow load aloft. A 6" pole can hold 125 sq ft and an 8 inch about 250. For this reason the better panels are used to get the most power out of the array. The better panels also have a better product warranty. Panasonic just lengthened theirs to 25 years from 12.

    I had a client who had a Panasonic fail at 10 years. I sent it back and their FA showed it was over torqued at the mounting. They gave him a new panel and they did not have to. He was lucky as most of the panels had over two times the torque spec. He bought a torque wrench and bought me dinner.

    The better panels also do much better at high temperature. The Sunpower and Panasonic are amazing and having 3 identical arrays here I can do testing on panels. I get some very nice offers occasionally. I have not tested the LG panels yet but I have sent them a letter telling them my shipping address :)
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • softdown
    softdown Solar Expert Posts: 3,885 ✭✭✭✭
    #13
    Dave Angelini said:
    Adding on to the good info...When one starts tracking an array,  the size of the panel (or efficiency) can allow more power from a spec that limits square footage for wind and snow load aloft. A 6" pole can hold 125 sq ft and an 8 inch about 250. For this reason the better panels are used to get the most power out of the array. The better panels also have a better product warranty. Panasonic just lengthened theirs to 25 years from 12.

    I had a client who had a Panasonic fail at 10 years. I sent it back and their FA showed it was over torqued at the mounting. They gave him a new panel and they did not have to. He was lucky as most of the panels had over two times the torque spec. He bought a torque wrench and bought me dinner.

    The better panels also do much better at high temperature. The Sunpower and Panasonic are amazing and having 3 identical arrays here I can do testing on panels. I get some very nice offers occasionally. I have not tested the LG panels yet but I have sent them a letter telling them my shipping address :)
    And yet you still talk to us?
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,101 ✭✭✭✭✭
    #14
    Dave is just a regular guy with tons of hands on, off grid systems experience which he is willing to freely share with us other regular guys.  He probably has tons of other experience as well. Thanks Dave.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,886 ✭✭✭✭✭✭
    #15
    No,  Thank-you littleharbor.  If anyone wants to comment on me please PM me and keep the threads pertinent. Thx.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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