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Domestic Solar for MHs versus 12V Modules

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  • 02-07-2016 9:03pm
    #1
    [Deleted User]
    Posts: 5,238 ✭✭✭


    Sir Liamalot wrote: »
    Whereas €425 can buy 300W of solar and a good controller giving you 1kWh on most days for 25 years far more reliably with no moving parts.
    kadman wrote: »
    Can you tell me more about this please.

    nerd.gif



    Admittedly K I did shoot this figure from the hip. biggrin.png
    Ok let's take CP's 140W modules as an example (cos I don't wanna trawl the internet for deals)
    280Wp @ £210
    with a 45A TriStar PWM (listing ended but you can get them for this price if you are patient especially in Winter when nobody wants them) = £90

    £300 plus shipping (say £40) and exchange rates.
    price per watt: £1.21

    Or if you want an even better deal lets take two domestic 60 cell modules which are far cheaper than 12V modules due to markets and economy of scale. These work natively for 24V or you can modify them for 12V.

    510Wp @ £200 + £90 = £290 + diodes, 2 backing boxes, epoxy & shipping
    Say £400 all in = £0.78 per watt.

    All you need to modify them is new diodes (10A each), extra backing boxes and 4mm² jumpers. You can cut away the backing material to get to the tabbing wire you need to split the strings and pull them back to new (parallel) terminations. You can make smaller strings with more diodes as a 10A diode will likely require a heatsink. Or you can run without diodes and risk overheating and eat the shading losses.
    Warranty void and assume own liability etc..
    390570.jpg

    Off the shelf 60cell PV (for 24V)


    390573.jpg

    Modified 60cell for 12v (double current, half volts)

    Third option is a ~300W module with MPPT.
    EPSolar 40A MPPT: £145
    290Wp Module: £185 {or use 2 of the Bimble solar in parallel for 510Wp @ £200}
    £330 + shipping (~£40) = £370
    price per watt £1.28 {£0.75 per watt with 2 x 255Wp}

    As regards the 1kWh a day figure; I've learned empirically that a panel gives you minimum 3 x rating in Wh on most grey days with poor exposure from Spring to Autumn and maximum 7 x rating on a good day. Regardless of mounting (tilt produces more at midday but horizontal produces all day long).
    Winter is another matter.
    Tiltability extends your seasonal range further into the darker months.

    The 280Wp system would range between 880W to 1.9kW per day.
    The 510Wp example should range between 1.5kW to 3.5kW per day.
    Expect +10% for genuine MPPT so the EP solar 290Wp would be 1kW to 2.2kW per day. {1.7kW to 3.9kW per day for 510Wp + MPPT}

    Better for batteries and more efficient too to be receiving power all day on demand than a quick aggressive charge followed by discharge.

    Best of all it works while you're away at the beach. ;)


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