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      CommentAuthorfostertom
    • CommentTimeJun 14th 2016 edited
     
    Posted By: ringithe resistance of the load need to be much in real time to the generation of the PV panel(s), therefore a converter/interface is needed between the PV and the load
    Explain more? Sounds like what you want if anything is a storage battery - an converter/interface (inverter?) seems neither here nor there?
    • CommentAuthorEd Davies
    • CommentTimeJun 14th 2016
     
    Wot ringi says. Practically, there will be an AC voltage intermediary between the panels and the use. If it's in a dc-to-dc converter it might be at a higher frequency and be a tiny bit more efficient than at 50 or 60 Hz but the gains will be pretty small. 25 to 35% swings in cost seem like an exaggeration.
    • CommentAuthorEd Davies
    • CommentTimeJun 14th 2016
     
    Posted By: fostertomExplain more?
    Try running a 3.3 V CPU or a 400 mA LED directly off a 48 V battery for a smoke-filled explanation.
    •  
      CommentAuthorfostertom
    • CommentTimeJun 14th 2016
     
    Sorry, it's not explained, to a non-electrician.

    Posted By: Ed DaviesPractically, there will be an AC voltage intermediary between the panels and the use
    is that inherent, or just how it is today?

    Posted By: Ed Daviesdc-to-dc converter it might be at a higher frequency
    how can dc be at any frequency?

    Posted By: Ed DaviesTry running a 3.3 V CPU or a 400 mA LED directly off a 48 V battery for a smoke-filled explanation
    so you say - doesn't engage any agreement by experience in me.
    • CommentAuthorEd Davies
    • CommentTimeJun 14th 2016
     
    Posted By: fostertomhow can dc be at any frequency?
    Dc-to-dc converters work in different ways but essentially they convert to AC, transform and convert back. It's not usually simply a transformer as such (at least in modern devices) but rather some sort of reactor (inductor or capacitor) network working to divide or multiply the voltage.

    E.g., modern light-weight wall warts basically ignore the fact that the incoming voltage is AC - they rectify it to high voltage DC then chop it at high frequency (10s of kHz, I think), use an inductor capacitor combination to divide down to the target voltage then rectify that.

    The advantage of the high frequencies is that the energy needs to only be stored for a small number of microseconds, rather than multiple milliseconds needed at 50 Hz, so they can be smaller and lighter. So the advantage of staying with DC between devices is not large.
    •  
      CommentAuthorfostertom
    • CommentTimeJun 14th 2016
     
    I see - hadn't thought how to 'transform' up DC.
    • CommentAuthorbillt
    • CommentTimeJun 14th 2016
     
    You need to use the same technique if you are reducing DC as well.

    Standard linear regulator or resistive dropper will waste about 9 times more energy than is used productively if going from 48V to 5V for example.
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