Solar cells for AC-DC conversion

Discussion in 'General Electronics Chat' started by coinmaster, Mar 9, 2016.

  1. coinmaster

    Thread Starter Member

    Dec 24, 2015
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    HI, I have a long list of experiments planned mostly involving vacuum tubes for audio purposes and I require a high voltage supply which requires expensive custom made transformers and high voltage capacitors which are also very expensive.
    The power supply will require about 600v bipolar at 1 amp.

    I have another project where I am planning on an off-grid cabin using solar and I just received 43 1.8W cells in the mail that I got for $15.

    This gave me an idea, what if I made a panel with a boat load of super bright LEDs and then sandwiched it together with a panel of solar cells.
    This would allow me to get the high voltages without the need for a transformer or super expensive capacitors.

    If I need 600v and I kept buying .5v 4.6A cells at a price of 15$ per batch of 43 then I could make a 600v "ripple free" supply for about $420 in cells (not counting LEDs yet).

    This would still be far cheaper than the smoothing caps and transformer and whatever that I expect to pay if I used a conventional supply.

    I have some questions though.
    Would such a supply truly be ripple free?
    Is there any "electrical noise" produced through this method?
    A capacitor free supply would be godly.

    Thoughts?
     
  2. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    You're kidding, right?
     
  3. coinmaster

    Thread Starter Member

    Dec 24, 2015
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    No?
     
  4. mcasale

    Member

    Jul 18, 2011
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    No such thing as a "ripple free" voltage supply unless there's no load on it.

    Remember that LEDs are not 100% efficient, and solar cells also have losses.

    Either way, you need to isolate the 600V for safety reasons.
     
  5. nsaspook

    AAC Fanatic!

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  6. coinmaster

    Thread Starter Member

    Dec 24, 2015
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    Tempting...but the goal is to create a supply for super hi-fi amplifiers, that thing has got to be running off of a SMPS or something which is probably noisy. Plus I'd like to rid myself of capacitors.
    All the big shots in amp tech new and old claim that power supply capacitors are just as much in the signal path as the rest of them, so the prospect of removing them is interesting. I've personally experienced huge increases in sound quality from replacing lytic caps with high quality film caps in power supplies, I don't really understand how they affect the sound quality but there's no denying that they do.

    I thought ripple was a byproduct of AC>DC conversion?

    Efficiency is not really an issue here.
     
  7. mcasale

    Member

    Jul 18, 2011
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    Yes, it can be due to conversion, but the basis of ripple is a varying load current (yours is in the audio range). You will need some type of regulator to ensure the voltage doesn't get too high (or low). That's why God invented capacitors;).

    Okay, but it will determine how many LEDs and solar cells you'll need. This thing could get big.
     
  8. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Audiophiles are oft in a class of true believers who state things that simply do not prove out.

    Are the power supplies in the signal path? Well, perhaps, but appear as short circuits, as long as you use enough of them.

    Note that means more caps, not less.

    Typically if you try to run an amplifier without caps across the power supply it will squeal like a stuck pig. I learned that back when I was 16.

    News travels slowly in some parts.
     
  9. coinmaster

    Thread Starter Member

    Dec 24, 2015
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    OH yeah, load ripple I'm not too worried about. I've got a regulator all worked out and if I really had to I could just throw a single high quality cap in there to handle it.
    It's mostly the high capacitance lytics in the pre-filter that I want to get rid of.

    Yeah, I'd expect it to take a large portion of a wall.
    That mostly applies to the consumers rather than the engineers. I listen to the engineers and mostly my own experience. Nelson Pass, John Brokskie, etc are not the type to claim that capacitors are in the signal path if they are not.


    Could you explain further?

    I'm assuming that applies to a situation where the supply is not ripple filtered? With solar panel conversion I would think the power source would be quite similar to a battery would it not?
     
  10. tcmtech

    Well-Known Member

    Nov 4, 2013
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    Why is that expensive? o_O

    To get 600 VDC from common line power all you need is a standard 230/460:115/230 step up/down transformer which costs under $50 and can be found anywhere online.

    Capacitor wise again 600 VDC working voltage is not hard to find either. Most any common motor run type with a rating of 400 VAC or more will work just fine on 600 VDC operation plus give you a ESR number a magnitude of order or better lower than any HV electrolytic will.

    In my books a very reliable custom made 600 VDC 1 amp power supply can be built for well under $100. $120 if you want a secondary inductor and capacitor filter stage for extra ripple filtering. ;)
     
  11. coinmaster

    Thread Starter Member

    Dec 24, 2015
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    Don't they have to be rated for the voltages you intend to use them for?

    . Yeah but at what capacitances? The only caps that aren't hundreds of dollars that I've been able to find are at low capacitance. Too low for a proper filter.
    Aside from the fact that capacitor cost is only half the issue, I'd like to eliminate them all-together as an experiment on sound quality.
     
  12. tcmtech

    Well-Known Member

    Nov 4, 2013
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    What be rated for the voltages? The transformer?

    It already is. If it can step 480 VAC down to 120 VAC it will step 120 VAC up to 480 VAC.

    Thae that 480 VAC and rectify it to DC add a capacitor bank and you now have 480 x √2 = 678 VDC. Toss some transformer step up losses on it and you have almost exactly 600 volts DC once the filtering is factored in.
    BTW that's also why a capacitor rated for 420 VAC or higher service will work on 600VDC just fine.

    Here's a 1000 VA 230/460:115 industrial transformer for under $85 including shipping.
    http://www.ebay.com/itm/SIEMENS-1-0...875237?hash=item3a957990a5:g:gA0AAOSwd4tT6n-L

    How much capacitance do you need for 1 amp of service?

    1200 VDC 88 uF for $15.
    http://www.surpluscenter.com/Electr...ors/88-MFD-1200-VDC-RUN-CAPACITOR-22-1120.axd

    Not big enough? How about these.
    350 VDC 2900 uF. http://www.ebay.com/itm/2-pcs-Mallo...231599?hash=item3abecd57ef:g:po4AAOSwP~tW2fJi
    Put them in series and you have a 700 volt 1450 uF bank.

    Here's a 1000 volt 35 amp bridge rectifier for $6 to finish it all off.
    http://www.surpluscenter.com/Electrical/Transformers-Bridge-Rectifiers/Bridge-Rectifiers/

    Use the center tap on the transformers 230/460 side for the center point of the two 350 VDC electrolytics and you're good to go without running one single component anywhere near its design limits.

    That too spendy or not big enough or too complicated for you? o_O
     
  13. coinmaster

    Thread Starter Member

    Dec 24, 2015
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    Oh wow, thanks. That does seem tempting...
     
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