[amsat-bb] Satellites and Solar

Robert Bruninga bruninga at usna.edu
Fri Apr 8 23:04:01 UTC 2016

> Newer grid-tie inverters allow for AC power (1.5 kW per inverter)
> to be drawn without primary power.

True.  And the newer models from SMA with the built-in 15 amp grid-down
inverter cost $60 LESS than their previous model of the same 3 kW wattage
without the backup (and weighs 30 lbs less!)



But even when the grid goes down, you still have all that DC power from
dozens of solar panels operating at 30VDC each usually connected in series.
So, my Armageddon plan is to just tap into my 14 pannel array at the 300
volt point (10 panels) and these days, 300 VDC will power almost every
modern electronics piece of equipment AS IS.

Just look at your laptop, cell charger, TV, stereo, PC, and most every
plugin supply and you will see most have universal supplies operating from
100-to-240VAC and if it is lightweight (has no 60 Hz heavy iron transformer)
by definition, that means it is actually a DC/DC switching power supply that
can run just as well on DC as AC, since all they do is first rectify to DC
before doing all their switching magic.  I have plugged in every such supply
and device into the 200 VDC of my preius battery and ALL work just fine.

In fact, I did a recent test of a half dozen laptop type plug in supplies
and they all worked down below 70 volts DC input!  Amazing supplies able to
deliver full rated output with ANY input from 70 VDC to 330 VDC and 100 VAC
to 240 VAC and not know the difference!

Remember, a full wave rectified 240 VAC source becomes 330 VDC at the first
input capacitor and that is why ANY DC from around 100 volts to over 300 VDC
can be used as is on any of these supplies.    And you can distribute almost
TEN TIMES the power at 300 VDC than at 100 V AC because the current is 1/3rd
and hence the I-squared- wire loses are 1/9th over the same wire.

CAUTION:  Although it is trivial, it is also dangerous if you don’t
understand what you are doing.  Do not do this at home.  A few cautions:

1) MOST of what you really need in a power outage WILL NOT RUN on DC.
Furnace, refrigerator, well pump, anything with a 60 Hz motor or transformer
2) Unless you add a snubber circuit to EVERY SWITCH in every device, you
will destroy the switch the first time you try to turn the device off on DC.
You cannot open a circuit with DC, because the arc will just keep flowing
and melt/burn everything in reach. Including your house.
4) NEC requires ALL in-house DC wiring over 50v or so to be in METAL CONDUIT
for this reason.
5) Workaround is to UNPLUG quickly and be amazed at the large Arc-Flash.
6) Shock hazard

SOoooo... here is my safe suggestion.  Keep your eyes open for  BODACIOUS
surplus DC/DC power supplies from server racks and anything else with huge
power supplies.  At last night's radio club, a guy showed me one the size of
a cigar box that was not only 100Amps at 5 volts but also 30 amps at 12v.
And its input was the universal 100-240VAC.  Meaning it would run perfectly
fine on 300 VDC from my solar array tap.  In fact your modern shack DC/DC
supply of 25A at 12 v will run from the 100-330 VDC input.

Then hook this to a 12v battery to provide some surge capacity and then hook
it to  a 1500W standard 12v-to-120 VAC 60 cycle inverter from any store
(about $150).  Bingo, you have  1500W AC with the grid down for $150 (and
the big DC/DC suppl you found at the last Hamfest to give you the 12 vdc at
high amperage from the HV DC at low amperage from your array..

Oh, also, EVERY HYBRID car (now there are 60 on the market) also has a
similar 100 AMP at 12v DC/DC supply to power the accessories in the car from
the 200 to 400 VDC car hybrid battery.  Get one of these from a junk yard,
and there too is a huge source of high power, high voltage DDC/DC supply
that can then run conventional 12v-to-120 VAC 60 hz inverters.

The ten panel tap at the 300v point in an 8 amps string can supply over 2400
W continuous power to this arrangement. Use two supplies and two inverters
to make full use of this string.

SO again, just because the grid goes down does not mean your solar array
stops producing.  It just means it stops producing grid-tie-energy.  You
still have all that DC to do all kinds of things with... including
converting back to AC off grid and/or burning your house down through stupid


On Fri, Apr 8, 2016 at 1:47 PM, Stephen Nelson
<steve.motorola.uranium at gmail.com> wrote:
> Talking solar with my non Ham friends and there is a misconception that
> solar can be used for emergency power, which at least in my area, it
> cannot be. Solar inverter shuts down once the utility main sense is lost.
> I have also heard strange rumors that the panels go bad just after the
> cost of the system has paid for itself. This might be a wives tail, as
> remote sites I have seen, the solar panels last much longer than 10 years.
> Sent via iPhone 5s.....73's KD6VEX
> Stephen N.
>> On Apr 8, 2016, at 9:35 AM, Robert Bruninga <bruninga at usna.edu> wrote:
>> Solar Rant:
>> Last night I gave a talk to a local Ham club about Emergency Power
>> (solar) for the Ham.  Turns out, I had given a similar talk on the
>> same topic to the same group 6 years ago (2010).
>> But the world has CHANGED (and most of us (and them) have not… except
>> get older)..
>> I began “How many of you pay about $200/mo for electricity?”  Most
>> hands went up
>> “How many of you went solar since my last talk?” (one hand went up).
>> “Why not?” I ask.
>> General response was, “.. it costs too much…”
>> I went on, “Do the rest of you with the $200/mo electric bill realize
>> you have spent almost $15,000 to the utility since my last talk, and
>> did not also take the $5000 tax credit, so you have wasted over
>> $20,000 and have absolutely nothing to show for it except another
>> $200 a  month for the rest of your life, and another $24,000 thrown
>> away every ten years (probably twice that with inflation)…”
>> “Don’t tell me it costs too much…. It costs too much to do nothing!”
>> “This other solar guy hardly pays anything now, or the last 6 years
>> or the rest of his life!”
>> Most people in the room said they would probably go solar “someday”.
>> But now they are starting to realize that every single month they
>> send another
>> $200 to the utility, that is another $200 thrown away… when instead
>> it could have gone for their solar investment which remains EQUITY in
>> their hands, on their roof, or in their yard and which pays back over
>> 10% annual return on the investment every year for the rest of their
>> life.
>> Sorry for the rant.  Every AMSAT station needs power.  Are you going
>> to continue to burn coal to supply your energy and pay the utility
>> forever, at higher cost, or are you going to do something about it
>> now and start getting free power forever and breath cleaner air.
>> See http://aprs.org/solar-now.html
>> AMSAT TOO:  I just looked it up. I gave this talk at the AMSAT/TAPR
>> Dayton Banquet in 2011.  In the 5 years since, you (with $200
>> electric bills) have spent over $12,000 in electric bills and have
>> not taken the over $3600 tax credit either.  How many more years are
>> you going to throw away good money every month and do nothing?
>> Sorry, if you have shade, you are out of solar luck, but hug your
>> trees and birds instead!  In some states, such as Maryland, you can
>> still invest in community solar where your solar panels will be credited
>> to your bill.
>> Also in Maryland and some other progressive states, if you have some
>> remote land or antenna farm somewhere else,  You can install your
>> solar panels there, and get that electric meter to provide 100%
>> credit to your own home bill.  Neat!  Its called “virtual-net-metering”.
>> It’s a whole new world of energy changing under your feet…. Every day..
>> Bob, WB4APR
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> _______________________________________________
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> to all interested persons worldwide without requiring membership.
> Opinions expressed are solely those of the author, and do not reflect the
> official views of AMSAT-NA.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
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