[amsat-bb] Re: Solar Power (I was wrong)

Edward Cole kl7uw at acsalaska.net
Fri Oct 2 09:05:58 PDT 2009

At 04:37 PM 10/1/2009, Robert Bruninga wrote:
>Since Satellite design is heavy into Solar power, and I talk
>about that a lot, you may have heard me compare my Solar car to
>Solar panels on the roof of your house as not economical, I WAS
>WRONG.  I was overlooking many recent changes in the
>1) Solar panels (PV) are 1% of what they cost in 1970
>2) PV dropped 40% this year due to 2007 Energy Boom and 2009
>economic bust
>4) $5,000 to $20,000 tax and cash back incentives for YOU
>5) Grid-tie systems operate at 95% efficiency compared to 70% of
>battery systems
>6) Local electric rates DOUBLED in the last 2 years
>7) Laws require utilities to pay you the same peak rates they
>charge you.
>8) Solar Energy credits can gain an additional $275 per 1Kw
>system per year
>9) Payback is at least 10% per year or better
>10) The same money in the bank gets 1% interest
>So I was wrong in not keeping current with all the changing
>environment, and now I am full speed to get my system approved
>and built and correct any miss-guidance I may have helped
>Sorry. I am claiming this particular email is on-topic because
>of public statements to the contrary I have made at satellite
>forums.  But this hot topic should probably spin off elsewhere.
>We need a HAM Solar Power group somewhere...?
>Summary:  Do NOT make the mistake (as most of us do) of thinking
>in terms of stand-alone Battery back-up solar power systems .
>They cost more and you don't need it in most places where you
>have access to the grid.  They cost $5 to $10,000 more, are only
>70% efficient (compared to 95% for grid-tie) and are a never
>ending maintenance headache.  Instead, most any enterprising ham
>should be able to provide his own backup power using a cheap 1
>kW inverter for about $150 from any auto store or radio shack
>running off his car's 12V system for any power outages.
>That, a few deep cycle batteries, (and using CFL lightbulbs in
>your house) will give you enough emergency power to operate your
>full Ham station, all the lights in the house you want plus your
>refrigerator for as long as you can buy gas.  But the other
>99.99% of the time, sell your solar power to the power company
>(at peak rates during the day) and buy it back cheap at night
>(you win and you don't even have to worrry about batteries)...
>And even if your grid-tie solar array produces nothing (in the
>way of AC power) when the grid goes out, you still have many
>Killowatts of DC power on your roof, that you can surely find
>lots of things to do with until the grid comes back.  For
>example, have the electrician wire a 250 volt string of the 200
>Watt solar panels in the array to a DPDT switch so they can be
>disconnected from the Grid Tie system and the 250 VDC can be
>available to you.  THen you can plug in as many modern DC/DC
>pwer supplies into that 250 VDC to give you LOTS of amps at 12
>volts, or ... almost any modern gizmo has a universal power
>supply input that will run on anything from 110V to 330V DC as
>Anyway, for similar hints www.aprs.org/FD-Prius-Power.html
>Sorry for the off-topic.  But  I was wrong. PV works! (even in
>Maryland).  If you live in the SW, you are lucky, and it works
>TWICE as much or at HALF the price!
>A Born-again Home PV junkie
>Bob, WB4APR
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Couple comments:

A 12-vdc battery back-up for your stations requires no conversion to 
AC, since most ham gear runs on 12v.  A PV to battery system will 
keep one going when "the lights go out"!  may not happen much down 
there in "civilization" but here in Alaska, several outages a year 
happen, some go for days.  We have a 2500w standby gen  that outputs 
240vac to feed the main ckt breaker (with mains isolated).  We have 
to load shed some areas of the house in that scenario.  The same ckt 
can be connected to my shack to feed a small breaker box that 
supplies 240vc to the HV Power Supplies.  (obviously we do not run 
the big amps when the power is out).

I have installed many PV panels in remote sites over the years.  They 
are much more efficient these days.  It gets more challenging to 
depend on solar year-round since winter sunlight is only 5.5 
hours/day.  At my company's sites we opted to use supplemental solar 
during the warmer months when there is long sunlight and have an auto 
switch that detects low voltage to switch to the primary 
oxygen-activated alkaline battery plant (15vdc @ 10,800 AH).  The 
primary batteries have a life of 3-years+ so we schedule their 
replacement (involves helicopter delivery= $2500) on the third year 
($5500).  Cheaper power exists but due to extreme weather on the 
mountain (-30F and >200mph winds), it is not feasible to visit the 
mountain 8-months/year!

If one is still planning to utilize a stand-alone PV electric system, 
then they should look at the sine-wave inverters that are very 
efficient (some at 98%).  They do cost more!

Side Note: one of Alaska's utilities is installing 27 wind generators 
to supply the grid (on an island 8-miles from Anchorage).  These are 
the 300-foot prop "babies"!  I'm sure that this implies megawatts.

73, Ed - KL7UW, WD2XSH/45
  BP40IQ   500 KHz - 10-GHz   www.kl7uw.com
500-KHz/CW, 144-MHz EME, 1296-MHz EME
DUBUS Magazine USA Rep dubususa at hotmail.com

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