[RFI] OT: RE: solar problems

Mon Apr 11 14:10:41 PDT 2011

The pricey high power whole house inverters and battery banks that need
maintenance, ventilation, and periodic replacement are the reasons the
microinverters are starting to catch on.  While they do not supply emergency
backup power they do reduce electric bills, and in some states like Mass
they provide income in the form of carbon credits that get sold to carbon
burning utilities. Thought cap and tax wasn't going to happen?  Well Mass
already has it, just like it had Romney care before Obama care came around.
Also, don't forget that big inverters and heavy dc wiring has more loss than
higher voltage ac, and that storage batteries have charging and discharge
losses, and a slow self discharge loss.  Plus if your inverter is not able
to backfeed the grid you must either use all the power you are generating
every day or lose it permanently

In my system and others like it a small 200w inverter is mounted on each
panel, no long high current dc wiring, each inverter puts out 220vac synched
to the line.  The inverters are daisy chained in various configurations
depending on the system and wired through a dedicated meter and breaker then
into the main breaker box in parallel with the utility power.  No need for
an expensive transfer switch since the micro inverters shutoff automatically
when utility power is gone.  Granted, you lose income when the utility power
is down and the sun it out, but that is a relatively small percentage of the
year in most places.  So during the day when the panels are making more
power than the house is using the meter spins backwards.  Another advantage
of the microinverters is that they provide real time monitoring of each
panel's health and history of production:

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net

> -----Original Message-----
> From: K8RI [mailto:k8ri at rogerhalstead.com] 
> Sent: Monday, April 11, 2011 20:44
> To: rfi at contesting.com
> Subject: Re: [RFI] OT: RE: solar problems
> On 4/11/2011 5:46 AM, Cortland Richmond wrote:
> > If it's a deliberate phase bobble, that's a clever  way for 
> power co's
> > avoid having to pay people for their solar power.
> They need to control phase, but there is no need for them to shut the 
> inverter down in the line power is shut off.   The inverter system 
> should have a transfer switch and immediately drop the  connection to 
> the power line.
> This allows the PV system to work off batteries as a back up. 
>  This type 
> of regulation completely defeats the back up ability of a PV system 
> which is why I'd install one in the first place.  That I can 
> get money 
> back from the power company is great, but not if I still have 
> to install 
> a 15 or 20 KW generator that runs off natural gas or gasoline plus 
> wiring it in with a transfer switch.
> Although we are close to a good size city, the power lines 
> run through 
> woods, and we lose power at least 2 or 3 times a year for quite a few 
> hours at a time.
> I purchased a 9500 watt generator back in 2000 *after* they went on 
> sale<:-))  That generator now has close to 200 hours on it is 
> just over 
> 10 years.  I'm afraid I'd have to forgo the money from the 
> power company 
> as it'd take quite a while for the payback to cover the 
> generator.  As 
> it is the payback which is highly touted would take many years.
> In another 4 or 5 years PV should be much cheaper but true sine wave 
> inverters with enough capacity to run refrigerators, 
> furnaces, and air 
> conditioners are going to be pricey.
> > Cortland
> >
> > -----Original Message-----
> > From: rfi-bounces at contesting.com 
> [mailto:rfi-bounces at contesting.com] On
> > Behalf Of Charles Coldwell
> > Sent: Sunday, April 10, 2011 7:36 AM
> > To: Allen Griffith
> > Cc: rfi at contesting.com
> > Subject: Re: [RFI] RFI Digest, Vol 99, Issue 5
> >
> > <snip>
> >> rid power drops ... or is crappy).
> > Indeed, this the "anti-islanding" requirement of UL-1741 
> for inverters.  The
> > idea is that the power company may have turned off the 
> power intentionally
> They should allow for transfer switches rather than turning off the 
> inverter.  These things always seem to end up far more 
> complicated than 
> they need to be.
> > to allow work on the line, so if your home generation 
> system is still
> > energizing the wires you could electrocute a lineman.
> I run far more power into the house than most home PV systems are 
> capable of generating and the power company has no need to 
> shut down my 
> generator.  Why can't they do the same if the phase gets out of 
> tolerance instead of shutting down the inverter.
> Here the regulations will not let you have a battery back up on the 
> inverter if it's tied into the power grid.
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