[amsat-bb] Waiting for Solar Panel Efficiency (Ha!) Grid stability

Robert Bruninga bruninga at usna.edu
Sat Jan 2 16:44:59 UTC 2016 

Concerning our solar powered satellite ground stations:...

> 6) [concerning]... grid stability. ..
> The cheap models I tested had two very dangerous features:
> A - they sensed each other as valid grid voltage,...
> leaving an engineer unable to cut the power...
> B - the grid frequency...would run away upwards

Which is why all grid-tie inverters must be compliant with grid standards.
Which is also why the local establishment requires permits and inspections
and UL certification of all solar grid tie installations and which is also
why ALL grid-tied inverters are required by the NEC and inspected to make
sure they comply with all relevant standards.

1) They shut down within one half cycle on loss of grid power
2) They shut down on over voltage
3) They shut down on frequency out of tolerance usually anything more than
0.5Hz away from 60 Hz
4) They willl not come back on line until after monitoring the grid for 5
minutes to make sure it is safe and within operating limts.

And lastly grid-tie inverters are not like a normal "inverter" at all.
They are simply AC current sources that sense the existing 60.0 Hz grid and
push current to lead the waveform and thus source power to the grid.  Lose
the waveform or any other condition, and it just stops.

[What about power when the grid is down?]

> 7) Our national grid has had 99.9999% uptime... with only 4 interruptions
in 2014.

Similar here.  Typically we  lose power about 4  hours a year which is
about 99.96% uptime.  And a simple deep cycle marine battery powers my
home's critical circuits then.   Or I plug into the Hybrid car.

Bob


> On Fri, Jan 1, 2016 at 10:14 PM, Robert Bruninga <bruninga at usna.edu>
> wrote:
>
>> > from a technical point of view there is a huge reason
>> > to hold off on all these extra feed-ins (net-metering).
>> > And that simple reason is grid stability.
>>
>> True and false....
>>
>> It is true that the grid of 1970 has to evolve to avoid problems with grid
>> stability.   But they have been aware of these problems and have been
>> evolving for the last 40 years to get away from the catastrophic results
>> of
>> business as usual and resulting half-country blackouts.
>>
>> Although the utilities are glacially slow to adapt, the growth of solar
>> and
>> wind has also been glacially slow because people just resist change even
>> when it is to their advantage.  But the GRID has seen it coming and has
>> been getting ready.
>>
>> 10 years ago, they said the grid will go unstable above 2% solar (because
>> they NEVER even looked at the weather to estimate tomorrow's load).  Now
>> the weather model is an excellent forcaster of available power an dload.
>> Then 5 years ago they were saying the grid would go unstable at 10%.
>> (Absolutely true if they still did nothing to improve their systems from
>> the 1970s way of dispatching power  But they have not been sitting still).
>>
>> Guess what, Hawaii has now passed 40% solar and the grid has still not
>> gone
>> unstable because every day they are improving how they manage the grid.
>> Back in 2013, Germany exceeded 60% solar and wind and their grid held up
>> fine.  Then this year, the Netherlands peaked at 100% solar/wind and their
>> grid did just fine.  The US can easily keep up with the evolving grid as
>> long as we dont get held back by the fossil fuel industry's opposition.
>>
>> So of course, the stability of the grid is a concern, but that is why we
>> have some of the best EE's on the planet working in parallel for 3 decades
>> with renwewable growth to stay ahead of the variability of renewable clean
>> power.
>>
>> So I don't fault anyone for commenting on the stability of the grid, but
>> it
>> is always last year's news and not keeping up with the day to day march
>> toward cleaner power.
>>
>> I attended an IEEE International Conference on Energy last year and
>> expected to hear gloom and doom.  I heard exactlly the opposite.  Every
>> paper showing techinques, and how to achieve stability and renewable
>> growth  were ten times as many as the few claiming doom.  And most papers
>> were showing how easy it was with positiv results and others how we will
>> be
>> able to grow the changes to make the grid more responsive.
>>
>> So keep a jaundiced ear to repetitions of decades or even last year's dire
>> predictions... the world is changing despite the billions of dollars being
>> spent by the fossil fuel industry to make sure they remain on top.
>>
>> Bob, Wb4APR
>>
>>
>>
>>
>> > So regardless of any tariff schemes and/or the power companies trying to
>> > keep their market, there is a substantial technical hurdle. I don't know
>> > how it is in the US, but I did some research during an internship on
>> this
>> > in The Netherlands, and as a result, some kinds of inverters were
>> outlawed
>> > in the EU because they were really dangerous to the grid stability, and
>> > also not safe in the end when instabilities did occur.
>> > (and not all of those were made in china....)
>> > Are they discouraging a growth beyond a certain size just to prevent
>> this
>> > issue?
>> >
>> > Maybe this is substantially different in the US, since the grid looks
>> > completely different.
>> >
>> >
>> > Wouter PA3WEG
>> >
>> >
>> >
>> >
>> > On Fri, Jan 1, 2016 at 5:36 PM, Burns Fisher <burns at fisher.cc> wrote:
>> >
>> >> I guess there are a lot of folks interested in this even though it is
>> only
>> >> peripherally related to satellites...I hope there are not too many
>> >> objections.
>> >>
>> >> But I wanted to ask if anyone has heard this rumor:  After a certain
>> >> number
>> >> of solar connections, power companies will no longer be required to do
>> net
>> >> metering.  I don't know whether a) they would just not allow any more
>> new
>> >> installations with backfeed at all or b) for new installations they
>> would
>> >> only pay wholesale, or c) somehow they average retail and wholesale
>> prices
>> >> for everyone who is backfeeding.
>> >>
>> >> I can surely understand why a power company would WANT to do that.
>> They
>> >> are usually getting power that they have to pay extra for at a time
>> when
>> >> they need it less.  But it certainly reduces some of the financial
>> >> incentive to install, if true.  Anyone know more?  It would probably
>> >> differ
>> >> by state...
>> >>
>> >> 73,
>> >>
>> >> Burns W2BFJ
>> >>
>> >> On Fri, Jan 1, 2016 at 11:21 AM, Robert Bruninga <bruninga at usna.edu>
>> >> wrote:
>> >>
>> >> > > If the project is not operating by now, it'll cost 30% more after
>> >> > midnight.
>> >> >
>> >> > No. The 30% federal tax incentive was to end by the end of 2016, not
>> the
>> >> > beginning.  AND does'nt matter anyway, since the do-nothing congress
>> >> > actually included an extenaion in the spending bill.
>> >> >
>> >> > > Putting solar on an asphalt roof ... is a bad idea.  Not a place to
>> >> screw
>> >> > up.
>> >> >
>> >> > Use a reputable contractor with guarantee.  They know how to do it
>> >> right.
>> >> >
>> >> > > 42 panels 50 lbs per (for 11 kW system)...
>> >> > > Remember statics and dynamics??
>> >> > > ... bracing rafters in a crawlspace is a mug's game.
>> >> > > In Florida in summer? Fatal.
>> >> >
>> >> > 50 lbs per panel over 18 sqft is only a load of 2.8  lbs per square
>> foot
>> >> > and is insignificant compared to the required building code roof
>> design
>> >> > figure of typically 30 psf.  (Though in Florida the snow load is
>> >> considered
>> >> > 0).  The good news elsewhere is that solar panels melt snow far
>> faster
>> >> than
>> >> > a normal roof, so there is no multiday buildup and icing load...
>> >> >
>> >> > > Today as of 3pm EDT the system produced  23 kWh.
>> >> > > Best day so far was 100% FL sunshine and a COLD day: 82 kWh.
>> >> >
>> >> > Congratulations, sounds like you did it anyway...
>> >> >
>> >> > > HF RFI? Undetectable.
>> >> >
>> >> > Thanks, that is great news!
>> >> >
>> >> > > I got the last (3) 3.8kW transformer based inverters in stock.
>> >> > > SMA makes nice gear. Cadwelds, IMC 3/4" conduit.
>> >> >
>> >> > I was totally shocked when I ordered an SMA inverter to add to my
>> other
>> >> > three XANTREX ones which only weighted 25 lbs.  The SMA was so heavy
>> I
>> >> had
>> >> > to invite my son to dinner just to get help getting it from the
>> porch to
>> >> > inside the house!  Then had to feed him again a week later to help
>> lift
>> >> it
>> >> > into place.  I think it is over 100 lbs? And compared to the XANTREX,
>> >> there
>> >> > were may nitpicks I did not like about the SMA at all.
>> >> >
>> >> > But then of course, XANTREX doesn't make grid-tie inverters any more
>> and
>> >> > SMA does seem to have very good reviews.
>> >> >
>> >> >
>> >> > On Thu, Dec 31, 2015 at 12:25 PM, Bob <WB4SON at gmail.com> wrote:
>> >> >
>> >> > > > Sort of off the AMSAT topic, but the most recent estimate is that
>> >> about
>> >> > > 20
>> >> > > > gigawatts of solar will be added in 2016 -- almost doubling the
>> >> total
>> >> > > > installed capacity of US solar power.  This is being primarily
>> >> driven
>> >> > by
>> >> > > > residential installations.  Utility-scale installations are
>> actually
>> >> > down
>> >> > > > 5%.
>> >> > > >
>> >> > > > One thing that was keeping mass market efficiency down was a
>> glut of
>> >> > > > production capability that existed through 2014.  Manufactures
>> were
>> >> not
>> >> > > > keen on investing in new processes at the same time they were
>> going
>> >> out
>> >> > > of
>> >> > > > business or consolidating.  That glut has been drying up,
>> prompting
>> >> > Elon
>> >> > > > Musk's to build a $1 billion dollar factory in Buffalo NY which
>> will
>> >> > > > produce 1 GW of panels annually by the end of 2016.  Those panels
>> >> are
>> >> > > > expected to be 22.1% efficient.  That's a pretty impressive gain
>> in
>> >> > > > efficiency.
>> >> > > >
>> >> > > > Often times market conditions, not technology, dictates what
>> reaches
>> >> > the
>> >> > > > mass market, and that has most certainly been the case in the
>> solar
>> >> > > > industry.  That 50% increase in panel efficiency doesn't
>> necessarily
>> >> > mean
>> >> > > > that the cost per watt will be reduced in the short term -- those
>> >> > panels
>> >> > > > may simply sell for 50% more.
>> >> > > >
>> >> > > > 73, Bob, WB4SON
>> >> > > >
>> >> > > > On Thu, Dec 31, 2015 at 6:07 AM, Nick Pugh wrote:
>> >> > > >
>> >> > > >> Good point Bob but include the real estate cost  in to the
>> equation
>> >> > and
>> >> > > >> they improve.
>> >> > > >> nick
>> >> > > >>
>> >> > > >> -----Original Message-----
>> >> > > >> From: AMSAT-BB [On Behalf Of Robert Bruninga
>> >> > > >> Sent: Wednesday, December 30, 2015 11:06 AM
>> >> > > >> To: amsat-bb at amsat.org
>> >> > > >> Subject: [amsat-bb] Waiting for Solar Panel Efficiency (Ha!)
>> >> > > >>
>> >> > > >> Compare the cost and efficiency of solar panels for cubesats and
>> >> for
>> >> > > your
>> >> > > >> house:
>> >> > > >>
>> >> > > >> http://aprs.org/Energy/solar/efficiency-comparison-cost.png
>> >> > > >>
>> >> > >
>> >> > _______________________________________________
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>> >> > expressed
>> >> > are solely those of the author, and do not reflect the official
>> views of
>> >> > AMSAT-NA.
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>> >> >
>> >> _______________________________________________
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>> >
>> >
>> _______________________________________________
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