PV Panels $1.98/Watt?

[vaughn]

Pull in your spam antennas. I have no connection to this company except I
bought an EU-2000 from them once, and I may buy a new PV panel from them
tomorrow if those prices are real. At that price, they have the SUN-130 and
SUN-150. The minimum number of panels they will ship is two. I hope to
drive down there tomorrow and pick up one.

http://sunelec.com/
http://sunelec.com/index.php?main_page=product_info&cPath=5&products_id=357

Two years ago we were talking about a silicon & carbon shortage and
impossibly growing PV prices. Is the PV industry facing over production
now? How quickly things change.

Vaughn

 

[Bruce in alaska]

Pull in your spam antennas. I have no connection to this company except I
bought an EU-2000 from them once, and I may buy a new PV panel from them
tomorrow if those prices are real. At that price, they have the SUN-130 and
SUN-150. The minimum number of panels they will ship is two. I hope to
drive down there tomorrow and pick up one.

http://sunelec.com/
http://sunelec.com/index.php?main_page=product_info&cPath=5&products_id=357

Two years ago we were talking about a silicon & carbon shortage and
impossibly growing PV prices. Is the PV industry facing over production
now? How quickly things change.

Vaughn

Hey Vaughn, If you can confirm those prices, I might just be interested
in getting a few up here...

BTPOST

 

[vaughn]

This might tell a bit of the story (mind the wrap):

http://blogs.barrons.com/techtrader...-firms-to-fail-analyst-says/?mod=yahoobarrons

Wow! "...could drop below $1 a watt next year, and to 50 cents a watt in
2011. If that happens, he says, up to half the more than 200 solar
manufacturers won't survive."

The next year or two could be a real "sweet spot" for those who are
considering a new PV system. After that, a combination of rising prices
from the expected recovery and lost production from the dropped-out
producers will swing the pendulum the other way.

Even with drastically lower prices, the economics of my little system are
simple. My PV system's calculated payback time is...NEVER. I consider my
system a hobby and also part of my hurricane preparations. If the power
goes out, there are a few lights in my house & yard that will stay lit as if
nothing had happened. Come back a week later, and they would *still* be
lit. No generator, no noise, no fuel, no "nuthing"; they just work.

Vaughn

 

[vaughn]

How much for shipping something of this size? Any idea?

Sorry, no clue. They have an AZ warehouse as well as their FL location,
which may help some folks. The shipping weight of the SUN-130 is 35#.

Vaughn

 

[vaughn]

Hey Vaughn, If you can confirm those prices, I might just be interested
in getting a few up here...

I just got back from Miami. Picked up one Sun-130 panel for exactly the
advertised price. It seems to be well made. It will take me a day or three
to get it installed & tested.

The place is right downtown & near the Port of Miami. Just like when I was
there before, it was cramped, crowded & busy. They have been in that
business for several years that I know of. Would not be surprised to find
out that their main market is in South America & the Caribbean. I purchased
my EU-2000 from them perhaps 5 years ago.


Vaughn

 

[Thomas]

Even with drastically lower prices, the economics of my little system are
simple. My PV system's calculated payback time is...NEVER. I consider my
system a hobby and also part of my hurricane preparations.

since I'm local in Ft Lauderdale, would you care to describe a little of the
components that you currently use?
perhaps I can start up a similar system using some of the learnings you might care to
share.

 

[vaughn]

since I'm local in Ft Lauderdale, would you care to describe a little of
the components that you currently use?
perhaps I can start up a similar system using some of the learnings you
might care to share.

My system started out as simply a way to keep my generator's battery
charged. For that, I was lucky enough to find 2 used, mismatched PV panels
that total about 100 watts in rating. To keep from overcharging my battery,
I added a new C12 solar controller. From there, I noticed that the C12
controller is designed to also control outside lighting, so I added 12 volt
compact fluorescent bulbs (1 amp of current draw each; 40 watts of equiv
light) in porch light fixtures in our front and back yards.

That was about 7 years ago. Over the years, I have upgraded the batteries,
but little else. Those outside lamps last forever! In the dark days
following our S. Florida hurricanes, My yard was the only one in the
neighborhood lit up at night, greatly confusing the neighbors, who were sure
that I somehow still had grid power.

Just lately, I have been gradually figuring out ways to pipe 12 volt
circuits inside the house. (I have an old Florida CBS house with no attic
access so running new circuits ain't easy. The first one was right between
our easy chairs in the family room, a lamp fixture with 2 of those 12-volt
CFL bulbs. It serves as our everyday lamp and is powered only from the PV
system.

As I add loads to the system and as my ancient PV panels age, I have been
noticing that my battery "fills up" later and later in the day. For that
reason, I am adding that new 130-watt rating panel to the mix.

Vaughn

 

[Thomas]

As I add loads to the system and as my ancient PV panels age, I have been noticing

that my battery "fills up" later and later in the day. For that reason, I am adding
that new 130-watt rating panel to the mix.

what's your take on the off-grid "complete systems"

http://sunelec.com/index.php?main_page=off_grid_systems

for example, they have a 2000 watt system and that would cover all my airconditioning
use 24/7 as all my systems are inverter controlled heatpumps (read: both compressors
and air handlers are inverters, running ac to dc conversion and use very little power
at start, slowly ramping up according to demand)

at the cost or about $8000, do you have any idea what they mean by "complete" or is
this an implied installation by sunelec or does it just mean that everything I would
need, is included but it's up to me to figure out how to install and where to install
?

 

[vaughn]

at the cost or about $8000, do you have any idea what they mean by
"complete" or is this an implied installation by sunelec or does it just
mean that everything I would need, is included but it's up to me to figure
out how to install and where to install

First, I would call the price "nearly $9,000", not "about $8,000".
Second, I really doubt that system would run your home's AC 24/7 for the
simple reason that the sun does not shine 24/7. Their "complete system"
does not seem to include installation labor, nor incidentals like the panel
mounting system.

(I am not saying that the system is a bad deal as PV system go, just trying
to fill you in on the "real world".)

A good conservative guess is that system would make about 10 kWh/day if
properly installed in South Florida (2 KW x 5 hours equiv full sunlight).
Check your power bill to see what you pay per kWh, but that will come to
less than $2.00/day worth of power. To the installed price of your system,
be sure to include an allowance for the use of about $10,000 and an
allowance to replace $1,080 worth of batteries every few years plus
allowance for whatever incidental maintenance the system may need..

I don't know what condition your roof is in, but are you ready to have a
crew drill a few dozen holes in it to mount the panel frames? Remember that
the installation job will need to be repeated if you need any roof work over
the life of the PV. system. That won't be free! Since you live in
hurricane country, you will want the very best panel rack system possible.
Further you will want to be sure that it is installed properly and
structurally tied to your roof beams so that everything does not take flight
in the next hurricane, leaving you with no power, a torn up roof, and
pissed-off neighbors who got their homes and cars torn up by the expensive
hardware flying off your roof.

Still sounding like a good idea?

I love PV, but you need to go into a project like that with your eyes wide
open.

Vaughn

 

[Thomas]

First, I would call the price "nearly $9,000", not "about $8,000".
true

Second, I really doubt that system would run your home's AC 24/7 for the
simple reason that the sun does not shine 24/7. Their "complete system"
does not seem to include installation labor, nor incidentals like the panel
mounting system.

ok. just to make you aware, I run a 1 ton 12,000 BTU all-inverter system at 72 F year
round,
heatpump, thus same coil produces both heat and cool, despite outside temps.
when it runs at full speed, max throttle, it consumes just 685 watts of power.

it would appear to be easy to meet the demand of this smart unit at such a low max
consumption,
both the compressor and air handler are full inverters, capable or running at any
speed.

my other inverter heatpumps are running on more conservative settings for the rest of
the house but
indoor temps never exceed 76 F in any part of the house

my entire house FPL powerbill is below $120 even during hotter months and this
includes pool pumps,
sprinkler pumps, water heater, stove, electronics, etc.

 

[vaughn]

my entire house FPL powerbill is below $120 even during hotter months and
this includes pool pumps,
sprinkler pumps, water heater, stove, electronics, etc.

That's pretty impressive. We do about the same in the Palm Beach area, (no
pool pump, gas hot water) but we do it by only using our whole-house AC a
few hours per day. At night we run a little mini-split in the bedroom, and
during the heat of the day we run a single high-efficiency window unit to
cool only the den.

Some day we will replace our central unit with inverter technology, but
probably not until the system we have dies a natural death. (At 4 hours per
day, 5-6 months per year, that may be a while) The mini-split is brand new.
It has efficiency that trumps any present window unit, but is not inverter
technology since I didn't get to choose. (It was a nearly-free
"brother-in-law" deal, so it has its own type of cost effectiveness)

Vaughn

 

[Bob F]

The page:
http://en.wikipedia.org/wiki/Variable_speed_air_compressor
"Variable speed air compressor"
says that
"A Variable Speed Drive (VSD) Air Compressor is an air compressor
that takes advantage of variable-speed drive technology."
and
"The most common form of VSD technology in the Air Compressor
Industry is a variable-frequency drive, which converts the incoming
AC power to DC & then back to a quasi-sinusoidal AC power using an
inverter switching circuit."

Are there any commercially available "inverter" systems that
can run directly from DC so as to eliminate the inefficiency
added using another inverter first to go from Solar or battery
DC to AC before feeding the compressor unit?

It may be that the efficiencies of the AC motor make up for the losses in the
inverter. Reading about electric car conversions, the AC seems to win
significantly over DC for miles per charge.

 

[[email protected]]

Are there any commercially available "inverter" systems that
can run directly from DC so as to eliminate the inefficiency
added using another inverter first to go from Solar or battery
DC to AC before feeding the compressor unit?

Not that I've heard of, and it would seem to be a niche too small.
It's the same with welding at my place - 24VDC gets converted to
230VAC, and then the welders turn it mostly back into 20 some volts
DC.

Wayne

 

[daestrom]

The page:
http://en.wikipedia.org/wiki/Variable_speed_air_compressor
"Variable speed air compressor"
says that
"A Variable Speed Drive (VSD) Air Compressor is an air compressor
that takes advantage of variable-speed drive technology."
and
"The most common form of VSD technology in the Air Compressor
Industry is a variable-frequency drive, which converts the incoming
AC power to DC & then back to a quasi-sinusoidal AC power using an
inverter switching circuit."

Are there any commercially available "inverter" systems that
can run directly from DC so as to eliminate the inefficiency
added using another inverter first to go from Solar or battery
DC to AC before feeding the compressor unit?

I think you'll find it's a bit more complicated than that.

Most variable speed drives are actually VVVF (variable-voltage,
variable-frequency) drives.

A standard motor for a compressor or blower can be run on variable
frequency *if* the volts/hertz ratio is kept nearly constant. If the
voltage is kept constant while the frequency is varied over a wide
range, you burn out the motor.

Of course if the inverter section was a pulse-width modulated type of
unit, you could get something similar to VVVF, but it would still be
hard on the motor (high harmonics in PWM). AFAIK, most hi-power VVVF
use a simple H-bridge for the inverter section and vary the voltage
output of the converter section.

So the AC-DC converter section is a variable DC voltage. If you have a
homepower system with DC, you'd have to find a way to vary the voltage
by a wide range. One common way to do that is with an
inverter-converter arrangement, but now you're right back where you
would be if you ran the VSD off of a typical inverter.

daestrom

 

[Bob F]

The point is that the compressor unit typically changes AC to DC then
uses its built-in special purpose inverter to run the motor. The home
power systems discussed in this group typically have DC available to
begin with, which is then fed to an inverter to get the AC; my
question asked if there were any commercially available units that
could be powered directly from DC, thereby eliminating the extra
inverter when powering the compressor unit.

Even with a 97.5% efficient main inverter, eliminating the extra
main inverter from the compressor power path saves is a 2.5%
and might lead to further system savings on the initial system cost
by allowing a smaller main inverter.

My misunderstanding.

 

[daestrom]

Most VFD's use three phase to drive the motor. how inductive current is
controlled depends on the output of the inverter. If it's a sine wave using
high frequency PWM through the motor inductor, like large VFDs use, then it
will vary the output voltage, and current, by adjusting the modulation. It's
called sine wave approximation. Supply voltage to the inverter remains
constant. But most consumer grade VFD's, and older large VFD's, don't use
sine wave output, that would cost too much money.

They use square wave output direct to the motor windings. They modulate the
winding current by shifting the pulse width. Remember, there is two ways of
controlling the current in the inductor, that is voltage, and duty cycle "on
time". It large units, that method will cause problems with harmonics, like
you said. But in small systems, it doesn't cause enough of a problem to
worry about.

When you slow down the motor, you either have to reduce the driving voltage
into each winding. Or you have to reduce the "on time" of each winding.

From what I've seen, modified-sine wave inverters and PWM all require
FET's of one form or another. If you're just using FET's or such, you
can turn them off whenever you want in the cycle to reduce the pulse
width. But highly inductive loads that can act as induction generators
will have a current that is out of phase with the applied voltage. This
requires some snubbers (filters) to absorb this reactive current.

In large VVVF drives, those suitable for several horsepower and up, the
reactive load can be more than what simple caps and resistors can handle
in any realistic way.

The large units I've worked on (50 to 500 hp) opt for SCR's in an
H-bridge circuit instead (well, the three-phase equivalent of an 'H').
To turn off an SCR in one leg of the bridge, the corresponding SCR
above/below it is turned on. This would be a direct short if not for a
center-tapped inductor placed between the SCRs that commutate the SCR
that was previously conducting current through the inductor when the
non-conducting SCR is turned on.

Using SCRs like this doesn't allow for any sort of PWM, so the supply
voltage to the bridge has to be controlled. Typically this is done with
a three-phase rectifier with the diodes replaced with more SCRs and
these are phase-controlled to control the average output of the converter.

I suppose the small motors in a furnace (fractional hp) could use PWM
and power FET's, didn't think about that much. I'm used to thinking in
larger numbers

daestrom