[RE-wrenches] SolarEdge v Enphase

[Exeltech]

Wrenches,

I wish this urban myth about electrolytic capacitors would
die, but it won't.  It's been a wonderful marketing ploy for
some time now.

Simply stated, existence of electrolytic capacitors in inverters
does NOT mean the inverters are less reliable.  Satellites
have been using electrolytic caps for decades, and look
how long THEY last!  (I know, because I've helped to design
power supplies for aerospace applications.)

What it boils down to is this: if a quality electrolytic capacitor
is used within its specifications, you can expect 60+ years
of life from it in an inverter application.  Conversely, if a
circuit is poorly designed, you can ruin any electronic part
in a very short time.

What defines capacitor "life"?  It's defined as the doubling
of the internal effective series resistance of the capacitor
from the value it had when it (the cap) was new.

This is energy lost.  It also causes the capacitor to operate
at a slightly higher internal temperature than when it was
new (all other factors being the same).

Result?  It all depends on how the circuit is designed.  In
our case, the inverter efficiency decreases approximately
a quarter to one half of a percent.   The waveform distortion
also increases, but it takes lab grade equipment to detect
the change.  If you're worried about a 1/2 percent drop in
the inverter efficiency, your concern is misplaced.  After all,
PV degrades over time much more than that!

So why the bad rap on capacitors?

Like tires, they DO wear out.  40 years ago, "premium"
tires were rated for 30,000 miles.  Could you wear them
out in less?  Absolutely!  Drive like a 16 year old kid with
a muscle car, and it's easy.  On the other hand, I just bought
a new set of tires.  The old ones still had tread, but at 88,000
miles, they'd seen their better days.  This is a far cry from 30k
mile tires.

Capacitors have progressed in the same manner.  A long time
ago, capacitors wore out in 5 to 10 years.  Today, it's an entirely
different story.

As long as the circuits in which the electrolytic capacitors are
used are well designed, you have nothing to worry about.
Electrolytic capacitors in a well-designed application will outlive
all of us.


Dan Lepinski
Senior Engineer
Exeltech


From: Andrew Truitt <atruitt at gmail.com>
Subject: Re: [RE-wrenches] SolarEdge v Enphase
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Date: Thursday, January 12, 2012, 12:25 AM


Does anyone have any experience installing SolarEdge?  The advantage that I see over microinverters from a reliability standpoint is that the power optimizers do not contain electrolytic capacitors.  The inverter is also supposed to last longer since it does not handle the MPPT duties so the electronics are less complex.


Marv - Do you have any SolarEdge reliability and / or performance data you can share beyond the white paper on the SolarEdge website?  Also, one issue that I've had with Enphase is an occasional loss of data transfer between inverters and the monitoring system - does SolarEdge have that issue?  If not, how have you overcome it?  Can you share a link to a live SolarEdge system monitoring interface?




Andrew TruittTruitt Renewable Energy Consulting


On Thu, Jun 9, 2011 at 12:40 PM, Mark Frye <markf at berkeleysolar.com> wrote:









Indeed.....
 
Yes it is 1v per module when not operating, but still 
>250V when operating. That means that all code requirements for >250V 
still apply to the DC wiring such as bonding bushings for conduit as required 
etc.
 
SolarEdge is 
making hay off of this safety feature, but this feature is inherent in 
microinverters as well. 
 
Mark Frye 
Berkeley Solar Electric Systems 
303 Redbud Way 


Nevada City,  CA 95959 
(530) 401-8024 


www.berkeleysolar.com  


 



From: re-wrenches-bounces at lists.re-wrenches.org 
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of benn 
kilburn
Sent: Thursday, June 09, 2011 10:54 AM
To: 
Wrenches
Subject: Re: [RE-wrenches] SolarEdge v 
Enphase


Mark,
I thought that the SolarEdge reduced the 'string' voltage to 1V per 
unit/module, reducing the high DC voltage risk factor, until the inverter switch 
was turned on?

The fact that by hitting the "off" switch on the inverter will reduce 
the potentially high DC voltage to 1V per unit/module could be an advantage from 
a safety perspective (maintenance, firemen/utility workers)


Labor/time-wise, it is like installing both a microinverter system and a 
string inverter system together, soooooo....


benn

DayStar Renewable Energy 
Inc. 

benn at daystarsolar.ca
780-906-7807 
HAVE A 
SUNNY DAY 

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