"Low Bid" is often the rule of the day, but so is 5 and 10 year
warranties, 20 year PPAs, maintenance agreements, and production guarantees.
A bit more money spent on an inverter that lasts longer is worth it.
Is buying a bigger inverter and running it at 60% of its rating going to
buy more MTBF (mean time between failures)
or should manufacturers consider selling a premier line with better
cooling fans, and all the upgraded goodies you mentioned. (along with
possibly an extended warranty?)
I've seen some very old inverters (Exeltech and Trace) still working
after 20 years, but those are indoors and not at full load every day.
Seems we need to do more to baby these Grid tie inverters (put them in
the shade, good air flow, surge arrestors, don't over load them, etc.)
Ray Walters
On 8/19/2011 11:18 PM, Exeltech wrote:
--- On *Fri, 8/19/11, Ray Walters /<r...@solarray.com>/* wrote:
> So is it fair to say that an inverter run at half it's design capacity
> might last twice as long?
It will last longer .. but as to how much longer .. there's no firm
rule. Much depends on how well the inverter is designed and built in
the first place.
Lifetime of some components is affected by temperature. In turn, the
temperature of various components is in part determined by the power
level at which the inverter is being operated. Other factors are: 1)
the ambient temperature of the inverter's environment; 2) the
inverter's access to free-flowing air.
Other considerations that come into play for component longevity are
how closely a component is operated to its maximum ratings, and for
how long a period of time it spends at the maximum(s).
Well-designed inverters .. ones that are designed from the onset for
longevity .. will be made to operate at their full-rated output at
their maximum ambient temperature, and do so without time limit. They
will use high quality components that are well within their operating
margins. This means parts that cost more.
A manufacturer may elect to skimp on the ratings of parts you can't
readily see .. such as the voltage breakdown rating of the
transistors. Lower voltage versions cost less, but aren't as robust,
and are more likely to fail in the event of a voltage transient on the
power line than higher voltage versions. Conversely, higher voltage
versions tend to be slightly less efficient than lower voltage parts,
so once again the manufacturer is boxed in.
Can inverters be designed and built that will last 20+ years? Yes.
Exeltech has been doing it for more than 21 years. Problem is .. well
designed and well built inverters cost a little more, and the American
public has been taught to shop almost exclusively based on price
alone. I'm sure you and the other Wrenches see this all the time in
the method most commonly used for awarding projects -- the infamous
two word qualifier: "Low bid".
Ray .. you asked very simple yet most excellent question. I wish the
answer were equally as simple...
Regards,
Dan
Sr. Engineer, Exeltech
--- On *Fri, 8/19/11, Ray Walters /<r...@solarray.com>/* wrote:
From: Ray Walters <r...@solarray.com>
Subject: Re: [RE-wrenches] Out of Warranty Inverter Replacements
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Date: Friday, August 19, 2011, 3:40 PM
HI Dan;
So is it fair to say that an inverter run at half it's design capacity
might last twice as long? What in your opinion would be the
sweet spot of enhanced reliability but still reasonable cost?
I'm sure Exeltech just like everyone else (including me) are being
squeezed from all sides to keep lowering cost. Its just ridiculous,
and a long term player like Evergreen Solar going under should
be a real wake up call for all of us. The solar industry's current
race to the bottom is sacrificing long term reliability (and our
future)
for lower $$/ watt today. I actually wonder if slowing some subsidies
might make for a saner playing field.
Ray Walters
On 8/19/2011 12:33 PM, Exeltech wrote:
Making equipment more robust, yet constantly lower in cost, are
diametrically opposing goals.
Dan
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