[RE-wrenches] Out of Warranty Inverter Replacements

[Ray Walters]

"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 /<ray at 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 /<ray at solarray.com>/* wrote:
>
>
>     From: Ray Walters <ray at solarray.com>
>     Subject: Re: [RE-wrenches] Out of Warranty Inverter Replacements
>     To: "RE-wrenches" <re-wrenches at 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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