miniture sine wave inverter [RE-wrenches]

[Joel Davidson]

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When I saw the first OK4U miniature inverter at a trade show in Europe, I 
immediately bought it and had possibly the first US installation on the 
Solec factory. When I saw the push to get AC modules in the NEC, I thought 
perhaps miniature inverters on the back of solar modules are the next wave. 
Then, reality settled in. Electronics really hate heat and solar modules get 
hot. In fact, all inverter manufacturers recommend installing their 
equipment out of the sun and hot locations. Multiple inverter redundancy 
seems like a good idea, but it also means more parts to go bad more often. 
Sunny Boy's success in Germany does not translate very well into the US 
market. Over there, contractors and customers monitor system performance and 
when, not if, a Sunny Boy fails, service workers quickly replace it to keep 
the feed-in revenue meter turning thanks to very active field work, swap-out 
from inventory and 24 hour restocking turn-around. Few US PV contractors 
have are capable of monitoring and providing 24 hour service to hundreds of 
installations. I like the Sunny Boy for small systems, but after having 
installed a 400 kW system with both a 225 kW inverter and 76 Sunny Boys, I 
feel like I'm learning my OK4U lesson again. Sometimes "small is beautiful" 
and a nice balance can be made with alternative energy and small scale 
appropriate technology. On the other hand, the Chinese have an expression 
"think little; think big." It is usually better (more appropriate) to not 
use a lot of small parts to power big loads.

----- Original Message ----- 
From: "Phil Undercuffler" <p.undercuffler at conergy.us>
To: <RE-wrenches at topica.com>
Sent: Friday, December 09, 2005 9:44 AM
Subject: Re: miniture sine wave inverter [RE-wrenches]


>
> I spoke at length some time ago with the good folks at Exeltech.  The
> advantage of the AC module as they see it is that it eliminates the DC
> disconnect and GFP issues of standard grid tied systems.  The inverters 
> are
> designed to string multiple AC modules on a single AC circuit; they 
> believe
> they can run about 8 150-200w modules on a single 12-2 conductor circuit.
> Also, they believe they can get it listed to use UF cable as the wiring
> method instead of current "esoteric" PV wiring methods.
>
> The disadvantage of their approach is that UL considers attaching the
> inverter to the module as part of the manufacturing process, so it must be
> under strict UL control and blessing.  No field installable versions are
> planned.  They don't know if they will try to buy modules and install
> inverters themselves, or sell the inverters to certain certified/listed
> assemblers, or what.
>
> Also, every new module/inverter combination must undergo the whole listing
> process.  They had one instance where the module they were working with
> changed the output spec by three watts, and they had to pay full pop to
> re-list it.
>
> Phil Undercuffler
> Tech Services Manager, ext 238
>
> Conergy, Inc.
>
> Our World is Full of Energy
>
> 888.396.6611 toll free
> 505.473.3800 phone
> 505.473.3830 fax
> www.conergy.us
>
>
> -----Original Message-----
> From: Christopher Freitas --- OutBack Power
>
> I am actually glad to see someone offer a product to fill this "nitch".
> Exeltech currently has very limited information on their website regarding
> this - but the FAQ has the following statements in it:
>
> I've got solar panels already. Can I purchase Exeltech PV AC Module
> inverters and attach them to my existing solar panels?
>
> No. Once again, safety regulations require that the Exeltech PV AC Module
> inverters be attached to the PV module (solar panel)
> by a UL-approved facility.
>
> Will Exeltech PV AC Modules ever be sold separately?
>
> No. They will not be sold separately to end-users. Exeltech PV AC Modules
> will be sold as individual units only to
> manufacturers, resellers, and others who are authorized by UL (or similar
> Nationally Recognized Testing Laboratory such as ETL,
> TUV, and others) to attach the Exeltech PV AC Modules to the rear of PV
> modules for resale to the general public.
>
> This is unfortunate and will limit the success of this approach in my
> opinion - in Europe the standards allow field installation and even
> "plug-in" installations in some areas.
>
> The ratings are 150 watts AC (I think) maximum and looks like they will
> offer a 12vdc and a 24vdc version.  No info on the maximum DC input 
> voltage
> however.
>
> Christopher Freitas
> OutBack Power Systems
> cfreitas at outbackpower.com
>
>
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