[RE-wrenches] 24V Module Query

Thu Jan 24 13:07:57 PST 2013

I'm not sure that AC coupling would work with the old SW inverters.
Assuming they are stacked for 240V, I don't see why it couldn't work. I
would actually like to know because I have dual SW5548's on my farm in the
Caribbean and I am considering adding more PV. Adding PV on the DC side
would be a bit difficult in this case. Since most of the load there is
during the day, I would rather avoid the losses through the batteries and
just add PV on the AC side of the off-grid inverter.

I was making more of a general statement. AC coupling would offset the
impact from reducing the DC PV rating if you lose modules and have to
reconfigure strings. It might not be the cheapest solution, but it might
make the best long-term sense. Every situation is going to be different...

*Jason Szumlanski*

*Fafco Solar*

On Thu, Jan 24, 2013 at 3:49 PM, Allan Sindelar <
allan at positiveenergysolar.com> wrote:

>  Jason,
> How do you AC couple some microinverters to cover the decrease in
> performance in an off grid system, especially with older equipment, such as
> an SW4024?
> Thanks, Allan
>
>
>  *Allan Sindelar*
> *Allan at positiveenergysolar.com* <Allan at positiveenergysolar.com>
> NABCEP Certified Photovoltaic Installer
> NABCEP Certified Technical Sales Professional
> New Mexico EE98J Journeyman Electrician
> Founder and Chief Technology Officer
> *Positive Energy, Inc.*
> 3209 Richards Lane (note new address)
> Santa Fe, New Mexico 87507
> *505 424-1112*
> *www.positiveenergysolar.com* <http://www.positiveenergysolar.com/>****
>
> *****************
> *
>
>  On 1/24/2013 1:38 PM, Jason Szumlanski wrote:
>
> I totally agree - old mods are usually not worth messing with at today's
> PV prices. In some cases it might be best to downsize the system and then
> AC couple some microinverters to cover the decrease in performance, or just
> replace the entire array if there are enough problems. There is a used
> market for smaller PV mods on Craigslist.
>
>  Back when I was installing Astropower 110W modules on single voltage
> Xantrex C40's, I never thought we'd be using anything but 12V nominal PV
> mods. Little did I know... Off-grid is really tough in these retrofit
> situations, but this applies to failed/broken mods on grid-tie systems as
> well. That's where I can make a good case for microinverters.
>
>   *Jason Szumlanski** *
>
> * Fafco Solar
> *
>
>
> On Thu, Jan 24, 2013 at 3:11 PM, Ray Walters <ray at solarray.com> wrote:
>
>>  Hi Allan;
>>
>> I've been in the same conundrum lately.  I found that AEE and others have
>> 12 v modules (Solartech), but the price per watt is double or triple.  My
>> take is that somewhere around 200 to 400 watts, its more cost effective to
>> go to the GT modules with an MPPT controller.  Blue Sky makes the 1524, and
>> 3024 that can take up to 57 Voc, so those would work at still fairly low
>> cost.  Unfortunately many of the other low cost MPPT controllers won't work
>> with the 60 cell modules.  At some point, it may actually be cost effective
>> to just use 60 cell modules with non MPPT controllers, and just forget
>> about the extra 24 cells.  (I know that sounds crazy, but PV less than $1/
>> watt is crazy too)
>>
>> I'm trying to add modules to an existing array of 8 Siemens 12 v modules,
>> and it just doesn't work out, except with separate controllers.
>> Also, its amazing how much PV you can throw at an off grid project these
>> days for $10k.
>> It almost makes messing around with the old modules a waste of time.
>> Perhaps the solution might be to remove old arrays for customers wanting
>> to really up size, and then reuse the old modules for small systems?
>>
>> Ray
>>
>>
>> On 1/24/2013 12:35 PM, Allan Sindelar wrote:
>>
>>  Wrenches,
>> We have years of installing 36-cell (12V) and 72-cell (24V) modules for
>> battery-based customers. Most of our systems are 24V or 48V nominal. Over
>> the last few years, sources of conventionally-sized 72-cell modules have
>> dried up - as cells have increased in size, most modules and most newer
>> factory production lines have either gone to 60-cell (20V) modules, or 72
>> cells in 300+ watt ranges. It seems that the formerly common 72 cell, 24V
>> modules in the 150-190 watt range, which are well-suited to integrating
>> into existing systems, are no longer available.
>>
>> 60-cell modules in the common 220-250 watt range can't be added to an
>> existing system unless run through a dedicated MPPT charge controller that
>> can convert voltage, such as an FM, XW60, Classic or TriStar; the added
>> cost of any of these controllers cancels out the low prices of the modules.
>>
>> Who continues to manufacture 72-cell modules? Which distributors carry
>> them?
>>     I am aware of three options - are there more?
>>     - Sunpower makes one module in the 245 watt range that can be used
>> negative ground, but it's very high efficiency (and with high Voc/Vmp as
>> well) and very pricey;
>>     - Sanyo/Panasonic has 225-240 watt modules, but also quite premium
>> and pricey;
>>     - Ameresco bought the rights to manufacture many former BP modules,
>> and I think they make some. But we had to replace lots of failed BP modules
>> in that size range, and are hesitant to use their technology, fearing that
>> the problems may persist in the continued line.
>>
>> Thank you for any discussion and recommendations.
>> Allan
>> --
>> *Allan Sindelar*
>> *Allan at positiveenergysolar.com* <Allan at positiveenergysolar.com>
>> NABCEP Certified Photovoltaic Installer
>> NABCEP Certified Technical Sales Professional
>> New Mexico EE98J Journeyman Electrician
>> Founder and Chief Technology Officer
>> *Positive Energy, Inc.*
>> 3209 Richards Lane (note new address)
>> Santa Fe, New Mexico 87507
>> *505 424-1112 <505%20424-1112>*
>> *www.positiveenergysolar.com* <http://www.positiveenergysolar.com/>
>>
>> *
>> *
>>
>>
>>
>
>
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