My favorite is the Sharp 175 for off-grid and solar pumping
applications; a sturdy, well built and consistent module for most
applications. You can even get them fairly often!
Matt T
Kirpal Khalsa wrote:
Allen..Greetings....yes indeed it is an issue. we have been addressing
with multiple charge controllers per system. we don't fight the
current (not electrical). In the future the way i see it- the
electronics will be more flexible and be able to handle the larger
variety of string voltages. For example the long long long awaited
apollo solar t100 which will allow voltages to exceed the 150V limit
we have had for a long time. They have apparently even lined up some
breakers which will work with these greater voltages. 3 modules in a
series will no longer be a maximum. I understand midnite solar also
has a charge controller which will allow the 150V max to go by the way
side. We are trying to be flexible as modules become less standard
and hope that the electronics will allow us to address thesee
challanges as time goes by.
One thing that we would love to see is more large wattage modules with
j boxes rather than pre-wired MC cables. In many of our off grid
systems the array is located in readily accesible locations and
crafting a fence or sticking the array over 8 feet of the ground is a
big hassle/extra expense. This has proven to be a bigger concern for
us rahter than the voltage variety. If you know of any 72 cell or for
that matter 60 cell modules which allow flex conduit between j boxes
we would love some info.......
--
Sunny Regards,
Kirpal Khalsa
NABCEP Certified Solar PV Installer
Renewable Energy Systems LLC
On Wed, Dec 10, 2008 at 12:16 PM, Allan Sindelar
<[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>
wrote:
Wrenches,
Here's an issue I haven't seen directly addressed, and I would
like to know what the rest of you are doing.
It's getting harder to get 24V nominal modules. Because the bulk
of industry growth is high-voltage grid-tied applications, modules
no longer have to be a standard voltage. Just pick the number of
modules to best fit the chosen inverter's string voltage range.
But for off-grid, the odd cell counts and resulting
"nontraditional" DC input voltages challenge the traditional rules
of off-grid design. I may be fighting a losing battle here, as the
industry changes so rapidly and fundamentally. I have been trying
to stay with 72-cell modules for offgrid, as this most readily
combines with existing systems with 36-cell modules (12V) and
72-cell modules (24V).
For example, I will use the new Canadian Solar 170-200W modules.
They are 60-cell modules, with a Vmppt of around 28 volts - too
low to charge 24V batteries with a standard charge controller. We
can use them in any new systems with an MX60 or similar
voltage-converting MPPT controller. Two or three in series would
charge a 24V battery; 3 in series would charge 48V. Four in series
would violate Code, as low-temp voltage would easily exceed 150V.
Unless 60-cell modules remain a standard in the future, any future
array additions would have to be on their own charge controller,
in order to match a different I-V curve and MPP voltages into the
same battery bank. Is this prohibitive? No, it just runs counter
to the longstanding standards of off-grid design that allow
modules to be added in the future: these modules will not add well
to existing systems, and will not easily allow additional
dissimilar modules to be added later.
I had this same objection to using Day4 modules, although they
were better at 16Vnom. Three made up a standard 48V array, so
strings could be combined with two-module strings of similar
24Vnom modules.
Who else is trying to stay with 24V modules? Anyone still using
12V modules in off-grid (residential-scale, not little apps)
designs? Who has a crystal ball and knows what modules will be
like in 20 years, or even two years? Wat are the rest of you doing?
Thanks, as usual.
Allan
Allan Sindelar
_allan_(at)_positiveenergysolar.com_
<mailto:[EMAIL PROTECTED]>
NABCEP certified solar PV installer
Positive Energy, Inc.
3225A Richards Lane
Santa Fe NM 87507
505 424-1112
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