Hi Mark;
Robin Gudgel at Midnite was talking about a setting on the Classic that
could do that. I'm not sure how far they went with the concept, but it
definitely is beyond mere theory. I'd check with them, and see where
they were at with that.
Ray Walters
On 1/16/2012 11:00 AM, Mark Dickson wrote:
I recall a conversation a while back about the possibility of
"reversing" the current in a solar module to increase the cell temp
enough to shed ice/rime. To follow-up, has anybody been successful at
this? I am guessing, if so, it would entail, removal of diodes,
increasing PV and battery capacity and some way to sense the ice at
the very least. . . It sounds good in theory, but I am skeptical as to
whether it will work in reality. . .
Best regards,
Mark Dickson,
NABCEP Certified Solar PV Installer ^(TM)
Oasis Montana Inc.
------------------------------------------------------------------------
*From:*[email protected]
[mailto:[email protected]] *On Behalf Of
*Allan Sindelar
*Sent:* Monday, January 16, 2012 10:52 AM
*To:* [email protected]
*Subject:* Re: [RE-wrenches] Request for Gennie Recommendation
Wrenches,
I very much appreciate this ongoing thread, thank you.
This actually feels like one of those "damned if you do, damned if you
don't" scenarios. The system is six years old, poorly designed and
installed. Two SW5548s, most likely chosen in order to run a 2HP
conventional well pump for this manufactured home. Thirty-two L16s in
four strings, in two unvented battery boxes in an unheated shed at
7800'. 1.66kW of PV plus an H40? wind generator, in an area not known
for great wind resource. The inverters either were never programmed
correctly or lost programming the first time a battery was replaced,
so the batteries never got above default 57.6V and were never
equalized. When the L16s started failing, the installer instructed the
owners to replace individual batteries, over and over until 17 of the
32 had been replaced, one or two or four at a time. With a continuing
stream of failing cells, each time the well pump came on the voltage
dropped to "must start" and the generator came on. With default
programming, the inverters would charge to 57.6V (if the batteries
would get up there - not sure if they ever did), then go through the
two-hour absorption, then shut off and soon the cycle would repeat.
The installer put a Link-10 in the home, but without a prescaler, so
it couldn't work on a 48V system. So he tapped off of part of one
string. All monitor programming was at default settings, so the system
monitor had been useless to the homeowners since installation. This
was designed and installed by someone in business doing wind and PV
since the 1980s. His website claims he is "the most experienced
contracting company in the Southwest specializing in
electric/electronic installation, service and repair of independent,
remote or utility integrated power generation power supplies. We
provide electrical engineering design, specializing in on-site
electrical power generation and related control systems." This is some
mighty poor work.
Our immediate "rescue solution" was to string together 16 of the
replacement batteries, program the inverters to corrective EQ, show
the homeowner how to change inverter settings, and replace the Link-10
with a TriMetric with prescaler, guessing at 500 amp-hours. At first
this appeared to have failed - the battery voltage rose quickly under
charge and then fell just as quickly. But we later learned that this
actually worked, as they told us that after running a long corrective
EQ, the batteries came back and the generator ran far less. But then
the existing generator failed to start; apparently just worn out, and
they're in bad shape.
We plan to add about 2-2.5kW of array, although we have no load
profile from them yet. The existing array is on two poles. The
(original) smaller array of 8 Sharp 80W 12V modules is shaded during
winter by the larger array of 6 Sharp 170W modules during the
mornings. The larger array is shaded by both a juniper tree on winter
mornings (until after 11 am) and by the power equipment shed on winter
afternoons (after 3 pm). The ground is frozen now, so we have no easy
way to either increase the array of move the existing arrays out of
where they shade each other.
They have two SW5548s, so need around 15kW at 7800' to run the
inverters at full capacity. The unknown is that we don't yet know what
size the new battery bank will be; my SWAG is about 1,000 a-hr in a
single string of industrial cells. Together the SWs can charge at
120A, so 1,000 A-hrs would be a good match. You are correct that the
generator run time will be greatly reduced once the array is
increased, the batteries replaced, and their loads reduced through
customer education. But they need a gennie right away, as their PV and
wind can't keep up and the system is shutting down. I'm hesitant to
recommend a generator of less than industrial quality, given their
experience to date with two residential units. And any good generator
has a 4-6 week lead time.
What would you do in this situation?
Allan
P.S. Chris Mason, your website doesn't jive...I went to
www.cometsystems.co <http://www.cometsystems.co> and got a site that
said "Comet Systems Ltd. is a Certified Reseller for Xorcom PBX
products and Ruckus Wireless." Doesn't appear to have anything to do
with either PV or generators. Can you enlighten us?
*Allan Sindelar*
[email protected] <mailto:[email protected]>
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
*Positive Energy, Inc.*
3201 Calle Marie
Santa Fe, New Mexico 87507
*505 424-1112*
www.positiveenergysolar.com <http://www.positiveenergysolar.com/>
On 1/16/2012 9:03 AM, Dave Palumbo wrote:
Chris,
It would be very helpful if you quote "run hours" rather than "years".
For example we have seen:
Inexpensive small generators (generally not worth rebuilding) 300 to
500 hours. These are gasoline models of various brands and Generac LP
gas models. 3kW to 10kW in size typically.
Honda gasoline generators 2,500 hours and then rebuild.
10kW Kohler water cooled diesel gen set still operating within specs
at 9,600 hours (rebuilt after 5,500 hrs). This has been in service for
16 years, the first 4 years without inverter/battery system, and
another 6 years before the client had us add a PV array to the system.
Since adding the PV array the generator has run 200 hours per year.
All are in off-grid service and loaded at 65% MAX continuous (see some
surges higher than 65%, typically run at 60%, or below, of rated power).
David Palumbo
Independent Power LLC
462 Solar Way Drive
Hyde Park, VT 05655
*/www.independentpowerllc.com <http://www.independentpowerllc.com> /*
NABCEP Certified PV Installer
VermontSolar Partner
24 Years Experience, (802) 888-7194
*From:*[email protected]
<mailto:[email protected]>
[mailto:[email protected]] *On Behalf Of
*Comet Systems
*Sent:* Monday, January 16, 2012 10:21 AM
*To:* [email protected] <mailto:[email protected]>;
RE-wrenches
*Subject:* Re: [RE-wrenches] Request for Gennie Recommendation
The Generac QT and commercial units do not come with an ATS, you can
buy just the bare machine or have a complete solution designed for
your load.
The Generac residential machines are good machines, as long as you
understand the intended use. We install lots of them. They are only
designed to be used occasionally, for residential backup. We get
customers who want to run their business all day on a 10KW residential
generator and are disappointed that the generator won't last ten
years. They are a cheap, lightweight and cost effective solution for
people who get occasional outages.
If your customer has worn out two generators already, then (s)he needs
to pay for a commercial level product. A 22KW QT is not that expensive
and will last ten years at a substantial load factor. If you give me
more information on the location, load factor and loading, I can have
engineering recommend a solution for you.
--
Chris Mason
President, Comet Systems Ltd
[email protected] <mailto:[email protected]>
www.cometsystems.co <http://www.cometsystems.co>
Cell: 264.235.5670
Int: +1305.767.2094
Skype: netconcepts
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