[RE-wrenches] Shedding ice

Mon Jan 16 10:08:30 PST 2012

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:*re-wrenches-bounces at lists.re-wrenches.org 
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of 
> *Allan Sindelar
> *Sent:* Monday, January 16, 2012 10:52 AM
> *To:* re-wrenches at lists.re-wrenches.org
> *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*
> Allan at positiveenergysolar.com <mailto:Allan at positiveenergysolar.com>
> 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:*re-wrenches-bounces at lists.re-wrenches.org 
> <mailto:re-wrenches-bounces at lists.re-wrenches.org> 
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of 
> *Comet Systems
> *Sent:* Monday, January 16, 2012 10:21 AM
> *To:* Howie at catamountsolar.com <mailto:Howie at catamountsolar.com>; 
> 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
>
> masonc at cometsystems.co <mailto:masonc at cometsystems.co>
>
> www.cometsystems.co <http://www.cometsystems.co>
>
> Cell: 264.235.5670
>
> Int: +1305.767.2094
>
> Skype: netconcepts
>
>   
>
>   
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