Spam detection software, running on the system "mail.homepower.com", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or block similar future email. If you have any questions, see @@CONTACT_ADDRESS@@ for details. Content preview: Your free subscription is supported by today's sponsor: ------------------------------------------------------------------- You could save Hundreds on your Car insurance We track down the best Car Insurance rates for you Click here if you are in the ma Content analysis details: (9.08 points, 6.00 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.3 DATE_IN_PAST_03_06 Date: is 3 to 6 hours before Received: date 2.9 USERNAME_IN_SUBJECT To: username at front of subject 0.1 CLICK_BELOW Asks you to click below 2.8 SAVE_ON_INSURANCE Trying to sell insurance online 3.0 FORGED_MUA_OUTLOOK Forged mail pretending to be from MS Outlook 0.0 NO_RDNS2 Sending MTA has no reverse DNS Received: from out009.topica-platinum-y.com ([66.227.60.29]) by mail.homepower.com (Merak 8.3.8) with SMTP id IBJ49901 for ; Tue, 4 Apr 2006 16:05:01 -0700 Return-Path: Received: (qmail 19153 invoked by uid 0); 4 Apr 2006 19:12:06 -0000 Received: from unknown (HELO mpls-qmqp-04.inet.qwest.net) (63.231.195.115) by inmta002.topica.com with SMTP; 4 Apr 2006 19:12:06 -0000 Received: (qmail 1602 invoked by uid 0); 4 Apr 2006 19:12:05 -0000 Received: from unknown (63.231.195.14) by mpls-qmqp-04.inet.qwest.net with QMQP; 4 Apr 2006 19:12:05 -0000 Received: from 71-32-100-185.albq.qwest.net (HELO ALLANLAPTOP) (71.32.100.185) by mpls-pop-14.inet.qwest.net with SMTP; 4 Apr 2006 19:12:05 -0000 Organization: Positive Energy, Inc. MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1506 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1506 To: New wrenches posting From: Allan Sindelar Subject: Followup on array upgrade [RE-wrenches] Date: Tue, 4 Apr 2006 13:10:50 -0600 Message-ID: <991948564-1463747838-1144191900@boing.topica.com> Errors-To: Reply-To: RE-wrenches@topica.com X-Topica-Id: <1144191765.inmta002.17864.1314971> List-Help: List-Unsubscribe: Your free subscription is supported by today's sponsor: ------------------------------------------------------------------- You could save Hundreds on your Car insurance We track down the best Car Insurance rates for you Click here if you are in the market for Car insurance http://click.topica.com/caaeE3lbz8Qcsbz9JC9a/Firstand10.com ------------------------------------------------------------------- Wrenches, When I request advice on this list, it seems to me that I should offer an eventual followup that tells you what we did and whether it worked, so here's one of these followups. In September I asked for advice on doubling an array on a Sunny Boy system where the original modules are no longer available. The original thread is copied below. The eventual solution was to replace the existing 7 BP SX140 modules with 12 BP SX170 modules. This took the array from 980W to 2040W. This was pretty close to David Katz' suggestion. We hooked up the customer with another of our customers who was looking for an array, and they arranged a private sale of 6 of the 7 modules; one remains in our shop to sell on consignment. As both were existing customers, we took no cut on that sale. Everyone's happy, and the SB1800 inverter has two matched 6-module strings. Thank you for the advice. Allan at PosE Esteemed Wrenches, How would you solve this? Two years ago we installed a batteryless system with a Sunny Boy 1800 and seven BP SX140s, with racks in place for a second 7-module array in the future, when the client could afford it. (This is the client that was featured in the RE Financing article in HP103:97, who financed his system through the Permaculture Credit Union.) He's ready to add the second row of seven modules now, and SX140s are no longer available. We can get 160s and 170s, I think. I would expect that as long as the MPP voltage is closely aligned (it's close but not perfect, 34V vs. 35 at mpp), and the cell type is similar (it is, polycrystalline), it should be OK to mix outputs, as the two strings are in parallel and combine prior to the inverter. Any thoughts on this are welcome. Allan at Positive Energy Allan, The BP 3160 is the silicon nitride anti-reflective coated version of the SX140. The temperature coefficient is identical. 6 or 7 volts of max power differential is not all that critical. It is not an ideal arrangement, but anything you do with this array will not be perfect. See if you can find some 3150 modules instead of the 3160's. They would just be lower spec 160s. They may not prominently display these modules on their website, but I bet they have some. They are on their spec sheet. I wouldn't go to the 3170 because the voltage specs are getting up there on voltage and you are not going to get the performance that you would get out of 150s or 160s (essentially you would be buying 170s and getting 150s worth of power). If you're curious about operating points, use the Maui software to produce IV curves for normal temperature operation. I think you'll be just fine-just don't make a habit of it. Given the way modules are changing so rapidly these days, you are lucky to still have modules with the same form factor. The color will be slightly different due to the silicon nitride, but that's not too big a deal. The lesson to learn here is size your inverter to your array and do not count on being able to upgrade down the road. It is better to match inverters and arrays as you go if you can. The saving grace these days is that inverter efficiency curves are so good down to 10% power, that if you were guaranteed identical modules in the future, installing half of an array is not nearly as evil as it used to be with the old Omnion inverters that were at 60% efficiency at 10% power. Bill Brooks, Brooks Engineering. Allan, Another option would be to sell the 140 watt modules and buy 14 matched modules. Since modules are hard to get, it would be easy to sell them, and they are probably worth more used now than they were new last year. Cheers, David Katz, President, AEE Solar, formerly Alternative Energy Engineering Allan: Adding another full string of the other module type is the right way to go and is probably the best you can do given the module supply situation. The higher currents of the larger modules should add in parallel without too much mismatch loss as long as they are in their own string. The different MPP voltages will cause the inverter to operate at an MPP between the MPP of each of the two parallel strings. It will not be optimal for either string but, as long as the number of modules in series is the same, it will be close to optimal for both. You can estimate losses to a reasonable degree by of accuracy looking at the voltage differential between the 2 strings, e.g. 7 Vdc (1.0 Vdc per module). Assume the inverter will operate at an MPP half way between the two sub-arrays, i.e. 3.5 Vdc (0.5 Vdc per module) low for the new modules and 3.5 Vdc (0.5 Vdc per module) high for the older modules. You can then look at the power curve for each module and estimate the losses by moving 0.5 Vdc per module towards Isc for the new modules and 0.5 Vdc towards Voc for the older modules. This should give you a ratio of "optimum theoretical" output to the "probable" output for each series string in the new configuration. You can then use this ratio and the historic system performance to estimate the future performance of the system including the mismatch losses. In actuality the inverter will operate at an MPP point that is not exactly half way between the two optimal points. IMHO, this is a second order effect and is likely insignificant when compared to the half way assumption. For a mental exercise you can more accurately estimate the mismatch losses through mathematical approximation. Starting with the half way between (50%) assumption calculate the sum of the power of the two strings. Repeat for 40%, and 60% to see if the sum of power goes up or down in one way or the other. If the power was higher at 40% then try 35% and 45%, etc. etc. You should be able to find the theoretical optimal MPP of the two dissimilar strings. This MPP then becomes the basis for your ratio to estimate future performance of the combined array with mismatch loss. I hope this was clearer than mud and is somewhat useful. Best Regards, John Berdner, President, SMA America Your free subscription is supported by today's sponsor: ------------------------------------------------------------------- Get your VoIP on with Packet8's Videophone. Crystal clear images of your loved ones. Free Month. 30 day money back guarantee. 1-877-868-1135 http://click.topica.com/caaeE3qbz8Qcsbz9JC9f/ TMONE ------------------------------------------------------------------- - - - - To send a message: RE-wrenches@topica.com Archive of previous messages: http://lists.topica.com/lists/RE-wrenches/read List rules & how to change your email address: www.mrsharkey.com/wrenches/etiquette.php Check out participant bios: www.mrsharkey.com/wrenches/ Hosted by Home Power magazine Moderator: michael.welch@homepower.com --^---------------------------------------------------------------- This email was sent to: michael.welch@homepower.com EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9.bWljaGFl Or send an email to: RE-wrenches-unsubscribe@topica.com For Topica's complete suite of email marketing solutions visit: http://www.topica.com/?p=TEXFOOTER --^----------------------------------------------------------------