Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string?
Jim, You have probably seen this already but it’s worth a mention here. Good article in SolarPro magazine April/May “Optimal PV-to-Inverter Sizing Ratio”. Dave From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jim MacDonald Sent: Monday, April 19, 2010 7:43 PM To: RE-wrenches Subject: Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? Im sorry, I meant to write “11 modules per string” below.. Been a long day.. From: Jim MacDonald Sent: Monday, April 19, 2010 7:41 PM To: RE-wrenches Cc: Jason Szrom Subject: RE: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? SB8000US only good for 480 Vac, we’re tying in at 208. 11 strings [11 modules per string] has been calc’d to be OK (600vdc) for record low -4 fahrenheit (-20 celsius). I think the big concern as mentioned is getting the Voc high early in the AM to wake the inverter up, also maintaining the Vmp later in the day to keep it running for as long as possible into the late afternoon/ evening. Will those extra kWh gleaned in the early AM/ late PM over the course of 365 days be more than the kWh clipped during peak production times with the 9.075 kWdc? NYC average summer highs between 79 and 84 fahrenheit early june-late august. Sunlink rack @ 10° on a silver-painted built-up roof. Time-of-use utility $ peak-shaving is not an issue here. Thank you ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string?
Hi Jim, I like using one of the design emulators for just this reason. PVSYST and PVSOL. You can model each scenario and see how the numbers crunch. You import historical weather data for the region to get as accurate as possible. You mention the silver painted roof, these emulators allow you to input albedo affects, too. Both packages offer free trial periods, so you could run just this case for free. If you like them then you spend the money for the license. -Wes Kennedy NABCEP certified PV Installer 303-653-3073 --- On Mon, 4/19/10, Jim MacDonald j...@solaresystems.com wrote: From: Jim MacDonald j...@solaresystems.com Subject: Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? To: RE-wrenches re-wrenches@lists.re-wrenches.org Date: Monday, April 19, 2010, 5:40 PM SB8000US only good for 480 Vac, we’re tying in at 208. 11 strings has been calc’d to be OK (600vdc) for record low -4 fahrenheit (-20 celsius). I think the big concern as mentioned is getting the Voc high early in the AM to wake the inverter up, also maintaining the Vmp later in the day to keep it running for as long as possible into the late afternoon/ evening. Will those extra kWh gleaned in the early AM/ late PM over the course of 365 days be more than the kWh clipped during peak production times with the 9.075 kWdc? NYC average summer highs between 79 and 84 fahrenheit early june-late august. Sunlink rack @ 10° on a silver-painted built-up roof. Time-of-use utility $ peak-shaving is not an issue here. Thank you From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Darryl Thayer Sent: Monday, April 19, 2010 5:58 PM To: RE-wrenches Subject: Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? The temperature correction is the concern. I have heard lots of stories of inverters dieing when it gets to cold. Look in the code book 690.7 at the temperature correction table. Go to weather.com and find your record low temperature. Find you Tc factor and will your senerios work? I have heard from a sunny boy rep that it is OK to over power by 1.25% darryl --- On Mon, 4/19/10, Dana d...@solarwork.com wrote: From: Dana d...@solarwork.com Subject: Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? To: 'RE-wrenches' re-wrenches@lists.re-wrenches.org Date: Monday, April 19, 2010, 4:31 PM Many times we switch to another module manufacturer as one will not fit or another inverter manufacturer. PVPowered has a more relaxed window and we have had fine success with them when SMA does not fit. Cold is the dictator and the 600 VDC threshold. Thanks, Dana Orzel Great Solar Works, Inc web - www.solarwork.com E - d...@solarwork.com V - 970.626.5253 F - 970.626.4140 C - 970.209.4076 We have been slow to give up on the myth of the Earth's generosity. Rather grandly, we have overdrawn our accounts. Barbara Kingsolver - Water is life. From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jim MacDonald Sent: Monday, April 19, 2010 2:37 PM To: RE-wrenches@lists.re-wrenches.org Subject: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? For a straight grid-tie system@ 10 degree tilt, 180 azimuth, zero/little shade, NYC avg 4.29 kWh/m²/day. Feed an SMA7000 with (3) strings of 11 Suntech STP275’s [9.075 kWdc] Or Do strings of 10, so itd be 8.250 kWdc into the 7 kWac inverter. Strings of 11= 491.7 Voc; 386 Vmp Strings of 10= 447 Voc; 351 Vmp The tradeoff would be power clipping at/around noon in the sunny months in the 9.075 kW scenario; Inverter sleeping late every morning and retiring early in the evenings in the lowered voltage scenario. Trying to figure out which would yield more kWh at the end of the year. Any ideas appreciated, thanks Jim MacDonald Solar Energy Systems, LLC Brooklyn, NY 11222 www.solarEsystems.com No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.801 / Virus Database: 271.1.1/2819 - Release Date: 04/19/10 00:31:00 -Inline Attachment Follows- ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios
Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string?
In the same issue of SolarPro as the “Optimal PV-to-Inverter” Sizing Ratio” article (April/May 2010), the lead article is “Production Modeling for Grid-Tied PV Systems” by Tarn Yates and Bradley Hibberd at Borrego Solar: http://solarprofessional.com/article/?file=SP3_3_pg30_Yates While your question below can’t be answered using PVWatts, it can be answered using the Solar Advisor Model (SAM), which was developed by NREL and Sandia w/ DOE funding. SAM is available for free download here: www.nrel.gov/analysis/sam/ David Brearley, Senior Technical Editor SolarPro magazine NABCEP Certified PV Installer ™ david.brear...@solarprofessional.com Direct: 541.261.6545 On 4/19/10 6:40 PM, Jim MacDonald j...@solaresystems.com wrote: SB8000US only good for 480 Vac, we’re tying in at 208. 11 strings has been calc’d to be OK (600vdc) for record low -4 fahrenheit (-20 celsius). I think the big concern as mentioned is getting the Voc high early in the AM to wake the inverter up, also maintaining the Vmp later in the day to keep it running for as long as possible into the late afternoon/ evening. Will those extra kWh gleaned in the early AM/ late PM over the course of 365 days be more than the kWh clipped during peak production times with the 9.075 kWdc? NYC average summer highs between 79 and 84 fahrenheit early june-late august.? Sunlink rack @ 10° on a silver-painted built-up roof. Time-of-use utility $ peak-shaving is not an issue here. Thank you From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Darryl Thayer Sent: Monday, April 19, 2010 5:58 PM To: RE-wrenches Subject: Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? The temperature correction is the concern. I have heard lots of stories of inverters dieing when it gets to cold. Look in the code book 690.7 at the temperature correction table. Go to weather.com and find your record low temperature. Find you Tc factor and will your senerios work? I have heard from a sunny boy rep that it is OK to over power by 1.25% darryl --- On Mon, 4/19/10, Dana d...@solarwork.com wrote: From: Dana d...@solarwork.com Subject: Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? To: 'RE-wrenches' re-wrenches@lists.re-wrenches.org Date: Monday, April 19, 2010, 4:31 PM Many times we switch to another module manufacturer as one will not fit or another inverter manufacturer. PVPowered has a more relaxed window and we have had fine success with them when SMA does not fit. Cold is the dictator and the 600 VDC threshold. Thanks, Dana Orzel Great Solar Works, Inc web - www.solarwork.com E - d...@solarwork.com V - 970.626.5253 F - 970.626.4140 C - 970.209.4076 We have been slow to give up on the myth of the Earth's generosity. Rather grandly, we have overdrawn our accounts. Barbara Kingsolver - Water is life. From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jim MacDonald Sent: Monday, April 19, 2010 2:37 PM To: RE-wrenches@lists.re-wrenches.org Subject: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? For a straight grid-tie system@ 10 degree tilt, 180 azimuth, zero/little shade, NYC avg 4.29 kWh/m²/day. Feed an SMA7000 with (3) strings of 11 Suntech STP275’s [9.075 kWdc] Or Do strings of 10, so itd be 8.250 kWdc into the 7 kWac inverter. Strings of 11= 491.7 Voc; 386 Vmp Strings of 10= 447 Voc; 351 VmpThe tradeoff would be power clipping at/around noon in the sunny months in the 9.075 kW scenario; Inverter sleeping late every morning and retiring early in the evenings in the lowered voltage scenario. Trying to figure out which would yield more kWh at the end of the year. Any ideas appreciated, thanks Jim MacDonald Solar Energy Systems, LLC Brooklyn, NY 11222 www.solarEsystems.com http://www.solaresystems.com/No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.801 / Virus Database: 271.1.1/2819 - Release Date: 04/19/10 00:31:00 ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
[RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string?
For a straight grid-tie system@ 10 degree tilt, 180 azimuth, zero/little shade, NYC avg 4.29 kWh/m²/day. Feed an SMA7000 with (3) strings of 11 Suntech STP275's [9.075 kWdc] Or Do strings of 10, so itd be 8.250 kWdc into the 7 kWac inverter. Strings of 11= 491.7 Voc; 386 Vmp Strings of 10= 447 Voc; 351 Vmp The tradeoff would be power clipping at/around noon in the sunny months in the 9.075 kW scenario; Inverter sleeping late every morning and retiring early in the evenings in the lowered voltage scenario. Trying to figure out which would yield more kWh at the end of the year. Any ideas appreciated, thanks Jim MacDonald Solar Energy Systems, LLC Brooklyn, NY 11222 www.solarEsystems.comhttp://www.solaresystems.com/ ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string?
Is using the SMA SB 8000US out of the question? http://www.sma-america.com/en/products/solar-inverters/sunny-boy/sunny-boy-5 000us-6000us-7000us-8000us.html On 4/19/10 3:37 PM, Jim MacDonald j...@solaresystems.com wrote: For a straight grid-tie system@ 10 degree tilt, 180 azimuth, zero/little shade, NYC avg 4.29 kWh/m²/day. Feed an SMA7000 with (3) strings of 11 Suntech STP275¹s [9.075 kWdc] Or Do strings of 10, so itd be 8.250 kWdc into the 7 kWac inverter. Strings of 11= 491.7 Voc; 386 Vmp Strings of 10= 447 Voc; 351 Vmp The tradeoff would be power clipping at/around noon in the sunny months in the 9.075 kW scenario; Inverter sleeping late every morning and retiring early in the evenings in the lowered voltage scenario. Trying to figure out which would yield more kWh at the end of the year. Any ideas appreciated, thanks Jim MacDonald Solar Energy Systems, LLC Brooklyn, NY 11222 www.solarEsystems.com http://www.solaresystems.com/ ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org David Brearley, Senior Technical Editor SolarPro magazine NABCEP Certified PV Installer david.brear...@solarprofessional.com Direct: 541.261.6545 Fax: 541.512.0343 Visit our Web site at solarprofessional.com (Sample copy available for download at: solarprofessional.com/sample) ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string?
Many times we switch to another module manufacturer as one will not fit or another inverter manufacturer. PVPowered has a more relaxed window and we have had fine success with them when SMA does not fit. Cold is the dictator and the 600 VDC threshold. Thanks, Dana Orzel Great Solar Works, Inc web - www.solarwork.com E - d...@solarwork.com V - 970.626.5253 F - 970.626.4140 C - 970.209.4076 We have been slow to give up on the myth of the Earth's generosity. Rather grandly, we have overdrawn our accounts. Barbara Kingsolver - Water is life. From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jim MacDonald Sent: Monday, April 19, 2010 2:37 PM To: RE-wrenches@lists.re-wrenches.org Subject: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? For a straight grid-tie system@ 10 degree tilt, 180 azimuth, zero/little shade, NYC avg 4.29 kWh/m²/day. Feed an SMA7000 with (3) strings of 11 Suntech STP275s [9.075 kWdc] Or Do strings of 10, so itd be 8.250 kWdc into the 7 kWac inverter. Strings of 11= 491.7 Voc; 386 Vmp Strings of 10= 447 Voc; 351 Vmp The tradeoff would be power clipping at/around noon in the sunny months in the 9.075 kW scenario; Inverter sleeping late every morning and retiring early in the evenings in the lowered voltage scenario. Trying to figure out which would yield more kWh at the end of the year. Any ideas appreciated, thanks Jim MacDonald Solar Energy Systems, LLC Brooklyn, NY 11222 www.solarEsystems.com http://www.solaresystems.com/ No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.801 / Virus Database: 271.1.1/2819 - Release Date: 04/19/10 00:31:00 ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string?
The temperature correction is the concern. I have heard lots of stories of inverters dieing when it gets to cold. Look in the code book 690.7 at the temperature correction table. Go to weather.com and find your record low temperature. Find you Tc factor and will your senerios work? I have heard from a sunny boy rep that it is OK to over power by 1.25% darryl --- On Mon, 4/19/10, Dana d...@solarwork.com wrote: From: Dana d...@solarwork.com Subject: Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? To: 'RE-wrenches' re-wrenches@lists.re-wrenches.org Date: Monday, April 19, 2010, 4:31 PM Many times we switch to another module manufacturer as one will not fit or another inverter manufacturer. PVPowered has a more relaxed window and we have had fine success with them when SMA does not fit. Cold is the dictator and the 600 VDC threshold. Thanks, Dana Orzel Great Solar Works, Inc web - www.solarwork.com E - d...@solarwork.com V - 970.626.5253 F - 970.626.4140 C - 970.209.4076 We have been slow to give up on the myth of the Earth's generosity. Rather grandly, we have overdrawn our accounts. Barbara Kingsolver - Water is life. From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jim MacDonald Sent: Monday, April 19, 2010 2:37 PM To: RE-wrenches@lists.re-wrenches.org Subject: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? For a straight grid-tie system@ 10 degree tilt, 180 azimuth, zero/little shade, NYC avg 4.29 kWh/m²/day. Feed an SMA7000 with (3) strings of 11 Suntech STP275’s [9.075 kWdc] Or Do strings of 10, so itd be 8.250 kWdc into the 7 kWac inverter. Strings of 11= 491.7 Voc; 386 Vmp Strings of 10= 447 Voc; 351 Vmp The tradeoff would be power clipping at/around noon in the sunny months in the 9.075 kW scenario; Inverter sleeping late every morning and retiring early in the evenings in the lowered voltage scenario. Trying to figure out which would yield more kWh at the end of the year. Any ideas appreciated, thanks Jim MacDonald Solar Energy Systems, LLC Brooklyn, NY 11222 www.solarEsystems.com No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.801 / Virus Database: 271.1.1/2819 - Release Date: 04/19/10 00:31:00 -Inline Attachment Follows- ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string?
SB8000US only good for 480 Vac, we’re tying in at 208. 11 strings has been calc’d to be OK (600vdc) for record low -4 fahrenheit (-20 celsius). I think the big concern as mentioned is getting the Voc high early in the AM to wake the inverter up, also maintaining the Vmp later in the day to keep it running for as long as possible into the late afternoon/ evening. Will those extra kWh gleaned in the early AM/ late PM over the course of 365 days be more than the kWh clipped during peak production times with the 9.075 kWdc? NYC average summer highs between 79 and 84 fahrenheit early june-late august. Sunlink rack @ 10° on a silver-painted built-up roof. Time-of-use utility $ peak-shaving is not an issue here. Thank you From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Darryl Thayer Sent: Monday, April 19, 2010 5:58 PM To: RE-wrenches Subject: Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? The temperature correction is the concern. I have heard lots of stories of inverters dieing when it gets to cold. Look in the code book 690.7 at the temperature correction table. Go to weather.com and find your record low temperature. Find you Tc factor and will your senerios work? I have heard from a sunny boy rep that it is OK to over power by 1.25% darryl --- On Mon, 4/19/10, Dana d...@solarwork.com wrote: From: Dana d...@solarwork.com Subject: Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? To: 'RE-wrenches' re-wrenches@lists.re-wrenches.org Date: Monday, April 19, 2010, 4:31 PM Many times we switch to another module manufacturer as one will not fit or another inverter manufacturer. PVPowered has a more relaxed window and we have had fine success with them when SMA does not fit. Cold is the dictator and the 600 VDC threshold. Thanks, Dana Orzel Great Solar Works, Inc web - www.solarwork.com E - d...@solarwork.com V - 970.626.5253 F - 970.626.4140 C - 970.209.4076 We have been slow to give up on the myth of the Earth's generosity. Rather grandly, we have overdrawn our accounts. Barbara Kingsolver - Water is life. From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jim MacDonald Sent: Monday, April 19, 2010 2:37 PM To: RE-wrenches@lists.re-wrenches.org Subject: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? For a straight grid-tie system@ 10 degree tilt, 180 azimuth, zero/little shade, NYC avg 4.29 kWh/m²/day. Feed an SMA7000 with (3) strings of 11 Suntech STP275’s [9.075 kWdc] Or Do strings of 10, so itd be 8.250 kWdc into the 7 kWac inverter. Strings of 11= 491.7 Voc; 386 Vmp Strings of 10= 447 Voc; 351 Vmp The tradeoff would be power clipping at/around noon in the sunny months in the 9.075 kW scenario; Inverter sleeping late every morning and retiring early in the evenings in the lowered voltage scenario. Trying to figure out which would yield more kWh at the end of the year. Any ideas appreciated, thanks Jim MacDonald Solar Energy Systems, LLC Brooklyn, NY 11222 www.solarEsystems.comhttp://www.solaresystems.com/ No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.801 / Virus Database: 271.1.1/2819 - Release Date: 04/19/10 00:31:00 -Inline Attachment Follows- ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.orghttp://us.mc519.mail.yahoo.com/mc/compose?to=re-wrenc...@lists.re-wrenches.org Options settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string?
Im sorry, I meant to write “11 modules per string” below.. Been a long day.. From: Jim MacDonald Sent: Monday, April 19, 2010 7:41 PM To: RE-wrenches Cc: Jason Szrom Subject: RE: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? SB8000US only good for 480 Vac, we’re tying in at 208. 11 strings [11 modules per string] has been calc’d to be OK (600vdc) for record low -4 fahrenheit (-20 celsius). I think the big concern as mentioned is getting the Voc high early in the AM to wake the inverter up, also maintaining the Vmp later in the day to keep it running for as long as possible into the late afternoon/ evening. Will those extra kWh gleaned in the early AM/ late PM over the course of 365 days be more than the kWh clipped during peak production times with the 9.075 kWdc? NYC average summer highs between 79 and 84 fahrenheit early june-late august. Sunlink rack @ 10° on a silver-painted built-up roof. Time-of-use utility $ peak-shaving is not an issue here. Thank you From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Darryl Thayer Sent: Monday, April 19, 2010 5:58 PM To: RE-wrenches Subject: Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? The temperature correction is the concern. I have heard lots of stories of inverters dieing when it gets to cold. Look in the code book 690.7 at the temperature correction table. Go to weather.com and find your record low temperature. Find you Tc factor and will your senerios work? I have heard from a sunny boy rep that it is OK to over power by 1.25% darryl --- On Mon, 4/19/10, Dana d...@solarwork.com wrote: From: Dana d...@solarwork.com Subject: Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? To: 'RE-wrenches' re-wrenches@lists.re-wrenches.org Date: Monday, April 19, 2010, 4:31 PM Many times we switch to another module manufacturer as one will not fit or another inverter manufacturer. PVPowered has a more relaxed window and we have had fine success with them when SMA does not fit. Cold is the dictator and the 600 VDC threshold. Thanks, Dana Orzel Great Solar Works, Inc web - www.solarwork.com E - d...@solarwork.com V - 970.626.5253 F - 970.626.4140 C - 970.209.4076 We have been slow to give up on the myth of the Earth's generosity. Rather grandly, we have overdrawn our accounts. Barbara Kingsolver - Water is life. From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jim MacDonald Sent: Monday, April 19, 2010 2:37 PM To: RE-wrenches@lists.re-wrenches.org Subject: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string? For a straight grid-tie system@ 10 degree tilt, 180 azimuth, zero/little shade, NYC avg 4.29 kWh/m²/day. Feed an SMA7000 with (3) strings of 11 Suntech STP275’s [9.075 kWdc] Or Do strings of 10, so itd be 8.250 kWdc into the 7 kWac inverter. Strings of 11= 491.7 Voc; 386 Vmp Strings of 10= 447 Voc; 351 Vmp The tradeoff would be power clipping at/around noon in the sunny months in the 9.075 kW scenario; Inverter sleeping late every morning and retiring early in the evenings in the lowered voltage scenario. Trying to figure out which would yield more kWh at the end of the year. Any ideas appreciated, thanks Jim MacDonald Solar Energy Systems, LLC Brooklyn, NY 11222 www.solarEsystems.comhttp://www.solaresystems.com/ No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.801 / Virus Database: 271.1.1/2819 - Release Date: 04/19/10 00:31:00 -Inline Attachment Follows- ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.orghttp://us.mc519.mail.yahoo.com/mc/compose?to=re-wrenc...@lists.re-wrenches.org Options settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
