Re: [RE-wrenches] Inverters Maximum Input Ratings
Marco, The applicability of your statement ... ... what’s beyond dispute is that when we size the solar array higher than the nameplate inverter output, there will be clipping that takes place….i.e., harvestable solar power that goes nowhere. depends to a great extent on the site climate .. as I'm sure you're aware. Overall, the blanket statement you make in this respect is not correct. Using Hawaii, and 65F/85F as low and high respectively, Solar World SW270 photovoltaic modules will nominally generate 243 watts at 65F, and 225 watts at 85F under conditions of 1 kW/m^2 irradiance and perfectly orthogonal to the sun. Microinverters rated 225 watts AC output at ~95% efficiency will input nominally 237 watts DC. Subsequently, the maximum amount of limiting that could take place under these conditions is approximately 6 watts. However, that too will not happen, as the 65F condition does not occur during mid-day. Since 65F occurs early morning, during periods of decreased irradiance, the sun angle will be fairly low, thus the SW270 photovoltaic modules won't be orthogonal to the sun .. nor will there be 1 kW/m^2 irradiance. Thus the PV module won't be producing 243 watts, but instead will be much less, depending on irradiance and sun angle (among other things). In your own Hawaiian climate, the SW270 is in fact an almost perfect energy match for the Enphase 225. Move the scenario to Phoenix, Arizona, and the cold/hot PV power output (using 5C/40F low, and 50C/120F high), the PV power output would be 249W and 202W respectively, again with 1 kW/m^2 and orthogonal to the sun. The likelihood of 40F during mid-day in Phoenix is exceedingly rare. Thus you can see that the SW270 module is actually a bit UNDERSIZED for an Enphase 225 in Phoenix. The amount of energy not harvested due to limiting in the Phoenix environment is essentially zero, even with a 270 watt PV module. Conversely, the SW270 / Enphase 225 combination in Minneapolis would not be optimal due to the extremely cold winter weather. Here, power limiting within the inverter WOULD occur when cold, resulting in less than 100% of the available DC energy converted to AC at an ambient temperatures of ~50F or cooler, and under conditions of 1 kW/m^2 irradiance with the sun perfectly orthogonal to the PV module. This would not be thermally harmful to the microinverter because it would be taking place during extremely cold weather. Conversely, during summer months, using 35C (95F) as the typical high temperature in Minneapolis, the PV module output would be reduced to 220 watts, all other conditions being equal .. thus LESS than is needed for maximum output by the microinverter. In summary, in warm-to-hot climates, the SW270 would in fact be a nearly ideal match for the Enphase 225 from an energy perspective. Regards to all, Dan Lepinski On Tue, 8/26/14, Marco Mangelsdorf ma...@pvthawaii.com wrote: Subject: [RE-wrenches] Inverters Maximum Input Ratings To: 'RE-wrenches' re-wrenches@lists.re-wrenches.org Date: Tuesday, August 26, 2014, 1:10 AM Look, guys, what’s beyond dispute is that when we size the solar array higher than the nameplate inverter output, there will be clipping that takes place….i.e., harvestable solar power that goes nowhere. The higher that oversize percentage, the more clipping will take place. If the design choice, as noted below, is to use a 270-watt module (from a manufacturer that learned last week that a recall notice was published by the U.S. Consumer Product Safety Commission https://www.cpsc.gov/en/Recalls/2014/SolarWorld-Recalls-Solar-Systems-with-Copper-Grounding-Lugs/ ), does it make sense to use a micro inverter that has a max output of about 225 watts (M215) or 250 watts (M250) when there are micros (e.g., ABB 300) that can handle the full output of the 270 which guarantees NO clipping? marco ___ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
Re: [RE-wrenches] Rapid shutdown questions
While I share Robin's optimism, I should also note the NEC 2017 690.12 committee referred to is not the code making panel. While it does have (at least) one firefighter representative among a majority of PV industry personnel, there's no guarantee that the Code Making Panel approves this committee's proposal. There could very well be a competing proposal from firefighters that requires cell-level shutdown every time a red truck drives within 1/4 mile of an array, because SAFETY! DKC On 2014/8/28, 15:16, b...@midnitesolar.com wrote: [Robin chiming in, below] Dan, The 2014 690.12 is worded poorly. That is why there is so much confusion. MidNite Solar is sitting on the NEC2017 690.12 committee. There are a lot of smart people in this group. The 2017 version says ALL PV SYSTEMS, not just on or in buildings. The 10 foot space gets reduced to 1 foot like it always should have been. There will be a lot of other clarifications too. The systems that use shunt trip breakers [with Remote Trip coil] and contactors are for string inverters. Shunt trip breakers will be used for battery based systems and grid tie inverters with an AC outlet like the SMA TL series. Micro inverters do not require anything like what our system is. They can use the existing backfed breaker in the main distribution box as long as it is labeled accordingly. Solar Edge has a system that meets the Rapid Shutdown requirement also. The UL standard for Rapid Shutdown has been written. It is going to go out to a task force for review, comment and changes soon. MidNite Solar will be on that task force. The MidNite Birdhouse is going through UL now and is being evaluated to this new standard. All of our disconnecting combiners and SOBs are already ETL listed. UL is modifying the new Rapid Shutdown Draft standard as they come upon things in the Birdhouse that the standard didn't consider. One of the biggies that has not been sorted out is a requirement for feedback. Contactors, power supplies and a switch will meet the requirement for 2014. The issue with this type of system is that when you push the button to turn off the contactors, there is no way to tell that they actually opened up. Without feedback that verifies that the contactors are actually open, you are taking a chance with people's lives. 600VDC contactors can weld themselves closed. If first responders don't trust the Rapid Shutdown system, they are going to let the house burn. We do have feedback on the birdhouse system. Contactors do not have feedback. It is not simple to add this feature to a contactor based system. Installing a switch 15 feet up on the side of a building or on the roof is not the intent of 690.12. This will not be allowed in 2017. The exact placement of the initiating device (Birdhouse) is not cast in concrete due to the differences in where main panel boards are located, but it will not allow things like mentioned here 15 feet up in the air or in the attic or on the roof. Battery based systems are the most complicated to meet 690.12. The NEC committee is deferring a lot of this to MidNite as we are already doing it and have gone over all the different ways things can go wrong. We started designing our system right after the Bakersfield fire 5 years ago. The Bakersfield fire is what got the NEC to require disconnecting combiners. We couldn't imagine why a fire fighter would want to get up on the roof of a burning building to look for a combiner? This is why we started the birdhouse project way before anyone ever thought of the words Rapid Shutdown. Turns out this was a good thing since battery backed up systems make the issue ten times more complicated. We spent years working out issues and there were lots of them that required a start from scratch approach numerous times. AC coupling to a battery based inverter does not automatically meet 690.12 as someone mentioned in this thread. That battery based inverter must also be shut off. The micro inverters would of course shut off when the utility is shut down, but the battery based inverters job is to keep things powered up when the grid is down. So the battery based inverter has to be shut down also. It would also make sense to shut off an auto start generator with the Rapid Shutdown button. Some generators are designed to start up upon loss of grid. Once the first responders have the meter pulled, that could start up a generator and cause risk of shock. If the generator is designed to start on low battery, it could start a day later when the fire has been put out, but that also poses risk of electrical shock when unexpectedly the part of the house that is left all of a sudden comes live with juice. The cost for a Rapid Shutdown system will vary a lot depending on what you want to shut down. You do not need to run conduit to all the boxes and switches. There is 600V Cat5e 90C USE-2 cable available that will suffice. I don't see a
[RE-wrenches] BP Solar Point of Contact
Has anyone a point of contact at BP Solar to discuss warranty issues of SX170Bs installed in January 2006? Thanks Peter T. Parrish, Ph.D. President, SolarGnosis 1107 Fair Oaks Ave. South Pasadena, CA 91107 Ph. (323) 839-6108, Fax. (323) 258-8827 ___ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
Re: [RE-wrenches] BP Solar Point of Contact
I've just been having contact with them this week in fact. laura.koutsostama...@bp.com -Original Message- From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Peter Parrish Sent: Friday, August 29, 2014 8:05 AM To: 'RE-wrenches' Subject: [RE-wrenches] BP Solar Point of Contact Has anyone a point of contact at BP Solar to discuss warranty issues of SX170Bs installed in January 2006? Thanks Peter T. Parrish, Ph.D. President, SolarGnosis 1107 Fair Oaks Ave. South Pasadena, CA 91107 Ph. (323) 839-6108, Fax. (323) 258-8827 ___ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org ___ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
