[RE-wrenches] P1 micro performance
Yes, I know that that screen shot was only a moment in time. Here it's only March and clipping is already taking place. Imagine what kind of clipping is going to take place at higher irradiance levels later in the year. Yes, the monitoring program cannot as of now quantify what kind of harvesting losses would take place over time compared to an identical array using Enphase micros. But the principle remains unchallengeable: not allowing for maximum kWh harvesting is plain and simple NOT the best design strategy. Some clipping is good? You've got to be joking. Not being able to harvest usable solar energy is good? What kind of optimal design philosophy is that? As module outputs have been going up, Enphase has a vested interest in continuing to move product with little regard for the harvestable energy being essentially lost. Using larger micros that reduce or eliminate that clipping is prima facie a good thing if one cares about maximizing kWh harvest. As more micro products come on the product with higher outputs than the venerable and solid M215, Enphase risks being left behind and losing market share. I for one find that white paper overly self-serving. marco From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Nick Soleil Sent: Thursday, March 21, 2013 8:04 PM To: RE-wrenches Subject: Re: [RE-wrenches] P1 micro performance Good points David, we are in peak season for inverters to be limiting power. Marco, your diagram shows that the modules are only overproducing the Enphase M215's output of 225 watts for a single 15 minute period during the day. That would only equate to about 3 watt-hours of lost power on a day when the modules are producing more than 1000 watt-hours. That tends to be in agreement with our study, which can be viewed at; http://enphase.com/wp-uploads/enphase.com/2011/12/Enphase_White_Paper_Module _Rightsizing.pdf. Averaged across the entire year, this loss of power would total less than 0.1%, and would be less than 0.2% for a 265 watt module. Keep in mind that with degradation accounted for, you will see even less limiting in future years. I'd encourage Wrenches to look closely at the attached document. It is based upon real system production data from Enlighten compared against actual irradiance data. Most analysts would agree that some clipping is good. You will have a better return on your investment when your DC to AC ratio is greater than one. In this case, bigger is better. ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address 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] P1 micro performance
Marco .. and Wrenches .. I'm going to take a run at this -- just once. First ... Without proper and *accurate* data acquisition equipment, there's no way to know what the actual available PV wattage is compared to the inverter's output wattage when its output is being *LIMITED*. This limiting action occurs in an inverter when there's more available power at the input than the inverter can produce at its output. Subsequently, you don't know how much potential energy wasn't harvested. Now then ... Let's say the inverter is producing 216 watts, and the PV *could* produce 227.3 watts at max power point under those specific conditions if every PV-generated milliwatt were used. Next, and presuming the inverter is 95% efficient, that's a limited loss of ONE WATT. 227.3 x 95% = 215.94 watts (OK, so I fudged 0.06 watt). Under what conditions (and since you're in Hawaii, I'll use 70F) would this occur, and with what size PV? I went to my magic spreadsheet and grabbed the first 270-watt-rated PV I could find. NESL DJ-270P,. YOU think it's producing 270 watts. It's not. At 77F (25C), and under the conditions of 100% irradiance, perfectly orthogonal to the sun at mid-day, light wind, that particular PV will produce 227 watts +/- its tolerance. (Let's say the tolerance is dead on.) Now, consider the benefit of increased energy output due to more rapid output wattage rise experienced during early morning, and the higher output later in the afternoon, AS WELL AS the increased power output realized during periods of less than 100% irradiance one derives from using larger PV compared to PV you might consider perfectly matched to the inverter. ALL of this adds up to more kilowatt-hours produced annually than had the inverter been connected to your perfect PV that doesn't produce enough wattage to have the inverter begin limiting its output. The shoulders of the output wattage curve are steeper than with lower-wattage PV. Granted you *could* connect the inverter to [say] a 450 watt PV module, and that would truly be a waste of the PV wattage. There *is* a broad sweet spot for AC Module inverters and microinverters alike, and it's actually on the higher side of the PV's rated output wattage versus the inverter's wattage rating. So, can you over-do it? Sure. But there IS an overall kilowatt-hours-produced benefit for *modest* over-sizing the PV. What I *can't* answer is the long-term effect this may have on the overall life of the inverter. THAT depends on various intricate design considerations that went into creating the inverter in the first place. This isn't an Enphase issue, nor are they trying to mislead you on this topic. It's an industry-wide issue. Wrenches face it every time you designed a string system, especially those being installed in regions with wide temperature swings. Trying to explain in depth the how and why slightly larger PV is of benefit to a customer is like trying to explain photovoltaic equipment to the general public. As a competitor to Enphase .. I'm not coming to their defense. However, what Nick said (below) IS fact. Whether you elect to believe this or not is up to you. Regards to all, Dan Lepinski, Senior Engineer Exeltech / Exeltech Solar Products With 41 years experience as a design engineer in solar energy. --- On Sat, 3/23/13, Marco Mangelsdorf ma...@pvthawaii.com wrote: From: Marco Mangelsdorf ma...@pvthawaii.com Subject: [RE-wrenches] P1 micro performance To: 'RE-wrenches' re-wrenches@lists.re-wrenches.org Date: Saturday, March 23, 2013, 4:04 AM Yes, I know that that screen shot was only a moment in time. Here it’s only March and clipping is already taking place. Imagine what kind of clipping is going to take place at higher irradiance levels later in the year. Yes, the monitoring program cannot as of now quantify what kind of harvesting losses would take place over time compared to an identical array using Enphase micros. But the principle remains unchallengeable: not allowing for maximum kWh harvesting is plain and simple NOT the best design strategy. “Some clipping is good”? You’ve got to be joking. Not being able to harvest usable solar energy is good? What kind of optimal design philosophy is that? As module outputs have been going up, Enphase has a vested interest in continuing to move product with little regard for the harvestable energy being essentially lost. Using larger micros that reduce or eliminate that clipping is prima facie a good thing if one cares about maximizing kWh harvest. As more micro products come on the product with higher outputs than the venerable and solid M215, Enphase risks being left behind and losing market share. I for one find that “white paper” overly self-serving. marco From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Nick Soleil Sent: Thursday, March 21, 2013 8:04 PM To: RE-wrenches Subject: Re: [RE-wrenches] P1 micro
Re: [RE-wrenches] P1 micro performance
Friends, I am a little puzzled by this topic. What has happened to the good engineering practice of sizing electronic equipment so that it is not driven to the maximum. My understanding is that the MTBF increases significantly the harder you drive the unit. This seems to be a case of overdriving the units for short term gain. Carl Emerson Free Power Co. Auckland N.Z. From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Exeltech Sent: 24 March 2013 5:50 a.m. To: RE-wrenches Subject: Re: [RE-wrenches] P1 micro performance Marco .. and Wrenches .. I'm going to take a run at this -- just once. First ... Without proper and *accurate* data acquisition equipment, there's no way to know what the actual available PV wattage is compared to the inverter's output wattage when its output is being *LIMITED*. This limiting action occurs in an inverter when there's more available power at the input than the inverter can produce at its output. Subsequently, you don't know how much potential energy wasn't harvested. Now then ... Let's say the inverter is producing 216 watts, and the PV *could* produce 227.3 watts at max power point under those specific conditions if every PV-generated milliwatt were used. Next, and presuming the inverter is 95% efficient, that's a limited loss of ONE WATT. 227.3 x 95% = 215.94 watts (OK, so I fudged 0.06 watt). Under what conditions (and since you're in Hawaii, I'll use 70F) would this occur, and with what size PV? I went to my magic spreadsheet and grabbed the first 270-watt-rated PV I could find. NESL DJ-270P,. YOU think it's producing 270 watts. It's not. At 77F (25C), and under the conditions of 100% irradiance, perfectly orthogonal to the sun at mid-day, light wind, that particular PV will produce 227 watts +/- its tolerance. (Let's say the tolerance is dead on.) Now, consider the benefit of increased energy output due to more rapid output wattage rise experienced during early morning, and the higher output later in the afternoon, AS WELL AS the increased power output realized during periods of less than 100% irradiance one derives from using larger PV compared to PV you might consider perfectly matched to the inverter. ALL of this adds up to more kilowatt-hours produced annually than had the inverter been connected to your perfect PV that doesn't produce enough wattage to have the inverter begin limiting its output. The shoulders of the output wattage curve are steeper than with lower-wattage PV. Granted you *could* connect the inverter to [say] a 450 watt PV module, and that would truly be a waste of the PV wattage. There *is* a broad sweet spot for AC Module inverters and microinverters alike, and it's actually on the higher side of the PV's rated output wattage versus the inverter's wattage rating. So, can you over-do it? Sure. But there IS an overall kilowatt-hours-produced benefit for *modest* over-sizing the PV. What I *can't* answer is the long-term effect this may have on the overall life of the inverter. THAT depends on various intricate design considerations that went into creating the inverter in the first place. This isn't an Enphase issue, nor are they trying to mislead you on this topic. It's an industry-wide issue. Wrenches face it every time you designed a string system, especially those being installed in regions with wide temperature swings. Trying to explain in depth the how and why slightly larger PV is of benefit to a customer is like trying to explain photovoltaic equipment to the general public. As a competitor to Enphase .. I'm not coming to their defense. However, what Nick said (below) IS fact. Whether you elect to believe this or not is up to you. Regards to all, Dan Lepinski, Senior Engineer Exeltech / Exeltech Solar Products With 41 years experience as a design engineer in solar energy. --- On Sat, 3/23/13, Marco Mangelsdorf ma...@pvthawaii.com wrote: From: Marco Mangelsdorf ma...@pvthawaii.com Subject: [RE-wrenches] P1 micro performance To: 'RE-wrenches' re-wrenches@lists.re-wrenches.org Date: Saturday, March 23, 2013, 4:04 AM Yes, I know that that screen shot was only a moment in time. Here it's only March and clipping is already taking place. Imagine what kind of clipping is going to take place at higher irradiance levels later in the year. Yes, the monitoring program cannot as of now quantify what kind of harvesting losses would take place over time compared to an identical array using Enphase micros. But the principle remains unchallengeable: not allowing for maximum kWh harvesting is plain and simple NOT the best design strategy. Some clipping is good? You've got to be joking. Not being able to harvest usable solar energy is good? What kind of optimal design philosophy is that? As module outputs have been going up, Enphase has a vested interest in continuing to move product with little regard for the
[RE-wrenches] P1 micro performance
From Dan at Exeltech: Trying to explain in depth the how and why slightly larger PV is of benefit to a customer is like trying to explain photovoltaic equipment to the general public. I still challenge those who believe that “some clipping is good” to make their case. And as far as the general buying public, I’m find that people do in fact understand when you ask them the following questions: Do you, Mr./Mrs./Ms. Homeowner, want a PV system that produces as much solar kWhs for your investment as possible? Usual response: absolutely. If I give you the choice of PV system using a 250-watt module paired with a COMPARABLY priced 250-watt micro inverter OR that same 250-watt module with a max output ~ 224-watt micro inverter that will never under any circumstances allow that 250-watt module to put out its max rated power output, which option do you think they’ll choose? They get that. It doesn’t take someone with an engineering degree or 10-40 years in the field to get that simple premise. For what it’s worth, being here in the tropics in the Hawaiian islands we don’t get those bright and sunny and cold late fall/winter/early spring days that will allow for an array to put out its STC-rated power. But seeing regular times during the day—any time of year—where the irradiance is more than 1,000 watts/sq. meter is not at all common. marco Yes, I know that that screen shot was only a moment in time. Here it’s only March and clipping is already taking place. Imagine what kind of clipping is going to take place at higher irradiance levels later in the year. Yes, the monitoring program cannot as of now quantify what kind of harvesting losses would take place over time compared to an identical array using Enphase micros. But the principle remains unchallengeable: not allowing for maximum kWh harvesting is plain and simple NOT the best design strategy. “Some clipping is good”? You’ve got to be joking. Not being able to harvest usable solar energy is good? What kind of optimal design philosophy is that? As module outputs have been going up, Enphase has a vested interest in continuing to move product with little regard for the harvestable energy being essentially lost. Using larger micros that reduce or eliminate that clipping is prima facie a good thing if one cares about maximizing kWh harvest. As more micro products come on the product with higher outputs than the venerable and solid M215, Enphase risks being left behind and losing market share. I for one find that “white paper” overly self-serving. marco ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address 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] Cable tray
I don't know your exact application, but I've used Carlon wireways for years. Our application most of the time was to use the 4x4 gutter in lieu of metal gutter under the inverters,disconnects, Panelboards, etc. http://www.carlonsales.com/wiresafe.php Max Balchowsky Design Engineer SEE Systems 1048 Irvine Ave Suite 217 Newport Beach, Ca. 92660 760-403-6810 Building a Better Future For The Next Generation From: Chris Mason cometenergysyst...@gmail.com To: RE-wrenches re-wrenches@lists.re-wrenches.org Sent: Friday, March 22, 2013 12:07 PM Subject: [RE-wrenches] Cable tray I'm looking for flat roof cable tray system that is cost effective. We previously used Cablofil and Cablo-port FSL 12 tray but it is very expensive for our current application due to the size of the roof. We need to install about 200' of tray and Cablofil galvanized is eating up the budget. Can anyone recommend a cheaper alternative. -- Chris Mason ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address 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 Change email address 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