Re: [RE-wrenches] high insolation value and inverter undersizing
I found the latest module rightsizing paper by Enphase pretty interesting. It does stand to reason that there are a lot of hours in the day where the inverter is producing less than rated power, so increasing the module size makes sense. Obviously there is an optimum point in every system where clipping exceeds gains, but that's virtually impossible to nail down due to so many factors being involved. I think the point would be that PV mods are coming down in price so much that rightsizing is basically equivalent to upsizing, within reason, of course. Spending an extra 25% on PV might increase the installed system cost by 5-10%. *Jason Szumlanski* *Fafco Solar * On Sun, Jan 27, 2013 at 6:00 PM, Marco Mangelsdorf ma...@pvthawaii.comwrote: I have had a concern for a long time that as PV modules have gone up in output that there is inevitably going to be more and more clipping taking place as they’re paired with comparatively lower output inverters. In effect, matching, say. a 260-watt module with a micro inverter with a max output of 225 watts reduces that 260-watt mod to 225 watts. It’s not a matter of if clipping will take place, but how much and how much actual harvestable energy will be lost. ** ** Out here in the tropics, even in January with the lower sun angle, we see irradiance levels well above 1,000 watts/square meter range. Take a look at what I copied today from a weather station that we installed at nearby installation. ** ** Given the clipping issue inherent in using undersized inverters, it seems to me that moving to larger output micros makes a whole lotta sense. I’ve got one of the first installs using the Power-One 250-watt and 300-watt micros and am so far quite impressed. Why use a 225-watt rated micro with a 225-watt or higher output mod when larger micros are now readily available? ** ** What are the views out there regarding this clipping issue? Is it as minimal as our Enphase friends suggest in their latest white paper or more of an issue as I conclude? ** ** marco ** ** ** ** Environmentals from Weather Station at a Hilo, Hawaii installation * * Sunday, January 27th 2013, 12:40:00 pm [image: https://easyview.auroravision.net/easyview/images/icons/weather/temp-red.png] *Ambient Temp.* 25.30 °C *Cell Temp.* 41.70 °C [image: https://easyview.auroravision.net/easyview/images/icons/weather/sun-yellow.png] *Insolation* 127.81 kWh/m² *Irradiance** 1,175.00 W/m²* ** ___ 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] Husqvarna 5500 and VFX3524 Compatibility
Carl; The Iotas we are using have an external jumper that you insert that allows it to get to EQ voltage. DAN On Sun, Jan 27, 2013 at 7:31 PM, Carl Hansen solar...@cybermesa.com wrote: Dan, You may be do this as well, but I frequently deal with homeowners with inexpensive generators, I find that the Outback and Magnum inverters are very tolerant but I do generally have to load the generator up to where I want it bulk charging the batteries, then adjust the generator speed to dial in the freqency to 60Hz using the throttle adj. screw. Do you find the Iota chargers can reach bulk charge voltages, or even EQ voltages ? Carl Hansen -- Dan Fink, Executive Director; Otherpower Buckville Energy Consulting Buckville Publications LLC NABCEP / IREC accredited Continuing Education Providers 970.672.4342 (voicemail) ___ 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] high insolation value and inverter undersizing
When looking at the various systems we have installed with different module/inverter combinations its hard to make a perfect performance comparison as tilt, orientation, module, and degree of transient shade vary considerably. Additionally many string inverters we have out there do not have web monitoring, and a number of M190 based systems have had numerous failures so they are not good for comparison either. That said, I did do a quick comparison of 4 systems that are about the same age, have the same tilt, orientation and are all shade free. The kWh/kW for 2012 are listed below: M190/Sharp240 1,336 kWh/kW M215/Sharp240 1,488 M215/SW245 1,411 SB5000/Sharp235 1,468 It seems the upper limit of Enphases recommended module wattage may be a little high for the Midwest, but its hard to say what will happen over the lifetime of the system as the module degrades. Previous to installation I suspected the 240 was a little oversized for the M190, but price decreases at the time allowed us to keep our installed price and give the customer a larger system. Pricing aside, I would likely not do it again unless there was an AC limitation, or non-ideal module orientation. Garrison Riegel Solar Service Inc [p] 847-677-0950 http://www.solarserviceinc.com/ www.solarserviceinc.com NABCEP Certified Solar PV and Thermal Installer From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jason Szumlanski Sent: Monday, January 28, 2013 7:30 AM To: RE-wrenches Subject: Re: [RE-wrenches] high insolation value and inverter undersizing I found the latest module rightsizing paper by Enphase pretty interesting. It does stand to reason that there are a lot of hours in the day where the inverter is producing less than rated power, so increasing the module size makes sense. Obviously there is an optimum point in every system where clipping exceeds gains, but that's virtually impossible to nail down due to so many factors being involved. I think the point would be that PV mods are coming down in price so much that rightsizing is basically equivalent to upsizing, within reason, of course. Spending an extra 25% on PV might increase the installed system cost by 5-10%. Jason Szumlanski Fafco Solar On Sun, Jan 27, 2013 at 6:00 PM, Marco Mangelsdorf ma...@pvthawaii.com wrote: I have had a concern for a long time that as PV modules have gone up in output that there is inevitably going to be more and more clipping taking place as theyre paired with comparatively lower output inverters. In effect, matching, say. a 260-watt module with a micro inverter with a max output of 225 watts reduces that 260-watt mod to 225 watts. Its not a matter of if clipping will take place, but how much and how much actual harvestable energy will be lost. Out here in the tropics, even in January with the lower sun angle, we see irradiance levels well above 1,000 watts/square meter range. Take a look at what I copied today from a weather station that we installed at nearby installation. Given the clipping issue inherent in using undersized inverters, it seems to me that moving to larger output micros makes a whole lotta sense. Ive got one of the first installs using the Power-One 250-watt and 300-watt micros and am so far quite impressed. Why use a 225-watt rated micro with a 225-watt or higher output mod when larger micros are now readily available? What are the views out there regarding this clipping issue? Is it as minimal as our Enphase friends suggest in their latest white paper or more of an issue as I conclude? marco Environmentals from Weather Station at a Hilo, Hawaii installation Sunday, January 27th 2013, 12:40:00 pm Ambient Temp. 25.30 °C Cell Temp. 41.70 °C Insolation 127.81 kWh/m² Irradiance 1,175.00 W/m² ___ 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] high insolation value and inverter undersizing
In a grid tied system the question becomes how much clipping and how often. Intuitively we all know little clipping is probably ok but a lot of clipping is a bad thing. How much is ok is the question. Ultimately we should all be concerned with economics (LCOE / ROI). The clipping experienced by one system design may or may not have a negative influence on LCOE compared to an alternative system designs. We run LCOE analysis frequently and have a field in the spreadsheet for clipping losses. For now we just use a fixed percentage but time of day metering makes this much more complicated. With TOD metering the value of energy varies both by time of day and seasonally so the energy lost to clipping can have a different value than the increased energy on the shoulders. Ideally one would look at the irradiance over a year and then do a distribution of the hours per year at various insolation levels. In places other than Hawaii you need to correlate irradiance to temperature since module power is varies with temperature (typically -0.5%/degree C), i.e. high irradiance on a hot summer day is less likely to cause clipping than high irradiance on a cold winter day. @ Marco: does your weather data source have a database of insolation and temperature over the year ? Best Regards, John Berdner General Manager, North America SolarEdge Technologies, Inc. 3347 Gateway Boulevard, Fremont CA 94538 USA (*Please note of our new address.) T: 510.498.3200, X 747 M: 530.277.4894 -Original Message- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of William Miller Sent: Sunday, January 27, 2013 8:05 PM To: RE-wrenches Subject: Re: [RE-wrenches] high insolation value and inverter undersizing Jesse: Do you have any way to compare the total harvest for the day for a given module in a clipping scenario versus an unclipping? The question I want to answer is: Do we improve production enough on the shoulders of the clip to justify the loss on the peak? Thanks, William Miller At 06:25 PM 1/27/2013, you wrote: A while back (3 years)I installed a system (bid spec) for a school that used 215W RECs and D380s on a dual axis tracker. With the ability to monitor the array, I see constant clipping. The modules will usually produce 199Ws regularly. A few days ago we had temps of -34F and clear skies. My array at home had one of its best days this winter. I have Tigos on so I can monitor watts, current, temp and voltage. I was seeing anywhere from 215W to 223W from my modules between 11:30am and 1pm. The modules on the tracker were still producing 199W. I didn't get an irradiance reading that day but my Tigos showed above IMP readings and way above VMP reading that day. I've only been doing this for 6 years, so I don't have the experience that some people on this list have, but it seems foolish to me to waste that production. It's kinda site specific, but where I live the cold temps and snow reflection seem like something we should be utilizing. ___ 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 CONFIDENTIALITY NOTICE: This e-mail and its attachments are intended only for the use of the individual or entity who is the intended recipient and may contain information that is privileged, confidential and exempt from disclosure or any type of use under applicable law. If the reader of this e-mail is not the intended recipient, or the employee, agent, or representative responsible for delivering the e-mail to the intended recipient, you are hereby notified that any dissemination, distribution, copying, or other use of this e-mail is strictly prohibited. If you have received this e-mail in error, please reply immediately to the sender. P Please think of the environment before printing this email ___ 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] Husqvarna......; Iota configuration
Hi Dan, The Iota jumper only raises voltage by 0.6 volts above the default setting. You will need to insert the jumper AND adjust the voltage POT (now internal) to reach the EQ range. For off grid systems, I usually turn up the Iota voltage POT fully since generator run time is rarely enough to cause a long over-voltage condition. Then when the customer wants to equalize, just continue running the generator. Sometimes I install a toggle switch in series with the jumper in case a lower voltage is desired. Larry Crutcher Starlight Solar Power Systems On Jan 28, 2013, at 7:41 AM, Dan Fink wrote: Carl; The Iotas we are using have an external jumper that you insert that allows it to get to EQ voltage. DAN ___ 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] high insolation value and inverter undersizing
For that particular site, no. As far as I know a database is not being maintained. That is, what you see at any given moment is what you get. But I will check. Once we get into Spring and Summer with higher sun angles, I will be able to see what kind of clipping would have taken place since I have 245-watt modules on 300-watt micros. (It's the one and only beta test site in the state for these micros.) Any time I see recorded outputs of 226 watts or higher, I will know that clipping would have taken place if I had used M215s instead. For me this boils down to several fairly simple points: 1) Clipping is not good since that represents harvestable solar energy that does not make it to the end user. 2) So when the choice of clipping v. no clipping is presented, no clipping is always, in principle, going to be the best choice. 3) Larger inverters--whether micro or string--are going to typically cost more than smaller ones. 4) Does it make sense to pay more upfront for more inverter capacity and reap the benefits of more delivered kWhs over time? One can perform detailed equations until the ripe mangoes fall from the trees (at least out here). But from an intuitive perspective, spending marginally more money upfront to minimize if not eliminate clipping, especially in areas like the tropics which can have frequent and lingering edge-of-cloud effects, makes the most sense to me. And, really, pairing up a micro with a nameplate rating of 215 watts and max output of 225 watts with a 255, 260, 265 watt or higher rated mod? Does that really pass the sniff test when there are not higher output micros out there? Put the choice to the consumer, educate them just a wee bit and how do you think they will decide? marco @ Marco: does your weather data source have a database of insolation and temperature over the year ? Best Regards, John Berdner General Manager, North America SolarEdge Technologies, Inc. 3347 Gateway Boulevard, Fremont CA 94538 USA (*Please note of our new address.) T: 510.498.3200, X 747 M: 530.277.4894 -Original Message- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of William Miller Sent: Sunday, January 27, 2013 8:05 PM To: RE-wrenches Subject: Re: [RE-wrenches] high insolation value and inverter undersizing Jesse: Do you have any way to compare the total harvest for the day for a given module in a clipping scenario versus an unclipping? The question I want to answer is: Do we improve production enough on the shoulders of the clip to justify the loss on the peak? Thanks, William Miller At 06:25 PM 1/27/2013, you wrote: A while back (3 years)I installed a system (bid spec) for a school that used 215W RECs and D380s on a dual axis tracker. With the ability to monitor the array, I see constant clipping. The modules will usually produce 199Ws regularly. A few days ago we had temps of -34F and clear skies. My array at home had one of its best days this winter. I have Tigos on so I can monitor watts, current, temp and voltage. I was seeing anywhere from 215W to 223W from my modules between 11:30am and 1pm. The modules on the tracker were still producing 199W. I didn't get an irradiance reading that day but my Tigos showed above IMP readings and way above VMP reading that day. I've only been doing this for 6 years, so I don't have the experience that some people on this list have, but it seems foolish to me to waste that production. It's kinda site specific, but where I live the cold temps and snow reflection seem like something we should be utilizing. ___ 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 CONFIDENTIALITY NOTICE: This e-mail and its attachments are intended only for the use of the individual or entity who is the intended recipient and may contain information that is privileged, confidential and exempt from disclosure or any type of use under applicable law. If the reader of this e-mail is not the intended recipient, or the employee, agent, or representative responsible for delivering the e-mail to the intended recipient, you are hereby notified that any dissemination, distribution, copying, or other use of this e-mail is strictly prohibited. If you have received this e-mail in error, please reply immediately to the sender. P Please think of the environment before printing this email ___ 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
Re: [RE-wrenches] high insolation value and inverter undersizing
Jason: Be careful of drawing false comparisons. There is no free lunch. Beyond the energy yield issues there are some reliability issues. You should also consider that running an inverter flat out all the time will shorten it's life (due to the Arrhenius effect). http://en.wikipedia.org/wiki/Arrhenius_equation Think of the inverter temperature in the same way you would the power output curve (the two are closely related). Moving the whole power curve up more on the shoulders also moves the whole temperature curve up as well. The average lifetime (all this stuff is only probabilities) was projected with certain assumptions about how many hours at what temperature. As module sizes increase a given inverter will spend more time at a higher power level, i.e. runs hotter longer, which non-linearly reduces the life of the product. Just my $0.02... With the high labor cost of replacement it might be better to undersize the module relative to the power electronics or vice versa. This may or may not increase the installed system cost depending on the products you choose. Running everything flat out all the time is probably not the greatest idea. Best Regards, John Berdner General Manager, North America [cid:image001.jpg@01CDFD3C.B73855C0] SolarEdge Technologies, Inc. 3347 Gateway Boulevard, Fremont CA 94538 USA (*Please note of our new address.) T: 510.498.3200, X 747 M: 530.277.4894 From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jason Szumlanski Sent: Monday, January 28, 2013 5:30 AM To: RE-wrenches Subject: Re: [RE-wrenches] high insolation value and inverter undersizing I found the latest module rightsizing paper by Enphase pretty interesting. It does stand to reason that there are a lot of hours in the day where the inverter is producing less than rated power, so increasing the module size makes sense. Obviously there is an optimum point in every system where clipping exceeds gains, but that's virtually impossible to nail down due to so many factors being involved. I think the point would be that PV mods are coming down in price so much that rightsizing is basically equivalent to upsizing, within reason, of course. Spending an extra 25% on PV might increase the installed system cost by 5-10%. Jason Szumlanski Fafco Solar On Sun, Jan 27, 2013 at 6:00 PM, Marco Mangelsdorf ma...@pvthawaii.commailto:ma...@pvthawaii.com wrote: I have had a concern for a long time that as PV modules have gone up in output that there is inevitably going to be more and more clipping taking place as they're paired with comparatively lower output inverters. In effect, matching, say. a 260-watt module with a micro inverter with a max output of 225 watts reduces that 260-watt mod to 225 watts. It's not a matter of if clipping will take place, but how much and how much actual harvestable energy will be lost. Out here in the tropics, even in January with the lower sun angle, we see irradiance levels well above 1,000 watts/square meter range. Take a look at what I copied today from a weather station that we installed at nearby installation. Given the clipping issue inherent in using undersized inverters, it seems to me that moving to larger output micros makes a whole lotta sense. I've got one of the first installs using the Power-One 250-watt and 300-watt micros and am so far quite impressed. Why use a 225-watt rated micro with a 225-watt or higher output mod when larger micros are now readily available? What are the views out there regarding this clipping issue? Is it as minimal as our Enphase friends suggest in their latest white paper or more of an issue as I conclude? marco Environmentals from Weather Station at a Hilo, Hawaii installation Sunday, January 27th 2013, 12:40:00 pm Ambient Temp. 25.30 °C Cell Temp. 41.70 °C Insolation 127.81 kWh/m² Irradiance 1,175.00 W/m² CONFIDENTIALITY NOTICE: This e-mail and its attachments are intended only for the use of the individual or entity who is the intended recipient and may contain information that is privileged, confidential and exempt from disclosure or any type of use under applicable law. If the reader of this e-mail is not the intended recipient, or the employee, agent, or representative responsible for delivering the e-mail to the intended recipient, you are hereby notified that any dissemination, distribution, copying, or other use of this e-mail is strictly prohibited. If you have received this e-mail in error, please reply immediately to the sender. P Please think of the environment before printing this email inline: image001.jpg___ 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
Re: [RE-wrenches] high insolation value and inverter undersizing
Another thing to think about when the system is oversized for the inverter being used (or charge controller) and it clips all the time (I call it current limiting), is that the input voltage will rise to reduce the output power (to keep it limited) which will usually make the inverter or charge controller heat up more. boB On 1/28/2013 9:40 AM, John Berdner wrote: In a grid tied system the question becomes how much clipping and how often. Intuitively we all know little clipping is probably ok but a lot of clipping is a bad thing. How much is ok is the question. Ultimately we should all be concerned with economics (LCOE / ROI). The clipping experienced by one system design may or may not have a negative influence on LCOE compared to an alternative system designs. We run LCOE analysis frequently and have a field in the spreadsheet for clipping losses. For now we just use a fixed percentage but time of day metering makes this much more complicated. With TOD metering the value of energy varies both by time of day and seasonally so the energy lost to clipping can have a different value than the increased energy on the shoulders. Ideally one would look at the irradiance over a year and then do a distribution of the hours per year at various insolation levels. In places other than Hawaii you need to correlate irradiance to temperature since module power is varies with temperature (typically -0.5%/degree C), i.e. high irradiance on a hot summer day is less likely to cause clipping than high irradiance on a cold winter day. @ Marco: does your weather data source have a database of insolation and temperature over the year ? Best Regards, John Berdner General Manager, North America SolarEdge Technologies, Inc. 3347 Gateway Boulevard, Fremont CA 94538 USA (*Please note of our new address.) T: 510.498.3200, X 747 M: 530.277.4894 -Original Message- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of William Miller Sent: Sunday, January 27, 2013 8:05 PM To: RE-wrenches Subject: Re: [RE-wrenches] high insolation value and inverter undersizing Jesse: Do you have any way to compare the total harvest for the day for a given module in a clipping scenario versus an unclipping? The question I want to answer is: Do we improve production enough on the shoulders of the clip to justify the loss on the peak? Thanks, William Miller At 06:25 PM 1/27/2013, you wrote: A while back (3 years)I installed a system (bid spec) for a school that used 215W RECs and D380s on a dual axis tracker. With the ability to monitor the array, I see constant clipping. The modules will usually produce 199Ws regularly. A few days ago we had temps of -34F and clear skies. My array at home had one of its best days this winter. I have Tigos on so I can monitor watts, current, temp and voltage. I was seeing anywhere from 215W to 223W from my modules between 11:30am and 1pm. The modules on the tracker were still producing 199W. I didn't get an irradiance reading that day but my Tigos showed above IMP readings and way above VMP reading that day. I've only been doing this for 6 years, so I don't have the experience that some people on this list have, but it seems foolish to me to waste that production. It's kinda site specific, but where I live the cold temps and snow reflection seem like something we should be utilizing. ___ 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] high insolation value and inverter undersizing
Hi John, It's important to clarify that the clipped power does not turn into heat within the microinverter. The microinverter only draws enough current to achieve it's max output rating, and the remaining current is left in the module, so to speak. So, the heat generated at peak times is the same, whether using a 260W module or a 280W module. Many string inverters actually work similarly. What's different for them, however, is their overall thermal situation. The primary thermal driver for a string inverter is the amount of heat generated by their electronics, and the ability of their fans fins to expel that heat. For example, a 5kW string inverter generates ~200W of heat at peak, and it has fans and fins sized accordingly. But, the effectiveness of the fans and fins depends on the ambient temperature (and on elevation/air mass), and if your inverter was operating at max power during hot weather (which would require significant oversizing due to the modules' temperature derates), it could exceed the capability of the fans and fins. This would then require the inverter to ramp-down output. (Actually, some string inverters can respond improperly--depending on whether their fan is continuous, load-controlled or thermally-controlled--and actually fry the electronics.) But, the thermal environment of a microinverter is very different. The main thermal driver in our situation is actually the external environment, not the electronics. Regardless of sizing ratio, an M215 generates less than 10 watts of heat at peak, whereas the heat radiated from the module at peak times will be substantially greater than that. Consequently, we've already over-engineered the microinverter for extreme heat management, and the thermal effects of sizing ratio are simply a drop in the bucket compared to the other factors. For that reason, we don't put limits in our warranty with regard to sizing ratio (which contrasts with at least some string inverter warranties), and we would not expect to see any microinverter ramp-down behaviors driven by sizing ratio. On Mon, Jan 28, 2013 at 11:06 AM, John Berdner john.berd...@solaredge.comwrote: Jason: ** ** Be careful of drawing false comparisons. There is no free lunch. Beyond the energy yield issues there are some reliability issues. ** ** You should also consider that running an inverter flat out all the time will shorten it’s life (due to the Arrhenius effect). http://en.wikipedia.org/wiki/Arrhenius_equation ** ** Think of the inverter temperature in the same way you would the power output curve (the two are closely related). Moving the whole power curve up “more on the shoulders” also moves the whole temperature curve up as well. The average lifetime (all this stuff is only probabilities) was projected with certain assumptions about how many hours at what temperature. As module sizes increase a given inverter will spend more time at a higher power level, i.e. runs hotter longer, which non-linearly reduces the life of the product. ** ** Just my $0.02… With the high labor cost of replacement it might be better to undersize the module relative to the power electronics or vice versa. This may or may not increase the installed system cost depending on the products you choose. Running everything flat out all the time is probably not the greatest idea. ** ** Best Regards, ** ** John Berdner General Manager, North America ** ** [image: SmallBannerPictEngnew] ** ** SolarEdge Technologies, Inc. 3347 Gateway Boulevard, Fremont CA 94538 USA *(*Please note of our new address.)* T: 510.498.3200, X 747 M: 530.277.4894 ** ** *From:* re-wrenches-boun...@lists.re-wrenches.org [mailto: re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Jason Szumlanski *Sent:* Monday, January 28, 2013 5:30 AM *To:* RE-wrenches *Subject:* Re: [RE-wrenches] high insolation value and inverter undersizing ** ** I found the latest module rightsizing paper by Enphase pretty interesting. It does stand to reason that there are a lot of hours in the day where the inverter is producing less than rated power, so increasing the module size makes sense. Obviously there is an optimum point in every system where clipping exceeds gains, but that's virtually impossible to nail down due to so many factors being involved. I think the point would be that PV mods are coming down in price so much that rightsizing is basically equivalent to upsizing, within reason, of course. Spending an extra 25% on PV might increase the installed system cost by 5-10%. *Jason Szumlanski* *Fafco Solar* ** ** On Sun, Jan 27, 2013 at 6:00 PM, Marco Mangelsdorf ma...@pvthawaii.com wrote: I have had a concern for a long time that as PV modules have gone up in output that there is inevitably going to be more and more clipping taking place as they’re paired with
Re: [RE-wrenches] high insolation value and inverter undersizing
The initial issue was concerned with waste power, but that presumes all power is priced evenly. Take a familiar situation, you specify and sell the system based on a number of 240W modules. Let's presume time passes and when you go to buy out the job, you find there is a deal on 260W modules which makes them as cheap as the 240W would have been. Why would you not just buy the larger output if all costs are the same. If they clip the inverter a little, oh well. On Mon, Jan 28, 2013 at 7:35 PM, Nick Soleil nsol...@enphaseenergy.comwrote: Hi John, It's important to clarify that the clipped power does not turn into heat within the microinverter. The microinverter only draws enough current to achieve it's max output rating, and the remaining current is left in the module, so to speak. So, the heat generated at peak times is the same, whether using a 260W module or a 280W module. Many string inverters actually work similarly. What's different for them, however, is their overall thermal situation. The primary thermal driver for a string inverter is the amount of heat generated by their electronics, and the ability of their fans fins to expel that heat. For example, a 5kW string inverter generates ~200W of heat at peak, and it has fans and fins sized accordingly. But, the effectiveness of the fans and fins depends on the ambient temperature (and on elevation/air mass), and if your inverter was operating at max power during hot weather (which would require significant oversizing due to the modules' temperature derates), it could exceed the capability of the fans and fins. This would then require the inverter to ramp-down output. (Actually, some string inverters can respond improperly--depending on whether their fan is continuous, load-controlled or thermally-controlled--and actually fry the electronics.) But, the thermal environment of a microinverter is very different. The main thermal driver in our situation is actually the external environment, not the electronics. Regardless of sizing ratio, an M215 generates less than 10 watts of heat at peak, whereas the heat radiated from the module at peak times will be substantially greater than that. Consequently, we've already over-engineered the microinverter for extreme heat management, and the thermal effects of sizing ratio are simply a drop in the bucket compared to the other factors. For that reason, we don't put limits in our warranty with regard to sizing ratio (which contrasts with at least some string inverter warranties), and we would not expect to see any microinverter ramp-down behaviors driven by sizing ratio. On Mon, Jan 28, 2013 at 11:06 AM, John Berdner john.berd...@solaredge.com wrote: Jason: ** ** Be careful of drawing false comparisons. There is no free lunch. Beyond the energy yield issues there are some reliability issues. ** ** You should also consider that running an inverter flat out all the time will shorten it’s life (due to the Arrhenius effect). http://en.wikipedia.org/wiki/Arrhenius_equation ** ** Think of the inverter temperature in the same way you would the power output curve (the two are closely related). Moving the whole power curve up “more on the shoulders” also moves the whole temperature curve up as well. The average lifetime (all this stuff is only probabilities) was projected with certain assumptions about how many hours at what temperature. As module sizes increase a given inverter will spend more time at a higher power level, i.e. runs hotter longer, which non-linearly reduces the life of the product. ** ** Just my $0.02… With the high labor cost of replacement it might be better to undersize the module relative to the power electronics or vice versa. This may or may not increase the installed system cost depending on the products you choose. Running everything flat out all the time is probably not the greatest idea. ** ** Best Regards, ** ** John Berdner General Manager, North America ** ** [image: SmallBannerPictEngnew] ** ** SolarEdge Technologies, Inc. 3347 Gateway Boulevard, Fremont CA 94538 USA *(*Please note of our new address.)* T: 510.498.3200, X 747 M: 530.277.4894 ** ** *From:* re-wrenches-boun...@lists.re-wrenches.org [mailto: re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Jason Szumlanski *Sent:* Monday, January 28, 2013 5:30 AM *To:* RE-wrenches *Subject:* Re: [RE-wrenches] high insolation value and inverter undersizing ** ** I found the latest module rightsizing paper by Enphase pretty interesting. It does stand to reason that there are a lot of hours in the day where the inverter is producing less than rated power, so increasing the module size makes sense. Obviously there is an optimum point in every system where clipping exceeds gains, but that's virtually impossible to nail down due to so many factors
Re: [RE-wrenches] high insolation value and inverter undersizing
Hi Marco Here is our experience with that knowing that we are at 6000 to 8000 foot elevations. We have seen significant differences in module delta temperature to ambient for ground mounts vs roof mounts and that is where we become concerned about oversizing the module or array. For a ground mount on a nice breezy day (especially in open areas or ridgetops) we have seen delta Ts at or below 10 degrees C. (SMAs string sizing allowed you to select mounting type so that delta T could be accounted for in sizing the inverter). Then add to that high irradiance and a low coefficient of power module and you have the perfect conditions for serious clipping. I would say that it is particularly true for trackers maximum irradiance at 9:00AM until 3:00PM with lower ambient temperatures during the morning. We also see very low delta Ts with white roofs where albedo is high and roof temperatures are low because of the reflected light. In this case, the decision on module size would depend on the tilt angle of the array relative to the seasons high irradiance levels and ambient temperatures. Thanks Randy Randy Sadewic Positive Energy Office: 505 424-1112 Cell:505 570-0137 From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Chris Mason Sent: Monday, January 28, 2013 5:16 PM To: RE-wrenches Subject: Re: [RE-wrenches] high insolation value and inverter undersizing The initial issue was concerned with waste power, but that presumes all power is priced evenly. Take a familiar situation, you specify and sell the system based on a number of 240W modules. Let's presume time passes and when you go to buy out the job, you find there is a deal on 260W modules which makes them as cheap as the 240W would have been. Why would you not just buy the larger output if all costs are the same. If they clip the inverter a little, oh well. On Mon, Jan 28, 2013 at 7:35 PM, Nick Soleil nsol...@enphaseenergy.com wrote: Hi John, It's important to clarify that the clipped power does not turn into heat within the microinverter. The microinverter only draws enough current to achieve it's max output rating, and the remaining current is left in the module, so to speak. So, the heat generated at peak times is the same, whether using a 260W module or a 280W module. Many string inverters actually work similarly. What's different for them, however, is their overall thermal situation. The primary thermal driver for a string inverter is the amount of heat generated by their electronics, and the ability of their fans fins to expel that heat. For example, a 5kW string inverter generates ~200W of heat at peak, and it has fans and fins sized accordingly. But, the effectiveness of the fans and fins depends on the ambient temperature (and on elevation/air mass), and if your inverter was operating at max power during hot weather (which would require significant oversizing due to the modules' temperature derates), it could exceed the capability of the fans and fins. This would then require the inverter to ramp-down output. (Actually, some string inverters can respond improperly--depending on whether their fan is continuous, load-controlled or thermally-controlled--and actually fry the electronics.) But, the thermal environment of a microinverter is very different. The main thermal driver in our situation is actually the external environment, not the electronics. Regardless of sizing ratio, an M215 generates less than 10 watts of heat at peak, whereas the heat radiated from the module at peak times will be substantially greater than that. Consequently, we've already over-engineered the microinverter for extreme heat management, and the thermal effects of sizing ratio are simply a drop in the bucket compared to the other factors. For that reason, we don't put limits in our warranty with regard to sizing ratio (which contrasts with at least some string inverter warranties), and we would not expect to see any microinverter ramp-down behaviors driven by sizing ratio. On Mon, Jan 28, 2013 at 11:06 AM, John Berdner john.berd...@solaredge.com wrote: Jason: Be careful of drawing false comparisons. There is no free lunch. Beyond the energy yield issues there are some reliability issues. You should also consider that running an inverter flat out all the time will shorten its life (due to the Arrhenius effect). http://en.wikipedia.org/wiki/Arrhenius_equation Think of the inverter temperature in the same way you would the power output curve (the two are closely related). Moving the whole power curve up more on the shoulders also moves the whole temperature curve up as well. The average lifetime (all this stuff is only probabilities) was projected with certain assumptions about how many hours at what temperature. As module sizes increase a given inverter will spend more time at a higher power level, i.e. runs
