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Should you use a micro inverter for your system like this Hyomiles micro inverter we'll be testing today? or should you be using a DC charge controller like this Victron unit or maybe you should consider a hybrid string inverter like this EG4 12K PV today's data might help you with some of those decisions I've been running some experiments on microinverters from Hoy miles and this is why the NEP microinverters that I put on my shed over a year ago have started to fail welcome back to projects with everyday date it's a charts and graphs day let's do some experiments to be fair I had an unbalanced load on the inverters that failed I had a little higher performance panel on one input than I had on the other but I don't think that should be enough to cause a problem I mean what if one of the panels was shaded or producing less power consistently they they shouldn't fail for that reason the question is what to replace them with Enphase has a very reliable system they are proven in the market there's lots of data on them but they're very expensive you have to buy one unit per panel that would be more than I would want to spend so I've always been looking for alternative solutions that are also reliable now fortunately I've made friends with a local installer Ed from off-grid Power Systems and he has very high confidence in these ho miles microinverters now you can get them in single input double input or quadruple input in this case I wanted to go with quadruple input Ed has a lot of experience with installing systems and he's very confident that these will last a long time so confident in fact that he gave me these two units so I could run the testing on them and prove it out that way I can give a completely unbiased Viewpoint of their performance since I have no connection to the supplier whatsoever so thank you to Ed at Offgrid Power Systems for sponsoring this install if you live in Ohio or nearby area and you're looking for someone to do a quality off-grid installation check out Offgrid Power Systems you can find a link in the description below now I've been using these for several months now on a test fixture and they've been working flawlessly I've had no issues the only problems that I have are with the software side the data collection is not my favorite you can't get the kind of granular data that I like to get now for most users that's probably not an issue I mean it gives you the standard information that any normal homeowner would want but I want to download stuff to excel down to the minute and I can't get that data however I use Emporia view for monitoring during my grid and so I've been able to get granular level data using Those sensors for the experiment we're doing today I split my wood rack array into two sections I have eight 460 W Sun gold power bifacial panels on this array and I did a previous video on the performance of these panels compared to standard panels if you want to watch it past Dave was thinking ahead and ran two separate sets of conductors to this array I'm going to run an extra set of lines here looking out for future Dave he's probably going to need more power at some point so now I can easily split it into two separate systems the first four panels connected in series produce about 131 volts and run through the Victron solar charge controller and monitored through the entire Victron system the last four panels are connected each panel individually to one of the four inputs on the ho miles micro inverter and since that produces AC I have a AC coupled to my system and monitored with this Victron monitor it also shows up in the Victron system so I can compare everything using the same monitoring equipment we're going to look at three sets of data a sunny day a snowy day and a cloudy day and then we'll draw some conclusions here we have a beautiful data set from a nice sunny day with no clouds but true Rarity in Ohio the blue curve is the DC power from the four panel series string and the orange data is the AC power from the four panels connected to one microinverter at first glance it almost looks identical which completely surprised me and in fact I've been checking the production periodically on the readout and sometimes the microinverter is outperforming the DC string and actually I'll link to this in the display you can watch this anytime and see how they're performing any time of the day the microinverter should be running at a deficit since it's converting from DC to AC and the DC charge controller doesn't have to do that looking at the whole days production it's almost identical with just a slight disadvantage for the DC production however there's some other factors we need to consider at first I didn't think it would be a big factor but after running the numbers it turns out to be quite significant and that is the line losses from the array to the house which is 110 ft away now if the strings were identical the losses would be the same and they would cancel out but they're not identical the microinverter is transmitting its power at 250 volts and the DC string is transmitting its power at 132 volts now if I had more panels put together I could boost it up but I'm trying to use the same number of panels for both voltage is very important when transmitting power the higher the voltage the lower the losses because the power can be transmitted at a lower current a quick calculation at a typical midday power level for these panels shows the DC string losing 28.7 Watts while the AC string loses only 8.03 watt so now I have to nominalize that to get a true comparison of the AC power delivered versus the DC power delivered since the losses vary depending on the current throughout the day I made a new graph removing the line loss to show the power delivered at the array for both system now you can see the distinct Advantage with the DC string since it doesn't have to account for the loss converting to AC the DC charge controller allows me to charge my batteries which are also DC without any additional losses converting to AC and then back to DC however there is yet another anomaly here if you look closely at the data you can see the DC string has an advantage in the morning and midday but then it loses that advantage in the late afternoon for some reason an analysis shows the microinverter has a 4% disadvantage Vantage in the morning and nearly the same 3.1% disadvantage midday but then suddenly in the afternoon that Gap closes to a disadvantage of only .4% fortunately I had an unusual combination of snow and sun which dramatically Amplified the abnormality one winter day I was walking past the array in late afternoon and the reflection off the snow and the white shed was very noticeable and I realized there was some asymmetry to the bifacial game that happens mostly in the afternoon this chart shows that sunny snowy day with no snow on the panels without adjusting for line losses you can see the DC string has an advantage in the morning and the AC microinverter actually has an advantage in the afternoon in this chart I've adjusted for those line losses and calculated the percent loss for the AC system the result is a 5.1% disadvantage in the morning a 3.7% disadvantage midday and only 2.1% in the afternoon one thing we can learn from this is by facial panels take advantage of every reflecting Sur surface around them so that's pretty neat fortunately we can mitigate the effects of the Reflection by looking at a cloudy day first I want to look at one more chart with this data I was beginning to think that past Dave had made a mistake now he did help us by running two separate strings when only one was needed at the time but he went the cheap route to save some money and put 12 gauge wire to the building instead of 10 gauge I wondered if 10 gauge wire would have been an advantage here so I calculated what the losses would have been for 12 gauge versus 10 gauge and it's easy to see from this data that the higher current lower voltage DC string does see some benefit from the 10 gauge wire but the higher voltage AC string sees almost no benefit and even with the 10 gauge wire it doesn't close the gap very well between the high voltage string and the low voltage string so I guess pass Dave's off the hook here 10 gauge wouldn't have solved this problem this is another great illustration of why voltage is so important you cannot overcome it with just a larger gauge wire well I suppose you could but the C get very prohibitive high voltage is your friend when it comes to transmitting power it's not your friend when it comes to getting shocked but just don't let that happen remember to turn the breaker off all right looking at the cloudy day with no line loss adjustment you can see that they are almost line online there's a strange deviation at the end of the day but I think that's a result of the sensors struggling to match the AC output which fluctuates towards the end of the day as the microinverters are turning on and off in the very low light condition that is one advantage to stringing multiple panels together you get that voltage boosted up a little bit in really low light situations and helps stabilize the input looking at the raw production numbers the output for the day for both systems is almost the same if I adjust the plot to account for the difference in line losses you can barely see a slight Advantage for the DC string since on a cloudy day we're also transmitting much less power therefore a lot less current then the voltage difference between the strings is less of a factor in this case the morning showed an overall smaller disadvantage for the microinverter at minus 2% in the morning minus 2.1% midday and ignoring the strange bounce at the end minus 1.1% for the afternoon this data seems to indicate a bit of an advantage for the microinverter on cloudy days with a significantly smaller Gap to the DC string than on sunny days the Hoy miles micro inverter claims a CEC Peak efficiency of 96.5% which would put it at about a 3.5% disadvantage to the straight DC string right in line with the gap that we saw in today's data I'm really impressed with the ho miles inverters they've exceeded my expectations and I've had them running for over a year now so let's hope they just keep going on and on now let's see what conclusions we can draw from this data first there's a lot of ways to build a solar system and it's highly dependent on your individual need microinverters have come a long way to provide some distinct advantages in certain situations here are some pros and cons compared to some typical options from a cost standpoint there are so many variables and options I just tried to give some general guidance in most cases the simple DC charge controllers and AC string inverters are going to be the cheapest followed by micro inverters and then these hybrid inverters are the most expensive but also the most capable if you're building your array on the Roof then you have a short distance to run and you have the advantage of module level shutdown built right into the micro inverter which saves cost and complexity a grid tie string inverter or a hybrid inverter will work with a roof install but you typically need to add PV shutdown modules on the roof which is an added expense the DC charge controller is typically used in an off-grid situation so that's not likely to be applicable if you're installing a ground array you'll be limited in how far from your building you can go since the voltage will be limited to 250 volts the string style inverters and charge controllers can typically handle 400 to 600 volts dramatically reducing the line losses like what we saw today if you're operating your system as a grid tie system they all work just fine except for the DC charge controller since it's designed to just charge battery most inverters these days have great efficiency but there's likely to be some Advantage for microinverters because they are able to take full advantage of each panel's individual characteristics if it's slightly shaded or the spec is a little different or it just underperforms the microinverter is going to get the most out of each panel individually if you're building an off-grid system micro inverters and grid tie string inverters are not the best solution but they can still be used when AC coupled with an off-grid system like the one I Illustrated today there are times when adding microinverters to an off grid system makes sense with the microinverter I used in this build you could take four panels you got on a discount and connect them to a microinverter and back feed the AC side of your grid tie system the panels don't have to match the rest of your system in any way and the power is already AC which reduces the load on your off-grid inverter during the day when it comes to charging batteries microinverters and grid tie strings inverters need a separate battery charger so they're not ideal systems when you want to have a battery backup the hybrid systems and the DC charge controllers are designed for battery charging from a future flexibility perspective micro inverters have a distinct advantage since each inverter is completely independent and you can easily expand with different panels in different directions without any concern for panel compatibility the other types of systems are limited by the number of independent MPPT trackers there are and that typically ranges from one two usually no more than four Offgrid Power Systems the local small business that supported this analysis has set up an exclusive discount of $50 off a purchase of $500 or more for my viewers they have the Hoy miles micro inverters available on their website if you're interested in purchasing one of them for your system they also have a wide assortment of batteries and everything you can imagine for Victron system I'll leave a link and the discount code in the description below I replaced all the inverters on my shed with two Hoy miles inverters and I'll be bringing that in video in the future if you want a hybrid system that can operate on or off grid with battery backup the eg4 12K PV has been working great for me I'll link to the install and the testing that I did for this one in the description below and at the end of this video signature solar also has a discount which is an automatic $50 off a purchase of 500 or more for my viewers using the link in the description below or on my website ProjectsWithDave.com where you can find a lot of other resources and discounts for your projects want to learn more watch one of these two videos videos like this one on my EG4 12K PV install. I finally hit 100,000 subscribers and that's pretty neat! I never had a goal of creating a YouTube channel I just posted my experience installing my own solar system a few years ago and here we are so thank you for your support through Corrections ideas and all the encouragement that you give me in the comments it's been a lot of fun and I'll see you next time! ...
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