Power Optimisers - What are they? And do you really need them?

so you're planning to get solar and some of the quotations recommend the use of power optimizers maybe you've got some shading issues and you've been told that optimizers will solve this or maybe the string inverter you've been quoted for requires optimizers to be fitted on all your panels whatever the reasons what benefits do these optimizers actually provide and are they actually worth the extra money let's find out [Music] hi I'm Gary and welcome back to my channel Gary does solar in any solar setup you need to convert the DC voltage and current generated by your solar panels into AC in such a way to maximize the total power output this can be achieved with a string inverter which connects to all the panels in series a string inverter will optimize the voltage of that string so as to maximize the current through the panels and therefore the DC power output this DC is then converted to AC and injected into the AC circuit of the home or instead of a string inverter you can install micro inverters onto all your panels each micro inverter optimizes the voltage of a single panel so as to maximize the DC power output which is then converted to AC at the panel Itself by the way if you're interested in learning more about micro inverters feel free to check out my video here the link is in the description now there is a third approach which is essentially a combination of the first two approaches here power optimizers are installed onto each of your panels these optimize the voltage of each panel to maximize the DC power output the string inverter then converts the total DC power output of all the panels into EC and here you can see how these optimizers are fitted they sit behind each panel clamped to the rail in this video we'll be looking at how these optimizers work the benefits they claim to provide some of the downsides of using this technology and whether they're actually worth the extra money let's start then with how these optimizers actually work shading is probably the best known reason for getting optimizers so we'll look in detail at the effects that shading has on solar panels and we'll see how optimizers might improve matters and before we do that we first need to understand how solar panels themselves work there are essentially three main types of residential solar panel in use today full cell panels typically comprising of 60 solar cells half cell panels where each solar cell is cut in half providing 120 half sales in each panel and shingled panels where cells have sliced into five or more pieces then recombine to form long strips for our analysis let's concentrate on the full cell panel as this is the easiest to understand the three components at the top of the panel are called bypass diodes and they play an important role in shading management which we'll talk about later if we ignore them for the moment you'll see that all the solar cells inside the panel are all wired together in series each cell in this panel has a voltage of about half a volt and will generate varying levels of current depending on the amount of sunlight shining on it these voltages add up to give a total voltage for the whole panel of 60 times half volt which equals 30 volts and if the panel is in full Sunshine we could expect there to be a current of say 10 amps flowing through the panel by the way if you're not too familiar with terms like voltage and current I thoroughly recommend you watch this video I made which explains things in just a few minutes so with 30 volts and 10 amps that gives us a total panel output of 300 watts let's introduce some shading then onto a few of the cells on this panel let's say from a nearby tree this type of shading is what we would call soft or diffuse shading and it reduces the current flow through all of the cells experiencing that shading let's say the level of shading is around 10 percent across those affected cells you might expect the impact on power output of the panel to be almost negligible after all there are only a few solar cells that are shaded and even then there's still 90 percent operational but here's the problem because the current flow is reduced by 10 in those affected cells this means the current flow through the entire panel is reduced by 10 percent and therefore the total power output is reduced by 10 also to 270 Watts let's see this in action here if I partially cover even just one cell by 10 percent the overall current and therefore power output of all the cells in the same string therefore the same panel reduces by that 10 percent okay you might be thinking I could maybe accept a 10 hit on production from the Shaded panel but if it's only one panel in a string of say five panels the remaining panels won't be affected and still generating 300 watts each so the total loss of production should only be around two percent in other words 1470 Watts instead of 1 500 watts that seems sensible but if we're to look at how the solar cells are connected across several panels you can see it's just a much longer string of solar cells and so unfortunately the same effect applies if there is shading on even just one of those cells it will reduce the current flowing through that cell and therefore if there's no capability in place to manage that shading the current flowing through the entire string of panels that means each panel will only be generating 270 Watts giving a total production for the array of 1 350 Watts so given this scenario how could power optimizers improve matters let's add an optimize to each of the five panels in turn and see what happens you can see that the first panel is now outputting at its maximum 300 watts again great and it's the same for the next three panels also great adding an Optimizer to the last panel makes no difference in its power output the shading on that panel is still reducing the power by 10 which is to be expected but why is the Shaded panel no longer affecting the other panels to answer this we need to delve a little deeper into how optimizers work and it's all about actively managing the voltage and current for each panel in isolation essentially what is happening is that the optimizers are trying to preserve the current throughout the array which here is 10 amps at Peak generation for the unshaded panels 10 amps can flow easily but the Shaded panel will only allow 9 amps to flow and if there were no optimizers in place that would restrict all the other panels to 9 amps as well but the optimizer on that shaded panel will work out that 9 amps is the maximum current that can flow through it and simply root the remaining one amp around the panel to preserve the overall 10 amps and it's worth noting here that in this particular example where only a single panel is affected by shading the optimizes on the other panel are not doing anything we can remove those and you can see that the effect Remains the Same so to counteract shading using optimizers you only really need to install them on the panels that are affected bear in mind though that some manufacturers such as solar Edge require you to have their optimizers fitted to all of your panels tiger another leading manufacturer of optimizers does not have this requirement okay we've seen the effects of 10 shading on one of your panels both with and without optimizers let's increase that level of shading now to 20 as expected then the power output of the panel reduces this time to 240 Watts this is because the increased level of shading only allows 8 amps of current to pass through now so the optimizer has to route two amps around the panel to preserve the power output of the other panels okay let's increase the level of shading now to 30 percent whoa what's happened this is strange the power output of the panel went to zero Watts yet there is a full 10 amps of current flowing through the panel what's going on okay let's remove the optimizer to see if we can figure that out nothing changes how can this be well remember these little components called bypass diodes despite their small size they actually perform a similar function to an Optimizer if these diodes detect a blockage and current within the sales they're managing typically anything above 20 reduction in current they will bypass all of the current around those cells and because there are three bypass diodes each diode acts independently on a third of the panel so if only a third of the panel is affected by shading the remaining two-thirds can still generate power crude but highly effective so as we've seen for certain types of partial shading like diffuse shading from a tree optimizers can marginally improve your array performance optimizers can also improve the performance if your array experiences shading from let's say a TV antenna or a service cable but for hard shading you're likely to find the optimizers perform little or no better than the solar panels can do themselves using their bypass diodes and this is especially true if your panels are half sale or shingled if you'd like to find out more about how optimizers handle shading I've made a two-part mini-series on the topic here and I recommend you check this out the links are in the video description shading is certainly one of the main reasons that people choose to have optimizers in their solar installations but what are the other benefits the accumulation of dirt over time can adversely affect array performance in this example here you can see that over a year or two Dirt has accumulated towards the top left hand side of the array the dirtiest panel on the top left is now only able to Output a maximum of 260 Watts if all the powers are connected to a string inverter without any optimizers for the same reasons we saw with shading the maximum power output on each of the other panels would also be limited to 260 Watts however if optimizers are fitted they will ensure that each panel is able to Output at its maximum level despite the dirt another area where optimizers can help out is with panel degradation solar panels today generally have a warranty of 25 years but over that time their performance will gradually degrade you can see in this chart here that panels started 100 efficiency but slowly degrade to say 85 efficiency over the 25 years but that degradation rate will not be the same for each panel as you can see here on a string inverter with no optimizers because these variances are all within a few percent of each other production efficiency will be reduced to that of the worst panel in this case to around 77 at the end of 25 years but having optimizers installed will ensure Optimum production from each panel regardless of any degradation variances of the other panels in the unlikely event that a solar panel should fail the make and model of that panel May no longer be available and even if you can Source a panel with the same dimensions it's likely to have a different most likely higher power rating if optimized are in place this presents little problem provided that the new panel does not cause the overall string inverter maximum voltage levels to be breached the more data you have about a system particularly right down to data for the individual components of that system the better informed you are about the system's performance in general and any problems arising for any part of that system a string inverter is certainly able to provide a comprehensive picture about how the system is performing as a whole here is example data from my own string inverter from give energy and whilst this level of data may show a problem in the system at some future time it can't pinpoint where that problem is for example which particular solar panel is not operating correctly and so this is another reason people choose to have optimizers fitted to their solar panels because these optimizers are able to perform detailed monitoring on each panel in the array here is the kind of data you can get with solar Edge optimizers on the left is data about the system performance as a whole and on the right is data for each panel this shows power output at the moment but you can delve deeper and show voltage and current it's also color coded so you can see at a glance if any of the panels are underperforming like this one on the top row if you have shading issues then monitoring like this can tell you a great deal about the effect of that shading on your system performance but if you don't have shading because the solar panels are extremely simple devices comprising solar cells bypass diodes and some wiring they're very unlikely to go wrong and actually the optimum is attached to those panels are more likely to fail than the panels themselves so do you really need optimizers in non-shaded situations many people Advocate it's always best to keep things on the roof as simple as possible given the lack of easy access and then the unlikely event that you do have a problem with one of your solar panels there are other ways to check this for example using an infrared camera here's the one I have made by Fleur which is a small device that attaches directly to your smartphone in our example here we can see the infrared image shows heat spots on the failing panel another important benefit of optimizers is all to do with safety rapid shutdown is a critical safety procedure of solar panel installations and it's required to ensure the safety of emergency responders and Electrical Workers during maintenance and repair activities during a fast shutdown procedure the electrical output of the solar panels is rapidly reduced to a safe level this is especially important in high voltage systems where the potential for serious injury or death is significant string inverters can certainly shut off to prevent the energy generated by the modules from getting past the inverter but the panels will continue to generate electricity when the sun is shining and this creates voltage and current on the cables between the panels and the inverter as a result most rapid shutdown regulations today require shutdown to occur at the panel level hence the use of module level Power Electronics such as optimizers or micro inverters to meet this function okay we've discussed the benefits of optimizers let's look now at some of the downsides in order that you are fully informed before making a decision and a good place to start is with failure scenarios of each of the three approaches a string inverter micro inverters and finally a string inverter with power optimizers consider a string inverter connected to 12 300 watt panels at Peak production this array will be producing 4.8 kilowatts but if the string inverter fails you'll lose all of that production it's essentially a single point of failure now today's string inverters tend to only last maybe 10 to 15 years they're easy to replace but you might experience a few weeks of loss production before you can organize for an engineer to swap out the failed unit with a replacement one and in the summer months that lost production including paid export could cost you quite a bit let's contrast this with the micro inverter approach here's the same array but now all the panels are connected to micro inverters and are all generating 4.8 kilowatts of power there's no requirement for a string inverter and therefore no longer a single point of failure micro inverters can still fail though and if one does you'll only lose the production for the panel it is managing here around eight percent and in my video on micro inverters we looked in detail at micro inverter failure rates they're incredibly low take for example an array of 10 panels connected with end phase micro inverters the chance of any of these micro inverters failing over a 25-year operational lifetime is only one in 200 and if you're very unlucky and a second micro inverter were to fail your system will still be operating at 84 percent of total capacity sure you'll want to get those failed micro inverters replaced but there's less urgency to do so there is a cost though as your engineer will need to access the panels on the roof and typically this requires some kind of scaffolding to help with that micro inverter warranty is typically not only cover the cost of the replacement unit but also reimbursement of at least part of the labor involved finally then let's look at the approach of a string inverter with optimizers similar to micro inverters if an Optimizer were to fail it will only affect the panel the optimizer is connected to in our example here reducing total production by eight percent each time Optimizer failures are not ideal but they don't create any urgency to fix and just like with micro inverters Optimizer warranties may include partial reimbursement of any labor involved and Scaffolding costs but this approach also has a string inverter to contend with and when it feels and it will fail during the lifetime of your system your production will go to zero creating an immediate urgency to fix if we're just looking at solution reliability I'd have to say that this approach seems to be the worst of Both Worlds the potential of Optimizer failures in addition to the requirement to replace your string inverter at some point and depending on the optimizers you've chosen for example solar Edge you may be locked into the same manufacturer for the replacement of the string inverter so if you're considering an optimizer-based approach you'll want to ensure that the benefits you're seeking markedly outweigh the downsides so I guess the big question is just how reliable are optimizers I found it quite difficult to find comprehensive analysis of this on the internet two of the most prominent manufacturers are solar Edge and tiger but neither of them publish fairly rate data on their products contrast that with enface who Market micro inverters they're not only not afraid to publish they're proud of their exceptional low failure rates of their products thankfully though Mark Kavanagh owner of MC electrical in Brisbane Australia has invested a lot of his time over the last few years shining a light onto the performance of both solar Edge and Tigo Optimizer products he's produced several reports and videos many of which I've Linked In the description for you to look at I find Mark to be highly objective in his analysis and so I trust the conclusions he comes to if you're considering an optimizer-based solution I strongly recommend you spend a little time reading and watching Mark's analysis thanks for taking the time to watch this video and if you found it useful I'd be grateful if you would like the video so that others will be able to see it and as you can see there's quite a lot to the topic of optimizers and it's a real shame that benefits are not as clear-cut as we would like please let me know in the comments your own thoughts on optimizers which can hopefully help others in their decision making until next time then thanks for all your support with the channel [Music] foreign

Channel: Gary Does Solar

Views: 65,347

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Length: 18min 42sec (1122 seconds)

Published: Mon Jun 05 2023