Half-Cut Solar Panels Explained: How they work // Are they better // What is the difference
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- čas přidán 22. 04. 2022
- Course trailer and Coupon Code: • Complete Solar Energy ...
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Renewable Energy Engineer Jesse Gorter explains what half cut solar panels are, how they work and what kind of performance gains you can expect.
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Hello Solar Energy Enthusiast!
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Jesse
Jesse Gorter
Renewable an Sustainable Energy Engineer, Master of Engineering
Mechanical Engineer, Energy Technology, Bachelor of Engineering
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#halfcutsolarpanel #halfcutpv #arehalfcutsolarpanelsbetter
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Very clear and concise explanation. Subscribed right-away.
I just noticed that you are a bit mis-understanding/not stating the point correctly at 8:20 onward section where you discuss shading on 1/6th of the PV Module.
Here is my take on it:
Your Said:
1: When a part of the Half-Cut PV Module is shaded, its adjacent cells of the loop will not produce any voltage and wouldn't be able to carry any current. Rendering that specific loop not produce any power etc.
2: The result of the shading will force the adjacent bypass diode to activate and will divert the current to next strings.
3: In the mentioned case of shading, you are approximating the power drop of 1/6th instead of 1/3rd of the total power.
My Take:
1: Shading will degrade the power output of the loop in which the cell is located and can sometimes render the whole loop produce no power.
2: As the loop has a diode which is shared directly with another loop, the diode will go into bypass mode only and only if both of the loops are not producing any positive power to raise the voltage across the terminals.
In the case of the single loop being shaded, it is quite possible and is often the case that the shared loop cannot keep up with the current to raise the voltage across the diode's terminal and will simply go into bypass mode. But once the diode is in bypass mode, all the strings attached to it will result in no addition to the power output (short circuit by the diode).
3: Considering the above explanation, the shading on the single cell will force the bypass diode to bypass all the current of the top loop as well as the bottom connected loop eventually resulting in the loss of 1/3rd the power of the PV Module, Not 1/6th.
Extra bits:
For anyone interested in how and why half-cut cells are used, you should know that Half-Cut PV Modules have More than One MPP (Maximum Power Point) Voltage points during shading scenarios. Paired with compatible inverter, their MPP voltage can be switched from either of the "Global MPP" or "Local MPP" voltages with efficiency in mind.
In the mentioned shading condition at 8:20, it is quite possible that the bypass diode doesn't even kick in and the inverter is able to track a MPP voltage with a smaller amperage but still utilizing the power of both the loops (top and Bottom in this case) of the shaded cell.
For Example, Let's take a generic Half-Cut PV Module with 6 Strings and a nominal MPP Voltage of 30V. Strings have a nominal voltage output of 10v with 5A (12*5=50Watts) each, resulting in 6*60Watts Strings = 300W Total Power Output.
With the Scenario at 8:20, lets consider the shading to effects the performance of the effected loop and dropped its power output current from 5A to 2A (60% Power Loss) , then in ideal conditions, this PV Module will have 2 MPP Points (Google "Global MPP" and "Local MPP" for reference)
MPP#1: The Bypass diode is active (the shaded loop cannot provide the 5A which each of the other loops can) and the MPP Voltage will be 20V with 10A of current resulting in 200Watts of power output. (1/3rd the Power Output as I am predicting in the scenario in this video)
MPP#2: As the panel is only limited to 7 Amps of current due to the effected loop (5A of the un-shaded part of the loop + 2A of the shaded loop), any more current draw will kick on the bypass diode and will render the 2 connected loops shorted and with 0Watts of power coming from them.
Also, the wiring malfunction is a bit different scenario than complete shading. Depending on the passing current, the Inverter may pick the "Global MPP Voltage" or the "Local MPPs Voltage" of the Panel/s.
The comment is getting very long and technical I guess. I'll be more than happy to respond to any question/query.
:-)
The bypass diodes only allow current when the string voltages drop to near zero (the diodes forward voltage drop, about 0.6V for silicon diodes). Therefore the diodes are only used when both its associated strings are blocked and their combined voltage is low. The difference is if one cell is blocked, it does not contribute any current, whereas the other string does, so you effectively end up with a reduced reverse voltage across that diode (no current through it), so the remaining working string contributes a lower voltage at the panel current (half the power, so half the voltage for the same panel current), so the panel system voltage drops by 1/6 instead of 1/3. In practice it is more complicated, as this behavior may shift the maximum power point MPP (the solar converter to the batteries attempts to adjust its load on the panels so that the V x I product is at a maximum) for the panel. In a system of multiple panels, a shaded panel may still adversely effect the system MPP performance by more than just a single string loss, unless each panel has its own MPP electronics, as is the case for microinverters.
Exactly.
Well explained thank you!
Having only one panel of Half-Cut module is kinda benificial, however, if you have multiple panels connected in series. It will work as a regular panel. Also, if the Solar Inverter / MPPT controller is not optimized to do a sweep function across the VOC, you might end up loosing upto 50% of the overall output as they will not be able to trigger the bypass diode, and forces rest of the string to work at a lower Amp.
This happens with my current setup which I am using. I get a small shadow from the east side wall, which happens to cover 3-4 cells till 9:30AM in the morning. The Vmp of each panel is 42V, and I have two of them in series. Now, if the MPPT is tracking at 70V, I get 8Amps. However, if it starts tracking at 84V, my Amps decrease to only 4Amps, and it stays like that till that shadow is gone by 9:30AM, where I start getting 10Amps.
So in conclusion, 70Vx8Amps = 560Watts, and 84Vx4Amps = 336W. Power lost due to poor tracking of MPPT = 224Watts.
In theory this sounds good, but in practical, if you do not have a really good MPPT controller, you might end up loosing a lot of power. Just with the two panels I am loosing 224 Watts.
You give the impression of being someone who is trying to understand what is actually going on, and not what is supposed to be going on.
With your observations in the real world, would you say that these panels in parallel with an mppt charger would give optimal performance in poor and very poor light conditions?
Optimal in relation to Mono, Poly and Amorph, not optimal as in maximum output, obviously.
@@robinhood4640 I have not used other types of panels before, but I belive a Bi-Facial panel is just a double glassed version of a MonoPERC panel. In sunny condition, the panel exceeds its Amp rating, generating anywhere between 10% - 50% more Amps based on the reflection of the surface.
In overcast conditions, I get around 20% of the output, and in cloudy conditions, I get around 50% of the output, and the voltage will be close to Vmp or higher due to no direct sunlight hitting the panels.
And whenever there is a sunshine, the overall output goes up to its maximum, totalling 150% power output. However, this happens for a very short time until those cells get heated up and goes above 25 degrees.
Your teaching is greatly appreciated here, thank you.
I'll be able to figure out what to do on my boat
Best of luck!
well explained about half cut and its purposes .
Thanks!
Enjoying your videos and ur great explanations & content here, thanks for all this good info.
I am wondering how the effect of one panel in a string effects the overall output of the string in this case, if one section has a leaf on it, I am not sure if we lose 1/6th the PV area or is it 1/3rd?
Also, even if it is only 1/6th loss of that panel, this would also have a roll on effect with any other panels in a string, bringing them all down a few volts of output to the lowest panel output voltage effecting the overall wattage output of that string, does this sound correct? TIA. Cheers
I'm not sure this is right @10:00. If the bypass diode is activated then you'll lose 1/3rd of the panel not 1/6th. When I did my own testing of this shade on 1 portion of the panel either resulted in losing half the panel (more likely) or 1/3 of the panel (If the inverter hunted low enough in voltage to see this). My working theory is that half cell modules are for 1. higher efficiency as less current running through each cell and 2. large arrays that are east to west trackers, with half cells if bottom portion is shaded by neighboring row it can still generate in the early morning and evening.
I'd like to see a real life test of this. I agree that the half-cut module should have better shade resistance. That was one of the obvious reasons for doing it when I first noticed half-cut panels, but I'm not convinced that you would only lose 1/6 of the power output. The layout essentially has 6 strings in a 3s2p arrangement with bypass diodes across each parallel pair of strings. If you shade a portion of one of the strings, that string is still coupled to its parallel pair and must therefore have the same voltage across it. Also, you still have to pass all the current output of the module through the strings somehow. If I had to guess, I'd guess that actual power loss in the partial shading scenario is probably more than 1/6 but probably noticeably less than 1/3. Again, it would be nice to see some actual test results for such a scenario.
If you are using only one MPPT controller for the entire string, you cannot take full advantage of this technology. You will need Power Optimizers or Micro inverters.
@@furyjk98 Optimizers and microinverters are generally used for a whole panel and so are not relevant in the discussion of the merits of cell layout within a panel or the power output considerations that arise from this.
@@brettski74 I understand your point, but Half-Cut cells will perform same as a full cell module. When there is shading, it will just lower the amps by half to compensate for high voltage, or lower the voltage for higher amps.
In a series of panels, just because one panel's 1/6 string got shaded, it does not mean the whole power output of other panels go to 50%.
This is the problem with Half-Cut modules, if the MPPT does not have a proper sweep function, it will be stuck at the higher voltage delivering less amps from all the panels.
Nice information Sir...👍👍👍
You are welcome Rafi, it is good to hear you are enjoying the content. All the best, Jesse.
The up and down cells are in parallel so the bypass diode cancels both of them...
Wrong. The bypass diode has a reverse bias voltage across it from the unshaded half cell string, and so with still pass current through the unshaded half string.
In theory with a regular panel if you have full sun blockage on one solar cell group You loose one third of your panel output. But with same blockage on a half-cut cell solar panel You loose half as much output of the solar panel which is 1/6 .. Very impressive . Half the output power loose.I bought four of these type panels last night. Can't wait to try them out. Fingers crossed LOL
Only if you have Micro-Inverters or Power Optimizers, it won't work if you only have one MPPT for the entire string.
So in a half cut panel, you have 2 series that then link together in parallel. If you cover a cell, the bypass diode kicks in. This means that you now have the series at different voltages.
So does this compromise the voltage on the good series.
Anyone able to help
Awesome
How does the kicked in "red" bypass diode not short the lower functioning string?
You need smarter inverter that lowers current through the whole module to prevent bypass diode to kick in, right?
It does bypass the lower string aswell.
Great info
Glad it was helpful!
Wonderful explaination
Hello sir , I'm working with a company where they have a generator using 4 car batteries but only two working at a time , can you advice me what's the solar system I should have from both quality and lifetime expectancy
How about the shengled type Sola panel?
To me it seems in this example once the by pass diode in the half cell panels is in by pass mode, it by passes for top and bottom string, no actual gain as opposed to full cell modules, still 1/3rd outage not 1/6th. Perhaps the schematic lacks parts? Something does not make sense here.
It seems logical that the current would be divided between the bypass diode and the unshaded cells. The unshaded cells are effectively a low resistance path so current would tend to flow through them. The shaded cells are like a resistor and the diode and unshaded cells are effectively two diodes in parallel.
Possibly you lose some efficiency in the unshaded cells, I'm not sure how much but they are still producing power.
Ur are right. The video explanes it just wrong ... if one substring is blocked the diode will not bypasse.
Jesse, can you please take a look at the comments here below? It is explained that the power output would be 1/3 instead of 1/6 for the half cut panel at 9:01 in your video. If so, can you please correct? Or only in certain shadow conditions? I'm a newbie so it is not clear to me, but I want to learn...thnx in advance!
To me it seems there is no bypass because the lower string still produces and provides a Voltage and the diode does not pass any current. Therefore, I think you are right and the power loss will be only 1/6, but please confirm :-)
Indeed, you loose 1/3 of the panel.
The bypass diode is active. So the voltage of the left section is -0.6 Volts. Same voltage applies to upper and lower half, so both sections are effectively switched off.
You effectively have two panels in parallel but no blocking diodes.
I assume that the half cells are half the voltage etc then when you link them in parallel you double the Amps. Am I doing ok do far.
Not really. Half cells have the same voltage but half of the current of full cells. once connected in parallel, you double (their originally half) current so that the total power (current * voltage) is the same as the panel with full cells. The advantage of panels with half cut cells are already described in the video so I won't repeat them here.
@@adon8672 We cannot have two halves in parallel with one half having the by pass diode activated and the other not. So no, I do not understand the advantage of panels with half cuts. This just doesn't make sense when used in parallel. The only advantage would be when using the two sections as two separate panels through separate inverters. In which case they cannot share by pass diodes.
It's like putting 2 small panels. Together
Are there PV panels that have more than the half cut cells? Lets say Triple cut cells? I ask this because shade is a problem on the roof of my house and I like to buy the best solar panels for colleting solar energy. I will be using micro converters, the IQ8 or IQ7 from Enphase. It depends on the availability. I like the IQ8 better because then I will have power during power outages and don't have to install backup batteries straight away reducing the initial investment. Curious to hear what the best solar panel type will be for (partial) shaded roofs. Have you made a video about that perhaps?
like tv.... hd ready , hd ,fhd, 4k, 8k , and act. Here we have all panel then half cut the 4cut and and and .........
If 2 mirrors of equal size to the panel are placed low down at an angle to reflect and focus sunlight upwards and central. Then a face down panel mounted over the mirrors central to their focal point will this give a better performance? There will be double the light and less heat on the panel face?
If the mirrors are larger but concaved to focus and reflect on to the panel face but not beyond will this be even better?
If a solar water heater is placed above the back of the panel this should keep the panel cooler in its shade and provide hot water at the same time? This should protect the panel from weather and other element damage. OR am I just being stupid?
just search on youtube, all your ideas were already implemented, mirrors facing the panels, water etc
I think your diagram at 8:00 is wrong. You shouldn't have the top and bottom shorted and you would probably have 6 diodes (yes?). The way you have the diagram there, one photo diode would short past both the top AND bottom cells, I think...
Thanks for your feedback Jeff. Let's agree to disagree ;)
@@SolarSolution Sorry. Not trying to disagree. Trying to understand. I think you're saying it is therefore NOT wrong and I'll go back and try to understand how that works then.
Found this site that does a great job describing the function of half cut cells IF YOU HAVE a global maximum MPPT generator that can detect and operate at the second local maximum and not get stuck at the bypass voltage. czcams.com/video/AZ8VQ_zmf1M/video.html
Clarifies what is presented here that it is simply the 5/6 string conduction (not typically true in most cases). There is ESPECIALLY good detailed discussion of what happens with half cut cells and shading when used in a string and not using per panel micro-inverters even with global MPPT. Makes perfect sense.
@@jeffmcclain You are correct, and this video is not. The one you linked however, seems to be correct.
The graphics in this video is just wrong! And the dude has no clue what he is talking. And no the bypass diode will not open if only one of the 6 substrings is blocked unlike his graphics suggest.
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You are oversimplyfying how the halfcut modules work, to the extent that you are incorrect. You do not only loose 1/6 of the module in the case that you showed. You lose 2/6, or (1/3) of the module since the current is flowing through the by-pass diode. However, if you have an inverter which can lower the current and raise the voltage of every individual string of cells, it is possible to engage the second local maximum and utilize 5/6 parts of the module. HOWEVER, it will be at a lower current, so you wont get 5/6 of the maximum power output, it will be lower.
Half cut cells will produce half of current in your case of shading and diode will not kick in unless the same 1/3 of string of both strings are shaded. What the hell is your background? This is why people like you can not do normal job and must be politicians and managers. There are many content creators like you unable to change caption apologise in description and tousends of watchers damage or degrade their PV system with rubish information! I am not wasting my time to write twice, consider what is your position in company with your poor understanding of electric circuits.
Well well, give him some credit Slavka, he might make a mistake here but at last he spends his time in explaining this and not all what he says is for everybody what it seems to be for you. I must admit you yourself are a real example of how to communicate these possible mistakes with the rest of the world. Maybe a good idea to explain what you consider the error and tell us what the real reason is for this cell cutting use on panels. Screaming and complaining is what I only know from left wing idiots promoting climate change and hell on earth, but you seems to me an engineer and I expect better of engineers.