Chinese PV manufacturer Longi Solar has announced its 72-cell bifacial half-cut monocrystalline PERC module has exceeded 450W power output – just on the front side.
There’s a bit of technobabble the above description of this module, so here’s more information breaking the elements down:
- 72-cell – just the number of cells that make up the panels – in this case, really 144 cells as they are half-cut
- Bifacial – a panel that can make use of light hitting the back as well as the front.
- Half-cut – as the term suggests, solar cells that have been cut in half; resulting in greater shade tolerance and lower electrical resistance that improves efficiency.
- Monocrystalline – cells with a single continuous crystal structure.
- PERC – Passivated Emitter and Rear Cell (or Rear Contact).
.. and for some follow up reading on an issue with PERC technology, check out Ronald’s article on Light and elevated Temperature Induced Degradation; or LeTID for short. On a related note, MC Electrical’s Ben Neville is keeping tabs on Longi and other manufacturers with regard to LeTID issues.
Anyhow, Longi Solar is pretty proud of their latest achievement, which they say was tested and verified by certification agency TÜV-SÜD.
“LONGi monocrystalline half cell module combines monocrystalline PERC cell technology and bifacial half cell module construction to effectively reduce package loss and increase average output by 5-10W,” said Vice President of LONGi Solar Dr. Lv Jun. “Half cell has obvious advantages in power generation under weak light and shadow conditions and excellent heat spot resistance.”
The “package loss” was a new term for me and I thought something may have been lost in translation. It apparently refers to the light loss associated with the typical “package” structure of a solar panel, i.e. glass, cells, adhesive layers and backsheet. I’m not clear on the “increase average output by 5-10W” statement.
A Very Long-i Module
As well as being big on power, these Longi solar panels would be big on size. While the specifications of this particular module aren’t on Longi’s site, the company’s 360-380 watt range of panels using the same technology have measurements of 2020 x 996 x 30mm and weigh in at a hefty 25.5kg. 60-cell panels commonly used for home solar installations are around 1650mm long/high and weigh around 19kg (but offer less power).
These may not be the type of solar panels you’d stick on your home’s rooftop, but it’s encouraging seeing the continuing progress of PV technology. Ronald sees potential for bifacial solar panels in Australian solar farms installed vertically in a line, with one side facing east and the other west.
Longi Solar is a major player on the PV scene and has racked up quite a few records. While they haven’t had a presence in Australia for long, reviews of Longi solar panels by Australians who have had them installed have been pretty positive and the company is included on the SQ trusted PV brands chart. You can also learn more about Longi here.
About Michael Bloch
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I live in Northwest Sydney and I have 5KW solar panels already with 5KW inverter. I have been monitoring the power output for almost 2 years now. I get around 3.5KW power, maximum, during most days of the year even during summer.
Question: Is the following feasible? I buy additional solar panels of 2KW to bring my solar power to 7KW and using my current Inverter which is 5KW.
The idea behind all this thinking is based upon the following calculation:
1. 3.5KW is 70% of 5KW.
2. 70% of 7KW is 4.9KW which is well within the capacity of my 5KW installed inverter. I wish to optimise the functionality of my 5KW inverter.
3. This way, I pay for the additional solar panels but avoiding the cost of additional Inverter.
Thank you.
Hi Oscar
It is possible for you to add to the current panel capacity of your solar system, but it won’t be cheap. If you have 3 phase power you adding a new separate new solar system with a new set of warranties is likely to be more cost effective.
You can only receive the STCs that lower the cost of rooftop solar if your solar panel capacity is up to 133% of your inverter capacity. So you could increase your current panel capacity up to 6.66 kilowatts. In practice that might be 1.5 kilowatts of extra panels. If your inverter is suitable you can go over the 133% limit but you will have to pay the full cost of the extra panels.
If you are adding panels to an existing system they should match the wattage of the current panels. Also, many installers don’t like to touch another installer’s work, so if the original installers aren’t available you may have trouble finding someone to do the job.
One option would be to replace your current 5 kilowatt inverter with a 4 kilowatt inverter and then install a small second system or a larger system that is export limited. You may want to wait until your current inverter fails or is older/out of warranty.
At present, there seems to be a rather long queue of people who are so totally fed-up with government policy failures regarding renewable energy, climate change and environmental pollution issues they are all now awaiting their turn to have the solar PV system they’ve ordered actually installed.
So, although it might be a possibility to maybe simply move 45% of your existing panels so they face West (assuming all your existing ones face North), you might have to wait quite a long time before it could actually happen, because you’ll be joining the end of that queue. . There’s a whole lot of variables that surround even that though, but what perhaps works in your favour is that your system is relatively new.
Personally, I’d be inclined initially to look more closely at firstly my usage patterns and try and maximise self-consumption, and secondly at ‘shading’ issues. The latter can be more significant than you’d anticipate.
A couple of mornings ago I was up early and while in the garage noticed that quite unexpectedly my solar system production was virtually zero, whereas normally at that time it should have been producing around 1000 watts and rising rapidly with every passing minute, Yet – there were clear skies, bright sunshine etc etc, very little difference from the previous day.
However, there were unusually VERY strong gusty winds about. Because I’ve got a Fronius inverter I can go online and look at what’s happening with the system, and the North facing panels were virtually flat-lining.
What I found was – because of the early hour, the shadows cast by branches on surrounding trees and shrubs some distance away were very long, and every 3 seconds or so, a strong gust would move them far more than normal, which was enough to briefly cast a long shadow from the East across nearly all my North facing panels. So the inverter never really had time to switch back to a higher output before the next gust arrived.
Anyhow, I trimmed the offending branches, and found when I checked the following day, that my kwh total output for the day was up about 2.5 kw, and also noticeably above the levels for quite a few of the previous days. Basically what had been going on was that the shading in the early morning had been gradually increasing for a while, but I’d assumed that all the decrease in my daily kwh system output was attributable to the progressively later sunrise and earlier sunset times. .
My point is, by paying some minor attention to my daily output ( a few minutes every day), and about 40 minutes of my time trimming branches etc I’ve basically reduced my next quarterly electricity bill by around $60.
I know a lot of people ‘can’t be bothered’ with the ‘minor details’, but putting it another way, assuming I keep up my present approach, in 4 years time that ‘insignificant’ .daily 75 cents is going to save me around $1000, and I won’t have worked very hard at all to achieve it.
What about ‘shading’ – its surprising how much you can lose at different times of the year or even during the day, if strong gusty winds are around causing foliage branches to suddenly shade portions of a number of panels for a few moments at frequent time intervals.
Is it possible to put bifacial panels on a 30 degree gable roof in a townhouse. The roof faces west but the available space is limited and a 3.6kw standard system is all that can be fitted as there is shading on on a section of the roof in winter. Micro inverters are a possible option. Bifacial panels would be a much cleaner solution for the limited space to get a higher output.
Hi Michael
If the panels are laid flush against the roof being bifacial will give them no advantage as there isn’t enough space between the roof and the panel for a significant amount of extra light to get in from the side and, unless your roof is very white and stays clean, the output will be lower as standard panels have a reflective layer of aluminium beneath the solar cells that does a better job of reflecting light back through the panel than any roof.
But if the bifacial panels were used to say make a verandah or carport roof with nothing under them to block light coming from underneath, then they may perform better than standard panels.