Solar Panels

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Just before we go onto other details with regard to my installation I will briefly talk about performance criteria.  a good site to look at for panel comparisons is .  When you look at solar panels you really are looking at area. Each solar panel will contain so many cells. In the case of 250w their are 60 cells making up each panel creating an area about 990mm wide and 1650mm long. . Peak efficiency gives you some idea of performance. In the case of TDG mono crystalline panels it is 15.3% which is similar to the Trina panels at 15.27% and a little bit less than the Yingli at 15.3%. But what is also important is how they perform under real conditions and not at  test temperature of 25°C. Generally solar panel performance deteriorate as the temperate of the cells heat up  which is actually what happens in summer. The temperature coefficient for TDG is -0.456% which means even for a 20 degree rise in temperature you could expect a 9% deterioration in performance. But actually this isn’t too bad and compares favourably with the other panels that I mentioned. But TDG is a monocrystalline panel compared with the others that I looked at and it has a completely different breakdown of voltage to current. It seems to have almost double the deterioration in voltage but half in amp age.What this means I am not sure.

But I choose TDG panels  not just because their performance was acceptable and even exceptional  but because of their association with APS microinverters. These micro-inverters seeme to be the first on the market that can handle 2 panels or 500w. Enecsys micro inverters are in strong competition and all the major manufacturers of solar inverters such as SBA and Aurora are looking at this market seriously. But APS system means that it can service 2 panels whereas most other micro- inverter suppliers have one inverter for each panel. This in reality means that they are to date uneconomic in larger systems.

The advantage of micro-inverters over traditional inverters is that each 2 panels operates independently of the array that it is in. In the traditional string arrangements the DC voltage goes from one panel to another with as many as 20 in a string. This can lead to string voltages of up to or more than 600v. There are problems with this strategy. Every panel has to be to the same specification, orientation and the overall performance is really controlled by the performance of the weakest panel in the array. If one panel breaks down then the whole system goes down, if one panel is in shade then the whole system deteriorates. Also with such high DC voltages the risk in the event of a fire event is much greater. High DC voltages in the event of breakage in the line are just like arc welders.

The other great feature of this system is that the units are plug and play. Every unit can be disconnected by a simple plug which is intrinsically safe, not much difference to changing a light bulb. This will have great ramifications to users although the code hasn’t caught up with this development yet. With the present code playing with solar panels is a no-go area for the reasons outlined above that DC is so much more dangerous at high voltages. And of course the other feature emphasized by the suppliers is the ease of installation. Whilst this is somewhat true we did have some serious issues with the present setup.

Obviously this duo system was designed only to be easily installed in portrait mode. In any non-standard configuration often either the DC leads were too short, the AC lengths were too short or the rails interfered with the inverter. When we received these panels they came in two1-DSCF6087 APS 500w inverter mounted under panel configurations. On the panel shown here the inverter is held by bolts thru 4 mounting holes drilled in the panel framework on the left of the panel connections. In portrait mode the leads were ok. The 2nd panel though which is the duo panel for this inverter came in 2 formats. One had the specification 900mm leads and the other one was 600mm. Unfortunately we were not aware that this was going to happen which meant that in some case we had to move panels around substituting one with long leads for one with short leads. Obviously this complicated the installation procedure.


Solar Panels — 7 Comments

  1. Hi Dennis,
    We are about to sign with solarmyhome with the TDG panels. Thanks for your page, it was really informative. Just wanted to know if you are still happy with your “solar system” as it is now February. Would you still recommend the panels?



    • Yes I am very happy. Some wonderful advantages with micro-inverters. we did have some problems with the electrical connections on the micro-inverters but the backup was good and they replaced the lot. I think it was a one off problem. Backup and warranty have been good so far and the ability to see what is happening at any time with every panel on line is a great feature.

    • Solar panels are still not that cheap to buy. However I see a future situation whereby panels such as I am using with micro-inverters could be installed by the handyman which would reduce costs. This is because the microinverters produce an AC output which could be just plugged into a circuit with simple safeguards. Obviously though if you are not connected to the grid and are on Dc then you are free to do whatever you like.

  2. Hi Denis,

    Like you we are currently looking at the TDG/APS combo, albeit on a much smaller scale – 2.5kW. It has been roughly 10 months now since your install and I’m just wondering how man of your 80 panels and 40 inverters have failed, and how you went about getting them replaced via direct manufacturer warranty, as you indicated that you had these directly imported?

    I’ve not heard very good comments about the TDG panels however I do realise that they are a cheap Chinese brand and as such would not expect them to last as long as some of the more reputable brands. Just a case of getting what you paid for I guess?

    I do like the idea of a micro inverter set up however there are just not that many options out there at the moment.

    • Ok I am ready to reply to your queries. To start with I am very happy with Australian Micro Inverters. I really like the idea that each inverter can handle 2x250w panels. there are a lot of advantages in keeping the system AC. Each inverter and in turn each panel can be monitored for performance. If one inverter goes down or performs badly in a string operation then the whole string’s performance is affected. This is not the case with micro-inverters. With DC setups then you only have a limited number of inverters which in your case would be only one. If that goes down then you have no power until it is fixed. Even under warranty it is my experience that getting things done can take a while. With 10 panels which is what you would require you would only require 5 micro inverters and I am told that would be cheaper to install.
      As reguard the TPG panels I suspect there isn’t much difference between makers even though large claims to the contrary might prevail. To stay in business the panels and warranty have to be good. TPG panels are warranted for 25years and it is a comprehensive warranty. And remember warranties are only good if the manufacturer stays in business.
      I have had no problems with the panels although I expect 1 or 2 are underperforming and when I have time I will try to resolve whether this is the case. As least I can see these performance figures and make such an assessment. The suppliers at AMI also have access to the performance criteria of my panels and have been very helpful in resolving any issues that I might have had.
      I did have problems with the inverters though. The electrical connections kept breaking. But again AMI replaced all the inverters including labour with an updated model.
      In summary I would look at the specs for TPG panels and compare. I would also talk to the supplier or your installer for more info. But for me I wouldn’t go any other way.

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