Hurrah! Eureka Farm is going solar. We have looked at the costs and have decided there could be no better time to install solar panels. Prices for the panels has dropped enormously as the world enters an over supply situation. Once the decision to go solar was made I became intrigue as to what system I should use. This included the type of panels i.e mono-crystalline or poly-crystalline , are some better than others, what size and then how to put them on the roof landscape or portrait and what sort of mounting would be best for us. Then there was the question of inverters and how to get it into the grid system.
My research led me all over the place but gradually the folklore around installations and the more real answers came to light. It was interesting to talk to suppliers too and hear their take as well. My neighbour Terry Stingle has a 5kw system installed and he too had done his home work well and gave me some good advice.
I eventually settled on 250w panels and ended up with a panel supplied by Diamond Cell. Now you just can’t use any panel but it has to have Australian Accreditation. And yes the panel given in the quote is accredited. I wouldn’t have chosen this one initially ( virtually an unknown brand) as I favoured the Trina Panels which had a reasonably smart specification and were being offered very cheaply.
The things you should look for besides the spec are the warranty. With the TDG-PV 250w solar panel shown above there is a 10 year product warranty and a 30 year linear performance warranty. I don’t place a lot of confidence in these long term warranties for if you have been reading the papers lately you will note that many large and first class manufacturers have given up largely because they cannot compete with China. But the large warranty supplied hopefully will last long enough to see that they go through one summer and one cycle thereby ensuring that most of the performance criteria is met.
It would seem that there are many businesses out there flogging their systems. Usually they seem to have a relationship with certain module manufacturers and are less particular about which inverter to use. It is very hard to distinguish the real costs of parts and installation and the Government rebates offered with many of these suppliers. Often you think you are getting a good price but are inclined to forget this price includes the SPC credits (Government rebates) which are returned to the user or his nominated supplier.
I must admit I began to suspect that there was a lot of fat built in these prices and was very interested to see what the actual wholesale prices would be for these materials. In our case at Eureka Farm we were looking at a 20kw system or 80x 250w panels.. It was large enough that certain wholesale suppliers were interested in quoting. As an example one wholesale quote for a 20kw wholesale price delivered to me including panels, 3 traditional composite string inverters and mounting came to $28000. Add the cost of installing the system and take away the credits this comes to about $20000 to $23000 including GST. This compares with having a package supplied by a solar installer of at least $31000 on the same basis a difference of up to $10000. This settled the course of action plan for me.
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 http://www.solardesigntool.com/compare-solar-panels-modules.html . 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 two 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.
We in fact eventually got all the panels on the farm shed roof to fit without using any DC extensions. We did however have to make up a number of connecting AC leads so that adjacent rows could be strung together. I think this is an area where the producers could make improvements and advise users what panels layoout choices they can have and what extras items they might need to facilitate this. I also think it would be desirable if both AC and DC extension leads could be purchased in say 600mm and 1000mm lengths. It would facilitate matters if such leads were available as making them on site can be very time consuming. Lastly we had one situation whereby the rails went parallel to the long direction of the panel and this meant it overlapped the position of the inverter. Unfortunately the inverter as installed is not flush with the mounting frame and this too meant that we had to make changes.
Lastly I should mention the ECU unit. This is a great piece of equipment and really highlights the beauty of this system. Every panel’s performance is measured and transmitted to this unit so that is possible to know in great detail how all the panels are working. The owner quickly can determine what and where his problems are occurring if at all.
To summarise I suggest everyone out there look at this unit before buying a conventional system. The price difference isn’t much .