Part II - As quotes come in, the design of the Solar Array emerges.
I started off by getting the usual 3 quotes. One was by word of mouth and two were from Solar Quotes. It is easy to get quotes from Solar Quotes website - simply enter some details in and ask for one to three quotes and they line up the installers who then send in the quotes. With decent Google Maps coverage, they usually don't need a site visit. The web site also provided a wealth of background material. While waiting for a response, I trawled the internet for as much information as I could handle. One installer got back almost immediately and the others took a bit more time. By this time I had enough information under my belt to evaluate the designs.
The roof size is about 200 sq metres but it is badly broken up. There seems to be no one who regrets getting too big a setup and almost everyone regrets not getting a bigger one. So I was trying to push for a setup as large as possible and this meant using almost every bit of roof space for a panel. There were going to be panels facing in every direction. Due to the limited space, higher efficiency panels were the go. The panels are LG Neon2 335W panels. They come with a 25 year warranty. Each panel was about 1.7x 1.0 m.
With panels in more than two directions, micro-inverters were the only choice. The quote used Enphase IQ7+ micro-inverters. They handle up to 290W which means the panels are over-rated by 15%. This is not unusual as the peak output of a panel is reached only under ideal conditions.
The micro-inverters come with an Enphase Envoy controller. I got an upgrade (at no cost) to the next one up. I am not completely sure what the upgrade entails but I should get panel level monitoring. I am also expecting consumption measurement hardware – what it does and whether it can handle all 3 phases and more is something I will know when I get it. The interesting bit is that it has wifi and a web server on it that allows you to query the device for real time monitoring. I can’t wait to tinker with it. A good starting point is thecomputerperson page on it.
My approach was to squeeze as many panels on to the roof as possible. A 5 KW system was OK but I pushed for a 10 KW system. It does push out the payback period as subsequent panels may not be in the ideal position. But the cost of the panels is not as much as you would expect as this is what the govt rebate covers. The micro-inverters are another story. Of the three responses, the one from Space Solar had a pretty good panel layout. They managed to squeeze in 32 panels with a bit of space left over on a south facing roof.
This web page gives the effectiveness of solar panels based on the pitch of the roof, the horizontal direction the panels are facing and the city you are in. I calculated the effective output of the solar array at its peak. I am based in Sydney so that is the city I picked. I wasn’t sure about the pitch of my roof and so calculated it for both 30° and 40°. The horizontal direction for north facing panels is 0°, for east facing it is 90°, south is 180° and west is 270°. The panel is rated at 335W and the inverter at 290W. So at their peak, panels are limited by their inverter so the inverter limits the wattage at high levels of output and then by the panels as their output drops below the inverter rating. For example, if your panel is south facing, chances are the panel and inverter are pretty well matched.
There are 32 panels in total, of which 14 are north facing. The total KW of the panels is 10.72KW but with all the losses due to orientation, worst case (roof at 40°), it should be 8.6KW at its peak. I am not even considering other losses related to time of day, season, cloud cover and shade. The whole setup costs about $23K. With the Govt STC rebate it comes to just under $17K. I live in Kuring-Gai council so throw in another $500 solar rebate from the council. I might use this money to get some cool drone photos of the roof before and after.
In the next blog I will compare my power usage with the expected solar output and look at the money I am hoping to save.
Disclaimer: I get nothing from the companies I mention here.
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