by rg767 » Sun Jan 31, 2010 9:26 pm
You surprised me with the 10kW Aurora inverter - I actually didn't know they were becoming available.
I honestly cant imagine how using PV as a shading device would be more cost effective than using insulation, but I will leave that one to you.
To clarify (hopefully),
Yes, a bigger system will generate more electricity, but only if it is not shaded. It could be that a shaded 10kW system will produce as much electricity as an unshaded 8kW system, with the additional benefit of the reduction in capital costs. Of course the shade might not be avoidable in either case, but it pays to consider which options actually makes sense. Sometimes none of them do, and in those cases, a high capital cost is less appropriate. You have mentioned a payback period, but that assumes full production (I assume).
Whatever system size you go for, keeping the efficiency high is important. If your roof is very shaded, I suspect a 10000TL will struggle for all of the shaded hours. I only ever use a central inverter when I know I am going to get 0% sunlight hours shading.
If I was spending the money I would make sure I had the shading nailed down, especially when choosing the inverter.
On the inverters, my comment of previous about not using multiples was more directly targeted at SMA 1100s for reasons of economic and system efficiency, but also because they might be more likely installed on a common phase. I would always be very cautious about any multiple inverters on the same phase however, although I would recommend multiples on multi-phase installations where something like shading or multiple facades makes them more appropriate.
On a side note: I am aware that the Auroras have been tested to work in multiples on same phase [edit: and there are probably others that would work], and I think you can get them to communicate with each other via RS485 connections, so I would be less inclined to worry that they would drop out through grid impedance, or even worse hold each other up when the grid blacks out.
With an Aurora 5kW you do get the dual MPPT, and so a chance to split the roof in two if necessary. The 10kW unit has dual MPPTs also. It is three phase, so you will need a three phase supply.
With the dual MPPTs there may be a chance that you can isolate the shading but I guess it comes down to the situation. I don't really have anything in mind, its just that shading a string or two of a central inverter with a single MPPT bothers me.
