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What can I get with 6m x5 m area


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Hi all,

I have a flat roof (well, it dips about 4° to the North) 6 m long (East to West) and 5 m wide (North to South). If I cover it with photo voltaic panels, what maximum total kW output can I expect ignoring cabling to the inverter? I was thinking of 12 x 320 W (or thereabout) panels, which are about 1m x 2m each and would fit nicely. Assume ideal conditions e.g. full sun, optimal panel orientation etc.

Thanks,

 

Marc. 

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1000W per square meter, and the panels are usually around 17% efficient. So your 30m^2 is good for 5kwp, times 4 or 5 hours a day, that's aorund 20kwh a day. Very very roughly speaking of course, it will depend on orientation, how much space you have to leave in between so one string doesn't shade the next...

Edited: To fix the math... my math teacher always did say if the numbers look wrong... they are.

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You are right @Marcb, you can fit 2 x rows of 6 panels next to each other on the roof = 12 panels

1 x 320w panel: Size: 1 x 2 = 2m square. Therefore 320/2 = 160w per square meter. 

How you calculate what you can expect is as follows:

12 x 320W = 3840 Watt

You multiply that with an efficiency of 3.5 = 13 440 Watt. That is what you can expect on average for the year. You would probably achieve an efficiency of 4.5 in summer @ 17 280 watts and say an efficiency of say 2.8 to 3.0 in winter @ 11 520 watts in winter. 

Just make sure you do not exceed the input volts on your inverter with 12 x 320 Watt panels.

Hope that answers your question.

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Quote

You multiply that with an efficiency of 3.5 = 13 440 Watt. That is what you can expect on average for the year. You would probably achieve an efficiency of 4.5 in summer @ 17 280 watts and say an efficiency of say 2.8 to 3.0 in winter @ 11 520 watts in winter.

 

These are kWh figures, so I have 3kW on the roof and get about 12kWh in winter and 15-18kWh in summer per day.

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And I thought I was brave with 3600W on a Axpert/Infini. 3840W is pushing it a wee bit, especially in winter. I would just mount the panels flat, i.e. bias for summer, and use a combiner box and Circuit Breaker to switch off one string of the 4x4 stings, if and when PV overloading occurs. But what I see so far with 3600W on a 3000W is that production seem to max out at 3200W, which could be caused by the SCC limiting (3200W-3300W+- 10%?). I would expect to see the same limitation, even with a higher PV production capability. 

Even in Winter, I see close to 3000W for my Summer (18 deg) panels (12 x 300W). So I will have to watch this carefully as the sun starts to move higher of the horizon.

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Food for thought, Sidewinder. I thought that I would max out my roof area as it will be more cost effective per W installed. I need about 2 500 W peak during the day with a grid tied system to get some power at night. Thinking of the future when our mayor will implement his co-generation plans. Well, that's what he said anyways.

I'm looking at a Danfoss ULX 3600 inverter with max PV system input of 3 900 W. Anybody with experience on this hardware? Any other suggestion? 

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Hi @Marcb. You can oversize your solar panels kw rating up to 30% without a problem, providing, you do not exceed the inverter input volts. There does not seem to be concern with the Danfoss Inverter. They can handle a lot of PV Input volts. The inverter might clip your output to 3900 watt output, but you will gain faster ramp up in the morning and die slower in the afternoon with oversized solar panels. The little power loss due to clipping at peak times will be negligible. 

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