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Clean sheet solar array design


Hagu13
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Yet another question from the noob🙄

I need to redo and expand my solar panel array. The site is a flat roof with no shading from trees, buildings etc and big enough to avoid the panels shading each other.

Target objective is to have as wide as possible PV bell curve rather than a high midday peak. I'll add panels as required to maximise generation. I currently generate enough/too much for about 8 months of the year so I'm happy to lose a little summer performance to gain in winter.

Current setup is 6x305W, facing north but angled very low (10 degrees) this was for water pumping in summer but that kinda dried up so first order of business is to raise them up. The're also in 3 strings of 2 but I see most people run them in strings of 3 so I'll try that. I assume better performance at dusk and dawn as the voltage threshold is reached quicker, and better peak performance due to lower line losses?

I'm thinking to lift these panels to around 45 degrees, then add more panels at different angles to catch early and late sun? If yes, do I aim due east and west, or northeast/northwest?

What would the greybeards do with a clean sheet approach?

MPPT is an Axpert, 145V, 3kW solar rated

 

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2 hours ago, Hagu13 said:

The're also in 3 strings of 2 but I see most people run them in strings of 3 so I'll try that

This depends on the specification of your inverter. For your 145V model that is the very max, and you should stay with around 118V as max. This means 2 panels in series and not 3. So I would not change this setup if I were you. 

If you do go with 3s, you might actually have more losses as you are using the same cable for more current than with 2s. With 2s you just have more cables spreading the load. 

2 hours ago, Hagu13 said:

I assume better performance at dusk and dawn as the voltage threshold is reached quicker

This is true, but in practice does not make that big a difference. You will see that as soon as the sun hits the panels it will just to it's preferred voltage. It is just the current that is low. So having the sun hit the panel at more of a right angle will give you more current, and that is what you want. Adding panels that catch the very early morning rays at a right angle (close to 90deg) will give you more current than rays at a very small angle (10deg). So I will say add panels east and west. 

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