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DIY ground mount solar PV install


ProDave
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On 16/12/2018 at 20:39, ProDave said:

This thread is to document the (probably slow) DIY installation of my ground mount solar PV

 

I have just bought the panels  I will be using 16 250W panels for the main 4KW array facing south which will leave me 2 spares that I will probably set up independantly on a small inverter facing east.

 

Amazing. DIY solar. Now that's aspirational for someone like me!

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  • 5 weeks later...
On 18/03/2019 at 14:34, ProDave said:

So continuing with the above post, I am now thinking of fitting these 2 spare panels.

 

As I have decided on one facing E and one facing W to try and squeeze a bit more out of both ends of the day, my thought are turning to a suitable inverter and how to connect them.

 

 

So how to connect them?

 

I would say connect them in parallel, as only one will be generating at a time.  The question is what effect witll the non generating panel have?  Will it zap some of the power or just sit there as a high impedance load doing nothing?  Should I put s series diode in series with each panel so only the higher voltage panel does anything and the other cannot back feed and zap power?

 

Someone must have done this befoe and know how best to connect them.

 

 

Just come across this video with some nice demonstrations of the effect of shading parts of a panel when there are two connected in series or parallel. If shading is likely to be a problem (as in @ProDave's case it definitely is) then this confirms that parallel is the right answer.

 

https://www.youtube.com/watch?v=1qD3mN8VotQ

 

Their results are very much in line with what I'd expect.

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  • 1 year later...

A couple of weeks back, I noticed there was nothing being diverted to my immersion heater.  A quick check in the shed revealed the main inverter was showing "Grid disconnected"  further investigation found the 32A mcb feeding the shed had tripped (but not the 16A inverter MCB in the shed)  So I reset that and the main inverter powered up again.

 

The cause of the trip was the little cheap Chinese inverter connected to my 2 spare panels had blown.

 

Having failed at just under 2 years old I was not particularly liking the idea of buying another, but there is nothing else available anything like as cheap.  So time to take it apart and see if a repair was possible.

 

Inside a PCB mounted fuse was blown and some basic testing found that 2 of the transistors that make up the H bridge that synthesises the output waveform were blown, short circuit.  So i ordered 5 of them from ebay from China for £5

 

They arrived yesterday and i fitted them and cautiously powered it up and it's working again, so this morning I put it back into service.

 

It will be interesting to see how long it lasts before failing again.  What I did notice is they were very short on the heat sink paste, with it only applied to one side of the insulating washer, so it's pasted up a bit better now.

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  • 2 weeks later...

Another observation about my repair of the cheap little Chinese inverter.

 

When testing it, I found it's output is pulsed, in very much the same way as my solar PV dump controller is. And just like that it appears the duty cycle is varied to adjust the power output.  I wasn't expecting this.  I guess it makes it easy to design the inverter as it only has to synthesise a simple grid sychronised output and vary the power by pulsing it on and off.

 

I wonder if the big "proper" inverters work the same way or not?

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  • 1 year later...

My original prediction was to self use £250 per year giving a 6 year payback.  Last year that was up to £300 and this year post April is likely to be £400 per year, so is likely to bring payback to perhaps 4 years.

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4 hours ago, ProDave said:

so is likely to bring payback to perhaps 4 years.

I am seriously thinking of doing like @ProDave as I have a south facing garage roof at 30’ that will take the panels, as many of you know i don’t do “tech” (Luddite me), but have been wondering if I timed the ASHP to only work between 10 am and 4pm then it will likely use excess lecky if it’s sunny and dump heat into my slab (if the room stat requires it) or the DHW cylinder( if the cylinder stat requires it.) Any excess after that will dump into an immersion in the DHW cylinder. I don’t fancy batteries yet but want to use or store as best I can without them. 🤷‍♂️

Edited by joe90
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