Inverter downsizing - Looking for advice

ispookie666

Your total energy output to the grid will be limited to 3.68kw not 3.68 for each device/equipment. 
G99 is a prospective one and G98 is done after install and something like self certification. 

Exiled_Tyke

Have you run the NW orientation through PVGIS (or whatever it is, I can't quite remember) to look at predicted output.  I'm not sure it's worth the extra for that section. 

Spies

2nd_time_buyer said:

flyinggoose said:

Spies said:

I didn't notice you said North west for one of your arrays, how many kwp in each orientation are you to have?

So they've confirmed 14 panels (360w per panel) will be the max I can get up there, so the end result should be:

South East Roof - 4 panels - 1.44kwp
South West Roof - 6 panels - 2.16kwp
North West Roof - 4 panels - 1.44kwp

I think you'll be fine with that split.

Have you considered the 10kwh Solaredge battery? It will be cheaper than the Powerwall. It is it DC coupled so will be more efficient as you are going DC to AC rather than DC to AC to DC to AC. It will also minimize clipping as it can store what otherwise would be clipped.

Agreed, only two elevations would be generating optimally at any one time.

Spies

Exiled_Tyke said:

Have you run the NW orientation through PVGIS (or whatever it is, I can't quite remember) to look at predicted output.  I'm not sure it's worth the extra for that section. 

The NW array will be useful in summer and when you have days of diffused light.

Martyn1981

flyinggoose said:

Spies said:

I didn't notice you said North west for one of your arrays, how many kwp in each orientation are you to have?

So they've confirmed 14 panels (360w per panel) will be the max I can get up there, so the end result should be:

South East Roof - 4 panels - 1.44kwp
South West Roof - 6 panels - 2.16kwp
North West Roof - 4 panels - 1.44kwp

Hiya, that's a relief, I was a tad concerned if the vast majority on the SE and SW roofs.

Looks like a great compromise. Personally if I had the choice between south, or SE + SW, I'd go for the later. Small reduction in annual total generation, but a better spread through the day. And then a bit of NW for the evenings Apr to Sept.

Totally unscientific, but my system can sustain 4.2kW generation in perfect conditions and say May to Aug, which pro-rata would be about 3.8kW for you, so not bad.

flyinggoose

2nd_time_buyer said:

flyinggoose said:

Spies said:

I didn't notice you said North west for one of your arrays, how many kwp in each orientation are you to have?

So they've confirmed 14 panels (360w per panel) will be the max I can get up there, so the end result should be:

South East Roof - 4 panels - 1.44kwp
South West Roof - 6 panels - 2.16kwp
North West Roof - 4 panels - 1.44kwp

I think you'll be fine with that split.

Have you considered the 10kwh Solaredge battery? It will be cheaper than the Powerwall. It is it DC coupled so will be more efficient as you are going DC to AC rather than DC to AC to DC to AC. It will also minimize clipping as it can store what otherwise would be clipped.

I have looked into the Solaredge battery briefly, perhaps i need to take another look though, it would mean no Tesla Energy Plan (although that could end at any time, of course) but like you pointed out the Solaredge battery would be more efficient so i'll do some more research, thanks.

Dolor said:

You may appreciate this already but a PW2 will not discharge to the Grid unless you sign up to the Tesla Energy Plan via Octopus Energy. My understanding is that all AC batteries require DNO approval as their inverters are treated as generators. I have a 6.35kWp array on two roofs with SolarEdge. My inverter is limited to 5kWs. Inverter limits not only have to take into account maximum power but also power outputs during the Winter months. Yes, at times my maximum output flatlines but as I am getting about 20% more than the predicted annual output, I am convinced that my installer’s modelling has got it right.

Yes i am aware of not being able to discharge the PW to the grid manually, thanks for pointing it out anyway though.

Exiled_Tyke said:

Have you run the NW orientation through PVGIS (or whatever it is, I can't quite remember) to look at predicted output.  I'm not sure it's worth the extra for that section. 

I did, initially the plan was to only have the panels on the SE and SW roofs but after doing some reading here it seemed like a good idea to just maximise the roof with solar panels if one could afford it, the installer gave me figures for what each roof orientation would generate but i take figures from solar installers with a pinch of salt, i just did my own calculations in the end and decided to have panels installed onto the NW roof aswell.

Reed_Richards

My inverter, made by Goodwe, has a software setting that limits the export.  Every time I read about people fretting about the 3.68 kW "limit" and how this will be accommodated I wonder why all inverters do not have this feature.  It seems to remove very many complications.

ispookie666

@Reed_Richards it's to do with certification and how much the manufacturer is willing to spend to get this done. 
I have come across manufacturers who will only do certification for newer products when legislation changes rather than get their entire stock certified. 

gefnew

Bit of an old post here.

jamesingram wrote: »

yep , low tech mag. is a great site all round .

over here's Sunny Slough .
3.68kW limited inverter, 18x240W schuco panels , sma 4000TL ( 2.4kW 35deg, 1.92kW 15deg) SE

Our system has same size inverter (3.68kW) but just the single array of SE oriented panels (20*185W) at 45deg. Interesting that we had almost identical outputs yesterday. Probably coincidence though as we are over 100miles apart.

Here was our output graph yesterday. You can see the kink at about 4pm when the panels are no longer in direct sunlight. Our panels are unshaded (except by the roofline later in the day) so all the deviations from the nice bell curve are clouds. Also this is the first time we've squeezed a drop of power out after 6pm:



The y-axis is kWh generated per 15min period, so multiple by 4 to give average power output per period (ie just under 3.2kW at peak). For 6 hours yesterday (8am-2pm) the panels were averaging over 2kW, and 8hrs over 1kW (7am-3pm). The inverter started up between 0615-0630 and shutdown between 1815-1830. Sunrise here was at 0615 and sunset 1822.

Cider Country Solar PV generator: 3.7kWp Enfinity system on unshaded SE (-36deg azimuth) & 45deg roof