Thoughts on an East/West split

[Graeme Harrold]

I have just surveyed a property that has a roof ridge running due north/south, therefore making the panels facing either East, West or a combination of the two. The have opted for a 4KW system and my thinking of spliting the array is to even out the daily production as the sun moves. Rather than getting a 4KW peak in the middle of the day then rapidly dropping off as the sun moves. Its now 7:30pm and Im getting over 650W/m2 due west.

The house is occupied by 2 elderly people, and they want to see the best return on electrical savings and I feel this split would achieve that.

Your thoughts warmly welcomed.....

 

[PVFIT]

Hi Graeme,
I agree. I do recommend you having a look at the Nedap PowerRouter inverter (see video at: Solar PV (Photovoltaic) Technology | PV FIT Ltd Leading MCS Accredited Solar Installers UK). The 3700W version has 2 independent MPPT which have a starting voltage of 100VDC and wide operating range. This should help maximise output during light transition periods. It also has some great features such as web monitoring, with installer login allowing you to monitor the grid, string voltage and current etc without having to visit the property. Let me know if you'd like further info...

 

[Graeme Harrold]

Thanks, was just checking I was on the right lines to smooth out the daily production. Sunnyboy 4000TL is the weapon of choice.

 

[Graeme Harrold]

OK...quick update. All installed, 8 panels each side, no shading, nice simple job on a bungalow. Slate tiles more brittle than a dry cracker, fortunately the customer knew this and had 20 or so spare. Only broke 4, so not bad going and he also had another 7 replaced that were already gone.

Went back today to do the full handover having commissioned last Wednesday (29 June) and the panels are performing well. Total generated over the 4 days was a whopping 94kWh and he is over the moon. Had a look at the daily figures and the peak was just after 1pm with roughly 3.2kW and the production curve was nice and even throughout the day.

Basically if faced with an East/West facing property look at splitting over the two aspects.

 

[Kram]

can you pls let me know what panels you were using on the east
west split, Can i assume similar benefits with a South and West split? encouraging to hear your success

 

[Graeme Harrold]

The benefit of a split is you almost have a sun tracker. I could have put all of the Sharp 245W panels on either side, however the customer is in pretty much all day and by splitting the array, I have smoothed out the daily production i.e. all west would have given me an afternoon power spike. To work out your benefit, you will have to do 2 SAP calcs and add them as you are on a south and west split - east/west is the same SAP value, so easy to work with.

 

[Kram]

many thanks for your help

 

[SolarCity]

94kWh over 4 days is fantastic going - I assume you're down south somewhere?

Encouraging to hear that East/West splits are so productive.

 

[Graeme Harrold]

The install is on the north west peninsula of Wales (designated as a sun hotspot by the Telegraph a couple of weeks ago). From all of the reading Ive done, there is definately a bias towards the western aspect over east. Having studied some of their daily readings Ive asked them to take, their self consumption in around 93%. This is mainly due to them being in all day, have a disabled son and a smoother production throughout the day. With all the negitaves out there about the 50% consumption figure, its down to the installers to provide sound advice on energy usage patterns to maximise on produced energy.

 

[spokes2]

Hi,
Sorry to bother you on your 3 years old post but can I ask you if the Sunny Boy 4000TL that you used for this east west install was a single MPPT input or a dual MPPT input. I have read posts by tech advisors of SMA (Sunny Design: Polystring Configuration | SMA Inverted)
and Fronius (http://www.energymatters.com.au/images/news/2013/east-west-solar-paper.pdf)
that you dont have to use a dual MPPT tracker for a split east west system. You simply connect the two strings, the East and the West string together in parallel (+ves together and negs together) before they are connected to the inverter. This is possible because the voltage of the two strings will be the same, only current will differ. There may be a very small percentage loss in efficiency but more than compensated for the use of a single MPPT tracker inverter. Additionally the inverter does not have to be the full 4Kw rating because the 4Kw will never be achieved with a split system. I would very much appreciate your comments. Thankyou.
Your post:

The benefit of a split is you almost have a sun tracker. I could have put all of the Sharp 245W panels on either side, however the customer is in pretty much all day and by splitting the array, I have smoothed out the daily production i.e. all west would have given me an afternoon power spike. To work out your benefit, you will have to do 2 SAP calcs and add them as you are on a south and west split - east/west is the same SAP value, so easy to work with.

 

[Gavin A]

Hi,
Sorry to bother you on your 3 years old post but can I ask you if the Sunny Boy 4000TL that you used for this east west install was a single MPPT input or a dual MPPT input. I have read posts by tech advisors of SMA (Sunny Design: Polystring Configuration | SMA Inverted)
and Fronius (http://www.energymatters.com.au/images/news/2013/east-west-solar-paper.pdf)
that you dont have to use a dual MPPT tracker for a split east west system. You simply connect the two strings, the East and the West string together in parallel (+ves together and negs together) before they are connected to the inverter. This is possible because the voltage of the two strings will be the same, only current will differ. There may be a very small percentage loss in efficiency but more than compensated for the use of a single MPPT tracker inverter.

the voltage won't be exactly the same, for example early morning in summer the east facing array will be in full sun, while the other array is in full shade with an MPP voltage about 10% different using fronius's graph.

If you use an oversized twin tracking inverter vs a correctly sized single tracker then the improved efficiency from the better size matching may well offset the reduction in output from the single tracking. However an optimally sized dual tracker will always outperform a single tracker, though the difference may not be huge, neither is the difference in cost.

Additionally the inverter does not have to be the full 4Kw rating because the 4Kw will never be achieved with a split system. I would very much appreciate your comments. Thankyou.
Your post:

that's true, a 3kw inverter's probably more appropriate and will produce more over the year than a 4kw inverter.

At the time of this thread though, SMA only made 4 & 5kW twin trackers, now they make 3kW so you have that option, the thread starter didn't.

 

[spokes2]

Thankyou Gavin for your reply - only just read it today June 20. I'm just completing a 3kw system with 12 250w panels 6 east and 6 west facing on a nth/sth house ridge roof. Still not sure which inverter to go for though. Spokes2.

 

[Gavin A]

12 x 300Wp LG panels, with SMA 3000TL or power-one out-d 3.0, or 330Wp benq panels with a 3.6 out-d / 3600TL