16 panels East or 8 panels east 8 panels west split

[The Launderer]

Hi Guys looking for your thoughts.

Quoting for a job where there the roof I suggested putting 16 x 250w panels is facing 93 degrees east. The customer has had an alternative quote and the installer has suggested splitting system 8 panels east and 8 panels west. The customer asked for my comments. I ran the alternative system through PV Sol (changed inverter to twin tracker) and the result showed a 120kWh lower output per annum.

I sent the customer the result and a bit of information. I suggested to her that putting the panels on an east west split would probably generate at a lower level but would give a better spread of generation throughout the day. The customer works from home so is in the house all day and we discussed the possibility that the lower annual output might be compensated by the customers demand on her power supplier being reduced and the east west split might actually be a better idea.

Don't think there is any way to quantify it but would be interested to hear other views.

 

[yellowvanman]

East - west thats what I put on my roof - so far generating more than predicted!

You will obviously have increased scaffolding costs.

 

[wstevew]

East - west thats what I put on my roof - so far generating more than predicted!

You will obviously have increased scaffolding costs.

8 East - 8 west. 90 degree 3.84kWp using 4000TL + suntech

Estimate 2803kWh/pa

+20% january
+50% February
+49% march

19% of estimate generated jan to end march.

But I would have probably only got 12 panels on a single orientation.

Feed in at end of march 7am to 7pm
>1kWh around 8:50am on clear day until around 5pm

 

[Glen Powell]

If working from home your customer would have a higher chance of using more of the electricity generated on an East / West system, the problem you have now is to win back the customers trust, as the other guy suggested it. Cost implications would imply that all on one roof is best for ROI but you do need to take lifestyle into account.

 

[FB.]

I'd choose a split system as it will provide a more balanced power generation throughout the day and therefore a more beneficial effect on household bills.

I get frustrated with my SE-facing system as it's like feast or famine; too much power to use it all in the mornings and only a trickle flow in the afternoons and evenings.
I'd trade a loss of 120kWh per year for a longer period of "peak" generation so that I might be able to use all of the power and not have to import from the grid in the afternoons.

 

[FB.]

Also.....

Let's suppose we have a "typical" week, and three different panel layouts.
8 East + 8 West
- or -
16 East
- or -
16 West

In that week, we have the following "English" weather:
monday: rainy day.
tuesday: cloudy day.
wednesday: sunny day.
thursday: sunny morning with cloudy afternoon.
friday: cloudy morning with a sunny afternoon.

Realistic daily total generation as follows:

16 East:
Mon: 4kWh
Tue: 6kWh
Wed: 16kWh
Thur: 14kWh (got all the sun in the morning)
Fri: 8kWh (missed the sun in the afternoon)

16 West:
Mon: 4kWh
Tue: 6kWh
Wed: 16kWh
Thur: 8kWh (missed the sun in the morning)
Fri: 14kWh (got all the sun in the afternoon)

8 East + 8 West:
Mon: 4kWh
Tue: 6kWh
Wed: 16kWh
Thur: 11kWh (managed to catch some of the morning sun which the W-facing missed)
Fri: 11kWh (managed to catch some of the afternoon sun which the E-facing missed)

So the split system also has a more even day-to day power output, along with a more even power output throughout the day.

 

[wstevew]

120kwh at current fit is £27 so you would need to find that from the "extra time"

 

[wstevew]

Also.....

Let's suppose we have a "typical" week, and three different panel layouts.
8 East + 8 West
- or -
16 East
- or -
16 West

In that week, we have the following "English" weather:
monday: rainy day.
tuesday: cloudy day.
wednesday: sunny day.
thursday: sunny morning with cloudy afternoon.
friday: cloudy morning with a sunny afternoon.

Realistic daily total generation as follows:

16 East:
Mon: 4kWh
Tue: 6kWh
Wed: 16kWh
Thur: 14kWh (got all the sun in the morning)
Fri: 8kWh (missed the sun in the afternoon)

16 West:
Mon: 4kWh
Tue: 6kWh
Wed: 16kWh
Thur: 8kWh (missed the sun in the morning)
Fri: 14kWh (got all the sun in the afternoon)

8 East + 8 West:
Mon: 4kWh
Tue: 6kWh
Wed: 16kWh
Thur: 11kWh (managed to catch some of the morning sun which the W-facing missed)
Fri: 11kWh (managed to catch some of the afternoon sun which the E-facing missed)

So the split system also has a more even day-to day power output, along with a more even power output throughout the day.

I agree, it's generation is as even as a south facing system just a tad lower in output. But as with all east/west split or not. A lot lower in the winter.

 

[FB.]

Also, I suspect that an East/West split will not need such a large inverter, since the panels will never all be in direct, straight-facing sun at the same time.

While 4kWp East-facing (or West-facing) would probably need a near-4kW inverter, I suspect that a split system with 2kWp East and 2kWp West would only need a (less expensive)3kW inverter.

 

[wstevew]

Also, I suspect that an East/West split will not need such a large inverter, since the panels will never all be in direct, straight-facing sun at the same time.

While 4kWp East-facing (or West-facing) would probably need a near-4kW inverter, I suspect that a split system with 2kWp East and 2kWp West would only need a (less expensive)3kW inverter.

You are probably right. I can't let you know that one until I have had it a year.

At the moment I see peak at 2.5kWh where some with south facing 30 degree see 3.5.

But I do have a 22.5 degree tilt so I'm hoping as the sun is higher it will increase and the inverter not be so inefficient.

 

[FB.]

Mine peaked the other day just over 3.4kW out from the inverter with slightly East of SouthEast facing, 40-degrees.
3.75kWp and 3.6kW inverter.
So the inverter was putting out 95% of its capacity.
Before DC->AC conversion losses, input power would probably have been 3.55kW (95% of the array's potential).

 

[The Launderer]

If working from home your customer would have a higher chance of using more of the electricity generated on an East / West system, the problem you have now is to win back the customers trust, as the other guy suggested it. Cost implications would imply that all on one roof is best for ROI but you do need to take lifestyle into account.

Not sure I have lost customer trust and still not convinced there's much in it either way. Customers like our no pressure sales and are impressed that we take the time to do proper shading analysis and provide detailed quotations.

Too many competitors use SAP2005 only and in this particular area of Scotland weather data produces a significantly lower output.

I am coming round to thinking that on balance it may be better to do an east west split but would like someone to really convince me

 

[wstevew]

That's pretty good. Although mine peaks lower the daily total isn't that far off.
01/4 15.6kWh
02/4 13.6kWh

 

[The Launderer]

Thanks for all the comments. In my opinion this is what this forum does best.

 

[wstevew]

Not sure I have lost customer trust and still not convinced there's much in it either way. Customers like our no pressure sales and are impressed that we take the time to do proper shading analysis and provide detailed quotations.

Too many competitors use SAP2005 only and in this particular area of Scotland weather data produces a significantly lower output.

I am coming round to thinking that on balance it may be better to do an east west split but would like someone to really convince me

I think here there isn't a wrong system just an informed choice you can offer your client.