Annual average solar irradiation

rolion

Hello,

I went trough many online resources reading about planning of PV arrays and other stuff.
Can someone help me with this question please.

Based on another forum,annual average solar irradiation for Dublin is at per below:

Dublin:
Jan: 1.202kWh/m2/day x 1.5sqm x 16 = 28kwh/day
Feb: 1.818 = 42
Mar: 2.885 = 67
April: 4.123 = 100
May: 4.818 = 115
June: 4.614 = 110
July: 4.720 = 108
Aug: 3.935 = 93
Sept: 3.445 = 82
Oct: 2.318 = 55
Nov: 1.419 = 38
Dec: 0.889 = 21

This will give an annual average solar irradiation for Dublin as 3.021kWh/m2/day.

I have 16 panels,giving 1.5sqm each.
Ive added to below table and it gives me some ...numbers.
Pleae help me to understand what those numbers means,in relation to my PV array design.

Thanks in advance.

quentingargan

It is more complex - the panel efficiency at different levels of light intensity, and the orientation and pitch of the roof all have an impact.

For this reason, most normally use a software package of some sort to simulate based on historic climate data. Good simulation packages cost €1K plus for a license fee. We use PV-Sol and PV-Syst, but Retscreen is an excellent macro-enabled Excel spreadsheet which works well and is free. Has good online tutorials.

Any way you do this will be inaccurate the only way to know the truth is with a test panel and a watt hour meter, or a pyranometer with data logging or a note pad, or Quentin's shiney software.

Let's take July for example. 4.72kwh per day with daylight. Let's assume that's 12 hours of light. Let's also assume 20% was lost due to panel angle and that 66% daily was harvested as result of being off angle. [NOC will vary.]

3776Wh exposure
2492Wh harvestable

66% for 4 hours 33% for 8 hours


1644Wh: 10am to 2pm = 1644 / 4 = 411Wm² per hour midday
822Wh: 7am to 10am & 2pm to 7pm = 103W/m² per hour dawn/dusk

Module standard test conditions: 300W@ 25°C & 18.3% efficiency with 1000Wm².
Array size 12.8m²
411 watts* .183 efficient * 12.8m² = 963W * 4 hours: 3851Wh midday
103 * .183 * 12.8 = 241W * 8 hours = 1930Wh dawn / dusk



5.78kWh harvest daily July.
6% lost in installation = ~5.4kWh useful power.

Or KISS and array size * 6 on a good day (14.4kWh p/d from a 2.4kW array)
and array size * 3 on a grey day (7.2kWh p/d from a 2.4kW array)
wrt: naff all in Winter.

+20% and maintenance for trackers.

Sir Liamalot

Sir Liamalot wrote: »

wrt: naff all in Winter.

I'm getting 33% Wp at the moment
Yesterday 0.04% Wp for 2 hours.

quentingargan

Sir Liamalot wrote: »

I'm getting 33% Wp at the moment
Yesterday 0.04% Wp for 2 hours.

I have a 1.5kw inverter and 1.8kw of PVs. You can see their production online here.

Getting 20 watts now - almost enough for my laptop. But yesterday for a while I was getting 1.5kw.

quentingargan

quentingargan wrote: »

I have a 1.5kw inverter and 1.8kw of PVs. You can see their production online here.

Getting 20 watts now - almost enough for my laptop. But yesterday for a while I was getting 1.5kw.

Haha! My 150W aimed module is thrashing your array Q.
55W!

quentingargan

Sir Liamalot wrote: »

Haha! My 150W aimed module is thrashing your array Q.
55W!

I guess that's why we have a grid. So I can use a panel in the midlands to power my laptop in W. Cork :cool:

jathclare

Not as technical in terms of productivity per sq/m but here are actualexport units figures from a 6kw array in Co.Louth (24 panels on southelevation)

Since August 2014 it has generated approx 7000kw (7mw)

Exports began mid-April 2015 and have exported 3885 units in total (net ofconsumption by a Passive house with MHRV & AWHP)

Needless to say, it shows how bad this summer and autumn were. The best days in summer can achieve nearly 50 units but they were few indeed. Even a bright clear Winter's day can achieve 15-20 units (January 4th was 11 units).

Month Units Exported
APRIL (3 weeks) 454 MAY 566 JUNE 817 JULY 529 AUGUST 490 SEPTEMBER 573 OCTOBER 263 NOVEMBER 118 DECEMBER 74

quentingargan

This is interesting Jathclare for a number of reasons. I would have expected a 6kw system to export more like 75% or 80% of its production. This is a much better rate of self-consumption.

Do you go to special lengths to run washing etc. on bright days or during the day?
Is there someone at home all day Monday to Friday?

7 MwHr is a bit lower than I would have expected. If you would like to PM me details of your system, pitch and orientation, I would be interested in comparing your real experience to a computer simulation.

rolion

Hi jathclare,

Thanks for info.

For a 24 panels setup array(s)...
-wat kind of panels do you have.
-what kind of parallel/series panels links do you use ?
-what type of inverter are you using ?
-are they fixed or on a tracker ?
-why did you went for the system ?

PM if you feel are confidential info.
Im looking to get a 16 array myself and based on numbers,they are all against it !

Thanks.

rolion

quentingargan wrote: »

If you would like to PM me details of your system, pitch and orientation, I would be interested in comparing your real experience to a computer simulation.

Hi Quentin,

How do i create "the interest" to run a simulation for my project !?

Thanks.

quentingargan

rolion wrote: »

Hi Quentin,

How do i create "the interest" to run a simulation for my project !?

Thanks.

You can send me roof orientation and pitch and I can do something up quickly...

rolion

quentingargan wrote: »

You can send me roof orientation and pitch and I can do something up quickly...

Thanks.
I appreciate the "favour" ,i'll make sure i will return it some day !

Is easy:
2 arrays,each with 4 x LG 300W panels,installed on a 3m height H section pole,tracking from East to West,in the back garden.
I have full South exposure for about 160 degrees,no obstrctions at the East and with a little bit of a single tree shading at the far down West.
Full Sun coverage in that section of the garden from February to October,with the remaining months not seeing the rays at all.

Regards

Beenlost123

quentingargan wrote: »

Getting 20 watts now - almost enough for my laptop. But yesterday for a while I was getting 1.5kw.

Love the data. Are these PVs flat or ?

quentingargan

Beenlost123 wrote: »

Love the data. Are these PVs flat or ?

They're at a pitch of about 45 degrees facing south.