Thursday, 29 September 2011

Sunlight & Solar Panels

I don't know about you, but when the salesmen were telling me about the advantages of generating electric using solar Panels I bet they told you; "You don't need sunshine to generate electricity, they work on daylight."

Well they're right, nearly.... My panels will produce power as long as there’s daylight, but boy do they produce more if the sun shines.

I produced the following figures when we had the system installed in June 2011, in an attempt to predict the potential output from the system based on daylight hours each month.
As you can see there isn't the relationship I anticipated between daylight and output. I'm either going to be a very happy man because every month of the year will produce significantly more than I hoped for, or the winter and early spring months will be universally awful.




Month
Average monthly daylight hours
Yearly percentage
Projected KW's per month
Projected KW's per day
ACTUAL KW’s PER DAY
January
8
5.4%
119
3.8
2.96
February
9
6.1%
133
4.8
3.88
March
11
7.5%
163
5.3
8.36
April
13
8.8%
193
6.4
7.86
May
15
10.2%
222
7.2
10.17
June
16
10.8%
237
7.9
10.6
July
16.5
11.2%
244
7.9
10.1
August
16
10.8%
237
7.6
8.1
September
14
9.5%
207
6.9
8.4
October
11
7.5%
163
5.3
6.0
November
10
6.8%
148
4.9
2.7
December
8
5.4%
119
3.8
2.3




Total
147.5

2,185




I'd be interested in anyone’s comment that has more experience than me regarding monthly output.





Icarus

9 comments:

  1. Find your figures interesting as we had a 14 panel system installed (went live mid-May) in Leics this year too. Ours uses Sharp panels and a SunnyBoy inverter but seems to be producing higher figures - perhaps the orientation/angle is better? For May-Aug we had 13.94/14.43/12.61/10.53 as daily averages with our lowest (also 26th Aug) at 2.56. Highest was 4th June at 23.59. Just had our first FIT payment (from EON) of £568 which is about 5% of installation cost so very good for 3 months!
    Regards
    Mike L

    ReplyDelete
  2. @Mike L
    Hi Mike. I doubt that there is very little difference between our systems orientation and angle. It’s as American drag racers used to say about their cars performance. “There’s no substitute for cubes”.

    The only lesson I've learnt after the event relates to PV panel wattage. I'm almost certain that the average output figures you're producing are from Sharp 245W panels? Mine are Schuco 190W and inevitably the additional 29% output generated by the panels is giving you a MUCH better return on your investment.

    Congratulations on making the choice you did. I'm hoping that I'll manage a 10% return on my investment each year. I'd be very interested in comparing the figures for the two systems after a year.
    Best regards.

    ReplyDelete
  3. These are my results over 18 months, (with a gap in the middle for some reason I can't recall):
    http://www.ccandc.org/cgi-bin/pv-status?START=20100316&END=now

    The Power graph shows (pale green fringes) that I can get 0-1550W (my maximum from 8x215W) throughout the year -- but sometimes it's only for a few seconds :-/

    The Runtime/Generated graph shows there's not much correlation between the time the inverter is running (magenta) and the power generated (green).

    Mmmm looks like I need to check where the current values are going.

    I suspect that local weather (and shading!) can make a big difference: I'm near enough to the coast for sea-frets and seem to have more sunnier mornings than afternoons. Unfortunately my panels face slightly W of South (the Sun is perpendicular about 13:30 BST).

    ReplyDelete
  4. @cbatjesmond
    Hi Chris.
    Good to hear from you again.It's a shame that your winter months data is missing as I now have some indication of my systems potential for summer generation, but am still uncertain about the short day, low sunlight winter output. I'll keep you posted.
    Best regards.

    ReplyDelete
  5. Hi Icarus
    Good site, although hard to see where one may comment? On the suggestion that new installations (like ours from last week) send in figures to you in order to develop a 'standard' figure, I liked your spreadsheet - although it crashes sometimes - but what is the 0.8 factor? Is it meant to mean 80% efficiency?
    Chrisso

    ReplyDelete
  6. @Chrisso
    Hi Chrisso. Sorry to hear the spreadsheet crashes.I will check the settings and try and improve it. The 0.8 factor does in reality mean efficiency.
    0.8 = Reducing factor (Solar energy the UK receives = 800W/meter for every 1000W/meter transmitted)
    If we lived in sunny Spain I suspect their factor would be in the 90's.
    Best regards.

    ReplyDelete
  7. Had my 4 KW system installed at the beginning of December 2013 with 9 panels facing South West and 7 facing South East, Output for December has been terrible at 46KW total up till the 29th, seems very low based on other peoples published figures, but installers insist it will catch up in the summer months when the sun is higher....

    ReplyDelete
    Replies
    1. Hi Anonymous. Your figures DO appear to be very low for a 4kW system, even in December.
      I'm anticipating 75-80kW from a much smaller system. If you direct mail me your email details I will send you other peoples December output so you can complain to your installer.
      Good luck.

      Delete
  8. Just seen your site, very useful to see how other installations compare. We had our panels installed in Nov 2011 so in the lowest generating part of the year. I put all the daily outputs into a database on my website so I can see the variation month by month. After 3 years it is building up some useful stats. You can see how December varies here (ours is a 3kWp system in the optimum orientation and angle)
    http://solar-panels-review.321web.co.uk/solar-panel-electricity-generated-december.php

    This page shows the difference between months which does back up the suppliers view - December for us is around 100kWh but summer can reach 400kWh so 4x the output from winter to summer.

    http://solar-panels-review.321web.co.uk/solar-panel-generation-months-compared.php

    ReplyDelete