Good end of month

Having passed the monthly total for January on the 21st with ten days to go, it was looking like being a fairly productive month. This was helped by a period of 4 clear days that really got the panels going, followed up by various mixed days that still produced a handful of units each day. Plus a few surprises - a few instances where cloud was forecasted but better weather materialized. It all helps.
 

Since then, it's been fits and starts. Firstly the highest ever spot reading on the Owl unit (see below) on Jan 26th. Not bad for a 3.43 kW system. I suspect part of this is due to the uneven nature of the weather - I don't get these higher values when the sun is constant. I wonder what the system will be capable of come high summer, given that the inverter is rated above the panels, at least I know whatever they kick out will get used, maybe I can get closer to 4 kW?

Secondly, Jan 27th was another perfect day - wall to wall sun and over 13 kWh generated. We still had the dip at 3:15 pm when the sun descends passed a tree on the horizon, but other than that it was a perfect trace with over 2500W being kicked out in the middle of the day. Not bad for January, it just goes to show how the slightly longer days & higher sun angle increase the output, and that's just comparing to a few weeks back. Roll on some proper spring days!

Jan 14th - Perfect Day

January 14th was a near perfect day weather wise and was my most productive day to date with 11.3 kWh generated. Clearly this will get surpassed later in the year, but it's quite impressive for January, when an average of less than 3.5 kWh is predicted.

The detailed plot for the day (below) is almost perfectly smooth, with just a couple of dips, so I suspect this is about as good as it can get for January. The early bias on the chart show the impact of being SSE facing, but it's hardly a major problem. I think the slow pick-up at the beginning of the day and the early and late dips are caused by trees on the horizon. Although I don't suffer from shading on the panels, I do have a broken horizon with lots of trees in the distance. Hence why the plot isn't exactly smooth. As the sun rises higher in the sky these will cease to be a problem, so it's not something I should worry about - not that I can do much about it anyhow.

Jan so far

January has been a little mixed so far - some poor days and a couple of better ones. Plus a couple of moderately good days (well beyond the forecasted conditions). It's always nice to get a handful of units produced that weren't expected.

However, it now looks like we're heading into a period of high pressure - clear skies, frosts and plenty of winter sun for the panels to lock into. Today (13/1/12) looks like being a 10 kWh day, but it's hard to tell exactly, but either way we wont be far out. If this weather holds for next few days than an average 7-8 units for 5 days will do wonders for the performance against target. Whilst I don't expect to beat the performance target by much, it's always nice to sit back and enjoy all that free power.

It's nice to see the evenings starting to get lighter, its only a few minutes a day, but given that this starts to overlap with my evening commute home, it's most welcome. The mornings wont start to change for my morning commute for quite some time (maybe March), but it's nice to see some signs that the seasons are starting to change.

On a separate note, I managed to get up the loft recently and get a rough measure of the pitch of the roof. According to my rough calculations, the roof's pitch is a little over 45 degrees, maybe closer to 47 degrees. For some reason I'd always assumed it was closer to 50, but now I know. I've subsequently reworked the power factor values for the table at the top of this blog to reflect this. In theory this will make a slight change to the performance of the system, but is likely to be slight.

December 2011 - all over

So the month finished at just shy of 160% of predicted output. Not quite as great as the first part of the month had promised, but you cant really complain when you've gone through the shortest day and come out again. I look forward to seeing the sunshine stats on the met office website - it'll be good to know how the month compared to average and see if over time a correlation exists.

January 2012 could be interesting, the prediction is a little higher than December, but it is the time of year where we often get snow, which will kill the system dead until it melts off the panels. We've had a couple of harder winters in the last few years, so who knows what this winter will bring?

Now I need to push on and get the spreadsheet and graphs updated. I'm convinced there's a better layout than the one I use now, all I need to do now is find it.

Slow Progress

So it looks like the monthly target of 170% of predicted output is going to be a stretch. 5 of the last 6 days have been cloudy and produced little more than 1 kWh per day. At this rate we're going to struggle to get to 160%. 

I shouldn't moan really, when we have a good day the output is excellent, but in times of prolonged cloud (as now and forecast for the next few days) it's less impressive. Still, the sun's angle is improving, the days are slowly starting to get longer and I'm still making some minor inroads into out electricity consumption - roll on spring and some decent weather.

It'll be interesting to see the hours of sun stats for the month when they're published in January - I wonder how well we've done when compared with the seasonal average. Time will tell.

Shortest Day

So I was having breakfast with a good friend of mine near Heathrow, watching the sun rise at about 8am and it looked like it would be a good day today. It was. 

Despite it being the shortest day of the year we still generated nearly 8.5 kWh today, the system seemed to top out at 2200 watts since there was a little wispy cloud around that never really went, but at this time of year you cant complain when good weather shows up. So that makes 112kWh for the month so far, and 146% of the expected yield for the whole of December, with 9 days still to go. If the current run rate continues (5.14 kWh/day) we could come in at over 200% of expected. I can't see it happening with the current weather forecast, but something well over 170% is a distinct possibility.

Playing

OK. So since I have a few day's off work for Christmas I've had some time to play with the Google docs links. I have a few more things working, have imported my original tracking spreadsheet and so will crack on with the graph conversion. This should allow a more automated update process in the future, however there are one or two teething problems to be resolved. 

One addition to the blog are the key sunrise/sunset stats etc at the top. This is linked in to a today() spreadsheet function along with a vlookup() which should automatically populate the table above for 5 days, centred on today. Well that's the theory, I shall see if it works automatically over the next few days. If not then I will remove the gadget and publish the full table elsewhere. 

Earlier I lost all my charts on the right and so have rebuilt the links. Hopefully this wont be a regular occurrence, time will tell. 

In the mean time, it's been a dull, damp day with drizzle after a promising sunrise. I don't have the figures yet, but I suspect I've generated less than a kWh today. But that's in line with the weather forecast, so I suppose I shouldn't complain. Any units at this time of year are welcome - it all helps.