Thursday, June 2, 2011

Solar comparison mid 2010- mid 2011

Diagram from www.sunnyportal.com
2 June 2011 : Our PV roof has burst through the 5,000 kWh mark (since installation) and it is time to reflect. Looking at the monthly PV graphs for the last 12 months, one can match the curve against the weather trends. Our PV roof seems to be doing quite well at the moment.
  May 2011 was nearly as good as June of 2010, and April 2011 was nearly as good as July 2010. It would have been better if we had some snap thunderstorm to wash the panels, but they got dusty in a month long period with zero rain.
   December 2010 has a surprising amount of sunshine for such a cold month, but our roof had snow on it for some of the month, and the Sharp Hill nearby makes our sunrise an hour later than it should be elsewhere. As our PV roof faces east (morning), this causes a dip in the figures. December is so low that the entire month is equal to two good days in June. We get used to it, so if you look at the meter in December and found you made 3.6 kWh in a single day that is an occasion for jumping up and down! The worst day in Dec 2010 was Zero kWh - less than 100 watt-hours in a day is too small an amount to meter!
    As we move from Feb to Mar, the sun no longer rises from behind the hill, and the monthly figures zoom upwards. This is amplified by the fact that February with 28 days is 10% shorter than a typical month.
    The equinox is at the 2/3 point of the month, not halfway, so September 2010 was slightly better than March 2011.
    I now wait to see what June will bring. First two days, sunny so far! The first week of June 2010 was also very hot, so for the first time in months, I won't be seeing record annual figures... the annual summaries are now stabilising. All the figures have been helped by having had the coldest winter in 150 years followed by the warmest spring in 150 years. If we have a very warm autumn coming up to New year 2012, we will see exceptional annual figures.

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