Tuesday, March 8, 2011

Sunniest days of the year

8 Mar '11: During the sunny day of Mon 7 Mar, the PV roof captured 13.3 kWh, and the Surya Sunboxes caught 20 kWh. And on Tue 8th Mar, the solar capture was 13.6 and 19 respectively.  There were only two days in the whole of last summer when they captured that much in a day prior to the fixing of the mirrors. After being amazed at Monday's harvest I was delighted that it was also sunny on Tuesday, and the sunboxes were dumping heat to the ground, plentifully.
   It was cold both days (below 10º and below freezing at dawn) and the sunboxes were in the high 20s most of the day. Monday and Tuesday were those rarest of days, when the GSHP consumption exceeded that of the house. The house imported 13.63 kWh and the GSHP consumed 13.65 kWh, and did even better on the 8th, 13.36 and 14.48 respectively. This can be seen by looking at my Metering page (see Links) It helps that in cold air temperatures, PV production is enhanced.
Deep Ground Temperatures August '09-March '11
Red line is the date of installation of Sunboxes

That is a rare condition.
• In the Winter, the PV produces little, and the house and GSHP burn much.
• In the summer, the GSHP only burns only 1 or 2 KW a day, and the PV roof produces enormously.
• There is a short cross-over period in the equinox when the PV can generate so much that it is driving enough power to run the GSHP and enough other devices in the house for it to exceed the import.
It managed this only 4 times last year.
  With the reduced consumption of the GSHP (due to nice warm ground) the fact that it only consumed 13.65 kWh on a day when the air temp never got above 10º and was below freezing during the night is remarkable. A year ago it was using over 20 kWh/day for weather conditions like this!
  Look at the temperature chart on the right - the deep ground temps are rising from their low point of January. They would have risen more, perhaps, if there had been more sun in February.
  Coincidentally, the 7th and 8th March of 2010 were also very sunny, and the Sunbox capture was lower than in 2011.
14 Mar '11 Postscript: Deep ground temperature was 10.7 degrees.

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