Monday, November 22, 2010

Ground Temperature is holding up!

22 Nov'10: A year ago today, the deep ground temperature was 8.10º. Tonight, while taking the usual Sunday night readings for the spreadsheet, and letting the GSHP pump glycol round for 20 mins, the deep temperature was 11.3º. I want it to be high, but this is far higher than I expected because the last week has been dire.... a small amount of sunshine last monday, followed by days of low fog and cloud with periods of drizzle.
   Perhaps this interseasonal charging lark is working!

   Because we seem to get quite a lot of sunny days in Feb and March, I am hoping that the usual springtime drop of ground temperature will not occur because the sun will come in early enough to prevent frosting. The lowest was in 10 January, 4.70º, with an average daily GSHP power consumption of nearly 30 kWh/day. Even if there are sunny days, we don't get much of them, due to Sharphill looming high to the South East of the house.

24 Nov: Higher consumption?
 My all time annual low of 3,996 kWh for the GSHP and 6,075 kWh for the house was achieved on 1st October'10, and since them the weekly-corrected figures for annual consumption have gone up, not down.  
   Some things are causing our consumption to be higher than last year... the calculation of the annual consumption is re-computed every Sunday. As each week is being added at the head, a week at the tail is snipped off, and I am snipping off a very warm autumn of 2009 and replacing it with a week of very cold autumn.

  We had an unusually cold Spring in 2010, and now, we are having a far colder autumn in 2010, with a cold snap in October and evening temperatures in single figures for most of November. It is still November, and a heavy fall of snow is predicted for the last week of this month.
  Another reason is that I have a deal with my wife (who is disabled and unable to exercise) to raise the thermostat to 22º whereas it was 21º last year. I am also allowing the room thermostat to have 'more influence' in the thermal algorithm of the GSHP (compared with the liquid temperature). One degree difference can greatly add to the annual heating load, perhaps another 180 degree-days.
  I will reduce the activity of the Sunboxes on non sunny days by raising the Triggering Delta-T to 6º C, instead of the previous 5º. This is from observation, that when temperatures are lower, the earning from the Sunbox is reduced, and a fast pump flow does not pick so much heat up. So one can reduce excessive pump hours by making it activate when there is a greater delta-T - either when the GSHPs' ground loop is much colder, or when there is a winter sun.

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