Friday, December 31, 2010

Graph of the Year 2010

31 Dec '10: This is a good time to summarize the year. In short, the graphs show a good story.
• The vertical line shows the date of the installation of the Sunboxes.
• The blue mound representing the deep ground temperature is clearly hitting the end of the year about 3 degs C higher than it was at the same time last year.
• The performance of the GSHP (yellow line) is far smoother and logically related to the air temperatures (red line).
I hope this results in a cost saving in electricity over the entire year, when we reach March, the anniversary of the Sunbox installation. If not, don't forget that we have had a very severe winter so far - this has not been a typical winter, in fact we have had the equivalent of 2 winters within 2010.
  Also there is the long term vision. The ground chilling effect is one that takes place over 5-10 years before it reaches a low steady state. If this system has the effect of maintaining a consistent warmish temperature every year instead of letting it chill, then it will have succeeded! But we shall never know how cold it would have got without this. Simply, if I knew someone else nearby with a GS heat pump in a similar sized house, one could test their ground temperatures as a comparator.

Ground Temperature
  Later in the evening, during our New Year's Eve party, I did a meter recording, and when the guests had gone I did a deep ground temperature test.... the result was 10.3º (higher than last week's 10.0º). I am assuming that this slight rise is due to the reduced rate of extraction, as the entire week has been above freezing, foggy and cloudy. No solar heat put down for a while week, but not so much heat required from the ground.
  In case you are wondering why there is more fluctuation earlier in the year, I can also say that as time goes on, I get more strict about standardising the procedure. I now let the heat pump sleep a full 4 hours after it has last done a heating cycle before running the temperature test - so I might turn it off at 9pm and test it at 1am, and the ground temperature has evened out. The test is run for 15-20 mins, and the reading taken after that time.

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