Saturday, October 15, 2011

Small disadvantage: short term borehole cooling

During October, the angle of the Sun
is almost 'straight on!' Photo taken about
1430 15 October 2011
15 Oct 2011:  I noticed that if the GSHP has been doing a heating cycle and then stops, the Sunbox system continues pumping for a while because a strong delta-T persists. There is an amount of much colder glycol still in the panels and pipes.  The cold stuff in the system has to be flushed through.
   So, temporarily, colder glycol is being pushed down than is coming up. At 5 litres/min, this takes a while as the capacity of the upper system is about 60 litres. This means that for perhaps 12 mins, there might even be a borehole cooling effect.
    Blaise warned me about this in 2010
http://chargingtheearth.blogspot.com/2010/05/short-term-cooling-balanced-by-short.html
when he analysed the first data logger readings a long time ago, but I can't see what can be done about this. It is the disadvantage of the serial 'trickle and whoosh' plumbing method. Considered overall, the advantages are too great for this to be considered important.
   If there is sunshine, the sunbox rapidly restores the normal order of things, and starts to pump liquid around which is re-warming the zone immediately around the borehole pipes, and on nice days, it is doing this in bucketful's.

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