Sunday, April 18, 2010

Interseasonal Thermal Storage - will it work?

18 April : Let's discuss Interseasonal Thermal Storage a bit more.
This was my original intention with this research project - I have observed on good days that the soil temperature around the pipes does indeed rise nicely, but by midnight, the heat has distributed outwards well, and the soil is at a stable temperature - not as cold as it would have been without the solar charging. Blaise will want me to turn off the sunboxes for a week, some time, to see if it makes a difference. As the timescale of this is seasonal, I can't really see the point of just three days. We have had three years without sunboxes, and should have measured then!

   What I can be sure of are the Realtime and the Diurnial effects, and we are seeing that every day during this equinoctial time. Later this year, in the Summer, any energy used by the circulating pump is freely supplied by the PV roof, so we shall store the thermal energy, even though we don't yet know how much will stay Interseasonally until Winter.

   I can be certain that with this system there will be an absence of the usual longterm Soil Chilling - it is already clear that the sunboxes are preventing chilling, every day.

We have got through the 2009-2010 winter now, and normally the soil in April would be chilled from a long winter of having heat pulled out for the house. After a month of operating the sunboxes, the soil is already at a temperature that you would normally expect to find at the end of a long summer (of not drawing heat from it, and for it pulling in heat from the vast surroundings).
    For research reasons, we will run the pump for the entire summer, of course, and we will continue to make measurements. The long moment of truth will be during the winter months of December-January-February-March, to see if the workload of the GSHP is made easier by warmer soil. Can some of the build up of summer heat be evident in the dark month of December?

13 Dec '10 Postscript: Yes it can!!
Ground temperature is 10.4°C at this date, whereas it was 7.2°C a year ago. This is a partially thanks to the summer charging, but I suspect is equally due to regular recharging by a good number of sunny days since the summer which keep the temperature from falling too much.
16 Jan '11 Postscript: Yes it still can!! 
Ground temperature is 10.6°C at this date, whereas it was 5.2°C a year ago. With the mild weather of early January'11, the deep ground temperature has been rising very slightly.
8 March '11 Postscript: Yes it seems to be proven! 
We got through the low point of winter with the ground temperature never falling below 10º, and it is now rising firmly, nudging 11º. Yesterday, the GSHP only used 13.63 kWh despite the air temp never rising above 10º and the night before having been below freezing.

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