26 May 2012: Saturday morning: We have had a fifth day running of sunny clear weather, and more expected on Sunday. I've got used to the daily running of the Kingspan Varisol evacuated Tubes. They are doing as well as they could considering their position, orientation, angle and area.
They are able to maintain a steady state for most of the sunny morning, with tube temperature of 23-24º, the heat exchanger at 20-22º and the incoming ground liquid at 14º. (Above, indicates the Tubes temp of 23º. Pressing the up and down button shows the other temperatures.).
During rest periods, the controller lets the tubes continue to pick up temperature, and rests the ground loop, then mostly, both pumps run at the same time. The running time for both pumps is about 5-6 hours/day, and the amount of heat being put down is 5-7 kWh/day. Does not sound much, but the heat pump is only using 2kWh/day and drawing 4kWh/day from the ground.
The Tubes and Sunbox together are contributing 18+6 per day, a consistent 24 kWh/day being pumped into the earthstore.
A little timing test
I tried turning the tubes controller off for a precise ten minutes. The temperature was 24ºC at the start. After 10 minutes, the controller shows that the temperature in the manifold was 44ºC, and this heat was rapidly downloaded to the heat exchanger.