Thursday, April 1, 2010

More student visitors

31 March: One of my dissertation students, Robert, came round with a friend Chris (a manufacturing engineering student, also at Uni of Nottingham) for a good look at the Sunbox system.  We have had 3 days of miserable grey weather, with rain, cloud, low air temperatures, so the sunboxes are less effective. However, when the Heatpump works well, they work too, so if the glycol going out is cooled, then the boxes respond thermostatically, even in the evenings. I notice that the morning and evening ground temperatures are lower than last week when we had sunnier weather.
  During R + C's visit, the pump came on and off a few times (automatically), as it was balancing the glycol flow temperature and the air in the boxes. The 3.0 degree C difference seems to be well judged - I feel that the difference needs to be at least 3 degrees to push heat though the polypropylene walls of the thermal collectors. One degree would mean too much yo-yo-ing. Perhaps I should try 5.0... ?
 Robert is building much of his dissertation around this technology of Charging the Earth, so is probably rather relieved that they are actually built and working. I have plans for a Mark 2 version, and will either need to find another house to try them on, or use up some of my remaining wall. If I  can move the design of that along, he may have time to mention it. I also have another student called Joel who was going to write about them, but haven't heard from him for many weeks..... :(

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