Monday, March 15, 2010

Ventilate or not ventilate?

15 Mar: During the winter, it is clear that the sunboxes should remain tightly shut to build up the temperature inside. Today, the internal temperature is 26 when the sun is bright, and 20 when it is cloudy, even though the external temperature is 8. Once the pump operates, the temperature goes down to 13.0 or less - this means that decent amounts of heat are pulled into the house.
   Later in the year,  the temperature in the boxes could be lower than the outside air if heat is drawn out too quickly. Pump speed plays a part here - if running too Slow, the liquid in the panels could reach optimum temperature when they are only half way through - the rest of their passage would achieve nothing. It is running slow at the moment.
  I hope that if I run the pump Faster, the thermostat would turn the pump off earlier if the sunbox temperature falls, thus reducing the energy consumption of the pump.
   During the summer, when the air temperature is above the ground temperature, even at night, it would seem better to open the louvres top and bottom to encourage the best possible airflow over the panels, delivering an infinite quantity of air at the higher temperature.
   Once we have a datalogger going, we will see the trend in temperatures. We will try to log the amount of heat staying in the ground.
  If interseasonal storage really proves to be a failure, we would not waste the pump all summer, and would rely on diurnial benefits only. So far, my hunch that this would work has proved better than expected, so I will continue with the experiment.
    I will just have to make a judgement about when this is right. The louvres can be controlled from within the house.
  The photos show the upper tilting rooflet, and the lower louvre.

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