Friday, September 30, 2011

New Sunbox versus old

30 Sept 2011: One question that the followers of this blog will want to ask is: "Do the newly designed Sunboxes make a difference?" Well, that is a question I want answered too.

What I can say is that from August 9 to Sept 30 in both years, the 2010 solar harvest was 492 kWh. For the same period in 2011, the harvest was 529 kWh. This is about 7% improvement - but that is a margin of change that could easily be varied by seasonal differences.
    Apart from the recent cold weekend (when the heating was on briefly), the weather is so warm that we are still in Summer conditions. This performance has been solely based on summer collection, i.e. inter seasonal storage with the low speed pump. (There is a brief moment of delta-T realtime operation when the water is re-heated every so often).
   The figures will continue to look good for a while because the weather forecast is for a week of sunny weather with which to close September and start October. We have had two days running of a daily harvest of over 20 kWh, which is a first time ever.
   The previous boxes managed to break the 20 kWh barrier 5 times in 17 months, and the new ones have broken that barrier 4 times in one month, including an all time record of 22 kWh in a day.
    The real test of it has to be over a longer period, with some part of that time occurring in the Winter when the GSHP is driving the glycol through the panels, based on delta-T.
     So far it does look like a slight improvement, and after a few more months have passed by, I shall post graphs comparing the performance. When there are chilly winds blowing, will the insulated construction yield benefits? When we are deep into the heating season, will the larger air volume (heating up when the Sun shines) make a difference?
   You will hear from it on this blog! And if I am wrong to have changed them, you will be the first to hear too!

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