Tuesday, October 25, 2016

Oct 25th- Exploratory- Solar Updraft Chimney-Progress Reports

Students continued to make progress building their designs for solar updraft chimneys.

 It is planned to test them on Friday.









Nicely engineered unit had black surface with holes and undersupports to encourage updrafts....


Discussion- Would heat production be increased if solar collector portion was made of material with a higher specific heat capacity than air- fox example, filled aluminum cans filled with water, painted flat black?  Water has a capacity of about 4 Joule/deg C/gm vs about 1 Joule/deg/gm for air.

Air Density: A cubic meter of air at 40 degrees C has a mass of about 1.100 kg, vs about 1.170 kg at 25 degrees C. So a solar updraft chimney containing a cubic meter of air might press upwards with a force of about 70 grams.  According to the Betz limit, the maximum efficiency for a turbine is 59%, so the most force that could be captured is about 42 grams.


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