How to use energy of the sun?  
 
One a little too often thinks of the photovoltaic cells.  
 
However, those are extremely expensive, and their use for one prolonged duration is not guaranteed,  
considering the ultraviolet rays even corrode their components,  
as well as the matter intended to seal the panels.  
 
I prefer, as far as possible, to turn me towards the solar chimneys, tubes of approximately 150 meters in height,  
placed above a conical roof in simple sheets, which enmagasinent heat.  
 
The heated air goes up at a speed of approximately 15 meters a second,  
with a rather important flow if the installation is well designed.  
 
These chimneys can then be provided d' a device allowing to produce electricity in day and even part of the night,  
if one placed stones which store heat in lower part of the heated roof.  
 
This last solution is, is necessary it to say, very good market.  
 
The Australian ones practically finished to build a solar chimney which will be also large as the Eiffel tower,  
chimney intended to feed a small town in electric current.