At 8:13 AM 4/14/5, RC Macaulay wrote: >BlankAdding to Horace's thread, the draft tubes could be simple 36 ft >diameter corrogated drainage culvert mounted on the incline in length >sections as long as the incline.
The rise column (or draft tube as you call it) should be cheaper to implement as a single flat cross section than as multiple tubes. The sides not against the mountain must be insulated to preserve the temperature of the air in the rise column, because its bouyancy is what drives the device. > >A converging cone of less than 15 degrees with a cone shaped prop >configuration positioned in the converging cone that > adjusts ( necessary for proper speed efficency) outward from the >convergence would drive the generator. Interesting effects could be >developed by use of a diverging cone of not greater that 7 1/2 degrees in >that it would provide the ideal " Gibson formula" venturi throat. Placing >small parabolic segments near the converging cone would induce a vortex >that would continue through the inclined draft tube and discharge out the >diverging cone. I think NASA did some work along these lines regarding a vortex tube windmill. Also of interest is that an effective solar tower power generator is not materially different from a big wind tunnel, except things run in reverse. The economics of the design choices don't differ much. >Adding moisture ( steam) into the inlet would increase the flow via >differential temperatures Adding water at the bottom of the rise column would decrease the temperature of the rise column and thus decrease bouyancy, and thus decrease power output, true? Also, any condensation higher up in the column would decrease air volume and thus decrease bouyancy as well. Preventing condensation is a further major advantage to an insulated rise column. >May make a weathermaker on the leeward side of the mountain. Be cheaper >than building a 3500ft solar tower. Yep, when you get rid of all the need for major structual support much of the cost goes away, that's the fundamental idea. It seems to me nonsensical to test the concept by building a stand alone tower instead of trying one built on a mountainside first, but I guess there aren't a lot of mountains in Australia. They could test their concepts in another country though. Interestingly, a mountainside solar tower concept might even work in the arctic, especially in the summer when the sun shines nearly 24 hours a day. Overnight heat storage could be accomplished using thermal wells drilled into rock or gravel and they could be heated using windmills at the top of the mountain. There would be some overall energy loss from this method, but the advantage is that energy generation would be far more uniform and more spread out through the day. In the winter power generation would be only from the windmills, but still would have the advantage of being highly smoothed out and controllable. A "solar tower" in the arctic, driven in part by heat generated from wind power, might more accurately be called a "thermal tower", "bouyancy tower", or "draft tower". There are several major factors that make a thermal tower more effective in the arctic than in the desert: (1) cool air is heavier in the arctic. The power comes from the *difference* in density between air in the rise column and outside. (2) Heating cold air is easier than heating already hot air. Heat pumps might not be necessary to make effective use of thermal storage. (3) Arctic air is dry. Much of the arctic is desert, and much precipitation is in the form of snow anyway. (4) Mountain bases tend to be close to sea level, so air density at the base is maximal, (5) Mountains are located in high wind areas, so auxiliary windmills on the mountain ridge are likely effective, as may be a rise tube exit which makes use of wind power to assist rise tube evacuation. This can be accomplished using wind spinnable devices or by venturi effects, some achieved maintaining orientation of the exit structure with the wind direction. Regards, Horace Heffner
