re: hurricane tower SOLAR.KnowledgePublications.com

re: hurricane tower
2 oct 1996
how about a tornado?

can we make some sort of artificial solar-heated tornado, on a village scale?

house-sized "helio-aero-gravity" systems have very poor efficiency. there is
lots of solar heat, 1 kw/m^2, but only 0.1% or so might end up as electricity,
maybe 20 watts, with a windmill at the top, and slowly moving warm air...
meanwhile, mother nature is making 100 meter diameter tornados with large
temperature and pressure differences and violently twisting winds that rip
roofs off houses and phase changes and rain and hail and power measured in
thousands of megawatts, ie gigawatts. what are we doing wrong here?

the franklin institute in philadelphia used to have a tornado simulator with
a small electric heater (50 watts?) at the bottom of a transparent tube about
a foot in diameter and 6 or 8 feet tall. when you pushed a button, the heater
turned on and some smoke was injected into the tube, and the smoke started
swirling. it's better to have a swirling updraft than a straight updraft,
if we are trying to make electricity with a turbine, no?  

what makes this thing tick, exactly, and how much power could one extract
with a windmill at the top, or the bottom?
 
how about combining some kind of low-speed vertical jet engine/vortex tube/
heat pump with a water tank containing a liquid that boils between ambient
and some slightly higher temperature? to paraphrase dr. p. n. sastry, who
is now on the way from singapore to rural devipuram, india:

  a liquid which is cheap, locally available or can be made, eg ethyl or
  methyl alcohols, or hexane, all of which have boiling points between 64c
  and 78c. the first two could be made locally; the last is available freely
  as a byproduct of petroleum industry. it would be nice if we can find some
  thing that boils at 50c, and has a low latent heat of vapourization.

recall "hand boiler" toys which boil and move a liquid from one glass bulb
to another, when you hold the first bulb in your hand?

should we start with something like a 2 meter diameter water tower, some sort
of teardrop-shaped ball full of water suspended inside but not touching the
sides of a larger steel or mud-brick cylinder, and surround it at the base
with a $300 80' square horizontal polyethylene film skirt 3 meters above the
ground, to gather 500kw (670 horsepower) of solar power, and put a large and
carefully-designed high pressure electrically-driven turbine fan inside the
cylinder at the base, like the front end of a jet engine, to compress and heat
and twist the air as it pushes it upwards, squeezing it past the ball, and
spray 4 gallons per minute of water into the hotter air from the ball full
of water, at the narrowest point to the cylinder wall, and let that water cool
the air, and then let the air expand and cool and make rain higher up (how far
would the 2000 pounds of water per hour have to fall, to make 10kw?), and
collect the rain as it falls back down into the ball, to power the input
turbine, and make more power than that, via a small waterwheel? is it worth
putting another turbine at the top of the structure, electrically or somehow
physically connected to the first, eg on the same shaft, to despin and
uncompress and slow the air, removing its energy on the way out, as in a
jet engine?

or should we use a cylindrical water tower, with some twisted heat exchange
fins on the outside, and another layer of steel outside that, and fill it up
with a liquid that boils at a lower temperature, and make that liquid boil
with the warm compressed air, and use the liquid vapor to power a turbine or
piston machine, before the liquid returns to the base of the tower? what do
we use for a cold sink, in this case? some pipes in trenches in the ground?
evaporating water? a few automobile radiators, and the 30 c ambient input air?

dr. john craven's group in hawaii has reportedly poured the foundation for
a modest-sized artificial hurricane tower, with a deep seawater cooling plate
at the top. they plan to make lots of fresh water as rain, and "several
hundred kilowatts of electricity." 

nick

references:

tornados, in the mcgraw-hill encyclopedia of science and technology
 
b. givoni, semiempirical model of a building with a passive evaporative
cooling tower, solar energy, vol 50, pp 425-434, 1993

   an experimental mathematical model that calculates the performance
   of a passive evaporative cooling tower (also known as a downdraft
   evaporative chimney) has been developed by cunningham and thompson.
   the model calculates the tower's exit air temperature, flow rate
   and the speed of the air exiting from the tower...

e. kessler, thunderstorm morphology and dynamics, 1986

r.e. peterson, proceedings of the symposium on tornadoes: assessment of
knowledge and implications for man, texas tech univ, 1976 

p.s. ray, mesoscale meteorology and forecasting, 1986

j.t. snow, the tornado, scientific american, 250:86-97, 1984.