Re: How will air travel work in a green solar economy?

['Chris de Morsella' via Everything List]

________________________________
 From: John Clark <johnkcl...@gmail.com>
To: everything-list@googlegroups.com 
Sent: Monday, July 14, 2014 8:51 AM
Subject: Re: How will air travel work in a green solar economy?
 


On Sat, Jul 12, 2014 at 8:50 PM, Russell Standish <li...@hpcoders.com.au> wrote:



> I saw that webpage, but it didn't quote anything, nor give any form of
>justification. [...] I'm thinking that the velocity factor needed to compute 
>maximum power
>ought to perhaps be exhaust gas velocity anyway. It seems likely to me
>that aircraft engines should be able to increase exhaust velocity and
>correspondingly reduce thrust as velocity increases, keeping power constant
>

You don't need to consider any of that to see if the figure I used, 140 
megawatts of average power, is in the right ballpark needed to keep a 747 in 
the air. At takeoff a 747 can hold 60,000 gallons of gasoline and stay in the 
air for about 12 hours, so that's about 5000 gallons a hour. One gallon of gas 
contains 34,000 watt hours of energy. So 34,000 watt hours /gallon * 5000 
gallons/hour = 170 megawatts.  


So it looks like my estimate that if you want to go with solar then a factory 
that covered 6 square miles of the Earth’s surface  would be needed to keep 
just one 747 in the air may have been a a bit on the low side.

It seems rather more likely that jet fuel will be provided by synthetic 
(engineered) algae grown in hot desert areas using brackish -- or sea -- water 
ill suited for agriculture on land that cannot be used for agricultural 
purposes -- because it is dry desert. 
The United States actually is fortunate to have some of the world's best areas 
for producing these types of algae biofuels -- in certain regions of southern 
Arizona (and in Sonora state in Mexico as well)  that have large brackish 
saline aquifers (or are near the sea) and have some of the worlds best solar 
profiles and critically stay hot throughout the night -- this is important to 
produce high yields (40+ metric tons of biofuel per hectare). These biofuels 
could be burned pretty much as is  in current jet engines.
Chris
 


  John K Clark


 

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