From: JMLayman@invalid.invalid   
      
   On 01/02/18 04:15, Bret Cahill wrote:   
   > Knowing ship owners are the cheapest folk on the planet, it's 100% certain   
   similar calculation have been done before:   
   >   
   > Vessel displacement:   1,000 kilo ton  (~300 m LOA)   
   >   
   > Prop power:  80 MW   
   >   
   > Na-S battery density:  0.150 MW-hr/ton   
   >   
   > Voyage time:   720 hours   
   >   
   > 57,600 MW-hrs   
   >   
   > 80 X 720 / 0.150 = 384 kilotons ~ 38% of the weight of the loaded ship   
   >   
   > The ship loses about a quarter of it's cargo capacity but can eliminate most   
   or all of the double bottom tank volume.   
   >   
   >   
   > Bret Cahill   
      
   Large ships make their money by moving goods as quickly and cheaply as   
   possible.  Turnaround time in port is often less than 48 hours,   
   sometimes less than 24. That means to partially recharge the batteries   
   they will need around a 1GW supplied every hour (based on your 57.6   
   GW-hrs figure). You're going to need quite a few power stations to be   
   able to supply that amount of energy on top of normal consumption (plus   
   that for all the proposed electric cars which will be around?).   
      
   --   
      
   Jeff   
      
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