Energy Sources and Propulsion Choices

by Web FishAug 11, 2012 @ 08:18am

Warning: scientific content. If you are easily bored, please scroll down for final conclusions.

Now that we've established the rules, first order of business would be to figure out our energy source and the associated propulsion system. Not being able to rely on stored energy for propulsion (at first read) automatically discard several obvious sources:

  • Any exothermic chemical reaction based process - internal combustion engine, most forms of jet propulsion (fuel-powered jet engine), most forms of steam engine (where fuel is used for heat generation);
  • Any direct chemical reaction energy conversion for which at least one of the reagents is stored on board - chemical battery bank, classic fuel cell, pseudocapacitor;
  • Any direct electric energy storage system - pre-charged super capacitor;
  • Any mechanical energy storage - flywheels, etc.;
  • Any nuclear power source (not that our rules are the main limiting factor there :) 

What is left then? Actually, plenty (not necessarily in order of practicality):

  • Harvesting electromagnetic wave energy (to simplify things we'll refer to it as sunlight, even though any EM waves could do):
    • Direct conversion of  into mechanical energy. Theoretically (and somewhat practically - this, this or this) possible, nothing available yet that will work with diffused sunlight and produce the levels we need;
    • Conversion into electric current and from there on into mechanical energy for propulsion and (optionally) into other types of energy for storage. Plenty of variations of propulsion and storage methods are available. Solar panels driving electric motor and/or charging chemical battery bank can be achieved with mainstream components;
    • Conversion of sunlight into chemical energy and from there on into electric current and so forth. Various forms of photocatalysis with 100% external reagents (chemicals from ocean water?), photosynthesis. Not much available within our budget and size;
    • Conversion of sunlight into thermal energy and from there on into mechanical, electrical and/or chemical energy. Heating water by (concentrated) solar energy and powering steam engine, turbine, jet propulsion, etc.;
  • Harvesting mechanical energy from the surrounding ocean water:
    • Direct use of mechanical energy of ocean currents for propulsion. All forms of ocean gliders; 
    • Direct use of the mechanical energy of ocean waves for propulsion. Wave gliders;
    • Conversion of mechanical wave energy into electric current and so forth. Wave power generation - certain possibility but energy density is minimal within 1 cubic meter under the surface;
  • Harvesting mechanical energy from the surrounding air (wind):
    • Direct use of wind energy for propulsion. All types of sails
    • Conversion of mechanical wind energy into other forms of mechanical energy (i.e. driving a propeller by a wind generator). Complete decoupling of wind direction from vessel direction;
    • Conversion of mechanical wind energy into electric current and so forth. All types of Wind power generation;
    • Conversion of mechanical wind energy into other forms of energy - thermal, chemical, etc. Mentioned for completeness;
  • Harvesting chemical energy from the surrounding ocean water:
    • Harvesting and converting energy of phototrophic organisms;
    • Exothermic chemical reaction triggered by catalyst carried on board but with reagents derived 100% from the surrounding environment. Way out there... but still a cool idea :)

Not too bad. We will revisit some of the options above in the (hopefully not too distant) future, but for the time being, based on the other two factors in the rule book (volume constraints and budget considerations) our finalists are:

  • Harvesting sunlight energy via photovoltaics;
  • Harvesting sunlight energy via heat engine;
  • All forms of wind energy harvesting;

Time to see if anyone of these can actually get us across the ocean.



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