History of energy trends
  Past Industrial revolution Today Near future
Fuel Wood Wood/Coal Oil/Coal/Gas Coal/Uranium
Energy content        
(MWday/ton) 72 72/172 288/172/216 172/1,00,000
Combustor Open fire Flame tube boilers Water tube boilers/ Gas turbines, reactors
      gas turbines  
Emissions Diluted and dispersed Confined and controlled    
Transport medium Air Brackish water Pure water/combustion Noble gas
Transport system Open Open Closed/open Closed
Conversion unit – Piston engine Steam turbine Power turbine
Efficiency <3% <10% 30% >40%