What if evaporative energy generation can be improved?

Ever since I read the amazing paper THE THEORY OF HURRICANES by Kerry A. Emanuel I have been fascinated with taking advantage of the fuel that powers this most aw inspiring phenomenon. in the paper he compares the inner working of a hurricane to that of a heat engine, however the disequilibrium that powers it does not come from the difference in air temperature between the ocean and the tropical air but from its under saturation with water vapor. According to his calculations "To bring the troposphere into thermodynamic equilibrium with the ocean would require the transfer of roughly 108 J / m2 of energy from the ocean" If we could tap in to even a fraction fraction of this energy it could supply a massive amount of power. There are a few devices which I have found that take advantage of evaporation the most well know of which is probably from the research out of MIT on fungal spores that drastically alter their size in response to levels of humidity. This effect can be used to generate motion which then can then be harvested and used in various ways. However, in my opinion the downdraft tower) and the Barton evaporation engine are far more interesting and promising. The down draft tower works by spraying water at the top of a tall tower which then evaporates cooling the air and creating a powerful downdraft which can then be used to generate electricity. The Barton Evaporation Engine works by evaporating water into a piston at low pressure, this reduces the pressure further allowing the piston to return to a piston further than its starting point. This difference can then be taken advantage of to generate electricity.Both the downdraft tower and the Barton evaporation engine take direct advantage of the evaporation of water. However, to me it seems they don't take advantage of the fact that the temperature of the flow is decreased. Why not take advantage of this temperature difference to try and further improve the efficiency of the device. I cant help but be so seduced by this idea. I dream of a future where ocean tankers outfitted with evaporative engines powering electrolysis filling their tanks with hydrogen and oxygen to bring back to port. perhaps even fleets of these tankers being strategically used during hurricane session to limit the build up of thermal energy in the ocean. Maybe even a water powered car, it wouldn't be practical, just to show it can be done. I know these are all crazy dreams, however I really do feel that the technology can be pushed much further. I am not physicist, so I am very interested to hear what people who know more than me think.