

Scientists Create the World's First Evaporation-Driven Engine - mparramon
http://www.popularmechanics.com/science/energy/a16045/evaporation-engine/

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FiatLuxDave
I also work in this space, so the headline caught my attention. This is far
from the first. Some other evaporation driven engines include:

[https://en.wikipedia.org/wiki/Drinking_bird](https://en.wikipedia.org/wiki/Drinking_bird)

[https://en.wikipedia.org/wiki/Energy_tower_%28downdraft%29](https://en.wikipedia.org/wiki/Energy_tower_%28downdraft%29)

[https://en.wikipedia.org/wiki/Barton_evaporation_engine](https://en.wikipedia.org/wiki/Barton_evaporation_engine)

The solar updraft tower and vortex engine also operate in a similar space,
meaning that all of them operate using the temperature difference between
ground and tropopause which feeds the water cycle.

It is my personal opinion that evaporation-driven engines (or something quite
similar) are the most promising energy source (on this planet). Essentially,
they are an alternative source of solar energy which doesn't have the problem
of needing the sunlight to be present to work.

The main issues, as with most new energy sources, are efficiency and cost. The
Columbia motor costs $5 for 50 microW, or $1x10^5 dollars per watt. You
generally want something nearer 1$/watt for primary energy use. The efficiency
in terms of water or thermal energy is not stated, but is likely similar to
dunking birds, which have a thermal efficiency around 0.01%. The theoretically
possible efficiency for the evaporative half of the water cycle is on the
order of 12%, so there is a lot of room for improvement.

