I was the only poster to the previous thread about this at: <a href="https://news.ycombinator.com/item?id=9732609" rel="nofollow">https://news.ycombinator.com/item?id=9732609</a>.<p>Here is what I wrote:<p>I also work in this space, so the headline caught my attention. This is far from the first. Some other evaporation driven engines include:<p><a href="https://en.wikipedia.org/wiki/Drinking_bird" rel="nofollow">https://en.wikipedia.org/wiki/Drinking_bird</a><p><a href="https://en.wikipedia.org/wiki/Energy_tower_%28downdraft%29" rel="nofollow">https://en.wikipedia.org/wiki/Energy_tower_%28downdraft%29</a><p><a href="https://en.wikipedia.org/wiki/Barton_evaporation_engine" rel="nofollow">https://en.wikipedia.org/wiki/Barton_evaporation_engine</a><p>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.<p>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.<p>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 drinking 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.
Aw. Anyone still have a drinking bird?[1] Same principle.<p>[1] <a href="https://www.youtube.com/watch?v=Yk71GY02diY" rel="nofollow">https://www.youtube.com/watch?v=Yk71GY02diY</a>
See also the rubber band heat engine, e.g. <a href="https://www.youtube.com/watch?v=dBXL93984cQ" rel="nofollow">https://www.youtube.com/watch?v=dBXL93984cQ</a>