Energy from evaporating water

[DrZoidberg]

When water evaporates it draws a lot of heat energy from its surroundings. About 2,200 kJ per liter.
Thats about 0.6 kWh of energy for every liter.
It should be possible to extract some of that energy.
The easiest option would be to simply blow air over the water so it cools down and then use a sterling engine and a generator to make electricity.
Let' s say the water cools down by 10 degrees celsius through evaporation. By the laws of thermodynamics that would mean the maximum efficiency for the sterling engine is around 3 to 4 percent.
So 3% of 600Wh i.e. 18Wh per liter.
That's quite small compared to gasoline or coal but water is cheap. Sea water is even completely free. So evaporation power plants could be build at the coast.
Especially in Africa that could be an interesting option since the air is dry and the temperature high the efficiency could by a lot higher. Maybe more then 10%.
Sunlight could be used to heat up the other side of the sterling engine to vastly increase it's performance.
Of course that would be essentially the same as a water cooled solar power plant.

It could even be used for portable power. A small device build from a peltier element could be used to recharge a cell phone with pure water. If carried on the body the body heat would increase it's performance.

[Super God]

In a refrigeration system, when the refrigerant evaporates it absorbs energy from the environment in the form of heat and will thus get cold.

[gcramer789]

Hello everyone I am Gary Carmer
Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid. Evaporation is also part of the water cycle.

Gary Carmer

[ibpointless2]

Water itself is truly amazing thing. I've seen motors made to run on evaporating water, I think they're called Puskas engines. Here are some Youtube video on some of the motors.

http://www.youtube.com/watch?v=GcIeMWNlIGI&NR=1&feature=fvwp

http://www.youtube.com/watch?v=auQjZwkia00&feature=related

So long as there is water in the containers the motors will work. It would be cool to be able to get electricity from these things. Imagine these on a large scale! 


Here's even a link to the guy water wheel that runs off evaporating water

http://www.overunity.com/watermotor/

[budden]

Hi!

There is professional, government-sponsored project of multi-MW evaporating plant.

http://physicaplus.org.il/zope/home/en/1124811264/1137833043_en
http://en.wikipedia.org/wiki/Energy_tower_%28downdraft%29

It was estimated that such plants can cover all current human's energy needs if many
are built in deserts. Also it was stated energy would be very cheap - cheaper than most
of current power sources including coal. No plants, no prototypes are built for now.
I have made a model of that tower

http://www.youtube.com/watch?v=sy3uLf8NMtY

but the tower must be very tall to work well, mine is 2 m tall so it could give
about 1 mW only.

Also there is project of piston evaporation engine of smaller scale, but air is
preheated first in solar collector:

http://www.sunoba.com.au/previous.htm
This kind of engine can be also built to work without air preheating.

Another working engine of this kind is "drinking bird" toy.

IMO this is very prospective power source.