

Battery turns saltwater into drinking water - voodoochilo
http://tech.slashdot.org/story/12/02/11/1415210/battery-turns-saltwater-into-drinking-water

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z92
If you don't want to read the article: "Battery" in its name implies that it
has got electrodes in it and that's all. It's neither an energy generator nor
an energy storage device -- if you were wondering.

Also here's the catch/

"The desalinated water that comes from the battery still contains too much
salt for drinking, La Mantia says: “We removed up to 50% of the original salt,
but we need to arrive at 98%."

~~~
ars
It's rather interesting how the word battery came to mean chemical storage of
electricity, since the original meaning of the word has to do with beating.
(For example with military weapons, or with a hammer to make forged metal.)

~~~
archgoon
Military weapons are indeed likely the source of the term 'battery'. Ben
Franklin coined the term in reference to arrays of Leyden jars. Presumably,
this was for experiments where he would 'load' the capacitors, and then
quickly 'fire' (discharge) them, resulting in a spark of some kind (which
probably is what led him to suspect that lightning was electrical in nature).

<http://www.etymonline.com/index.php?term=battery>

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mbateman
original story: [http://cen.acs.org/articles/90/web/2012/02/Battery-
Desalinat...](http://cen.acs.org/articles/90/web/2012/02/Battery-Desalinates-
Seawater.html)

actual paper if you have access:
<http://pubs.acs.org/doi/abs/10.1021/nl203889e>

~~~
voodoochilo
thnx.

------
ars
You may be interested to know that it takes energy to remove salt from water.

There are proposals to mix freshwater from the mouth of streams with seawater
and capture the energy released.

~~~
alephnil
> You may be interested to know that it takes energy to remove salt from
> water.

Yes, the osmotic pressure is similar to a head of about 240 meter. In practice
it will be less in practice (110-120m), but still significant.

> There are proposals to mix freshwater from the mouth of streams with
> seawater and capture the energy released.

Not only proposals, but there is a prototype in production on Norway that
opened in 2008.

<http://www.statkraft.com/energy-sources/osmotic-power/>

I think the problem for such power plants is to make the membranes efficient
enough, and given that they have problem to remove all salt in this "battery",
I guess that they have the same problem. For reverse osmosis I'm pretty sure
it is more efficient with lower gradient, so these techniques could be
combined.

Since osmotic power is better with larger salt gradients, a power plant that
use the gradient between the ocean and the Dead Sea would be perfect. The Dead
Sea sinks one meter per year because of excessive use of water for irrigation.
There is probably not the right political climate in the area to achieve such
things however.

~~~
ars
The dead sea idea is interesting. The political climate is fine actually -
Israel and Jordan have a pretty good relationship.

There are already plans to collect energy from the elevation drop - adding the
salinity change too could be pretty nice. This seems like a rare environmental
win - get free energy, and replenish the water level at the same time.

