Battery Turns Saltwater Into Drinking Water

An anonymous reader writes "German researchers have developed a battery that can remove sodium and chloride ions from seawater. In theory, their invention could be far more energy efficient than thermal desalination or reverse osmosis. This would cut the cost of using salt water for drinking or irrigation. It could also be used to make compact desalination systems for boats and life rafts, or crops. Each battery is made with manganese oxide nanorod electrodes, which absorb sodium when an electrical current passes through them. When the current is reversed, they dump the sodium ions out into waste water."

Comments

How much energy?

[CapOblivious2010]

Interesting, but how much energy does it take to run this thing? (they call it a 'battery', but I don't think it actually generates electricity). Many of the places that are short on fresh water are also short on electricity (especially "green" energy), so this may not be as helpful as it sounds.

Re:How much energy?

[Smallpond]

They call it a battery because it is a series of electrical cells. The term "battery" means the series arrangement; it comes from a military term for a series of guns. Generating electricity is the best-known use of an electrical battery, but isn't the definition.

Re:How much energy?

[jonadab]

Batteries don't generate energy. They store it, chemically. (Well, the ones we usually think of as "batteries" work chemically.)

Nonetheless, I don't know how they propose to be more energy efficient than a mirror-based distillation rig. Besides keeping the parabola aimed at the sun, which requires negligible energy, the main costs of running such a rig are keeping it supplied with water to distill and flushing it out with solvent once in a while to prevent salt buildup. (You can even use filtered seawater for the solvent.) The latter costs seem unavoidable for electrical-cell-based desalination, and the former is, as I said, negligible.

Of course, it only works in parts of the world that get a lot of sunshine, so for example it would be a non-starter in northern Ohio. (Not that we need desalination in Ohio. Most of our water management issues involve finding ways to get the water to drain away more efficiently so it doesn't flood our basements; that seems likely to be common in places that don't get enough sunshine to boil water with a parabolic mirror... but I suppose there could be exceptions.)

Re:How much energy?

[brusewitz]

Of course, it only works in parts of the world that get a lot of sunshine, so for example it would be a non-starter in northern Ohio.

I think the fact that Ohio is not near any source of saltwater would be the real non-starter.

Re:How much energy?

[Anonymous Coward]

A report reviewing some of the research as of 1980: Health Risks from Drinking Demineralised Water.

Low-mineral water markedly: 1.) increased diuresis (almost by 20%, on average), body water volume, and serum sodium concentrations, 2.) decreased serum potassium concentration, and 3.) increased the elimination of sodium, potassium, chloride, calcium and magnesium ions from the body.

Almost there!

[cashman73]

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%.”

Not sure what math they're using when 50% removal of ions is considered "de-salinated". I guess they're getting there, so by publishing this article, maybe they'll be able to snag some venture capital?

Hmm

[RenHoek]

Of course, (good) reverse osmosis cleans out a LOT more out of the water then just salt, e.g. bacteria, viruses.

Re:a total bust, not energy efficient at all

[TheRaven64]

I remember in the '90s the Innovations catalogue sold inflatable thermal desalination rafts. You inflated them and they floated on the sea concentrating sunlight on the surface like a greenhouse. The water evaporated and then condensed on the inside of the glass and trickled out into the edges. They produced about 2 pints of water per day and were intended to be kept on life rafts (they couldn't operate on them, but they could float beside them and work, as long as there was sunshine). I presume they haven't stopped existing in the last 15 years...