New Rechargeable Battery Uses Water

fergus07 writes "Scientists at Stanford have developed a battery that uses nanotechnology to create electricity from the difference in salt content between fresh water and sea water. The researchers hope to use the technology to create power plants where fresh-water rivers flow into the ocean. The new 'mixing entropy' battery alternately immerses its electrodes in river water and sea water to produce the electrical power."

Comments

Just think of the possibilities!

[naich]

We could use the generated electricity to power desalinisation plants.

Re:Just think of the possibilities!

[ShanghaiBill]

We could use the generated electricity to power desalinisation plants.

I think you are trying to be funny, but this actually makes sense, and there are proposals to do exactly this. Here is how it works:

• Step 1: Concentrate brine in large evaporation ponds
• Step 2: Generate electricity from the osmotic difference between this brine and normal seawater
• Step 3: Use the electricity to split seawater into fresh water and brine
• Step 4: Recycle the brine back into the evaporation ponds
• Step 5: Profit!

The reason this works is that you are effectively collecting the solar energy that shines on the evaporation ponds.

Isn't this already in practice elsewhere???

[dr.Flake]

I know the plans to put one of these into service are almost finalized in The Netherlands, spanning the "afsluitdijk"
http://wikimobi.nl/wiki/index.php?title=Zoet/zout_watergrens

But i think the Norwegians beat us all to it:

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

Re:Isn't this already in practice elsewhere???

[wjousts]

...spanning the "afsluitdijk".

Cat just jump on your keyboard?

Re:Great News for Environment!

[MadKeithV]

Toyota already did with their Prius. I think the official term is "smug".

Re:ALready an energy shortage there.

[gr8_phk]

I think he's talking about taking water and sending it to Arizona where it then evaporates in the desert and doesn't actually make it to the end of the river. I'm guessing of course. But as for these "inexhaustible" supplies under ground, you should read about the supply in the midwest which requires drilling to new depths because it is being depleted. Should you think going deeper is always an option, you may want to read the recent stuff of fracking to see how the deeper water is being deliberately contaminated. There are solutions to these, problems, but what we are doing vs what we could be doing don't really match.

As always, it's a scale problem.

[tacokill]

So, 13,000 gallons per second of fresh water flow and we can get around 100MW. Let's go on a math exercise, shall we?

The average combined cycle plant is (at a minimum) around 400MW. Not including co-gens, etc. Just normal power plants sitting out in the middle of nowhere. Fukishima is around 4900MW. Fukishima isn't really fair because it is, by any measure, a large nuke plant. But, 400-1200MW is not an unreasonable range for "typical" power plants in the US, regardless of the technology used (coal, nuke, combined cycle, direct fire, etc)

At 400MW, you are talking 52,000 gallons PER SECOND of water flow. That, by any measure, is a shitload of flow. At 1200MW, we are talking 156,000 gallons per second.

For comparison, I just looked up the flow rate of the Mississippi river at the high water dam near Lake Itasca. Going thru the Upper St Anthony's falls lock and dam, the flow rate is around 90,000 gal/sec.

So for ONE reasonably sized power plant, you would need fresh water flow that is the equivalent of the Mississippi River.

As I said, it's a scale problem.