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Harvesting Power When Freshwater Meets Salty

samzenpus posted about a year ago | from the power-up dept.

Power 151

ckwu writes "As a way to generate renewable electricity, researchers have designed methods that harvest the energy released when fresh and saline water mix, such as when a river meets the sea. One such method is called pressure-retarded osmosis, where two streams of water, one saline and one fresh, meet in a cell divided by a semipermeable membrane. Osmosis drives the freshwater across the membrane to the saltier side, increasing the pressure in the saline solution. The system keeps this salty water pressurized and then releases the pressure to spin a turbine to generate electricity. Now a team at Yale University has created a prototype device that increases the power output of pressure-retarded osmosis by an order of magnitude. At a full-scale facility, the estimated cost of the electricity generated by such a system could be 20 to 30 cents per kWh, approaching the cost of other conventional renewable energy technologies."

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Cool (2)

CheezburgerBrown . (3417019) | about a year ago | (#45578965)

How well does it scale?

Re:Cool (2)

fisted (2295862) | about a year ago | (#45579199)

1. Make freshwater river
2. Make saltwater river
3. Connect at both ends
4. ???
5. Infinite Energy

Re:Cool (1)

perpenso (1613749) | about a year ago | (#45579965)

Why not just use the river to turn a turbine?

Re:Cool (0)

Anonymous Coward | about a year ago | (#45580313)

mgh.

Re:Cool (1)

Luckyo (1726890) | about a year ago | (#45580881)

Advantage of this is that you can do both. The energy in question here is not potential energy that is converted by convential hydro, but osmotic pressure (effectively chemical energy) from having large sources of fresh and saline water.

It's basically a new kind of hydro that uses a different energy source.

Re:Cool (2)

The Grim Reefer (1162755) | about a year ago | (#45580247)

That and how long does the membrane last, and does the system produce more energy in that time than it takes to produce the membrane? Either way, it's pretty cool.

I pay 11 cents per kWh (0, Troll)

Anonymous Coward | about a year ago | (#45578991)

Renewable is going nowhere until they're at parity.

No amount of greenwashing and tree hugging circlejerking will change the fundamental economics of this.

Re:I pay 11 cents per kWh (4, Insightful)

mcrbids (148650) | about a year ago | (#45579101)

Unless maybe we stop subsidizing fossil fuels?

Re:I pay 11 cents per kWh (1)

Iniamyen (2440798) | about a year ago | (#45579135)

He/she's making blanket statements as an industry insider would, and then applying logic from the point of view of an average consumer. So I'm pretty sure he/she's just trolling.

Re:I pay 11 cents per kWh (1, Informative)

cirby (2599) | about a year ago | (#45579227)

You should note that, despite what many believe, we don't really "subsidize" fossil fuels to any major degree. The majority of the "subsidies" people whine about are just plain old tax deductions - the same ones that other businesses get. The oil companies didn't even get those deductions for a long time, and people complained when they finally got to deduct for exploration and drilling expenses in the same way normal businesses deduct for operations.

There are a few real deductions they get, though - alternative energy research, for example. And, technically, the Strategic Petroleum Reserve counts (although that's just the government buying and storing oil in case of an emergency - and counts for about 2/3 of all actual subsidies). Compared to the size of the industry, it's tiny. Overall, the "subsidies" fossil fuels get don't affect the end-user price much - maybe a half-cent per kilowatt-hour in some markets.

Compare to the various alternative energy sources, which get massive subsidies - and are still three to five times as expensive.

Re:I pay 11 cents per kWh (4, Informative)

crioca (1394491) | about a year ago | (#45579445)

You should note that, despite what many believe, we don't really "subsidize" fossil fuels to any major degree. The majority of the "subsidies" people whine about are just plain old tax deductions - the same ones that other businesses get. The oil companies didn't even get those deductions for a long time, and people complained when they finally got to deduct for exploration and drilling expenses in the same way normal businesses deduct for operations.

Bullshit:

http://www.nei.org/corporatesite/media/filefolder/60_Years_of_Energy_Incentives_-_Analysis_of_Federal_Expenditures_for_Energy_Development_-_1950-2010.pdf [nei.org]

http://www.elistore.org/Data/products/d19_07.pdf [elistore.org]

Re:I pay 11 cents per kWh (3, Interesting)

kartaron (763480) | about a year ago | (#45579931)

If you actually read the first article it states the primary source of 'subsidy' is tax credits and limits on taxation for certain circumstances. From a 60 year total of around 800 billion, 47% is for direct tax benefits., 20% is for perceived imbalanced price controls and the costs of government oversight (ie the Nuclear regulating agency: NRC), 10% is (mostly to hydroelectric plants) for construction of Dams, access to shipping ports and operations of the Dept of Interior. Which leaves grants for operations of shipping, 6 billion, and R&D expenditures, 153 billion. Thats about 3 billion a year on average of actual subsidy. That is well in line with US government subsidy of other industries... like the 3 billion insurance program for small business loans, or 3 billion for 'improving teachers', or 4 billion for insurance against milk profit margins for farmers. etc, etc http://funding-programs.idilogic.aidpage.com/ [aidpage.com]

Re:I pay 11 cents per kWh (1)

gewalker (57809) | about a year ago | (#45580379)

The subsidy situation varies widely from country to country. Some countries do subsidize the oil price of oil to consumers, rather heavily in some cases.

Re:I pay 11 cents per kWh (1, Flamebait)

NatasRevol (731260) | about a year ago | (#45579581)

Let us know when alt energy gets 10s of billions of dollars in tax deductions.

Re:I pay 11 cents per kWh (1)

gewalker (57809) | about a year ago | (#45580301)

Well, considering you need large profits to make large tax deductions possible, this is not likely to be a large number for quite a while yet.

2009, $14B of taxpayer cash for fake green energy (0)

raymorris (2726007) | about a year ago | (#45580339)

Too late, that started in earnest in 2009.
So far, Obama has handed over $14 billion of your money and mine to "alternative energy" companies. Oil companies, like every all other companies, don't pay taxes on profits they don't make because they had expenses to pay. That's the majority of the "subsidies" the morons complain about - not being taxed on non-existent earnings. The solar and wind companies, on the other hand, get taxpayer cash delivered to them, often just before the CEO closes the company and retires with a wad of your money. It's gotten so bad that last year, most wind subsidies went to build windmills placed in locations with significantly below average wind. You're supposed to put windmills on hilltops, where it's windy. It makes no sense to put a windmill in a valley - unless you're building the windmill just to collect the government kickback, with no intention of producing usable electric power.

Re:2009, $14B of taxpayer cash for fake green ener (1)

gewalker (57809) | about a year ago | (#45580415)

I would agree, if those things could be labeled "tax deductions" as they are clearly not. You can call them tax policy I suppose. Tax deductions are only useful to offset profits -- you never make a profit, all the tax deductions in the the world do you no good.

Is this a sock puppet? (1, Troll)

Okian Warrior (537106) | about a year ago | (#45579765)

The original post:

You should note that, despite what many believe, we don't really "subsidize" fossil fuels to any major degree

The response:

Bullshit: [with references]

Is this an example of an industry shill?

I've been turning my attention to sock puppets and industry shills lately, the first question being: how can we tell the sock puppets from the regular folk?

Here is a well-formulated partisan post which is completely contrary to conventional wisdom, and is contrary to facts supported by references and evidence. It is trivially refuted by easily-found references. I expect it was "modded up" based on clarity and construction. It certainly *seems* like an informativie position by an expert in the field.

An actual expert in the field would not expect to gain esteem by posting something so easily refuted (they would expect it to be modded down immediately). I'm left to wonder what the original posted hopes to gain.

Any ideas?

Re:Is this a sock puppet? (0)

Anonymous Coward | about a year ago | (#45580235)

You left out the reply to the response, wherein an analysis of the so-named "[with-references]" tends to confirm the claim of the original post. That is, the fossil fuel industry is not particularly subsidized (in a way that many people would interpret the unqualified use of that term) any more so than many other industries.

So will you now redo your analysis in light of this? Perhaps expand it a little to wonder about a responder that leaves links implying strongly that they claim something that they possibly do not.

Then extend your analysis to your own post, in which your seemingly objective meta-analysis seems to have failed to perform even a very basic due-diligence. Motivated reasoning as an explanatory factor should be explored.

Re:Is this a sock puppet? (0)

Anonymous Coward | about a year ago | (#45580983)

I would guess he's a recipient, not the producer, of these politically useful "facts", simply because those are far more common. This is precisely the kind of thing you find in higher-class political media, an apparently authoritative support for a party sponsor's policies that sounds quite convincing to those who don't know better and don't check, mostly because they wish to be convinced. I don't know how we can tell if he's a liar or if he has been lied to.

Re:I pay 11 cents per kWh (1)

AK Marc (707885) | about a year ago | (#45579797)

Yes. And what's the cost of the oil to BP that BP pumps out of the ground in Alaska? Alaska gives it away for free, in exchange for services provided by BP (at least according to BP accounting). Yes, an outsider would comment about money changing hands, but BP's accounting indicates that the State of Alaska "gives" it billions of dollars of oil, for free.

clueless. oil pays ALL Alaska's expenses + more (1)

raymorris (2726007) | about a year ago | (#45580567)

Wow that's an impressive level of cluelessness.
Most of Alaska's government revenue is paid by oil companies. Individuals pay no tax in Alaska, but rather get a check from the oil fund. So not only does BP pay the state of Alaska, that payment ends up as cash in the hands of residents (along with also paying for all roads, police service, etc.)

Re:clueless. oil pays ALL Alaska's expenses + more (1)

AK Marc (707885) | about a year ago | (#45580757)

You are the one that's clueless. I note you didn't object to the facts in my post, but to the tone and implications. Try addressing the facts.

Oh, and we still have property tax to pay for things like police and local roads (and some towns have sales tax to help fund roads and police). But don't let facts interrupt your uninformed rant. Guess where I live. You might want to try first guessing what the AK in AK Marc stands for.

the fact that you don't know what production tax i (1)

raymorris (2726007) | about a year ago | (#45580809)

The facts in your post? The fact that you either don't know how to read a financial report or don't know what "oil and gas production tax" is?

Re:the fact that you don't know what production ta (1)

AK Marc (707885) | about a year ago | (#45580891)

BP claims the oil is free, a gift by the State of Alaska. That's a fact. Prove it wrong. Should be easy, if it's so wrong. But no, you just attack the messenger. Have you ever even been to Alaska?

your quote, you produce it, or see the annual repo (1)

raymorris (2726007) | about a year ago | (#45581179)

The first link in Google for "BP annual report" will show exactly what BP claims. See all those millions for oil and gas production tax? That's some of the money they are paying the government for the privilege of extracting the oil. See the other millions for land leases?

You are claiming that someone at BP, somewhere, some time, said something different. You're claiming they said that, feel free to back up your claim. You think I should prove that at no time in history did anyone at BP say anything that you could have misconstrued that way? If you want to play "prove the negative", okay - You posted on Slashdot that you enjoy humping large dogs. Prove you never said that.

Re:I pay 11 cents per kWh (0)

Anonymous Coward | about a year ago | (#45580011)

Even saying that deductions are not an issue, there is still the fact that it would be better to have the ability to produce our own power than having to buy from foreign interests. Yes, I am a proponent of not drilling in the states so that they can act as a proper reserve instead of a CD. Profits from reserves should go to the state (the owners on proxy from the citizens) and not the company that mines them.

At the time the subsidies made sense ... (0)

Anonymous Coward | about a year ago | (#45579523)

Unless maybe we stop subsidizing fossil fuels?

Another poster mentions that the subsidies were for exploration and drilling. I'll add that these subsidies were put into effect when oil prices were very low and it just wasn't profitable to explore for more oil, and the government wanted to increase production in the Gulf of Mexico. So at the time the subsidies made sense. The problem is that the subsidies had no sunset provision, for example phasing out as oil prices rise and exploration becomes profitable once more.

So other interesting info:
"Between 2007 and 2012, the oil and gas industry paid an effective tax rate of almost 45 percent ... Oil and natural gas companies posted a 7.3 percent profit margin ... Those figures translate to relatively unexceptional earnings overall according to experts, especially given the size of the industry as a whole and the high cost associated with energy exploration and production. Over the past five years, average net income in the oil and gas industry has averaged about 8 cents for every dollar of sales"
http://www.usnews.com/news/articles/2013/04/24/is-the-oil-industry-really-getting-a-sweet-deal-on-taxes [usnews.com]

Re:I pay 11 cents per kWh (1)

mtthwbrnd (1608651) | about a year ago | (#45581341)

In what way are they subsidized?

A few years (0)

Anonymous Coward | about a year ago | (#45579115)

Renewable is going nowhere until they're at parity.

No amount of greenwashing and tree hugging circlejerking will change the fundamental economics of this.

And in in a few years when demand outstrips supply yet again, the Europeans, Chinese, and every other country on Earth who actually developed these "tree hugging" energy sources will look down smuggly (rightfully so!) at us for our short sightedness.

And in the meantime, our economy will be severely hampered because of the inevitable higher costs of energy with plenty of outcry from the ingnorant masses of "Drill here; drill now!" or some such.

Right now, as long as oil stays above $80/barrel, the multinatinal oil firms are currently drilling in VERY deep water because that's where all the new oil is currently. After all of that is used up, there's no place to go for oil after that.

But beleive what you want. Those who know and are capable of anticipating would is probably going to happen in several years will plan accordingly.

I plan on buying a nice big wind powered (sail boat) with the results of my planning and live in the Carribean.

Re:A few years (0)

Anonymous Coward | about a year ago | (#45579239)

...and by renewable you mean coal and gas mining? That's a laugh

You know what will happen? Fossil fuels will gradually get more and more expensive to the point that tips the scales on other sources, things will just shift. The same thing happened before with whale oil.

I mean how many mother fuckers were driving hybrids before gas prices started soaring, the fact that I can say "hybrid" and you know I'm talking about an automobile says something, 15 years ago it wasn't a thing people would take seriously (who killed the electric car indeed!)

But no it's more fun to fantasize about some weird resource cliff that will never exist.

Kindly take your smug air of superiority and stuff it.

Re:A few years (1)

Anonymous Coward | about a year ago | (#45579915)

The hybrids are powered by electricity generated from coal and natural gas, and will remain so for decades. Renewables are the future but decades of research and engineering are still needed. You may desperately wish otherwise but this is reality.

Re:A few years (1)

MightyYar (622222) | about a year ago | (#45580469)

Most of the hybrids are powered by gasoline.

Re:I pay 11 cents per kWh (5, Insightful)

Tumbleweed (3706) | about a year ago | (#45579153)

Renewable is going nowhere until they're at parity.

No amount of greenwashing and tree hugging circlejerking will change the fundamental economics of this.

The problem here is you're not comparing apples to apples. The 'cost' of fossil fuels doesn't include environmental cleanup that isn't necessary with renewables. It also doesn't take into account the real cost - when you take out all the tax incentives for fossil fuels, the math becomes quite different.

Also, the cost of fossil fuels will continue to go up due to environmental laws and more difficult to process sources (like tar sands), fighting unnecessary wars to secure foreign oil sources; meanwhile, while the cost of renewable technology keeps going down.

Re:I pay 11 cents per kWh (0)

Anonymous Coward | about a year ago | (#45579973)

I pay 8 cents per kWh.
Tar sands aren't going to get more difficult to process, they're already doing it for under $60 a barrel. There is a ton of the stuff in Alberta and Saskatchewan that will get taken out of the ground, and if anything the price per barrel will be going down as places like Fort Mac are better able to cope with the influx of people.

Re:I pay 11 cents per kWh (1)

Tumbleweed (3706) | about a year ago | (#45579183)

Also, my (mostly) hydropower-sourced electricity here in Seattle is billed at 4.75 cents per kWh. :)

salmon (0)

Anonymous Coward | about a year ago | (#45579267)

Also, my (mostly) hydropower-sourced electricity here in Seattle is billed at 4.75 cents per kWh. :)

And how are the Salmon fishermen doing? (That was rhetorical: google "damns salmon pacific northwest fishermen" and have a read.) Wild Salmon (farmed salmon is shit: taste, "greeness" - it takes more pounds of wild caught fish than one pound of farmed salmon!) prices have increased significantly where I live.

My point is that ALL energy sources have some sort of environmental impact and why it is of utmost importance to have a portfolio of different sources.

Re:I pay 11 cents per kWh (1)

ShanghaiBill (739463) | about a year ago | (#45579631)

Also, my (mostly) hydropower-sourced electricity here in Seattle is billed at 4.75 cents per kWh. :)

So then don't build this osmosis generator in Seattle. Meanwhile, in Hawaii, where every ounce of fossil fuel is imported, electricity costs about 40 cents/kwhr. This could make a lot of sense there.

Re:I pay 11 cents per kWh (0)

Anonymous Coward | about a year ago | (#45579925)

Also, my (mostly) hydropower-sourced electricity here in Seattle is billed at 4.75 cents per kWh. :)

So then don't build this osmosis generator in Seattle. Meanwhile, in Hawaii, where every ounce of fossil fuel is imported, electricity costs about 40 cents/kwhr. This could make a lot of sense there.

Probably not. There are not a lot or rivers running into the ocean. Its more freshwater percolating throughout the ground and seeping into the ocean. The seeping is quite visible in many areas.

Re:I pay 11 cents per kWh (1)

MightyYar (622222) | about a year ago | (#45580495)

I bet there are some sewage treatment plants pumping millions of gallons of fresh water into the sea, though.

Re:I pay 11 cents per kWh (0)

Anonymous Coward | about a year ago | (#45579777)

Bet on Natural Gas!

Re:I pay 11 cents per kWh (1)

MaskedSlacker (911878) | about a year ago | (#45580325)

I pay 44 cents per kWh, so...

Re:I pay 11 cents per kWh (1)

Luckyo (1726890) | about a year ago | (#45580887)

If this statement was true, we'd still be using things like freon in our fridges and so on.

Reality is that "green" option doesn't need to be as good. It just needs to be good enough.

not PC (0)

Anonymous Coward | about a year ago | (#45579003)

instead of 'pressure-retarded' should have read 'pressure challenged'

Re:not PC (0)

Anonymous Coward | about a year ago | (#45579111)

That's retarded.

Re:not PC (0)

Anonymous Coward | about a year ago | (#45579213)

Challenge accepted.

waste of time (1)

Anonymous Coward | about a year ago | (#45579025)

The energy density of this system is crap, plus it has all the problems of water fouling and so maintenance will be a pain. IMO, we should focus our efforts on developing cheap organic photovoltaics, and then paving the desert with them. We need more government funding injected into fundamental materials research. Disclaimer: although I don't pursue this line of research I am a researcher!

Re:waste of time (0, Flamebait)

Anonymous Coward | about a year ago | (#45579461)

Ok, what do you research? Barbie doll fashion trends? Or alternative semiconductor materials?

Re:waste of time (0)

Anonymous Coward | about a year ago | (#45580355)

I suspect it's newspaper clippings.

Big problem here... (4, Informative)

Andy Dodd (701) | about a year ago | (#45579031)

It requires saline that is MUCH more concentrated than seawater... So you need to somehow concentrate the saltwater before using it.

Although this might allow for some rather unconventional solar power projects - feeding brine from salt concentration ponds might be workable here.

Re:Big problem here... (4, Insightful)

Acapulco (1289274) | about a year ago | (#45579087)

I know this will probably cause a host of issues that I'm not thinking here, but the (to me) most obvious solution would be to pair this with a de-salinization plant. What if instead of de-salinizing all the water they stop at X% of water remaining in the solution, and then use that super-concentraded saline water with the power generation plant.

Re:Big problem here... (1)

Anonymous Coward | about a year ago | (#45579147)

but the (to me) most obvious solution would be to pair this with a de-salinization plant.

I think that would be the worst thing, trying to extract energy from a process on the one hand that you are using energy to reverse in the other. I think people are so often overlooking the importance of clean water in the search for energy - for example, corn for ethanol, and this as well...

Re:Big problem here... (1)

dominux (731134) | about a year ago | (#45579223)

If you have a river then you probably don't require a desalinisation plant. It is just about plausible that concentrated saline from a desalinisation plant could be transported to a distant river (by boat) where it would be used for power generation like this.

Re:Big problem here... (2)

viperidaenz (2515578) | about a year ago | (#45579465)

If it's concentrated enough, why can't you use sea water as "fresh", since it is powered by the difference in salinity, not the absolute value.

Re:Big problem here... (4, Informative)

ShanghaiBill (739463) | about a year ago | (#45580007)

If it's concentrated enough, why can't you use sea water as "fresh", since it is powered by the difference in salinity, not the absolute value.

Research has been done [rsc.org] on this, and I believe that a pilot plant may be built in the UAE or Oman in the next few years. It will use brine, concentrated in solar ponds, as the source of NaCl, and plain seawater as the sink.

Re:Big problem here... (1)

perpenso (1613749) | about a year ago | (#45579957)

If you have a river then you probably don't require a desalinisation plant.

If you have a river you probably don't require a pressure-retarded osmosis power generating plant, just using the kinetic energy of the river to turn turbines.

Re:Big problem here... (0)

Anonymous Coward | about a year ago | (#45580471)

Most rivers have little to no potential or kinetic energy. If you can build a dam in a delta you'd obviously do that.

Re:Big problem here... (0)

Anonymous Coward | about a year ago | (#45580745)

If you have a river then you probably don't require a desalinisation plant.

If you have a river you probably don't require a pressure-retarded osmosis power generating plant, just using the kinetic energy of the river to turn turbines.

Not if the river drops a whopping 3 feet from its source to its mouth over its 150-mile course. Plus, Florida's St. Johns River is heavily navigated. Among other things, by oil barges heading towards the power plants near Orlando.

Then again, I don't know where you could stretch an osmotic barrier there either.

Re:Big problem here... (0)

Anonymous Coward | about a year ago | (#45579283)

I don't see where it would necessarily have to be clean water, just less salty water. So you have salt water coming in, fresh water is removed from it and the brine then goes past another salt water intake to produce energy. So instead of just dumping the brine, you also get energy out of it.

Re:Big problem here... (0)

Anonymous Coward | about a year ago | (#45579305)

I know this will probably cause a host of issues that I'm not thinking here, but the (to me) most obvious solution would be to pair this with a de-salinization plant. What if instead of de-salinizing all the water they stop at X% of water remaining in the solution, and then use that super-concentraded saline water with the power generation plant.

You must be one of those people who thinks that you can use electricity from your car battery to perform hydrolysis on water to get hydrogen to burn in your engine to improve fuel economy.

Re:Big problem here... (1)

blackraven14250 (902843) | about a year ago | (#45579955)

It's not free energy (which is what you're thinking), it's using the brine from the desalination plant, which is normally considered waste, as the saline part of this type of plant.

Re:Big problem here... (4, Insightful)

Dahamma (304068) | about a year ago | (#45580371)

No, more like using electricity generated from your brakes to charge your battery and improve fuel economy. What a concept!

Re:Big problem here... (2)

bobbied (2522392) | about a year ago | (#45579317)

I know this will probably cause a host of issues that I'm not thinking here, but the (to me) most obvious solution would be to pair this with a de-salinization plant.

Well if the process requires fresh water, why would you have a desalinization plant? Wouldn't it be easier to just treat the fresh water?

Re:Big problem here... (1)

rrohbeck (944847) | about a year ago | (#45579507)

Sounds like a perpetual motion device to me.
Oblig.: In this house we obey the laws of thermodynamics!

Re:Big problem here... (1)

Dahamma (304068) | about a year ago | (#45580349)

No more than regenerative braking. Better to reuse the potential generated by desalinization than just dump the brine back into the ocean like most plants do today.

It's all about energy efficiency, and desalinization is basically just charging a big chemical battery. Why waste it?

Re:Big problem here... (1)

rrohbeck (944847) | about a year ago | (#45580843)

No, the desalination will require more energy than you get out of this method. Conversely, if you have freshwater, why use desalination?

Re:Big problem here... (3, Informative)

AcidPenguin9873 (911493) | about a year ago | (#45580927)

Yes, desalination obviously requires more energy than you get out of this method. But the point of the desalination is not energy production, it's freshwater production. You get freshwater out of your desalination plant. That requires using some amount of energy X. Instead of dumping the waste product of the desalination plant (highly-concentrated brine) somewhere, you use it with one of these devices to produce some amount of energy Y where Y is less than X.

The net result is that you end up with freshwater, and instead of spending X energy to get it, you had to spend only (X - Y) energy.

Re:Big problem here... (1)

rrohbeck (944847) | about a year ago | (#45581089)

Instead of dumping the waste product of the desalination plant (highly-concentrated brine) somewhere, you use it with one of these devices

... for which you need freshwater.

Re:Big problem here... (1)

AcidPenguin9873 (911493) | about a year ago | (#45581297)

Nope. Osmosis operates off a relative concentration difference. Regular ocean saltwater is much more dilute than brine and would work just fine as the "freshwater" side of this power generator.

Re:Big problem here... (1)

rrohbeck (944847) | about a year ago | (#45581367)

You'll still lose enery on the round trip. Your overall energy consumption would be lower if you ran your desal plant at a lower power level and produced less briny output than producing very briny output, diluting it and producing energy from that.

Re:Big problem here... (1)

AcidPenguin9873 (911493) | about a year ago | (#45581397)

Pick a "brininess" and energy consumption you want to run at. By definition, the brine produced will be more concentrated than the ocean water flowing into your plant. Run the more-concentrated brine and less-concentrated ocean water through this power system and produce whatever energy you can get from it. It will always be less than the energy that you used to produce the freshwater+brine, but it will always be more than 0 which is what you get if you dump the brine back into the ocean. How you want to slide the bars in terms of brininess and energy consumption is up to you. But either way, you're ahead with this system. Get it?

Re:Big problem here... (1)

Dahamma (304068) | about a year ago | (#45581401)

No, you just need sea water with less salinity than the brine. The potential energy is in the DIFFERENCE, of course.

And it can in fact use less energy, chemicals, etc to desalinate relatively clean seawater over more polluted river water. New York is investigating this now.

Speaking of perpetual motion (0)

Anonymous Coward | about a year ago | (#45581263)

Back in middle school I heard that lasers were 8000x brighter than the sun, so I made these magnificent plans to acquire a laser and a small solar cell, and then let the laser's 8000x brightness dominate the area ratio so it would yield more output than input. I was totally convinced that this would work, and that it would solve the world's energy problems. After months of dreaming I finally told my science teacher, and she said "no, that won't work" without even hesitating. Dreams crushed.

Sigh.

I've still never owned a laser, but some day I will test my theory!!!11

Re:Big problem here... (1)

BitterOak (537666) | about a year ago | (#45579945)

Interesting. You were modded +4 Insightful for suggesting that we power a desalinization plant by mixing fresh water with salt water. Slashdot really does manage to surprise me every day.

Re:Big problem here... (2)

Dahamma (304068) | about a year ago | (#45580331)

Well, if you think about it a bit more, it's the *difference* in salinity that matters. Desalinization is basically creating an osmotic potential, just like in a chemical battery. You could then use that hypersalinated water (aka brine) with regular sea water as described to extract the energy back, rather than just dumping it back into the ocean (which is what normally happens). Or you could use the hypersalinated water with river water to make the technique more efficient (foreshadowing, here...)

In fact, desalinization plants are often combined with power plants because they can use the waste heat from the power plant for thermal desalinization. In this case, it could make sense to supplement the power plant with this "pressure-retarded osmosis" technique. Especially - and this is the whole point of the article - if someone can make that technique more efficient, which the researchers DID by using hypersalinated water!

So, it turns out that combining pressure-retarded osmosis power generation with desalinization is not only interesting/insightful, it's an active topic of research - go look it up. Here's an interesting presentation to start with: http://www.caldesal.org/downloads/pdfs/Amy%20ChildressCal%20Desal%2010-13.pdf [caldesal.org]

Hopefully Slashdot surprised you again today :)

Re:Big problem here... (1)

d'baba (1134261) | about a year ago | (#45580281)

Desal is a big thing here on the left coast. Propose projects up and down the coast because ground water and surface water are being oversubscribed. It won't run the desal process but it should at least be looked at to see if using the concentrated saline could give us a little in return. It's in the same category as regenerative braking in e-cars. Every little bit helps.

Re:Big problem here... (2)

ganv (881057) | about a year ago | (#45580725)

No, you already input energy to separate the water and the salt. Remixing them will release part of the energy which could be harnessed, but inevitable losses in conversion will make it better to just use your original energy if you didn't need the fresh water. One nice thing about this article is that they explicitly state the most important point...that it is impractical to use this method in the only context where it would have potential for significant impact which is in the mixing of fresh water rivers with ocean water.

Re:Big problem here... (0)

Anonymous Coward | about a year ago | (#45579275)

"Now a team at Yale University has created a prototype device that increases the power output of pressure-retarded osmosis by an order of magnitude"

So there you go, pressure-retard.

Re:Big problem here... (0)

Anonymous Coward | about a year ago | (#45579399)

While that's a problem, the real issue is the cost. Asking people to pay more for electricity when we have cheap natural gas and nuclear power available and working already. We have already solved our energy problems, we just refuse to take the next step to reduce coal power.

Re:Big problem here... (1)

Luckyo (1726890) | about a year ago | (#45580897)

As I understand it, this is a project for power plant located at the point where river meets an ocean. You have ocean level salinity meeting fresh water, all available in one place.

Parsing the summary (3, Insightful)

Idarubicin (579475) | about a year ago | (#45579155)

At a full-scale facility...

So, we're guessing about imagined economies of scale that may or may not, hypothetically speaking, materialize, in the best-case scenario of a fully-developed, mature technology, probably some decades hence.

...the estimated cost of the electricity generated by such a system could be 20 to 30 cents per kWh...

Our wild-assed guess ranges over a factor of 1.5 anyway.

...approaching the cost of other conventional renewable energy technologies.

"Approaching", in this instance, meaning "costing twice as much as" pholtovoltaic systems, which already sit at the expensive end of the renewable spectrum.

Also known as an "estuary" (1)

Anonymous Coward | about a year ago | (#45579187)

Where salt meets fresh is often an estuary. These are unique and productive habitats. Even traditional political opponents have come together to save these environments in certain cases--the green coalition from the Democrats and duck-hunting and fishing Republicans don't want these places ruined.

Tread lightly on this. The loss may be greater than what's gained.

Continuous Flow (3, Insightful)

yanom (2512780) | about a year ago | (#45579201)

It's worth noting that this would have something most other renewables (solar, wind, ... ) lack - a power output that is more or less constant day and night.

Re:Continuous Flow (1)

Anonymous Coward | about a year ago | (#45579987)

I'm pretty sure hydro works day and night, and is the most used renewable on earth.

Wow, only 2.5-4 times what I pay now! (0)

Anonymous Coward | about a year ago | (#45579403)

At a full-scale facility, the estimated cost of the electricity generated by such a system could be 20 to 30 cents per kWh, approaching the cost of other conventional renewable energy technologies."

20-30 cents per kWh? I currently pay a little more than 8 cents per kWh - which is pretty typical in the U.S., outside of California, Florida, Hawaii, and the NE states.

Re:Wow, only 2.5-4 times what I pay now! (0)

Anonymous Coward | about a year ago | (#45580467)

In New Zealand, we pay around around 23 cents per kWh. It used to be a lot lower, but the market was deregulated to promote competition and price decrease. Unfortunately, as expected by the majority of the population, the prices increased. Hell, a few years ago there was a massive backlash against (I think it was) Contact Energy, as the CEO put the prices of power up significantly, and then got a large bonus of approximately the same as the price increase would generate. They lost millions of dollars, and many customers, over that one...

Can I carry it in a tank? (1)

Mister Liberty (769145) | about a year ago | (#45579533)

If not: problem! Lose lose.

Antarctica (0)

Anonymous Coward | about a year ago | (#45579729)

Since we're melting the whole continent down there, let's ring the whole place with these. That should provide the whole world with power until the process is over in a hundred years or so.

Bad news for Mangroves (1, Insightful)

tp1024 (2409684) | about a year ago | (#45579769)

The only thing they will do is to remove zones of brackish water from the environment, that are usually highly prized by greenies as having high biodiversity and such stuff. Of course this is all swept to the wayside once you can make "green energy" out of all this green stuff. You'll even find conspiracy theories thrown out by eco-nuts blaming "big oil" for preventing such "innovative alternative technology" from coming to market. If that should happen, very soon they will have an epiphany, realize that in fact those osmotic power plants destroy important ecological niches ... and by this point, of course, osmotic power plants are run by "big energy" without any respect for the environment. And of course, everybody in the green movement has always been against such a stupid idea.

How far fetched is this scenario ... look no farther than bio-ethanol.

Re:Bad news for Mangroves (0)

Anonymous Coward | about a year ago | (#45581029)

Wow, a strawman AND a conspiracy theory wrapped up in one. Nice!

Summary (1)

The Cat (19816) | about a year ago | (#45579775)

It'll never work it doesn't scale science is my religion thermodynamics cat meme Mythbusters everyone who worked on this is stupid internal combustion is the pinnacle of energy science neckbearding is my religion I know more than rooms full of PhDs everything sucks meh minecraft the graphics suck I want to be entertained for free I will never have a girlfriend I'm a programmer because I know some javascript oil is the only energy source everyone is wrong but me let's all lather up and have a big atheist circlejerk. /thread

Cheaper than renewables how? (1)

WillAffleckUW (858324) | about a year ago | (#45579875)

If fossil fuels paid the true cost, according to the methods described by Adam Smith, the Father of Capitalism, which include the removal of mercantilist tax subsidies such as cheap extraction leases and no cost for pollution, then it might be competitive.

But we have artificial trade barriers in the use of subsidies and exemptions for fossil fuels that drive down the cost of fossil fuels. Things like free naval shipping lane protection by the US navy and air force given to China without cost.

Fix the source problem first.

What makes it better than hydro electricity (1)

vux984 (928602) | about a year ago | (#45580061)

As per the subject, What makes it better than hydro electricity? Hydro is great, is clean, is renewal; really the only downside the ecological destruction associated with damming up the rivers.

I speculate that this new solution is going to have all the same issues as hydro does, at scale. If not, why not? I see a 'membrane' across the mouth of the river, i see turbines, I see "environmentalists protesting that the fish hatchery is being disrupted..."

Re:What makes it better than hydro electricity (2)

gewalker (57809) | about a year ago | (#45580367)

You missed the biggest downside of hydro power. Most of the viable hydro power is already being used. There is a good reason for that -- hydro power is the low-hanging fruit of power generation, so naturally we used it when it was available. Yes, there is some hydro not being used - small basins. The total is quite small compared the the amount we use. Lots of hydro power is not used in base load conditions, it is more valuable for peak production due to it fast ramp-up and the fact that the total water available for power generation is less than needed to run the hydro plant at full load 24x7

You don't want to dam the Mississippi for good reasons, so this "hydro power source" will never been used effectively -- damming is by far the most efficient way to extra power from rivers. So, you can't count these solutions as viable.

hydro is great - for three spots per continent (1)

raymorris (2726007) | about a year ago | (#45581433)

Hydro is great, if you happen to have a gigantic dam handy holding back a huge lake before the water falls hundreds of feet. In North America, that means Hoover Dam, Niagra Falls and a couple others. For the other 99.9% of the population, you need another solution. Texas, for example, is the second largest state and I don't think there are any hydro falls anywhere in Texas. I live 120 miles from the coast and my elevation is about 60 feet. You're not going to get hydro power from the river here.

Capt. Nemo (1)

Gothmolly (148874) | about a year ago | (#45580107)

"I use salt from the sea to charge special batteries that I've made."

Another application - Make potable water (0)

Anonymous Coward | about a year ago | (#45580121)

Another application for the energy produced by such a plant could be to power a desalination process.

So you take 1000 litres of non-potable water flowing out of some river mouth. It could be downstream from some city and, potentially, dirty as hell. Run it through one of these PRO plants and generate the energy (electrical or pressure) to power a seawater desalination plant. The brine from the desal plant can then be back-fed into the PRO plant to increase/sustain output.

So what if you only get 100 litres of potable water, or even just 10, as output. If you have megalitres (or gigalitres) of water flowing out the river, just scale up. One of the biggest downsides to desal plants is their electricity usage. It should be possible to design a PRO+desal plant that is totally off-grid. ...and as a previous poster has said, the plant runs 24/7.

pressure-retarded osmosis (0)

Anonymous Coward | about a year ago | (#45580387)

The preferred term is pressure-learning-disabled osmosis.

Pressure-retarded (-1)

Anonymous Coward | about a year ago | (#45581331)

They prefer to be called pressure-disable - you insensitive clod!

Not a particularly good idea (0)

Anonymous Coward | about a year ago | (#45581369)

This process turns fresh water (a rapidly declining resource) into salt-water (an abundant resource)
The world doesn't need more salt water.

Sounds like a gay nigger faggot came up with this one!

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