Harvesting Power When Freshwater Meets Salty 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."
Cool (Score:2)
How well does it scale?
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1. Make freshwater river
2. Make saltwater river
3. Connect at both ends
4. ???
5. Infinite Energy
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I think you've misunderstood the article. It's more like:
And carry on from there.
Oh, and the energy isn't infinite ; it's going to be limited absolutely by the flow rate of the river and the salinity difference between the two water bodies. Which could be substantial (most people are so inconsiderate of the power of the sun to drive such th
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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.
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Why not just use the river to turn a turbine?
Typically in the coastal plains (where a river would meet with saltwater), a river will widen up and it's current slows to a crawl (due to the lack of a "downhill" presence).
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Why not just use the river to turn a turbine?
Typically in the coastal plains (where a river would meet with saltwater), a river will widen up and it's current slows to a crawl (due to the lack of a "downhill" presence).
Sure, but we can put water wheels, turbines or something other than a dam up river a bit. Or many along the river. We don't need to be in the mixing zone.
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That's fine if you're an island nation - as Britain is (currently) and the US is (largely). But generally it can be more complex.
I can't think of a realistic example in Britain (the Anglo-Scottish border fairly closely follows a break of slope). But as I struggle to remember the details of my North American geography I think of the routine flooding in North Dakota (?) due to the low slope of the Red River (?). Say that
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waste of time (Score:1)
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!
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Valid points. Are you sure you intended to post as an AC?
If you've got large fresh-water (or even brackish water ; the system will work, but the energy density will be even crappier) rivers, then there's a good chance that you don't have lots of desert to pave.
Just because
Big problem here... (Score:5, Informative)
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... (Score:5, Insightful)
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.
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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...
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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.
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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... (Score:5, Informative)
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.
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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.
Don't need a dam for turbines ... (Score:2)
Most rivers have little to no potential or kinetic energy. If you can build a dam in a delta you'd obviously do that.
You do not need a dam to harvest the kinetic energy of a river. Think of an old fashioned water wheel turned by small rivers and large streams. Or turbines submerged into a large river, as they are experimenting with in New York City.
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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?
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As I understand it, it doesn't require fresh water, per se. It requires a large difference in salinity. So, technically, you could use discharge brine from a desalinating plant as the "saline" part, and regular sea water as the "fresh" part, as long as the difference in salinity is enough.
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Yeah, or you could use your brain for half a second for something besides sarcasm. Consider:
It takes X watts of power to desalinate 1000g of fresh water
In desalinating 1000g of fresh water, you get enough brine suitable for generating Y watts of power, where X > Y.
So, would you rather have 1000g of water, or 1000g of water + Y watts of power? And is X - Y watts of net power used better than X watts of power used, where Y > 0?
Is regenerative braking on an electric vehicle also perpetual motion in you
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Sounds like a perpetual motion device to me.
Oblig.: In this house we obey the laws of thermodynamics!
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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?
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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... (Score:4, Informative)
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.
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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.
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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.
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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 t
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Obviously you'll lose power on every round trip, it's not a perpetual motion machine any more than an electric car with regenerative brakes. The point is to use the energy you put in more efficiently, not make it self-sustaining.
Also, part of the advantage to this is that power plants are *already* commonly paired with desalination plants because thermal desalination can use the waste heat generated during power generation. This would effectively be an additional component to a traditional power/desal pla
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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.
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Someone, several someones, seems to think that desalination plants produce highly concentrated brine. They don't. It's only a few percent more concentrated. Say that you take 2m^3 seawater (35) into your plant and discharge 1m^3 of fresh water (essentially 0) and 1m^3 of "concentrate", what is the solute concentration in the concentrate?
Answer : 70 Which is still not terribly concentrated.
One of the const
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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 fac
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So turning waste from an activity you're already doing into energy is somehow not more energy than you were getting by just pumping it out a long pipe into the sea?
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Re:Big problem here... (Score:5, Insightful)
No, more like using electricity generated from your brakes to charge your battery and improve fuel economy. What a concept!
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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.
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You didn't RTFA - this new "breakthrough" depends on the availability of brine that is significantly more concentrated than the ocean.
Basically this "breakthrough" provides zero benefit compared to existing technology when used for ocean water.
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Actually, you didn't understand it. They are pushing to solve the solution where pressure building up in the membrane breaks it, and the higher the pressure, the more efficient the system becomes.
So while the plant is designed, according to TFA
"They have designed methods that harvest the energy released when fresh and saline water mix, such as when a river meets the sea."
They tested it out with salinity up to five times that of sea water to stress test the membrane and see if the pressure will break it (the
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No it doesn't ; it requires two fluids of differing concentration of a solute.
I think you need to go back to your sophomore year chemistry notes and revise osmosis.
Parsing the summary (Score:4, Insightful)
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" (Score:1)
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 (Score:4, Insightful)
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I'm pretty sure hydro works day and night, and is the most used renewable on earth.
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Sure, but that's not really what you want. Far from it. You want output that follows the consumption. Many existing hydro plants can do this by virtue of the storage in the dam.
On a related note, cost/kWh figures can be deceptive. For instance, say the cost is 0,20 USD/kWh 24/7. That's great - except at night consumption is low so you may not be able to sell the energy, or will have to sell at a much reduced price; you can still do that if the marginal costs of keeping the plan running are lower than compet
Can I carry it in a tank? (Score:2)
If not: problem! Lose lose.
Bad news for Mangroves (Score:2, Insightful)
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
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Wow, this potential "Greenie" evil you are talking about sure is diabolical. People who want clean air, water and land sure are mean and evil.
Let's stick to REAL examples on what bad people do -- it's not like the world has run out of bad decisions, good intentions going wrong, or inefficiency. You are just being too lazy to prove your point.
Now unleash the hypothetical hounds to defeat the mythical tigers!
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How far fetched is this scenario ... look no farther than bio-ethanol.
Ethanol, made primarily from corn is pushed by ADM, Monsanto and some other corn producers. They make more money when corn is used -- go figure! There are various "greenie" organizations who have called it wasteful and not particularly green. Perhaps the MEDIA driven by the big pockets of corporations failed to mention the controversy around ethanol.
Of course, I could spend 2 seconds to verify this claim; http://green.autoblog.com/2013/02 [autoblog.com]
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Thank you for illustrating my point with a real life example.
I'm pretty sure I was just hallucinating webpages like these:
http://edugreen.teri.res.in/explore/renew/biomass.htm [teri.res.in]
http://www.seai.ie/Archive1/Files_Misc/REIOBiomassFactsheet.pdf [www.seai.ie]
http://www.ratical.org/renewables/biomass.html [ratical.org]
http://www.biofuels.fsnet.co.uk/challenge.htm [fsnet.co.uk] ["The author of this paper, following a long-standing interest in renewable energy, obtained a small Sustainable Communities Award from the Millennium Commission in 1998 to study the
Cheaper than renewables how? (Score:1)
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
What makes it better than hydro electricity (Score:2)
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..."
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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 ava
hydro is great - for three spots per continent (Score:2)
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.
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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.
Gee, that's too bad, since Bonneville Dam [wikipedia.org] is at 70 feet of elevation and 146 river miles from the Pacific, and generates 1200 MW.
Granted, the Columbia isn't the average river, but elevation and distance from the ocean are only a couple of values that matter.
At bottom of the gorge, surroundings are 1000 feet (Score:2)
The area around Bonneville Dam has an elevation of around 600-1,600 feet. Bonneville Dam itself is 197 feet high.
Since the land around it is about 1,000 feet elevation, the water is easily contained.
> but elevation and distance from the ocean are only a couple of values that matter
Elevation controls. If the elevation isn't high enough, you can't build a high dam, period.
Filling a 197 foot reservoir in central Texas would require flooding the gulf coast up through the entire eastern seaboard, north to N
Capt. Nemo (Score:2)
"I use salt from the sea to charge special batteries that I've made."
So how much power can we realistically expect? (Score:3, Informative)
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with a water usage of 10 litres of fresh water and 20 litres of salt water per second
That's the flow from a good fire hose.
B.t.w, this plant uses PRO or Pressure Retarded Osmosis, not Reverse Osmosis.
In the Netherlands alone, more than 3,300 m fresh water runs into the sea per second on average, that would deliver in excess of 1MW.
In 2005 we had an experimental plant near Harlingen with an output of 5kW.
Dutch research is especially looking at Reverse Electrolysis.
Freshwater Meets Salty (Score:2)
He's a straight-laced by-the-book detective straight out of the academy.
He's a grizzled fisherman from the wrong side of the docks.
Freshwater and Salty - Wednesday at 7, 8 central, on CBS.
Oh good (Score:2)
Environmental Impact? (Score:2)
Estuaries tend to have interesting ecosystems associated with them--Everglades, mangroves, etc that are also important in hurricane protection, among other things. What's the likely environmental impact of building these sorts of power plants?
Re:I pay 11 cents per kWh (Score:5, Insightful)
Unless maybe we stop subsidizing fossil fuels?
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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 - altern
Re:I pay 11 cents per kWh (Score:4, Informative)
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]
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Let us know when alt energy gets 10s of billions of dollars in tax deductions.
Is this a sock puppet? (Score:2, Troll)
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
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Or maybe it's just some guy on the internet who holds an opinion? Sometimes the opinion is unpopular and contrary to others. Sometimes it appears incorrect (depending on your evaluation of the facts). Sometimes, like many personal opinions, it isn't entirely unbiased.
It can happen, isn't illegal, and kind of the point of having the discussion.
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References are nice, they are helpful in doing further research but, they are not proof of anything. I can give you a link to the communist manifesto and claim that
Thanks for the post (Score:2)
Thank you for the well-reasoned response.
I'm now of the opinion that this isn't a sock-puppet post. I've reviewed the user's history and it doesn't seem especially partisan and it doesn't have other clues, such as infrequent posts or recent creation.
I'm still on the lookout for sock-puppetry. This is made more difficult by the automatic backlash from many readers, which you don't seem to have. I'm still wondering how to detect false opinions and other manipulation of the board - if you have any ideas, pleas
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clueless. oil pays ALL Alaska's expenses + more (Score:2)
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.)
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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 (Score:2)
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?
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your quote, you produce it, or see the annual repo (Score:2)
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 tha
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Alaska depends on oil taxes, royalties and fees (Score:2)
"Kelly, like many lawmakers, believes Alaska's tax structure discourages oil companies from finding and developing more crude. That impacts the state because Alaska depends on oil taxes, royalties and fees to fund most of state government. Even though ACES has created billions of dollars in surplus funds, Parnell, some lawmakers and business leaders worry that the tax is so high that oil companies aren't investing in new
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The more interesting question is "why".
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The more interesting question is "why".
Whether its called a payment, tax, royalty or fee is just an accounting gimmick. Perhaps by calling the per barrel money transfer from the oil company to the state a tax there is a federal tax benefit, or some financial report benefit for wall street. Whatever the case, I'm sure the state would be accommodating in calling the per barrel money transfer whatever helps out the oil company. The state could thereby collect a little more than it otherwise could, a win/win for company and state.
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And yet we invade Oil rich nations, and then multinational oil cartels get access for pennies on the dollar. What nation have we invaded to procure cheap sunlight?
Then there is a huge infrastructure around fossil fuels; refineries that are antiques. You also have the cost of pollution due to fossil fuels like Coal being shifted to the population. Do power companies pay for the thousands each year who will get sick or die decades earlier than they otherwise would?
We need a more comprehensive word than Subsid
Re:I pay 11 cents per kWh (Score:5, Insightful)
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.
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Also, my (mostly) hydropower-sourced electricity here in Seattle is billed at 4.75 cents per kWh. :)
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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.
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I bet there are some sewage treatment plants pumping millions of gallons of fresh water into the sea, though.
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I pay 44 cents per kWh, so...
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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.
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Most of the hybrids are powered by gasoline.