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Harvesting Power When Freshwater Meets Salty
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."
How well does it scale?
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.
retrorocket.o not found, launch anyway?
Unless maybe we stop subsidizing fossil fuels?
I have no problem with your religion until you decide it's reason to deprive others of the truth.
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.
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.
~Idarubicin
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.
"That's either incredibly asinine or the most brilliant troll I've ever read. Not sure which." -Anonymous Coward
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
http://www.elistore.org/Data/products/d19_07.pdf
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/
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.
So how do they arrive at the 20-30 cents/kWh? Infinite durability? This has been tried in Norway http://en.wikipedia.org/wiki/Statkraft_osmotic_power_prototype_in_Hurum with rather underwelming results, outputting 4kW (not a typo) under ideal conditions. Granted this new plant is rated as 60 times more efficient it seems like a long way from a sound investment as the upfront cost is just to high.