This seems like an interesting idea, the feasibility may drop with scale though.
College Park, MD (August 3, 2010) — Researchers at the University of Hawaii at Manoa say that the Leeward side of Hawaiian Islands may be ideal for future ocean-based renewable energy plants that would use seawater from the oceans’ depths to drive massive heat engines and produce steady amounts of renewable energy.
The technology, referred to as Ocean Thermal Energy Conversion (OTEC), is described in the Journal of Renewable and Sustainable Energy, which is published by the American Institute of Physics (AIP).
It involves placing a heat engine between warm water collected at the ocean’s surface and cold water pumped from the deep ocean. Like a ball rolling downhill, heat flows from the warm reservoir to the cool one. The greater the temperature difference, the stronger the flow of heat that can be used to do useful work such as spinning a turbine and generating electricity.
The history of OTEC dates back more than a half century. However, the technology has never taken off — largely because of the relatively low cost of oil and other fossil fuels. But if there are any places on Earth where large OTEC facilities would be most cost competitive, it is where the ocean temperature differentials are the greatest.
Analyzing data from the National Oceanic and Atmospheric Administration’s National Oceanographic Data Center, the University of Hawaii’s Gérard Nihous says that the warm-cold temperature differential is about one degree Celsius greater on the leeward (western) side of the Hawaiian Islands than that on the windward (eastern) side.
This small difference translates to 15 percent more power for an OTEC plant, says Nihous, whose theoretical work focuses on driving down cost and increasing efficiency of future facilities, the biggest hurdles to bringing the technology to the mainstream.
“Testing that was done in the 1980s clearly demonstrates the feasibility of this technology,” he says. “Now it’s just a matter of paying for it.”
More information in the project, see: http://hinmrec.hnei.hawaii.edu/ongoing-projects/otec-thermal-resource/
The article, “Mapping available Ocean Thermal Energy Conversion resources around the main Hawaiian Islands with state-of-the-art tools” by Gérard C. Nihous will appear in the Journal of Renewable and Sustainable Energy. See: http://jrse.aip.org/jrsebh/v2/i4/p043104_s1
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It’ll work but it’s going to suck energy from the oceans and put it into the machinery and the atmosphere. Then what?
those with an interest in Ocean Thermal Energy might find this story from Amerian Heritage Invention and Technology interesting.
http://www.americanheritage.com/articles/magazine/it/2009/4/2009_4_24.shtml
“Sixty miles east of Havana, along Cuba’s north coast, swimmers and skin divers like to gather at a squarish pit filled with lovely aquamarine water, hewn into the rugged basalt just off Matanzas Bay. From a distance it has the look of a Stone Age swimming pool, until one sees electrical wires protruding from aged concrete.
This is the sole remnant of a power plant built by a French inventor so far ahead of his time that his time still has not arrived: the proud and prolific Georges Claude, known as “the Edison of France” for his breakthrough developments of neon lights, industrial gases, and synthetic ammonia. But it was on this gouged reef that his fortune began to founder. Cubans still regard him as the father of ocean thermal power—a process of harnessing energy from the sea—and mark this spot as its birthplace. If so, the child has been a long time aborning. No ocean thermal plants of commercial scale have been built, and the power output from the scattering of pilot plants to date could be exceeded by firing up the generators at a single big-box home improvement store. Still, today’s volatile mix of energy politics and economics is stirring long-dormant hopes among the faithful.”
The greater the temperature difference, the stronger the flow of heat that can be used to do useful work such as spinning a turbine and generating electricity… or pumping cold water up from the ocean floor?
Wouldn’t it make much more sense to tap the geothermal energy of the hotspot, than minor variances in the sea temperature. How hard would it be to drill to a depth where the temperature would superheat steam, explode a device to create a chamber, run some piping to a turbine and bada bing, clean green energy.
this is beyond old news … studied this in the ’70’s at the Naval Academy … it just doesn’t scale up to real power … the better technology combines waves and wind turbines with ships … think of it like this … ship with large holes/columns open to the sea … as waves pass by the ship at anchor the water in these columns rises and falls … wind turbines at the top of the columns generate power on both the upstroke and the downstroke … simple, workable and buildable … though not sure if it will ever compete with gas and coal on price …
Another “grant” black hole. This is not a project that is going to deliver ‘cheap’ energy to the peoples of Outer Mongolia.
If the efforts and finical resources, were deployed in research to obtain ‘economical energy’ like a ‘ no cost additive’ to water to produce electricity then 99.9% of the worlds lights could stay switched on 24 hours a day, now who is going to be the first to write a patient on this ? Any Static?
I’m sure the enviro-wackos will find some way to declare this a crime against Mother Gaia.
They need to do an environmental impact study on the little critters that live down in the deep part of the ocean. Heck, one of them might be a snail darter or something. But more seriously, this has always been tomorrow’s next big thing in renewable energy. I suspect the status will not change.
Thanks for the great picture. It appears the windward side of the island has much cooler waters. Since they claim all warming is from man made CO2, that set of islands must really be cranking out CO2 to warm the water so much.
Sounds like a very good idea. Also, transferring heat to the bottom of the ocean should stir up nutrients via convection and help feed marine life.
However, the technology has never taken off — largely because of the relatively low cost of oil and other fossil fuels
“Now it’s just a matter of paying for it.”
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So it’s going to cost more……
At least pumping nutrient rich water up to the surface will fuel more phytoplankton, which will consume more CO2.
Wonder if any of these things really work, and what would happen if we really did them and lowered CO2 levels too low.
A Carnot engine is the best that you can do in terms of classical heat engine efficiency. The maximum possible efficiency = (T1 – T0)/T1, where T1 is inlet temperature and T0 is outlet temperature, in degrees Kelvin.
Here, we have
T1 = 24 C = 297 K
T0 = 18 C = 291 K
Carnot efficiency = (297 – 291)/297 = 2.02%. The best you can do is extract 2% of the total energy represented by the temperature difference between two volumes of water.
If we increase the temperature difference by 1 C (=1 K), then the efficiency increases to 2.34%. That is an increase in efficiency of about 15%, like the article says. The reason 1 C helps so much is that you are starting with soooo little.
You can try to make up for the crappy efficiency by increasing the flow. But that, of course, requires much more energy to move all that water.
I think you’ll find that some of that warming is caused by a lovely lady called Pele.
“Now it’s just a matter of paying for it.”
Ah. There’s the rub.
Back in the ’60s, Analog SF had a story about such a generator. It seems it was torn up by a large squid. A very large squid.
It’s not a reasonable way to generate large quantities of power. Some form of fission is the only real way to provide long term, cost effective power. Oil will become too valuable in the future to burn. At that point, we’ll see lots of fission plants, but not until then.
This is a simple Carnot cycle engine. The theoretical (maximum) efficiency is given by:
eff = 1- (Tc/Th)
where Tc is the cold temperature (Kelvin) and Th is the hot temperature (also Kelvin).
So the best thermal efficiency (extracted energy compared to energy moved from the hot to the cold reservoir) is about 1 – (277/301) = ~8%. Take into account the energy needed to pump all that water around, and the inevitable less-than-theoretical efficiency of any real Carnot engine, plus the losses in conversion of mechanical energy to electricity, and it becomes clear that this whole enterprise is unlikely to be economically useful. Enormous capital investment is required, and very little energy is produced. Heck , the concept has been studied to death already; it was and is an economic loser.
Does provide nice funding grants for professors and their staffs though…
So testing in the 80s shows the feasibility; “now it’s just a matter of paying for it.” If it doesn’t soon pay for itself, in what way is it feasible? It sounds more expensive than conventional (fossil-fuel) generation; hence, not feasible.
I fear ShrNfr is close to the truth on the EIS problem. Seems all the alternative energy ideas end up either uneconomical or un-approvable due to enviro issues.
While not energy related, the enviros in the NW lobbied against rainwater harvesting when the legislature tried to reconcile this with the Washington Water Code. Their issue? It would allow folks to build a home in areas where groundwater or surface water could not supply domestic needs.
Similarly, the enviros in forever green state oppose aquifer storage and heat pump technologies. Storage because they believe that drinking quality water “might” negatively alter the chemistry of groundwater. Heat pumps because the change in groundwater temperature “might” harm groundwater bacteria.
What the enviros fail to comprehend (or perhaps understand all too well) is that any human activity affects the environment. The only way to eliminate human impacts on the environment is to eliminate humans (again, this may be their goal).
“Testing that was done in the 1980s clearly demonstrates the feasibility of this technology,” he says. “Now it’s just a matter of paying for it.”
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Here we go again! Money! Money! Money! It’s always about Money!
Someone needs to hold a Press Conference and tell the President and Congress that there ain’t no more money!
We’re broke! Busted! Up to our keesters in debt! We’re where the Brits were in 1945.
Maybe we can “Lend-Lease” Hawaii and Alaska to the Chinese for 99 years with an option to renew.
Think we can do the same with the Mexican and Cloumbian Drug Pushers? Texas and California to Mexico and Florida and New York to the Columbian Mob? Hay! I think it just might work!
The trouble with the world is that scientists and engineers are not economists. We love to tackle an engineering challenge but are reluctant to face the annoying truth that many things are not cost effective.
I would think that if you insisted on using the ocean for power, wave power would work better.
Well, I guess this should work, although how much it will cost doesn’t really bear thinking about.
Here in the UK the BBC is droning on about the latest gee whizz “renewable energy scheme”, harnessing wave power.
http://www.bbc.co.uk/news/uk-england-cornwall-10808260
technical details at:-
http://www.southwestrda.org.uk/working_for_the_region/areas/cornwall__the_isles_of_scilly/wave_hub/documents1.aspx
So that looks like £43.5 Million of taxpayers’ money. And counting.
And, without wishing to be a grouch, isn’t wave power going to suffer the same problems as wind power? Have they not heard of calm seas?
Meanwhile, we have some of the biggest tidal ranges in the world. There has been talk of building a tidal barrage across the Severn estuary for at least 60 years. And anyone can predict when high and low tide is, even 90 years from now. Which is more than anyone can say about climate predictions (or even weather forecasts for more than a few days ahead). But, of course, the Greenies and amateur bunny huggers won’t hear of the idea.
But it’s nice to know that “An independent economic impact assessment has estimated the £42m project could create about 1,800 jobs and inject £560m into the UK economy over the next 25 years.”
Yeah. Right. And I could get to be Pope next month.
But this Wave Hub is rated to produce a stonking 20MW. Presumably if the sea is rough enough. £43.5 million to produce 20MW. Hmmmmmmm.
There being No Free Lunch, pumping and moving the massive quantities of cold water to the surface, and altering temperatures in general, that would be required to produce the energies needed, neglecting the whole problem of transporting the energy to WHERE it is needed, would probably invoke The Law of Unintended Consequences, altering aspects of the oceans that would affect other features.
Just like large scale wind and solar energy, the best sources of these intermittent (and, thus, inferior) energy sources are not where they are needed, yielding them even more inferior for industry.
Wind and solar are going to be most useful at the smaller scales, where homes can use current technology to lower their draw from the grid, freeing up more power for industrial purposes and lowering the need for more.
You can try to make up for the crappy efficiency by increasing the flow. But that, of course, requires much more energy to move all that water. chris y
Here’s a way to generate fresh water and power at the same time:
Take a large vertical tube and mount it vertically in the ocean. It should be long enough to reach substantially cooler water and wide enough to allow for a large water vapor flow. Mount a turbine generator in it. Evacuate all the air from the tube. Allow warm water from the surface to evaporate at low pressure in the tube (allow for the resulting brine to fall out) thereby driving the turbine and condensing at the bottom of the tube as fresh water. Pump out the fresh water with power from the turbine. Sell remaining power and fresh water.
Another ill advised attempt to tap diffuse sources of energy. As has been pointed out above, the 2nd Law will eat your lunch. How? Large capital investments would be needed to get the power. It is always capital investment dollars per watt that count.