Harnessing Vertical Sea Temperature Gradient

Sterling D. Allan writes "Sea Solar Power Inc., run by three generations of James Hilbert Andersons, has developed a solar power technology that does not fluctuate with the weather, but is available constantly. Their solution is to harness the solar energy stored in the sea by tapping the thermal gradient that exists naturally between the surface and deep waters, using a reverse refrigeration cycle. The modeling and testing done by the Anderson family over three generations since 1962 predicts that the cost of energy generation through this method will be within a price range comparable to nuclear, coal, natural gas, and other contemporary grid power plants. Ocean Thermal Energy Conversion, or OTEC, was invented in 1881 by a French scientist, Jacques Arsene D'Arsonval. SSP should be ready to build their first full prototype 2-3 years from now."

Are there environmental effects to be considered?

[mmell]

For example, they're talking about exchanging a thundering lot of heat here. Will this affect existing ocean currents? Might the thermal change not impact on the underwater ecosystem (a system we are only now beginning to even be able to see)?

Further, what of the potential for secondary effects? Climate changes brought about by changes in ocean current temperatures? Remember, el nino/la nina are caused by a change of only a few degrees. That's not unforseeable for a large-scale technology such as this.

Oh, and BTW - it makes a lot more sense to base this on something like an oil rig, rather than a ship. Just sayin', is all.

This isn't news

[remy]

I did a report on OTEC when I was in junior high--18 years ago--based on an article in Scientific American. There are prototype facilities in a number of countries--I visited the facility in Hawaii five years ago, which was at least a decade old then.

It's an intriguing idea, but this smacks of somebody trying to get publicity to bring in venture capital or something of the sort.

waves?

[User 956]

why not just harness the wave energy [freeenergynews.com]?

Local?

[MAXOMENOS]

If this technology gets adopted widely enough, I doubt the problems will be local for long.

The parent is right on. This is just trading one environmental stressor for another.

Someone will object

[sycodon]

There will be some group, somewhere, objecting to something about this.

Hurricane Control

[truckaxle]

Set up shop in Caribbean or Gulf of Mexico and maybe as a added benefit, such energy harvesting, could decreasing hurricane potential by cooling surface water temperature. This would be win-win, but I am sure that it would also be disruptive to some marine life so maybe a win-win-lose sometime you just can't have it all.

Re:Unfortunately, it's not a passive energy source

[lilmouse]

True. What we need is something like Trantor [wikipedia.org] - use the (negative) heat gradient from deep in the earth instead of the gradient in the oceans. Of course, we'll have to do more research drilling, but we're already getting close [msn.com] to the mantle!

--LWM

ps - no "think of the earthworms", please.

Re:Unfortunately, it's not a passive energy source

[Some Random Username]

First of all, the turbines killing birds myth is getting really tired. Buildings kill birds too, but we seem to be building those. Properly located wind farms do not kill significant numbers of birds. This myth comes from the fact that one particular wind farm was placed directly in a valley that birds migrated through, giving them no choice but to go through and risk being killed. There's tons of other wind farm installations which show birds who have a choice to go around them, do go around them.

And what do you think that solar energy is going to do if you don't turn it into electicity? The sun already raises the temperature last I checked.

Re:Solar????

[JesseL]

Nuclear power doesn't derive its energy from the sun.

No, but it does derive it's power from heavy elements that were created by the explosions of older stars.

No, the ocean is too massive

[jgardn]

The ocean is so grossly unimaginably big that we would need an absolutely huge operation to even cause a measurable effect. If you really tried to change the temperature by even a fraction of a degree using this method you would have to pump extremely large quantities of water---quantities so large that I don't think anyone would ever consider building something so massive.

People sometimes forget the scale of things. On a global scale, we are not even part of the equation.

But you also have to consider the opportunity costs of doing this. If we would raise the global atmospheric temperature 1/10 of a degree with all the carbon we were burning, what will the net effect be if we can convert a significant portion of our energy sources from burning carbon to mixing a small amount of cold and warm water?

Nuclear = Geothermal = Stellar Power

[Roger W Moore]

Actually depending on how strict your definition of solar is current nuclear power could be considered as such. If you allow solar to mean "from a star" and not just "sol" (which is not unreasonable since we talk of "solar systems" around other stars now) then fission reactors are actually using "fossilized" solar powered.

Fission reactors, our only current form of nuclear power, split uranium nuclei into smaller fragments and thereby release energy. However, to form the uranium atom in the first place from smaller constituents therefore required energy. This energy is thought to have come from a supernova ~6 billion years ago, predating the formation of the solar system. Thus current reactors are, by some (possibly warped!) definition, still using fossilized "solar" power. The same can also be said of geothermal which relies mainly on natural decay of nuclei formed by the same supernova.

Only if we ever get fusion reactors working then we really say that we are no longer reliant on solar based power...and that's because we will have made our own mini-sun.

Lets get on with replacing coal

[caviare]

It seems to me that there are a number of technologies that have the potential to replace coal at a reasonable cost: 1. nuclear (have you ever heard of the integral fast reactor?), 2. wind backed by hydro used as an energy storage facility, 3. aquathermal or what ever it is we're going to call it. So why don't we stop arguing about which one it's going to be and just get on with it? Do all of them, find out which is the cheapest. Do we really know?

Re:Unfortunately, it's not a passive energy source

[NeutronCowboy]

And what do you think that solar energy is going to do if you don't turn it into electicity? The sun already raises the temperature last I checked.

Right - and a good chunk of the world's ecosystems rely on this to continue. Remove the sunlight, transfer the energy somewhere else, and you've just removed local heat. Good? Bad? Who knows, as it largely depends on the circumstances. But it is something to consider.

And now for some math...

[Anonymous Coward]

The US generates and uses about 3800 billion kwh of electricity per year.

ASSUMING this thing can convert a 40 degree F (22 C) temperature gradient into electricity at 100% efficiency (which it can't, just looking for order of magnitude kind of thing here) then a 6ft (2m) diameter pipe sucking water in at a 20fps (6m/s) velocity will suck up enough water to generate 1500MW.

Ignoring peak demand and all that, it would take 300 (300) of them to power the entire US.

Assuming an average ocean depth of 1000ft (300m), which I suspect is considerably on the shallow side, it would take 230,000 years (7.25 Ts) to suck up the entire contents of the oceans. By this time, perhaps the sun would restore the temperature gradient to its original magnitude.

All in all, one of the less moronic alternative power schemes I've heard of.

p.s. - I'm not sure if I'm assisting or mocking our metric friends.

go nuclear

[circletimessquare]

pebble bed reactors don't go china syndrome. environmentalists attitudes about nuclear is based on decades-old technology and watching too much "silkwood"

thermocline, solar, biodiesel, wind, tidal turbine, wave generated, etc.: these are all very cute boutique energy sources. but when all put together and maxed out in terms of realization of potential they won't dent 5% of our energy needs

oil and gas and coal are incredibly dirty and even geopolitically dangerous and increasingly expensive

put it all together and pebble bed reactors are an environmentalist's and energy policy maker's best friend

now we just need the lowest common denominator of uneducated environmentalist's opinions to catch up with reality

ps: YOU CAN'T MAKE BOMBS OUT OF IT

educate yourself, don't let your uneducated fears dictate your opinion

as time goes by, nuclear is only going to look more and more attractive to this world, once everyone gets a real education of the positves and negatives of nuclear compared to everything else

because the biggest thing going against nuclear really is only inertia and ignorance

Re:Unfortunately, it's not a passive energy source

[Rutulian]

I think really what we need to do is spread out the burden. All power generating facilities are going to cause environmental damage, but they are going to do it in different ways. Small perturbations aren't going to be as bad as large perturbations. So a few wind turbines will cause some noise pollution, but if you stick them out in the middle of Oklahoma and use them for that local area, it won't be such a big problem. You can setup a few solar plants, nuclear plants, coal plants, geothermal/aquathermal systems, etc...in different areas where geographically best suited. Then you don't have to worry about powering the entire world with aquathermal and causing changes in the ocean currents. Of course, multiple power-generating facilities results in a larger burden for the utility companies, especially since some methods are more expensive than others. So we probably won't see anything like that in my lifetime.

Isn't it 4 degrees all the way down?

[GrahamCox]

Correct me if I've got my wires crossed, but I thought the sea temperature was about a constant 4 degrees all the way down, once you get below a certain distance of the surface. The reason being, that water colder than 4 degrees has lower density, therefore always floats upwards. That's why the ocean isn't frozen at great depths. It doesn't mean you couldn't tap that gradient anyway, but the depth required presumably wouldn't be all that much as long as you'd got at least as far as the 4 degree level.

Non-Photovoltaic Solar

[Ironsides]

There is a version of solar that does not use photo voltaic cells. Remember the Sim City 2K solar power plant? It looks a lot like that. An array of mirrors reflects light into a dome atop a tower. The dome contains a circulating supply of water that is heated up into steam and used to drive a turbine. The mirrors are automatically angled to reflect the sun (at pretty much any angle) into the dome.

No really nasty chemicals involved, and it uses technology that has been available for a really long time. I'm not sure about efficiency.
http://en.wikipedia.org/wiki/Solar_power#Solar_the rmal_electric_power_plants [wikipedia.org]
See Concentrating solar power (CSP) plants.

Reading over it, it looks like it is not always water.

Ah. Yes.

[Amiasian]

Yet again, I am reminded of Marshall Savages thought-provoking work, Colonizing the Galaxy in Eight Easy Steps [google.com]. His belief is that the use of OTECs will relieve the world's energy problems, in addition to providing power for floating sea colonies, thus relieving population density. Furthering his premise, if I recall, the warm water will lead to an abundance of blue-green algae, which can be processed and used as a food source. These things, interestingly enough, are only a stop-gap until we can begin to expand life to places outside of this current biosphere.

Okay, maybe a tad off-topic, but I certainly find it fascinating.

Re:Interesting Tech, but Geographically Limited

[Anonymous Coward]

Woods Hole institute also found that there are serious problems with big long pipes into the ocean. Those darn ocean critters and coral keep fouling the pipes.

The areas of the oceans with the deepest water and greatest thermal differences to exploit also have some of the poorest countries near them. Also, no land or other natural resources to speak of, and better yet, no industries to use the power. The efficiencies are still too low to build small OTEC plants. You have to design for something to generate 100MW to have it make any sense at all. Guam thought about it in the late 70's, but it came down to who is going to build a 500 million dollar powerplant for an island population of 100K people? Okay, so you build it, then, now that you have 100MW, what industry can consume that energy or allow it to be moved to the 4000 miles away places that need it? Hmm.... Convert it into another medium again. Crack seawater into hydrogen. Run those cars on the hydrogen. Export the hydrogen via ships to Asia, Hawaii, and the Americas.

While you are at it, convert everyone's PC into a treadle-pc.

Re:Are They Kidding?

[dbIII]

Okay, let's just pretend for a second that all of the "science" in this plan is on the up-and-up and that

It's very simple thermodynamics for the basic idea - doing it cheaply is the hard bit, which I suppose is why they are using sea water and not something obvious like ammonia for the working fluid - which would be a 100+ year old method really (refridgeration cycle).

If some random French guy nobody's ever heard of had it figured out 120 years ago

Over a hundred years ago this sort of method of using hot and cold water was used to generate electricity in a little town on the edge of a desert in the middle of Australia (Thargomindah - using the temperature difference between hot underground water and water at ambient surface temperature). If you get the water really hot it's easier to get more energy out of it - even more so if it's pressurised steam - which is why we've been using coal/oil/etc instead.

Re:Sound too good to be true? Perhaps it is...

[ltbarcly]

Abundant power plus abundant fresh water has the potential to completely remake the countries in the equatorial region...

For 20 years. Then the population will have had time to exceed the newly available resources, and they'll be in the same condition they are now, except there will be 5x more of them. The third world doesn't need energy, medicine, water, or food. Not the long run, as no matter how great the supply much of it will be stolen or ruined, and the population will just grow to exceed the supply. The third world needs education and the rule of law. Until they are able to form governments which aren't just 'top strongman of the week' they will never be able to harness resources for the good of the populace, and if they DO form such a government that can enforce laws and reduce corruption they will have no need for all these things, as they will be able to produce them rather easily. They have plenty of resources and mineral wealth. They just need to keep strongmen from stealing it long enough to harness what they have.