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Thursday, March 23, 2006

Energy Storage >> Out in the Sea

Today, an idea developed into my mind while reading a physics chapter. Its about energy storage in the sea, to be used with the Offshore Solar {earlier post} project.

Its a quite intuitive idea. You might have observed a phenomenon while playing with water { I do it daily}, that when you try to put an inverted mug into bucket full of water, you have to push it downwards into water and it bounces back when let free.
While pushing it, you are actually trying to oppose a force applied by water from downwards. This force is called buoyant force {discovered by Archimedes}.

Now, I'm trying to visualize a similar thing, for sea.
Imagine a large and heavy hollow tower with closed top {say, a giant pipe with closed end}. Immerse this tower into sea water so that water goes inside and fills it up enough so that it floats. Lets call it "Energy tower"

This tower is now closed from the bottom too, so that water stays inside. Valves are used for opening and closing on both ends.

Imagine that we're generating huge amount of energy from the Solar Rig. To store some energy for night use we'll use a fraction of energy generated during the day to Pump out water from the Energy tower. As water is pumped out of the tower, it rises, due to buoyant force, just like a balloon rises in water, when inflated.
But, its huge weight tries to keep it down and so a very high water pressure starts to build outside the Energy Tower.

As Evening sets in, power production from the Solar Rig ceases and now, our Energy Tower comes to life.
All air and water valves are let open, and instantly, Water gushes in, with huge force.
Simply, place a water turbine at this end to produce power from the gushing water, just like turbines used in Hydro Projects {Dam}.

This I think, is an easy way to store energy at sea and it has virtually unlimited capacity.
I guess it'll work great with Solar Rigs

What do you Say? Tell us by clicking on "comments" below. I wanted to put some pictures here, but couldn't, due to lack of time. I'm preparing for college entrance tests these days.
Also, I've developed a Flash based "Easy read" feature to be used with text based sites like blogs, so that users can easily read text on screen. It's partially developed and it'll take some more time, due to my tests.


Anonymous said...

do u think it is practical?
In ur case solar enery generated will be more than energy generated by water rushing in.So it is better to store solar energy directly.Y to complicate things?

Mridul said...

Thanks for the reply,

To know its practicality we have to do a viability test.
But, I think.. yes that may be possible.

Now, how can you store Solar Energy directly? Light can't be trapped.. (as yet)

So, either save it as electricity or as potential energy {as in a Dam}.
For electricity, you need Batteries.. and as you know, batteries are not feasible at such large scales so that's why alternatives {like this} are required.
And moreover, Solar energy is not constant because sky is not always clear. So, energy storage is essential to provide constant power supply. That's why batteries are used with Solar cells.

Keep your comments coming in! Thanks!

Kat Marsen said...

Better idea, to store even more power, have a fixed permanently enclosed buoy with no moving parts. Attach a strong cable to it, and run that cable down to a pulley at the bottom of the sea floor, and back up to the rig, attached to an electrical motor.

During the day you slowly tow your buoy down to the bottom. Every meter lower is more potential stored. The weight of water is pretty fantastic and increases dramatically as you go deeper. I imagine even with a small buoy you could store quite a lot of energy.

Then of course at night, you let the force of the buoy run the generator. Then you have no need for a turbine/pump system, and which can be expensive and inefficient.

Neat idea though. ;-)

Kat Marsen said...

Btw, you could do a similar thing on land, by compressing air during the day. In my shop I have to wait 10-15 minutes while the air compressor charges up, but once it's charged, it last a few hours. That's cheap, simple, stored potential.

Well, very LOUD stored potential, mind you, but... ;-)

Or, how's this for a bizarro idea-- you know those earth-quake-proof buildings that are hydraulicly suspended and can be raised/lowered by compressors a few inches? Imagine if their solar panels raised them up during the day, and at night, the buildings slowly sunk down on their pistons again!

Mridul said...

Thanks for the reply,

Regarding your first comment; very nice idea indeed.
But, I want to take your attention to some points.
You said that potential stored increases dramatically with depth of the buoy, but I doubt it 'cause once you go below the surface of water, buoyant force remains the same throughout, no matter how deep you get. An air filled buoy at some depth may actually float because of the sheer amount of pressure of water overhead {air will compress}. I know this sounds weird but is true.
So, once the buoy goes into water, its potential energy would increase steadily (i.e. will not increase dramatically).
In my post, Energy Tower is initially weightless (appoximately) as it is filled up with water. When water is pumped out, a portion of the tower comes out of the surface and the weight of that portion is exactly equal to the weight of the water displaced by the pump. It is this weight we utilize to get energy.
Both energy tower and buoy ideas will work but, I favoured Energy tower 'cause if we made an offshore Solar Rig, its four legs will act as energy towers, you see. And imagine the added weight of rig above, it'll work fine.

Regarding your second comment; yes this works. I heard some time back in TV that a car has been invented which runs on compressed air! Strong pipes attached below the chassis store highly compressed air and an internal combustion type engine is used to extract power. Yes, it has potential.
And this "bizarro idea" looks too bizarro ;), but can be a reality!

You see, people in 19th century used such energy storing techniques 'cause then used steam engines weren't powerful enough. But today with the advent of oil burning and more efficient engines these things are not required. So, nobody bothers about it.
Now, as oil goes away, we're looking out once again for energy storing devices, but this time, source is much greener than before! Isn't it?

Mickslam said...

You couldn't store enough energy this way. It would be simpler to use create a large 'tidal pool' and pump water into this. Water pumps are about 80% efficient.

E = mgh

Anonymous said...

And you can also use the tide to improve efficiency and you will become combined solar/tidal poweplant with a buffer :-)

Mridul said...

Great idea,
I know abt those underwater wind turbines type of thing. And a person in UK is also busy developing a running water turbine for tidal energy. visit Hales Turbine

reema said...

u r really hardworking guy..keep it up...up.........up...........

Anonymous said...

- Tidal energy should be the pursuit of every country with a coastline. The link above is to a tidal turbine testing project off the Canadian West Coast.

- The compressed air cars mentioned above are from a French company called MDI, which has just recently announced a development deal with Tata Motors, and has received approval for sale in the United States as of 2010. :)

- Personally, I think the potential energy in displacement might be better combined with Wave Power units.