Science Interviews

Interview

Tue, 15th Mar 2016

Superconducting for super energy

Dr Suchitra Sebastian, The University of Cambridge

Listen Now    Download as mp3 from the show Cambridge Science Festival: Battle of the Brains

Suchitra Sebastian is a Cambridge University physicist on a mission to transformLevitating Superconductor the way we use energy globally and she’s planning to do it all with the help of a type of material called a superconductor. She starts off by explaing what the problem is that she's hoping to fix...

Suchitra - I’m trying to work towards a world in which we use less energy. If we’d like to move to renewables like solar energy.  This is made in the middle of the desert where not many people live, so to get the electricity from there to the most crowded cities, this is not easy to do.

Smith - It’s a big transmission problem. You’ve got to move the electricity from where the sun shines to where the people live, and they’re not the same?

Suchitra - Yeah so if we used regular electric cables like we have here that you plug into the wall, we actually lose quite a bit of energy.  So if you put electricity through we waste quite a bit as heat so, if we were to extend this to over thousands of kilometer, you’d end up wasting a lot of that precious energy.

Smith - So you're saying it might be possible if we can make the transmission system not lose all that energy along the way?  To make lots of energy, electrical energy where it’s sunny and transport it much more efficiently to where we need it?

Suchitra - Absolutely, and for this the kind of material which I’m going to be talking about is perfect.  It’s known as a superconductor- it’s a perfect conductor.  So you're familiar with metals, conductors in which electricity is not transported because electrons (the little objects that transport electricity), they’re bumping into each other and bumping into the crystal walls, so there’s a lot of energy lost because of these kinds of processes but in superconductors, the electrons all move perfectly in sync.  So, when you take a superconductor, you cool it down gradually at some special temperature and they suddenly, almost by magic, all become aware of each other and all click perfectly into sync with each other. So over giant distances, over hundreds of kilometers, you get perfect transmission of electricity.

Smith - It’s a bit like rather than having a contraflow on the motorway and everyone’s going here there and everywhere, and changing lanes, and bashing into each other; we’ve got everyone in the same lane, no HGVs and everyone’s going along at the same speed?

Suchitra - Absolutely - no traffic jams!

Smith - Is this feasible?

Suchitra - I can actually show you today an example of a superconductor and some of the unique, and particularly exciting, effects of a superconductor.

Smith - Right let’s do it - what have you got?

Suchitra - What I have here is a container; this is about -200OC so yes, it’s quite cold.

Smith - In there is a clear liquid which is bubbling away - that’s what?

Suchitra - This is liquid nitrogen, and this is a very effective way of cooling down whatever’s in this liquid to -200O.

Smith - Sitting in there are two very thin black squares, maybe 2 inches down each side of the square, bubbling away at the bottom - what are they?

Suchitra - These are actually pucks made of superconducting material.  So I’m cooling them down in order for these materials to be perfect conductors, they have to be cooled down so that the electrons start behaving in sync with each other.

Smith - And when we’ve got them really cold, what are we going to do with them?

Suchitra - Okay.  So what you see here is a giant ring - well when I say giant- it’s about 1m across.  It’s a ring with shiny little squares that are very strong magnets.

Smith - Right, so all the way around - it looks like a glass coffee table actually - but all around the outside rim of the coffee table are little silver squares and those are powerful magnets?

 Suchitra - When I put the superconductor over the magnet you will see what happens.

Smith - This does look magical actual, because what we’ve got is this glass coffee table like thing with all these magnets around the edge and this flat sheet of material (the superconductor) that we’ve just put onto it is literally wizzing around following the path of the magnets in a circle and it is floating about an inch off the surface.

Suchitra - It’s floating, it can go in any direction…

Smith - You give it a nudge with the forcep…

Suchitra - Yes…

Smith - … And then off it goes?

Suchitra - Yes.  I give it a nudge in one direction and it goes round and round in that direction and the only thing that would slow it down is friction…

Smith - From the air?

Suchitra - Yes, friction from the air or if it were to get warmer.  As it will gradually get warmer you will see it descending slowly.

Smith - Right - now the hard question.  Why is it doing that?

Suchitra - To put it as simply a I can, it’s because currents are set up on the surface of the superconductor…

Smith - Electrical currents?

Suchitra - Yes, so when perpetual currents are set up on the surface of a superconductor, it creates a magnetic field that repels a magnetic field from these very strong magnets, and since this magnetic field of this superconductor is repelling expelling or the magnetic field from these very strong magnets, it’s floating on top of this.

Smith - I get it.  So, the magnetic field makes an electrical current flow in the superconductor which makes it’s own magnetic field which repels the magnetic field from the table, and the two oppose each other and it just bobs there forever?

Suchitra - Yes, exactly.

Smith - Until it warms up, obviously?

Suchitra - : Yes, that’s right.  Yes.

Smith - And the practical application of this if we wanted to use this practically to solve the problem that you were saying at the outset, which is getting electricity around the world and that kind of thing.  How could we do this?

Suchitra - The levitating effect that I showed you, for example, is used in magnetically levitating trains to reduce friction with the track.  But actually, these transmission solutions are really important for the world’s energy problems and they are already used in some parts of the world; so a kilometer long superconducting transmission line is used in Germany for example.  Actually, if you’ve actually had your head inside one of those MRI machines, that’s a superconducting magnet so it’s not so alien that you only see it in the laboratory but, what we really need to do to help solve these big energy problems, we need to cool it down.  At the moment, the superconductors that are best known, we need to cool them down.  This is okay in an ice cream tub in a demo or over a kilometer, over hundreds of kilometer this is quite challenging and also, the material you see here…

Smith - It would be a big ice cream tube, wouldn’t it?

Suchitra - Yes, you would need a lot of cooling yes.  Lots of ice cream or superconductor cooling.  And also what you see here the superconductors - you can come up and look at them - they’re quite brittle; they’re not actually shiny like a metal; they’re not malleable.  So they’re not great to make into wires and they’re quite expensive so, really, we’d like to find better superconductors.

Smith - So if you do want to improve them, how can you make them better?

Suchitra - We’re not that great at building superconductors from scratch (so designing them), but what we do is to take existing materials, for example, there are magnets which are very close to being superconducting.  We put giant pressures on them, like the pressures near the earth’s core that Chris was talking about.  You can create a diamond from peanut butter. Just like that you can take a magnet, put a giant pressure on it and make it into a superconductor and so this is what we’re doing to design superconductors in the laboratory and hence work to a better superconductors, which you don’t need to cool, which are cheaper and that we can make these transmission lines out of.

Smith - They’d still be cool though - wouldn’t they?

Suchitra - They would be cool.

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