Powering the Future

Where will our energy come from in the future: wind, solar, or even piezoelectric power?
07 October 2014


For years we have relied on fossil fuels to produce the light, heat and energy we need to live and work. But these supplies are diminishing, and polluting our environment. So can renewable resources step into the breach annd produce enough energy to power the world? In this special Naked Scientists show, live from the Cambridge Science Centre, we talk to some of the researchers trying to do just that, as well as conducting some energy-related experiments of our own...

In this episode

Wind Power

02:30 - Harnessing wind and wave power

We need to increase performance of wind and wave powered systems to better harness the potential of these free, clean sources of energy.

Harnessing wind and wave power
with Dr Richard McMahon, Cambridge University

Wind power is a widely used form of renewable energy, but improvements can stillWind Power be made to better harness the power of the wind. Wave power, however, is much more difficult as the up-and-down motion of the waves is harder to convert into useful energy. Dr Richard McMahon from Cambridge University works on improving the output of both types of technology. 

These types of power rely on simple generators. Ginny & Dave explain exactly how and why generators create energy from movement. 

Richard -   Wind power is relatively mature.  It's making a big contribution to the generation of electricity in many countries.  The thing is to reduce cost, improve reliability.  I work on generated technology that will achieve that.

Chris -   When we say wind power, how are we trying to harness wind power?  Is that just with windmills or are there other ways of doing this?

Richard -   The way that's emerged if you like as the sort of standard way of doing it now after a lot of years of development is the thing that I think most of us are familiar with, which is the horizontal axis 3-bladed wind turbine which you see everywhere.  People have tried other different forms of wind turbine, but the main one for the foreseeable future is the one I have described, the 3-bladed horizontal axis machine.

Chris -   How does that actually work?

Richard -   Well, you need some wind to start with and the wind blows on the blades.  The force of the wind turns the blades and if you look at these wind turbines, you see the bit behind the blades which is called an nacelle.  In there, you think it might all be electrical generator - actually, the generator is about 1/3 of it.  The biggest thing is the front bearing because you've got all those weight of the blades on the front of the turbine and there's probably going to be a gearbox as well to increase the speed from the very slow rotation of the blades to high speed for the generator.

Chris -   How much electricity do we produce with wind in Britain at the moment?

Richard -   Somewhere around 6% to 7%.  I mean obviously, it fluctuates.  Some years are windier than others and the aim is by 2020, is to get to 1 in 7 kilowatt-hours produced from wind.

Chris -   It's quite a lot isn't it?

Richard -   I'd agree with you, yes.  I mean, it shows that wind is really making a significant contribution and of course, it's genuine green energy.

Chris -   Indeed, but the wind doesn't always blow.

Richard -   That is quite true.  We've got a couple of problems to look at.  At the moment, we can balance wind with other forms of generation - so, there's no worry about the lights going off.  In some countries like Germany and Spain where the wind penetration is getting high, we're having to look at sort of low balancing things, and that's where these smart grids come in, can we manage the load, so as to match the generation.

Chris -   So, this is where the wind stops blowing.  So, we need something else that can step in and fill the gap while the wind isn't blowing.

Richard -   Well, depending on the time of day.  My friends in the solar business I'm sure could help and of course, my other topic is wave power which, as another colleague points out, you can buy the tide tables for about 20 years ahead.

Chris -   Indeed.  Who's got some questions about the future of wind power?  Who shall we start with?  Hands up.  One over here.  Let me just get to you.

Nelson -   I'm Nelson.  How much wind power is produced a year?

Richard -   To give it in its sort of form or units, they're actually called terawatt hours - its a little bit difficult But if I go back to a sort of percentage, it's about 7% of our national consumption.  We burn about an average of 40 gigawatts which is 40,000 million units of electricity. If somebody is good at sums, you can multiply 7% of 40 gigawatts by 365 times 24.  I can't do that in my head I do apologise.

Chris -   Neither can I.  So, if we already are doing this, what can a researcher like you add?  Is it just more turbines or are we trying to make these windmills better in some way?

Richard -   Well, the analogy I use is that suppose we're in the 1930s and we bought a car, we think it was a pretty hot car.  We could get to 100 miles an hour, it would be really exciting, but look how much car technology has advanced.  I think, although it's sometimes hard to envisage, in 30 years, today's wind turbines will seem rather basic and the ones of the future will be cheaper and more reliable, less noisy and all the good things that we want.

Chris -   Shall we find out actually how we generate electricity with a turbine, Ginny?

Ginny -   The way that wind turbines work is they have to convert that motion that the wind is turning the blades around.  You've got a lovely model of it there, haven't you?  So, the wind is going to hit those blades and turn it around.  But then we've just got movement and that's not what we want.  We want electricity.  So, how are we going to turn that movement into electricity, Dave?

Dave -   First of all, we need someone to produce some movements.  So for this, I need a volunteer.

Ginny -   What's your name?

Innes -   Innes.

Ginny -   And how old are you?

Innes -   10.

Dave -   So Innes, if you can just stand at the side of this.  What I've got here is 2 coils of wire and 2 magnets.  The coils of wire are just wired up to this meter which measures how much electricity is being produced.  At the moment, how much electricity is being produced?

Innes -   Zero.

Dave -   All we've done is wired some wire into a meter and nothing is happening.  Now, what I'd like you to do is to take this magnet and poke it into the middle of the coil.  If you move it forwards and backwards, can you start to see that needle moving a little bit?

Innes - Yeah.

Dave -   Try a bigger magnet.

Innes -   It's moving a lot.

Ginny -   So, the needle is moving backwards and forwards every time you move that magnet in and out of that coil isn't it?

Innes -   Yeah.

Ginny -   So, what's going on there, Dave?

Dave -   So, if you move a magnet near a coil of wire, what you're actually doing is pushing little tiny subatomic particles which are parts of the atoms, pushing them around those coils, they're called electrons, pushing electrons around the coil, and that's what we call electricity.  And the faster you move the magnet and the bigger the magnet, the harder they're pushed, the higher the voltage, and so, we get a bigger reading here.

Ginny -   So, why did it work better with the second magnet than the first, because the first one was a bit rubbish, wasn't it?

Dave -   So, yeah, the bigger the magnetic field, the more magnetic field you're changing inside that coil, the bigger the voltage and the molecules that you produce.

Ginny -   So, the second magnet was bigger so we got a bigger difference.  Brilliant!  So, that's very interesting.  If you wiggle a magnet near a coil, you can make some electricity.  But that's not really what's going on inside a wind turbine, is it?

Dave -   Pretty much, that is what's going on inside a wind turbine.  You're moving magnets past coils of wire.  Sometimes the magnets are created by putting electricity through the coils of wire which sounds a bit circular, but it works.  Engineers are very good at that sort of thing. And if you move a magnet near a coil of wire, you produce electricity.  So here, I've got a whole series of coils with the magnet in the middle.  If I turn it upside down so the magnet can roll through it...

Ginny - There are little lights on each of the coils and I can see them flash as the magnet falls through that particular coil.  So again, this is just a slightly more high-tech version rather than having someone there to move the magnet in and out of each coil.  You can turn it and make the magnet fall through the coil.

Dave -   That's right and basically, everything apart from solar power is based on this principle - you move magnets near coils of wire and then produce electricity.

Ginny -   That still doesn't seem very efficient.  You're having to stop every time and turn it back over.  There must be a better way of doing it inside wind power generators and that sort of thing.

Dave -   So normally, if you arrange your magnets in a circle, in the coils in the circle, you could keep on going round and round, and round - you don't have to keep starting and stopping.  You can also use gears to speed it up.  Remember the faster the magnet moves, the more power you generate.  So, you can make everything go in circles, and it's much more efficient and you can use a lot of power with quite a small device.

Ginny -   And that must be quite easy for wind turbines because they start off by going around in circles.  Is that right?

Richard -   That's right, Ginny.

Ginny -   But you also look at wave generation and waves don't go around in circles, do they?  They go up and down.  Do you have to do something more like what we have here where you actually have something turning over and does that make it more difficult?

Richard -   You're spot on, Ginny.  Sometimes we can use, if you like, underwater wind turbines where we've got a tidal current, a stream of water from the tides.  But if we want to get power from the actual waves - the bobbing motion - that's difficult.  People have come up with a lot of really clever things going right back to Salter's duck in the '70s tlil today and we've got a lot of things on test.  But we haven't - I think got the right answer yet.

Chris -   What is Salter's duck?

Richard -   Essentially, it's a duck.  It's a thing that sits on the water that bobs up and down with the waves, and uses that to convert it to oscillatory motion, you know moving motion and then you can do something quite complicated and this is the problem you can pump say, some hydraulic oil, and then you can use that to turn a hydraulic motor which is going around and then you can use what your rotary generated.  Sounds complicated, it is a bit complicated.

Chris -   So, it doesn't work then.  Is that a long answer to say, 'don't work'?

Richard -   No, it's not that it doesn't work.  As we know, we don't want to pay too much for our electricity.  So, we'd like to get the system simpler.  So A, they run longer without trouble and B, it doesn't cost so much money to generate the electricity power.

Chris -   Any questions on air or wind, or waves?  Let's just head this way...

Jess -   My name is Jess from St. Yves.  My question is, have we crossed the threshold where we make more energy than it takes to make the wind turbine?

Richard -   Very definitely.  If you think about the embedded energy in a wind turbine, sure, there's steel and copper, and concrete in the foundations.  But on a good site, you'd expect to pay the energy back in under a year.  There's a slightly more subtle question in that as wind turbines get cheaper, you might put them in less windy sites where it takes longer to pay back.  So, maybe that's a worry, but I'm quite comfortable that we can pay the energy back quickly.

Lowen -   Hi.  This is Lowen from Cambridge.  Do you think that in the future, we'll have bigger wind turbines to capture energy or smaller, more efficient ones?

Richard -   I think both things will happen.  On land, there doesn't seem to be a really big push to increase the size.  The plan there is generally a standard unit, you know Henry Ford kind of policy, 'make it cheap, put them up.'  Offshore, it's a different story because it's a lot of effort to put foundations in.  So, if you're going to put a foundation and you probably want to put the biggest wind turbine, you reasonably can.  So, we'll see I think growth in offshore size, but on land, I think it'll go for the mass production option.

Edward -   I'm Edward from a town called Swavesey. What's the biggest windmill  you have ever made?

Richard -   Me personally? I've never had the privilege of building a whole windmill because a lot of things go into a windmill, but the biggest generator I've built is a prototype, is 250 kilowatts which is about enough for 200 houses.  But the real size ones are now in the megawatts.  And actually, we're building a prototype at the moment.  So maybe in a year's time, if we're on the show again, I can show you.

Frank -   Hello.  My name is Frank.  I'm from the United States.  I was just wondering, is there any kind of technology - you say you're doing wave technology as well - but putting these wind turbines on some kind of buoy system if they're going to be offshore to harness the wave energy in, the wind energy at the same time.

Chris -   Now, there's an interesting idea - a hybrid, so you can bob up and down and collect the wind.  What do you think?

Richard -   It's an interesting point.  We like, so far, to put our wind turbines on nice solid foundations both on land, and sea.  And people are thinking, well, it would actually be quite nice to have some kind of floating system.  The only trouble is that it's quite a bit of work to make sure it all is reliable and doesn't tip over and so on.

Alisha -   I'm Alisha, I'm from the USA.  You always hear about bats and migrating birds and things flying into the wind turbines and getting killed.  Is that still a big problem and if so, is there anything being done to mitigate that?

Richard -   Well, I'll have to be honest.  Wind turbines do kill birds.  They kill bats.  You said, "Is it a big problem?"  And that's quite a difficult question.  I mean, in terms of things that happens to birds, they're not very likely to get hit by wind turbines.  There are much worse fates for birds.  So, I'm not pleased that we kill any but I mean, you got to keep in perspective.  And I think we're quite good.

Steven -   Steven Halliday from Cambridge.  Is there any way of storing electricity which is generated by wind turbines and not used when it's generated?  For example, a windy night, lots of energy from wind turbines, no one wants it.  Can we store it and use it later?

Richard -   Absolutely.  The difficulties with that is, we can store it as so-called 'pumped hydro' - you can pump it up to a high reservoir and let it come out.  There are other means.  You can use batteries.  The only trouble is that we would need an enormous number of batteries.  At the moment, the economics do not favour a lot of storage.  So, we just say, run a gas plant a bit harder or not so hard, or you have Norway as a neighbour.

Holly -   This is Holly, and I'm from Florida.  You said you're building a prototype.  Just exactly what is a prototype?

Richard -   When you design something new, you've got to find out whether it works.  We've designed a new type of generator.  We need to build it, test it, to see whether first of all, does it generate power and does it comply with all the sort of rules and regulations that you need for a wind turbine generator.  Actually, we tested it in Norwich and we managed not to blow up the Norwich electrical supply, so we're very happy.

Chris -   I'm not sure if that's a slight on Norwich or a slight on your engineering.

George -   I'm George from Ely.  I'm just wondering, how do wind turbines catch the wind?

Chris -   Yeah, good question.  So how does the blade there that you've got on your nice model, how does that actually convert the motion of the air into electricity generating motion?

Richard -   Well, I can't blow strong enough George, but the wind coming in has a certain amount of momentum and the blade shape is such that the wind is deflected off the blades and that produces the turning force.  You know how like an airplane flies - the wind cuts through the air and produces some lift.  It's the same principle.

Chris -   So, what you're saying is that the air hits the blade and because the blade pushes the air in a certain direction, the air pushes back on the blade.  And so, you actually make the blade move in a certain direction.

Richard -   That's right, yes.

Chris -   Any other questions or we're going to let this man off the hook?  We have one more over here.

Joe -   Hi.  My name is Joe from Caldecote.  My question is, as I've heard about wind turbines, that they cost a lot of money to maintain. I just wonder is it efficient and effective enough for the money we generate from the wind turbine to support the maintenance?

Richard -   Well, if I were an investor in a wind farm, I would be very concerned about those issues.  The general view now is that wind power on land is the cheapest form of generation including the maintenance costs.  That's particular so in very good sites in the American Midwest.

Heat generated from the nuclear fusion in the Sun

16:40 - Spray-on solar cells

Scientists promise us a future where solar cells can be sprayed onto surfaces, so cars, buildings and streets could be covered in them.

Spray-on solar cells
with Michael Price, Cambridge University

Traditional solar cells are made using silicon crystals. While these have their the sunbenefits, such as efficiency, they are relatively bulky, expensive to make, and can't be bent. So now scientists are looking into new materials for solar cells which may have better properties. Michael Price works on organic solar cells which can be made cheaply and are thin and light. Unfortunately, at the moment, they aren't as efficient as conventional cell. Michael showed Chris Smith how he's looking for ways to improve the efficiency of these materials. 

Michael -  I'm looking mostly at the physics of new types of material for solar panels.  We call them solar cells and a solar panel is just made up of lots of solar cells.

Chris -  Now, when you look on the roof and you see these solar panels, what are they actually doing?  How do they work?

Michael -  Yeah, so to convert the energy of the sun which is obviously our most abundant resource of energy, there are a number of steps that you need to undergo.  So, we think the first step that you need to achieve in good solar cells, you need to absorb the light.  So, if you can think of light as particles - we call them photons - you need to absorb that particle of light in your solar material.  In the second step, in the process of absorption, you create an excited electron.  So, your photon comes into your material, hits that material and it's going to excite an electron, got a bunch of these electrons sitting dormant in your material, in your semiconductor and once you've excited one of these, the electron needs to travel through the material and then out into a conductor like just a normal copper wire. And that flow of electrons is what we call electricity.  There are a bunch of problems that could happen.  The electrons can crash into each other.  They can crash into other atoms and you lose energy as heat.

Chris -  So, the light coming in from space is hitting the material and is dislodging some electrons or putting them into a state where they can actually flow around a circuit.  How does that get into the grid because obviously, people want to use their cells on their roof to reduce their energy bill don't they and they do that by selling the electricity back to the grids.  So, how does that happen?

Michael -  As we all know, grid power works on an AC (alternating current) and so, you need to convert your direct current because the sun is a constant source. It doesn't flick on and off at frequency of 50 hertz.  You need to have just an electronic device to convert your direct current from the sun into an alternating current and then you've got power for your microwave.

Chris -  Sounds like a done deal.  I mean, how good are these panels, the ones you see on people's roofs?  How much energy are they converting into electricity they can use and sell?

Michael -  So, 90% roughly of the solar panels that you see on people's roofs are made from silicon.  These are pretty good.  People have been working on them for 20 years and they're getting up towards 20%.  Maybe most...

Chris -  So when you say they're getting up towards 20%, you mean, of the energy that hits them, about 20% turns into useful electricity.

Michael -  Yeah, that's right.

Chris -  What happens to the other 80% then?

Michael -  A lot of what I study, the goal of improving efficiency of solar materials is to get that number up.  But there's a fundamental limit.  The most efficient single layer of solar panel you can get based on thermodynamics, that's just looking at the principles of energy conservation - the energy you put in has to equal the energy you get out and 30% is the number that we talk about.  That's the upper limit.  Of course, you can make solar cells more efficient by putting them on top of each other or concentrating the light that goes in on them.

Chris -  So, tell us about this that you've got in front of you - a little demo there.

Michael -  This solar panel is made of plastic essentially.  That's the active material.  If I hold it really close to the light up here, it's going to make a really annoying buzzing noise which is perfect for radio.  So, I'm just holding it up, really close to a light on the roof simulating the sun and it's attached to this frustrating little buzzer here.  And you can see at the same time, I can flex the solar panel.  It's really thin.  It's really light because it's made of electrically active polymers - plastics rather than...

Chris -  So, this is different than what you would find on top of roofs.

Michael -  And this is what we study in my lab, different types of materials.

Chris -  So, you're trying to re-invent what's on people's roofs at the moment and make thinner, cheaper, lighter materials.

Michael -  Yeah.  We're not necessarily going to replace what's on people's roofs.  We might be able to put a very cheap coating onto silicon and improve their efficiency.  In fact, that's happened in the last couple of years, but there are a whole bunch of uses for cheaper, perhaps not quite as efficient, but cheaper, lighter solar.  It's really useful on the developing world.  For instance, there's still a billion people who are off-grid who don't have mains power.  If we can supply them with something that's cheap, that's not going to break if you drop it then that could be a really good thing.

Chris -  Who's got some questions about solar panels, how solar cells work?

George -  My name is George from Ely.  I'm just wondering how you can get the solar cells into a material.

Michael -  Basically, what consists of a solar cell, you need two electrical contacts, so they're going to be made of metal.  The way we do it, we start with a piece of glass and then we have a transparent kind of metallic conductor and then we - just because the materials we work with don't require extreme processing, we just squirt them on.  We can just squirt these materials and then we evaporate on another metallic contact.

Chris -  What's the recipe for the stuff you can just squirt on?

Michael -  Well, so there's a whole range of things you can do.  I was reading today, there's a guy that's been harvesting salmon sperm for use in LEDs which are just like solar cells in that a solar cell will convert photons to electrons, electricity.  An LED will convert electricity to photons.  But in our lab, we use our polymers, plastics.  We also have been researching this new type of material called perovskite solar cells.

Chris -  Yeah, that's getting a lot of attention, isn't it?  What's special about that?

Michael -  Basically, they have all of the good things of polymer solar cells there.  They're cheap, flexible, you can just squirt them on.  You don't need to grow them painstakingly like you need to grow a crystal of silicon.  And they're also really efficient.

Chris -  So, could you have a paint that you could slap the stuff up the wall and turn your garden fence into solar cells?

Michael -  People always ask about painting solar cells, but you need the electrodes as well.  So, it's not quite as simple as just...

Chris -  Maybe wallpaper or some things like that.

Michael -  There's already Oxford photovoltaics who pioneered another work on these perovskites.  They're working on building integrated photovoltaics.  So, that means that all of the glass that goes on your skyscrapers could have a thin layer of semi-transparent solar panel on that glass and so, they could generate electricity while you work.

Chris -  While you're zapping the buildings across the street which happened with the building in London last summer, wasn't it?

Michael -  Yeah.

Holly -  This is Holly.  I've seen lots of solar panels everywhere in England but it's always cloudy.  Do they still work?

Michael -  Yes, they do.  The new types of materials that we're working on actually work better in low light than the crystal and silicon ones.  But it's obviously true that there are places that are better for solar than England.  Yeah, the solar panels will work in low light levels but just not particularly well.

Will -  Hi.  I'm Will from Swavesey and I was wondering, does the colour of the cells change the amount of light it absorbs?

Michael -  Yes, that's a really good question.  The ideal solar cell is a black one because it absorbs all of the light in a visible spectrum but you can make solar cells of all different colours.  But a transparent solar cell that lets all of the light through that our eyes can see is not going to be as efficient as something that harvests that light.  You can make transparent solar cells that absorb the infrared.  So, those are the really long wavelengths of light that our eyes can't see, but they're not going to be very efficient.

Chris -  So, just let them sort of model-T Ford of the solar panel world.  You're going to have any colour you like as long as it's black.

Michael -  Exactly.

Dwight -  I'm Dwight.  I'm also from Ely.  Why do the solar cells wear out and why do you have to replace them after a while?

Michael -  That's also a very good question.  In an area of active research there are an awful lot of reasons.  Most solar cells, we try and encapsulate to protect them from the elements.  Usually, if the encapsulation fails, then the solar cell is going to wear out.  In the case of silicon, these solar cells lasts upwards over 20 years.  The reasons for that can be varied.  It can be due to oxygen degradation or water or probably, before the actual material fails, the electronics associated with it are going to fail as well.

Anthony -  Hi.  I'm Anthony from Cambridge.  I was wondering, how long does it take a solar panel to generate as much energy as was used to manufacture it?

Michael -  Again, similar to the wind question, the energy payback time for our solar panels obviously varies greatly with where it is.  If it's in a very sunny place, then the energy payback time actually can be very small and the energy payback time is going down on time, but I think I've heard, less than a year, it can be.  But if you put it in a cloudy place, the energy that you've used to create the thing has been - if you haven't made it very efficiently, then the energy payback time is going to be a bit more.

Chris -  What is that thing that looks like a giant till roll in front of you?

Michael -  This is a giant roll of polymer solar panel.  It's rolled up here because it's a really good demonstration of the fact that you could print these solar cells off like newspaper and that's the goal.  That's what can make them so much cheaper.  I also got - it says it on the front here - you're looking at the world's first coloured production really plastic display that is flexible.  This is from Plastic Logic which is a spinoff company of one of the professors in my group and basically, it's a flexible kind of eReader like if you can imagine your Kindle was in colour and you could bend it.

Chris -  I mean, handy because the people in customs did that to my Kindle when I was travelling recently.  It didn't take too kindly to it.  What's your name?

Malcolm -  My name is Malcolm and I'm from Long Stanton.  So, the dark of the colour of the solar panel means, the more sunlight it absorbs and the more electricity is made.

Michael -  Yeah, that's it in a nutshell.

Sycamore Maple (Acer pseudoplatanus)

26:44 - Artificial photosynthesis

Plants are hugely efficient at creating energy from sunlight. Now researchers are trying to capture sunlight to make hydrogen the same way.

Artificial photosynthesis
with Dr Erwin Reisner, Cambridge University

Many people agree that hydrogen is one of the fuels of the future. It doesn't releaseMaple Leaf pollutants when used, and can be created from water. However, currently, to break water down into hydrogen and oxygen takes a lot of energy. Many scientists are looking into cheaper and more environmentally-friendly ways of producing hydrogen from water. One of these is Dr Erwin Reisner, from Cambridge University, and he explained to Chris Smith how he uses sunlight to drive the process.

Ginny Smith and Dave Ansell also have a go at splitting water into hydrogen and oxygen, with explosive results!

Erwin -  What we try to do is really produce a renewable fuel such as hydrogen as an example.  So, I think it can be perceived as an extension of photovoltaic research where we take a solar panel, instead of producing electricity, we just try to produce hydrogen directly from water as an example.  In a nutshell, you have water, you shine light on it and hydrogen comes out.  Hydrogen is a very interesting chemical because it's energy rich, it's a fuel, and we can store and transport it.

Chris -  How does this work?  How can you actually split the water up like that?

Erwin -  So essentially, we heard the first part was heavily inspired by photovoltaic research.  So, we need a light absorbing material where we essentially harvest the photons, what we've heard about, and then instead of producing electricity, we just transfer energy directly to a catalyst.  The catalyst is a substance that facilitates a chemical reaction.  This catalyst we're using is a catalyst that withdraws hydrogen from water as an example.  Essentially, yes we are physics and when we talk about fuels, we need some chemistry.  That's my specialty and that's why we try to make fuel cell.  Hydrogen is only one example.  We can think all about liquid fuels to replace fossil fuels and with liquid form in all kinds of possibilities.

Chris -  So, you would have a material which would have access to some water.  It could split the water into hydrogen and oxygen.  How do you get the energy back?  What would you do with the hydrogen?

Erwin -  The hydrogen needs to be stored.  Essentially at the moment, what you would do is you would just pump hydrogen out and compress it, and then store it, and transport it.  Or you'd convert it directly into a liquid form of fuel.  That's another possibility.  So hydrogen can be converted into all kinds of liquids by established industrial processes.  It's done under mega ton scale at the moment...

Chris -  They're not dangerous though.  I mean, Hindenburg didn't go down to - well, it did go down, that was the problem, but it wasn't too much of a success story from a chemistry and engineering perspective, was it?  Isn't there a bit of a danger associated with hydrogen?

Erwin -  Yes, hydrogen is explosive that's for sure, but so is actually natural gas and gasoline is also actually quite dangerous and explosive.  So, I think we definitely have the technology to handle hydrogen as a gas and it's not much more dangerous than other forms of fuels we're actually handling at the moment.

Chris -  Well, before we hear more about the technology, I think we should hear a bit more about hydrogen.  Ginny and Dave...

Ginny -  So, we're actually going to look at a more conventional way of getting hydrogen out of water.  So, water is H2O which means it's made up of hydrogen and oxygen.  So, if you want to get hydrogen back out, you have to split those molecules up.  So, how do we go about doing that?

Dave -  So, what you want to do for that - so first of all, I have a pot of essentially water.  There's a bit of salt in there called magnesium sulphate.  This basically means it conducts electricity a bit better and makes something work a bit better.  What we've also got is a power supply and this will apply a voltage to these two screwdrivers.  And so, what I'm going to do is I'm going to make one of the screwdrivers positive and one of the screwdrivers negative.  Now, if you think of water, it's H2O.  The H is a slightly positive and the O, the oxygen is slightly negative.  So, if you put a large voltage across water, the oxygen will be attracted to the positive electrode and the hydrogen will be attracted to the negative electrode.  If you put enough voltage on, that will actually split those water molecules apart and you should get gases coming off.

Ginny -  Okay, so we've got a small beaker full of liquid and you're now putting a contraption made of two screwdrivers taped together into it.  This looks a little bit dodgy.

Dave -  We'll try.  So, I've now turned it on and something quite interesting is happening.

Ginny -  Yeah, can you see what's happening?

Boy -  I can see bubbles.

Ginny -  You can see bubbles, exactly.  So, those should be bubbles of hydrogen and oxygen.

Dave -  That is the idea, yes.  So, we'll let those build up nicely for a while and there's an easy way to see whether it's likely to be hydrogen and oxygen; we'll be trying setting fire to it because we can basically release the energy we put in by putting electricity through the liquid and splitting hydrogen and oxygen in from water.  if we set fire to it, the hydrogen will burn with the oxygen to create water again and release lots of energy.

Ginny -  So, we've just talked about how explosive and dangerous hydrogen is.  Now, we're going to set fire some of it.

Dave -  Sounds like a good plan to me.

Ginny -  Everyone thinks that sounds like a good plan?

Audience -  Yeah.

Ginny -  So, we've got quite a good layer of froth on top of this little beaker now and I can see Dave is ready with a box of matches.  Do I need to get back?

Dave -  In a minute, yes.  The reason why it's creating a froth is a little bit of washing up liquid in there which catches the bubbles, so they're trapped nicely.

Ginny -  Because otherwise, they just escape and go off into the atmosphere and we will be able to set fire to them which should be no fun at all.

Dave -  Okay, so here we go.  I'll light a match and I'll put it down to the froth at which part... 

Ginny -  Did anyone notice that that bang sounded a little bit funny?

Boy -  It sounded like a balloon popping.

Ginny -  It did sound a bit like a balloon popping.  It was quite kind of squeaky wasn't it and that's characteristic of hydrogen.

Dave -  It was a very, very sharp bang, which is because actually it wasn't just hydrogen you're burning.  It was a mixture of hydrogen and oxygen.  If you mix hydrogen and oxygen together, it will burn exceedingly fast.  Actually, if you get the mixture right, they will burn faster than the speed of sound and you get what's called a detonation which is really destructive.  If it is not perfectly mixed then you won't get a detonation.  With air, it doesn't detonate quite so well, but yes, you have a very, very violent bang.

Chris -  Ginny and Dave, thank you very much.  (applause)  So Erwin, presumably your experiments don't quite go like that.

Erwin -  No, it's safer.  Shall we show it?

Ginny -  So Erwin, you've brought an example of how you create hydrogen.  It's a little bit different, right?

Erwin -  Yes, so this is a very simple system that's why I brought it here.  eEsentially, what I'd like to show is in a test tube essentially, how you can generate some hydrogen with our energy saving light bulbs which are not very energetic.

Ginny -  We need quite a lot of power to put through our mixture to separate the water out.  You're going to do that using less energy.

Erwin -  I will try, yes.  Essentially, what we have here, this is really just water with some buffer at pH 7.  There's nothing unusual about it.  We'll just pipette this out quickly and you can see as normal water, it's just fully transparent.  This means if you want to generate hydrogen with this mixture, it's very bad because no light is being absorbed.  That's why it's transparent.

Ginny -  So, we need to absorb the light for the energy to split the water and transparent things don't absorb light very well.

Erwin -  Precisely.  That's why I brought this dye here.  You can see that the deep red coloration and essentially, I just take a bit of that.  It's just an organic light absorber.  It gives some colour.

Ginny -  Okay, so now, it's got a nice bright red colour.

Erwin -  Yeah, exactly.  So now essentially, this dye will absorb light, but we still don't have this catalyst I mentioned before.  So, at the moment, we absorbed the light, but it's not good enough to generate the hydrogen.  So, we really need this catalyst, this substance that helps and facilitates the evolution of hydrogen.

Ginny -  And a catalyst is just something that is used in a reaction that helps something else be produced but doesn't actually get used up itself.

Erwin -  Precisely, yeah.  This catalyst is what we develop in our laboratory.

Ginny -  So, that would mean you could use the same catalyst over and over again, just adding more water.

Erwin -  If we have a very good catalyst, yes, but at the moment, they do not exist, except they're very, very expensive and like platinum.  But this is a very cheap material, a very cheap catalyst.  At the moment, they're not sufficiently efficient to run for very long.  So at the moment, all I do is shake it.

Ginny -  And it's a nice little bright orange colour now.  It almost looks like it's glowing.

Erwin -  Yeah, it is exactly.  What I will do now, I will just put it here in the back and it will probably take a couple of minutes but then we will see the formation of hydrogen.

Ginny -  So, you're going to pop that under a light that's going to effectively, you'd normally do this with sunlight, but it's evening and we're inside.  So, we're going to put it by a lamp instead.  We're cheating basically.  And then we're going to come back to that...

Chris -  How will you know the hydrogen has been made?

Erwin -  Essentially, we can also light it up or we use analytical facilities in a chemistry laboratory.  We know precisely what gas is being formed.

Ginny -  Setting fire to it sounds like more fun.

Erwin -  Precisely, yeah, I agree.

Chris -  We'll come back to that in a second.  So, tell us a bit more about how you actually are working on this?  The ultimate goal then would be, so that we have ways of converting plentiful sunlight into a supply of hydrogen.

Erwin -  Yeah, so that is the idea.  At the moment, this is a very new line of research compared to wind technology or solar cells, which means we have no commercial applications at the moment.  So, these are really being proposed at the moment, but it will still take a considerable amount of time really to bring this to the market place.

Chris -  Is it just visible light or can it use heat?  So, if we took a waste industrial process that produces loads and loads of heat or a data centre.  I mean, one statistic is that the data centres that run the internet are chucking more heat into the sky than they're actually using to run the data centre in aircon.  And also, they're contributing more CO2 than the airline industry.  So, can we turn that waste heat into something with this technology for example?

Erwin -  Yeah.  Heat is certainly very interesting and I think should be used much more in the future, but we focus only on solar technology.  If you use solar technology, either you run it like our systems just at room temperature or you work on solar thermal approaches where essentially you also work with heat, with solar concentrate, that's where you work at a thousand and more degrees Celsius also to produce fuels that way.

Chris -  Who's got some questions for Erwin on how hydrogen works?

Bryan -  Hello.  I'm Bryan from Cambridge.  My question is, we heard early on that the solar panels turned about 20% of the solar energy into electricity.  When you then generate hydrogen, what percentage of the energy is transferred then?

Erwin -  So at the moment, depending on technology, we have two ways.  Either we convert energy directly, which means sunlight goes directly to fuel.  This way, the record efficiency is about 13%.  But these are achieved with very expensive materials and effectively, systems do not last very long.  An indirect approach would be to couple a solar cell plus an electrolyte system as we've just seen before.  With such technology, we can probably reach 15% to 20% or even 30% very easily on an industrial scale.

James -  Hi.  My name is James.  I'm from the United States.  You said the technology is new.  However, what commercial applications were you looking for this technology and also, what are hurdles that you face going to towards that?

Erwin -  The main hurdle is essentially - there are several - but the main problem at the moment is the cheap price of hydrogen produced from fossil fuels.  So at the moment, all the hydrogen we see which might be quite interesting is effectively not renewable hydrogen.  We might see all the green hydrogen buses driving around but this hydrogen is all produced through industrial processes from fossil fuels.  And this hydrogen at the moment is about an order of magnitude cheaper to produce than any renewable forms of hydrogen.  So at the moment, what is really letting us down is the very low cost of hydrogen derived from fossil fuels.

Joe -  Hi.  It is Joe.  My question is, can we use dirty water or sea water to generate hydrogen because pure and clean water, we are so of it in this world anyway?

Erwin -  Yes, it's certainly feasible and people have shown that this is possible.  So essentially, with seawater, we mainly deal with highly saline water, full of sodium chloride.  But in principle, there's nothing that holds you back to use seawater to generate hydrogen renewably.  In fact, it might even help because there's an electrolyte already in the water.

Chris -  What does that mean?

Erwin -  Electrolytes are simply a conductor in the aqueous solution.  So, if you want to electrolytise  water for example you need a conductor in electrolytes.

Ginny -  So, we had added one to our demonstration here in order to make it carry the charge better.  So actually, if you were doing this kind of electrolysis to split it, it would probably be better with seawater.  In fact, it works very, very slowly if at all, with pure water.

Dave -  The only disadvantage with electrolytising seawater is that instead of producing oxygen in the other end, you'll produce chlorine which is a chemical weapon, so you have to be careful with that one.

Ginny -  We decided not to go for that tonight.

Erwin -  Chlorine is also produced by the industry at the moment.  It's quite available chemical, so we might even be able to use this one and produce renewable chlorine this way.

Chris -  How is your catalytic breakdown of water going?  How are you getting on?

Erwin -  Okay, so at the moment, we have produced the first couple of bubbles of hydrogen which I'm happy to share with Ginny as an example.  Yeah, gently as I said, our light source is very weak...

Chris -  Gently, He says gently - is this because it's explosive?

Ginny -  Can you see?

Erwin -  No.

Ginny -  There are some bubbles appearing.  What is that in the bottom of the test tube?

Erwin -  This is hydrogen that comes from water.

Ginny -  There's a little white thing.

Erwin -  This is stir bath.  This is just to stir the solution.

Ginny -  Okay, so there's something in the bottom to stir it and you can see on there, we formed little bubbles of hydrogen.

Erwin -  Yeah, the bubbles like to accumulate at the stir bath.

Ginny -  Okay, so if Dave takes it around, you should be able to see - there's not very many.  I think ours was more impressive, but you did do it with light and we had to use a very high voltage to get that much.

Chris -  Are you effectively trying to recreate photosynthesis here?  I mean, plants are very good at gathering energy from the sun and turning it into a chemical form of energy that they can use elsewhere in the plant or store as sugars turned into starch.  So, is that sort of what you're doing?

Erwin -  Precisely.  So actually, we do look at natural photosynthesis, try to learn from it and try to mimic the processes.  The field is in fact called artificial photosynthesis.  So, we do try to adopt with chemistry, materials chemistry to adopt and mimic processes in photosynthesis.


40:02 - Powerful vibrations

Tiny sensors that harvest energy from passing cars, people or even the flow of your blood may one day be powering sensors inside you...

Powerful vibrations
with Dr Sohini Kar-Narayan, Cambridge University

Piezo-electric materials produce an electric current when they change shape,Electricity usually by being squeezed or hit. Dr Sohini Kar-Narayan, from Cambridge University works on nano-scale piezo-electrics which are sensitive enough to respond to tiny vibrations harvested from the environment. The output is small, but nonetheless sufficient to power tiny sensors in clothes, the environment or even embedded in the body. Sohini told Chris Smith how this could power a blood sugar detector with your heart beat, or a temperature sensor in a room simply from the vibrations of cars driving past. 

Plus, Dave Ansell tests his very own piezo-electric crystal he made at home!

Sohini -   So, you've heard about producing big energy and looking for big energy solutions.  I work at the other end of the spectrum which is looking for small energy solutions.  In particular, I'm looking at harvesting energy from ambient sources in our environment to power devices which don't require a lot of power really.  You might wonder, small power should be a lot easier but it isn't because as the devices are shrinking in size, the batteries which you would normally use for example to power them, they aren't quite keeping up.  And so, to enable this technology to progress, we need to look at alternative energy sources.  And this is piezoelectric materials come in.  piezoelectric materials are a special class of materials which when you distort their shape, so basically, literally, when you squeeze them, they produce an electrical charge which you can then access via circuit.  The reverse is also true.  You can actually apply an electric fuel to a piezoelectric material and it will change shape.

Chris -   Is this how your crystal in your clock keeps time?

Sohini -   Absolutely and even the way your microphone works, it basically converts the vibrations from sound.

Chris -   Lighters, the barbecue lighter.

Sohini -   Absolutely, yes.

Chris -   So, squeezing a crystal.

Sohini -   Exactly, to produce a voltage essentially.

Chris -   Why does that happen?  If I squeeze a crystal, why should squeezing a crystal make some electricity come out?

Sohini -   So, certain crystals can be thought of as being made up of charges which are separated within them and we call these dipoles.  So imagine a crystal with a positive and a negative charge separated.  Essentially, what happens is when you squeeze this, you change the position of the positive and the negative charge.  So essentially, you can imagine that you're creating more of a charge across the surface and I think Ginny has a demonstration.

Ginny -   Yeah, so we were thinking about this this afternoon and we were thinking it's quite a difficult thing to imagine.  So, we came up with a little way that you might be able to imagine it at home.  Okay, so what we've got here is a pillow case and you can imagine that this is like one molecule inside the crystal.  So, I'm going to ask Dave to hold one end of the pillow case and so he needs to hold the other end.

Dave -   So, the actual crystal will be made up of millions and billions of these, all lined up next to each other and stacked in every possible direction.

Ginny -   So, if you stretch the pillowcase out nice and tight - now, what we've got here is a Ping-Pong ball with a plus sign on it.  So, that is a positive charge.  So, if you imagine our molecule has its positive charge at one side, like so, then if we change the shape of the crystal by moving where your hands are...oops!  It falls off.  But you can see that if you bring...

Dave -   So, the side of it squashed it, the ping pong ball is rolling towards it.  So, we squashed the side towards the audience the ping pong ball is moved towards that.  If we squashed the other side, the ping pong ball moves away.

Ginny -   So, you can imagine that being like, if every molecule in the crystal is being squashed in the same direction then your charge is going to move from one side of it to another.

Dave -   And so, if you imagine, each molecule has a little bit of charge that move from one side to the other then the next molecule, the same bit moves, the same bit moves.  So overall, a charge is moved effectively from one side of the crystal to the other side of the crystal.  And that piece is quite a large voltage and you can produce sparks with a gas lighter with it.

Chris -   If you take the voltage out of the crystal, so those charges flow around a circuit like they do in say, a barbecue lighter, doesn't that leave the crystal without some charge?

Dave -   And then if you let the crystal relax then the charge will want to flow back the other way and then you have the second spark because you get a spark when you crush the crystal and you get another spark when the current goes the other direction when you uncrush the crystal.

Chris -   And so, you're saying Sohini that this is a way that we could harness this to extract energy that we would otherwise throw away in the environment.

Sohini -   I mean, that's really the key thing.  this is energy that is available to us.  It's widely accessible.  It's pretty much everywhere.  You're probably always going to be situated near a source of vibration.  So, it seems like a good place to start.  What I need to stress is that the amount of energy that we're trying to harness or to harvest is actually quite small.  But this is important because if you think of the applications for the small energy, they're really limitless.  So, a big thing which you might have heard of is the internet of things which is essentially having everything really connected via sensors.

Chris -   Someone told us the other day that he bought a slow cooker which is on the internet and he said that he's discovered he can dial in from work to turn on the slow cooker.

Sohini -   Exactly.

Chris -   But then he discovered that it's the same log-in and password for every single one of those slow cookers that everyone owns.  So then he said, "I can ruin someone's beef stew if I just know where to find it."

Sohini -   Indeed.  I mean to be honest, there are lots of security concerns with the internet of things, but then that's a debate to be had possibly.

Chris -   But the question is, how do you power them?

Sohini -   Exactly and the point is, you can look at the energy crisis from two angles.  We are running out of fossil fuels and we need to look at renewable energy sources.  So, one way to do it is to look for new ways to produce energy, but the other way to do it is to try and save energy.  So, the energy which I'm trying to harvest is not necessarily going to light up this building, but it can light millions of sensors in this building, such that you can save up to 30% on your electricity which sounds like a good deal.

Chris -   So, would this be then say, air current sort of wafting past something or if you did it say, on a light bulb, you could get air currents near a light bulb because it's hot.  You could get those vibrations or something.

Sohini -   Sure, absolutely.  So like I said, these are ubiquitous really.  So, you could imagine sticking it on your washing machine.  That vibrates while it's on.

Chris -   So, anything that moves, you can get energy out of it.

Sohini -   Yes, including yourself.  I mean, I think this is still a bit far off but in principle, if you could make these devices on a large scale and if you could integrate it for example into your clothing which is very possible.  As you walk, as you move, you could generate enough electricity to charge your mobile phone.

Chris -   Will that make walking really difficult though?

Sohini -   As I said, piezoelectric materials have been on for a long time and usually, research has been focused on bulky ceramic crystals which as you said are quite hard to move around with.  My research focuses on nano piezoelectric material.  We're looking at really tiny amounts of these materials which the idea is that they should be able to blend into the environment, into your clothing and practically be invisible for all practical purposes.  So that you're not aware that they actually exist, but they are constantly harvesting energy.

Ginny -   So, we actually have an example of one of those super bulky piezoelectric crystals that Dave made yesterday.  That's quite impressive Dave.  How did you make one of these?

Dave -   I basically made them by using cream of tartar and if you heat it up and dissolve it, that's an acid and then I reacted it with some sodium carbonate.  I spent about 3 hours carefully adding the two together and mixing it up and eventually, the solution went clear.  I let it cool overnight and you get these really beautiful quite large crystals.

Ginny -   So, they look a bit like a really huge salt crystal.  You can actually see some beautiful geometric shapes on the side.

Dave -   Because a crystal is when you've got lots and lots of acids and molecules lining up in a very organised shape.  So, repeating again and again, and again.  The reason why you see the edges of that is that kind of zoomed out in huge scales if you've got billions and billions of them together.  You get these sharp shapes because that's the shape of the fundamental crystal underneath.

Ginny -   So, what are we going to do?  I'm not sure I believe that those are piezoelectric.  They just look like crystals to me.

Dave -   It's taken a while to persuade myself that they are, but now, I'm fairly sure they are.  What I've done is, it's a bit delicate, so I've got it sitting here.  I've put one in a vice and I've put two tinfoil electrodes connected to this crystal and I've wired it up to an audio amplifier and attached that to a speaker.

Ginny -   So, the vice is just to hold it still and to hold the electrodes that it's connected to onto it.

Dave -   Yeah and so, the idea is that any electrical signals that's produced will be amplified by the amplifier and then should be turning into sound which you should be able to hear.

Ginny -   Let's give it a go then shall we?  

Dave -   So effectively, what I've built is a very, very rubbish microphone.  With rather better engineering, you can produce a perfectly good microphone and actually, quite a lot of the cheap microphones are made like this.

Chris -   But the point is, you're squashing the crystal, putting a force onto the crystal and that is, as you say, moving charges around and making them go on to the electrodes, flow to the amplifier and those little clicks we were hearing, they're the surges of current coming off the crystal.

Dave -   That's exactly right, yeah.

Ginny -   But we weren't making very much electricity there and it's quite a big crystal.

Dave -   So, the trick is to A. if you can bend the crystal a bit more, you'll get more voltage out of it.  Also, if you use much better materials, which is I think what you've been doing over there.

Chris -   Yours better?

Sohini -   I'd like to think so, yes.  In fact, a lot of research into piezoelectric materials concerns ceramics.  So what Dave just showed you was a ceramic material and the image that comes to mind when you think of ceramics is they're brittle, they're stiff, and that's exactly the problem.  We're talking about an energy harvester which can sustain repeated vibrations, or heatings as you may want to think about it.  And so, it's important that this material can sustain that level of impact.  The problem with ceramic materials is that they're stiff and hence, they're prone to mechanical failure.  And so, I work with piezoelectric polymers which are slightly less well-studied class of materials.  But they're very interesting because being polymers, they're flexible which means that they can take a lot more beating and bashing as it were.  They have several advantages over ceramics.  For example, they are actually relatively cheap and easy to fabricate which is important if you want to make commercial devices.

Chris -   How much electricity will they make?

Sohini -   So, with these nano generators, we're looking at anywhere between 10 nanowatts to a microwatt and I know that that doesn't sound like a lot, but a lot of wireless sensors these days, their power consumptions are also coming down.  So, it might just be enough to power these devices.  The other thing that you need to remember is, a lot of these devices don't need to be on all the time.  So, imagine a glucose monitor embedded within your body.  You don't need to read your glucose off every second.  I mean, you might want to but it might not be necessary.  But you might be able to generate enough energy by just your blood flowing across one of these nano generators to emit a signal every 6 hours maybe and that's all you need really.

Chris -   How far away are you?  Have you got this actually working?

Sohini -   So, I can show you a device which I've brought here and hopefully, it will work.  If I just hold it up, the little circle there that you see consists of about 10 billion piezoelectric polymer nanowires.

Chris -   So, just for the benefit of the people at home, what we've got is something, it's about 2 inches long by about an inch wide slide of glass.  And what's the circle in the middle of it?

Sohini -   The circle is the device.  So, the circle is basically about 2 cm in diameter.  It's about 60 microns thick which means it's about as thick as the width of your hair.  As I said, it's packed with these piezoelectric polymer nanowires.  If I can get this to work, it should respond to my touch and that just shows you that it creates a voltage.

Chris -   So, at the top of the box, we've got lots of little red LEDs and as soon as you touched it, they all lit up.

Sohini -   That's right.

Chris -   They're all powered by you, touching the device and pressing on it.

Sohini -   So, that's really an indicator that you're generating some voltage and that is sensitive to how much I touch.  So, just a light tap would give you that.  A big push would give you that.  So yes, they are quite sensitive.

Chris -   So, it's like world's strongest man competition where you have to hit the thing with a big hammer, but for microscopic people.

Sohini -   Something like that, but to be fair, with that particular device, you would need to tap on it, not very hard for about 20 minutes to generate enough electricity to power an LED.  So, that doesn't sound very exciting sitting around tapping for 20 minutes.  But the point is that if you can upscale the production, if you can make more of these and connect them in series then you can bring that time down to a lot less.  And that's really the goal - to be able to make lots of these in a cheap and reproducible and reliable manner.

Chris -   Any questions from the floor?

Malcolm -   My name is Malcolm and I'm from Longstanton.  Why can't you just put a weight on top of the button and leave it for about 20 minutes to power a LED?

Sohini -   That's a very good question and I'll take you back to the demonstration that Ginny and Dave just gave.  The point is that if you leave a weight on, yes, you will generate some charge, but then that's about it.  In order to make a current flow in a circuit, you need to be able to do this repeatedly over a prolonged period of time.  so, by moving back and forth on that material, you produce what is known as an alternating current.  And then you can rectify that and use that to power something.  But just leaving something on there would just produce a spike of current and that's about it.  But you want this to work repeatedly.

Jasmine -   I'm Jasmine from Cambridge.  What's the smallest touch that you can do?  As in, what device can you touch really lightly and it works very well?

Sohini -   So, these piezoelectric materials as you've just seen, they're very sensitive to the touch and nano piezoelectric materials are supersensitive to very little forces.  We're actually looking at applications where you can put these into say, biological samples so that you can actually detect cellular motion.  So, really very, very tiny forces which you would not even be aware of, these can pick them up.  So yes, the answer is, very tiny forces and if I should put a number to that, we're talking on the scale of piconewtons or less.

Chris -   So, pretty small.

Sohini -   Very small, yes.

Chris -   Any other questions for Sohini.

Lowen -   Lowen from Cambridge.  So, with this material, you can have it in potentially nearly any electrical device.  How easy would it be to recycle it from one device to the other when the device was finished like clothes, etc.?

Sohini -   Again, that's a very good question.  I think one of the drawbacks of these kind of generators is that it is dependent on the actual source of vibration and that can be very intermittent in nature.  So obviously, if you had one of these in your shoes for example, you wouldn't be walking around all day at the same pace for example.  So, to move that into a different application will probably not be trivial.  And so, I would say that these nano generators need to be designed with specific applications in mind.

Holly -   I'm Holly from Florida.  People use phone every day.  Do you think you guys could start putting the stuff into screens on your phone?

Sohini -   In fact, I think there's a similar prototype being developed where you have it at the back of your keyboards because as you're typing away furiously, you can use that energy.  The beauty really is that you can integrate it into just about anything.  So yes, I can see applications where you have them on touchscreens where you can harvest the energy of just swiping or clicking on things, absolutely.

Dave -   I guess the phones would have to get a lot more efficient before it becomes very useful because they're using watts at the moment, not microwatts.

Sohini -   Indeed.  Sorry, so yes, so I should say that the energy which you would get out of it is still limited just because there isn't that much energy to harvest.  So, this would power maybe one function on your phone, but not necessarily charge your phone.  Having said that, as you correctly pointed out, we're at a very unique stage with a power consumption of modern electronics is reduced to such an extent that it is now slowly becoming feasible to power them from vibrations in our environment.  So, who knows?  Someday maybe.

Chris -   So, if you could have an amazing device that you're going to power on your things, what would it be?

Sohini -   Gosh!  I can think of so many of them at the top of my head, but I'm really interested in biomedical applications really.  So, tiny sensors which are implantable and which can just run off just your say, blood flowing through your veins and then which can give out vital information about your blood pressure, temperature, what have you.  I think it will make an enormous impact on healthcare.

Ginny -   So, I've got a question that's coming from social media and (Steven Pates) asks, "How can the UK be self-sufficient for 100% of its energy needs?"  So, he wants us to not be importing oil, coal, nothing.  So, I think that's kind of a question for the whole panel.  Do you see that in the future and how far away is it?  Who wants to come in on that first, Richard?

Richard -   Well, I was saying to someone today, what is the price of not trusting the French?  And if we were not to rely on our imports and exports to France, that would cost us a lot of money in extra kits.  So actually, I think 100% energy sales efficiency is not a good goal.  I think we should share with our neighbours.

Ginny -   But do you think it would be possible if we did want to or have to?

Richard -   Of course, but it's probably not the cheapest solution.

Sohini -   I think that energy saving will become more important as we go into the future.  And also, as more cities are being built, the concept of having smart environments will reduce basically how much energy goes into pretty much everything that you can think about starting from resource management to waste pickup.  So, if you have lots of sensors in the environment, they can more effectively communicate with each other and also, make energy use more sustainable and then that will have an impact.


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