How Fuel Cells Work | Spring Into STEM

I’m Rhodri Jervis or Rhod for short I work in the chemical engineering department here at UCL and specifically within a larger research group called the electrochemical innovation lab and there's a picture of some of us here with our fuel cell powered car in the in the quad of UCL and the electrochemical innovation lab covers a wide variety of electrochemical technologies one of which I'll talk about today and that's the fuel cell but this can also include things like batteries and super capacitors basically any devices and materials that go into these devices that can power our our lives really from from consumer electronics up to transport and potentially bigger sort of storage and stationary storage solutions as well we we study all aspects of these right down from the nanoscale what's happening at the atomic interactions in in all the materials being used up to the sort of systems level engineering that we that we do here in the group and we're a growing group now of probably about 100 researchers looking into all of these areas of technology and fuel cells and particularly hydrogen fuel cells and the hydrogen generation that that needs to be done to produce green hydrogen for fuel cells is a real focus of what we're doing at the moment and a real focus of of research in general in the UK and the government's sort of road map towards a net green future as well so I'll talk a little bit today about how fuel cells work I think we've probably got quite a mixed group of people here so please you know do ask questions if I don't give enough detail or you don't understand some of the technical things in this but I'll try and keep it fairly high level so that we can look at the various different aspects of fuel cell materials and fuel cell device engineering that goes into whether they work well or not and cover a little bit of the sort of research that goes on here at UCL in this area and I've put here that fuel cells are a multi-disciplinary and multi-scale problem we'll see that a bit more as we go through the slides but but this is really true we have researchers coming from all sorts of backgrounds from physicists physicists chemists chemical engineers obviously mechanical engineers electrical engineers mathematicians looking at modeling and things like this so really any sort of science background can be applied to fuel cells and of course policy is very important here as well and and even sociological science sciences and studies about how we can make our environment a more green and nice place to live in and fuel cells are a big big part of that I think in the future so what is a fuel cell well put simply it's just a device that converts chemical energy into electrical energy and it does this directly via things called electrochemical reactions so most all all chemicals have chemical energy tied up within their bonds within the bonds of the atomic level of various different molecules and and things like fuels for example and we can convert that energy into other forms of energy by doing various things one common way is via combustion to produce heat for example and this is how a lot of electricity is generated for example by gas turbine generators we take natural gas methane and burn it produces a lot of heat heats up water makes steam and that steam drives turbines to generate our electricity and because of all of those different steps there the combustion the steam generation the mechanical movement of all of the generators etc. it's actually quite an inefficient process and of course as we know using fossil fuels for this kind of process has severe impacts on the environment on sustainability and our and our way of life as well and obviously co2 production and other greenhouse gases is a real issue at the moment we're looking to try and electrify various different sectors of of our life basically in order to be able to use renewable energy renewable electricity and become more sustainable and reduce the impacts of greenhouse gas and that can be done in electricity generation in general which is great we've got increasing amounts of wind and solar on the grid now producing green and sustainable electricity which is brilliant but there are some sectors whereby that's very difficult to actually to actually implement so for example you can't put a wind turbine on your car and drive your car like that so we have to use we have to use electricity distribution obviously battery electric vehicles are quite commonplace now you'll see on the roads a lot but there are some issues with batteries and there are some sectors of the transport for example where batteries are just not going to be able to do what we need them to do for example in larger vehicles perhaps aviation where battery weight is quite quite key and so we need to look at other technologies as well and I'll focus on fuel cells as a technology of electricity generation today largely focused around the automotive sector but the fuel cells are actually quite scalable you can make very small ones and very large ones and the amount of electrical power that they produce is related to that size of that fuel cell so you see a few examples there in those images there's a big what we call stack there in the background of the image that's lots of fuel cells stuck together to produce a quite a high power output and then there's a smaller sort of single cell being held by the person in the photo and that would produce sort of you know on the order of a few watts or so of power so we could put these we could conceive of putting these fuel cells into any device that requires electricity and as I say because we're doing this in a direct electrochemical reaction we're producing this electricity straight from the inherent chemical energy in the in the in the chemicals that go into the fuel cell and in a lot of cases that will be a fuel such as hydrogen combined with oxygen often from the air to produce power directly and so we'll be talking about hydrogen fuel cells a lot here but fuel cells can run on other things like methanol ethanol even methane as well at high temperatures in solid oxide fuel cells but hydrogen is a really is a really attractive fuel because it's the most common element in the universe although it's banged up in other compounds normally so things like water for example h2o or fossil fuels like natural gas which is ch4 and we have to extract that hydrogen somehow once we have and if we do that with renewable electricity then that's called green hydrogen we can use that hydrogen somewhere else and later on in date with with with either storage or distribution of hydrogen on a sort of gas network for example and use that to to power devices particularly mobile devices like like vehicles and we can get our electricity back from the electricity we put in to generate hydrogen so that's what we're going to sort of focus on today fuel cells have actually been around quite a long time and actually predate the the combustion engine in at least in their concept and sort of simultaneously conceptualized by by a couple of different scientists christian schonbein and sir william grove who's from swansea my hometown and was an amateur scientist actually so there's hope for us all to do some really excellent science even if you're not studying science directly as a as a profession or as a in university for example but the concept of how a fuel cell works took a long time to be able to be packaged into a useful workable device and a lot of that is down to the materials advances that were being made that allowed fuel cells to become practical and in the 60s a series of fuel cells used on the apollo missions by nasa for example provided the electricity for for the for the lunar modules and the and the space exploration that was going on in the 60s there are lots of different types of fuel cells today we're going to focus on PEM fuel cells but they all use this sort of basic idea of electrochemical generation of electricity and that basic idea is actually quite simple we'll see later that there are a lot of materials and engineering factors into making fuel cells work well but the fundamental concept behind them is really quite simple and as I say it's about all about this electrochemical reaction we'll talk a bit about what an electrochemical reaction is in the in the next slide but this is the sort of experiment that william grove used to to generate power from hydrogen and oxygen all the way back in the in the 1800s electrolysis was known about that point and that and this is where we we put an electric current into water which forces the bonds to break and form oxygen and hydrogen gases from the constituent elements of water h2o obviously and in this case we put we put some electrical current through some platinum electrodes and we generate this gas he collected that gas in the in some upturned test tubes and found that when he stopped putting current into the system and just let the system relax naturally the presence of that oxygen and hydrogen gas on the platinum electrodes actually generated some current generated some electricity and that's basically how a fuel cell works we have some fuel like hydrogen for example some oxygen which acts as the oxidant and the two things combine separately on two different electrodes to generate electricity via some external circuit and and this is what's happening really in an electrochemical reaction so let me just move my video pane here so we can see so so normal chemical reactions all chemistry really is about the transfer of electrons in normal chemical reactions such as combustion for example we talked about burning natural gas to produce heat that electron transfer happens on a very small scale between atoms that are very close together the beauty of electrochemistry is that we actually separate that electron transfer from from the atoms on the surface of an electrode for example so we can see what actually happens is the reactants come close to the surface of electrode they they either donate or accept their electrons from the electrode and that electron transfer process is separated into an external circuit and so instead of a reaction happening on the atomic and molecular scale that we can't really control or do anything about this reaction is happening generating a current or using a current in the case of an electrolysis reaction for example and we can control that current using various devices and actually make use of that electricity produced so this electron transfer separation makes the electrochemistry really useful compared to sort of normal chemical reactions let's say it means you can it means you can control the generation of various different reactions but in the case of fuel cells here what we're doing is is extracting those electrons that current from the electrochemical reaction and using it to power something useful so this is what a basic sort of electrochemical reaction would look like we have two electrodes called the anode and the cathode and that's where these reactions these electrochemical reactions happen and they're often classified into oxidation reactions or reduction reactions basically oxidation is where is where electrons are lost and reductions where electrons are gains gained it doesn't really matter too much for the sake of this but then crucially what we have to separate these reactions and to make use of those electrons I.e the current that is produced is that we have a we have an electrolyte in the solution that allows ions to transfer between the two electrodes but not the electrons and so the ions would be the charged species that aren't electrons so for example if you dissolve salt sodium chloride in water you end up with sodium plus ions and cl chloride minus ions okay that's what's called an electrolyte and then the two electrodes are connected electrically via a circuit and that allows the electrons to transfer between the two of them so we have this flow of ions in solution in the electrolyte and a flow of electrons countering it through the through the electrodes and that allows the electrochemical reactions to happen at each of those electrodes as we saw in in grove's experiment there's a fairly basic sort of setup with these platinum wires for example that allow these things to happen and one of the reasons why fuel cells didn't advance very much from that state is that actually those reactions were producing very small currents and the currents are quite related to the the contact area of the surface area of these electrodes because the more electrochemical reactions that happen per second the more electrons generated and the more electrons that are generated per second the higher current we have because current is just the rate of flow of electrons basically there was also a large distance between those electrodes and so that gives a lot of resistance in the ionic flow between those two electrons electrodes and so a lot of what a lot of what makes fuel cells work today and work much better than william grove's original experiment is down to materials and engineering to increase the surface area or the contact area where these electrochemical reactions happen and to reduce other resistances within these electrochemical cells and so there's a huge amount of engineering that goes on to make these electrochemical cells work at a practical level for devices and that's really where I think modern engineering particularly chemical engineering is really exciting because chemical engineering traditionally is traditionally been a lot about oil and gas for example separating products from fossil fuels etc or maybe pharmaceutical approaches but I think that the the really interesting modern areas of chemical engineering that we're looking at a lot in UCL and that you would have the chance to study as an undergrad at UCL as a chemical engineer around these electrochemical devices so obviously we need to think about the chemistry of what's going on here but we also need to think about the chemical engineering which really packages that chemistry in the most efficient most effective way to produce practical devices that are going to change our lives really change the world as is the UCL motto so modern fuel cells look very different to this sort of experiment that grove set up all those years ago and you can actually see there in the bottom right hopefully you can see my mouse an example of a sort of role of of fuel cell electrodes and electrolyte essentially this is the working part of the fuel cell it's called an MEA and we'll get on to that in a second but essentially this is what fuel cells look like now basically a piece of piece of plastic with something printed on it and that can generate electricity directly from a fuel and from an oxidant in the air if we look at a sort of schematic of how this works is you can see already that there's a lot more stuff going on here the the fundamental sort of process of of fuel cells is say these electrochemical reactions they're actually known as half reactions because we have these two electrodes happening each half reaction happens on each electrode and these are separated into something called the hydrogen oxidation reaction the HOR and the oxygen reduction reaction and to get those reactions to happen at a reasonable rate we have to use some catalyst and so what happens is the flow of the gases the hydrogen and the oxygen at the anode and the cathode respectively diffuse into the catalyst and and and the electrochemical reactions occur so hydrogen gas which is h2 is split into protons h plus and electrons those protons travel through the electrolyte we'll come up to the electrolyte in a bit more detail and they're met at the other catalyst on the cathode where there's oxygen present that oxygen is combined with those protons and the electrons from the external circuit which go around the circuit here powering something on their way and that could be you know a mobile phone a laptop car or even a whole building for example in backup power and they combine with oxygen on the other side in the case of hydrogen as a fuel that gives us just pure water as an output and so if we're driving a fuel cell vehicle the only emissions from the from the exhaust pipe are water essentially very pure water at that but there's lots of engineering factors that go into making these things work really well we'll talk about all of these in a bit more detail the catalyst is quite key because that sets how fast these reactions can occur but even if you've got the best catalyst in the world if you don't make a very good fuel cell if you don't have good engineering surrounding it you're not going to get much power or much efficiency out of your fuel cell even things like how the gases are distributed across those catalyst layers the electrodes essentially is really quite important and obviously we've got to have conductive pathways that allow the electrons to travel from the surface of the catalyst where the reactions are happening back out through the fuel cell and round into the cathode and again to that catalyst layer okay we have to then also have really good ionic transport in the case of pro of hydrogen fuel cells these are protons and we're trying to minimize these distances make everything as small and compact as possible to increase the energy and power density of our devices okay so this is shown in a bit more detail in this animation here you can see h2 splitting into h plus and electrons and then all recombining at the catalyst on the cathode side with oxygen from air and producing just just water as an exhaust gas and it's that transport of or the separation of the electron transport through the external circuit and through the device in this case a light bulb there that allows us to utilize this chemical reaction as an electrochemical reaction generating electricity so really useful things if we look at even even more detail you'll see that these reactions these processes happen on on multiple different scales and we're talking about very small sort of scales here micrometers so sort of the width of a human hair and less sort of thing we have quite a thin electrolyte which is a a special type of plastic we'll come on to that in a second and we have these very thin catalyst layers about 10 microns thick where we have very very small particles of catalysts and these are normally nanometers in size a few different nanometers we then have materials that allow the diffusion of these gases to be spread nice and evenly across the catalyst surface and they tend to be sort of 100 microns in thick in thickness and then we will have interconnects that are electrically conductive but also allow for the macro transport of these gases across the electrode surface and the way that they're engineered is really quite key as well it also helps with water removal remember we're generating water here in our reactions and sometimes depending on how much power we're drawing from the fuel cell we might be generating quite a significant amount of water which can actually block some of these materials and stop the gases the hydrogen and the oxygen reaching their desired point in the catalyst okay so I mentioned a few different materials already the key working parts of the fuel cell are the electrodes and the electrolytes and if we think back to that basic electrochemical cell earlier those are the key parts of an electrochemical cell along with the external circuit or the electrical connection between those two electrodes but the electrodes are composed of of a catalyst the electrode the electrolyte in in the case of of polymer electrolyte membrane fuel cells which is what we're talking about today proton exchange membrane fuel cells sometimes they're called pem fuel cells basically is a special type of polymer often called nafion is the sort of industry standard a polymer developed by dupont back in the 60s I think and it's essentially the same as a non-stick polymer teflon that you might have on your on your frying pans at home with some modification of the structure in this bit here which we call a side chain and essentially this has a charged element in the in the chemical structure here which allows these these protons these h plus things that that drive the reactions in the fuel cells to travel through this polymer and so essentially it's a sheet of plastic but what it does is allow these protons to travel through it and allows ionic transport transport and therefore for the for the device to act as an electrochemical device the catalyst here we have a very highly magnified image of a fuel cell catalyst here essentially what we have is these very small nanoparticles often of platinum and we'll get on to that in a little bit as well and they're decorated on these larger particles of carbon conductive support but essentially we try and minimize as much catalyst as possible in these electrodes because obviously things like platinum is very expensive and so we have these tiny particles of catalyst spread over this larger surface area of carbon remember when we think back to those original experiments by grove increasing the surface area here is going to increase the rate at which these electrochemical reactions can can occur that means more electrons per second essentially and therefore higher current so we're trying to increase the surface area in these cases but there are lots of other peripheral bits of bits of kit in a fuel cell as well and they all rely on good material properties as well we have current collectors in this and and these obviously help establish that connection electrical connection in the fuel cell and onto these things we often machine what's called a flow field that's where the gas flows over the surface of the electrode and even the design of these flow fields can be quite key to the import to the to the performance of the fuel cell so depending on how you arrange those flow fields how big they are how wide the channels are etcetera that can really influence the performance of the fuel cell but essentially the working part of the fuel cell the bit where that does all of the electrochemical reactions you might call it the engine of the fuel cell is just this thing called the mea the membrane electrode assembly so we have this membrane this special plastic that acts as the electrolyte and on either side of that we have two electrodes which are essentially printed catalysts okay so it looks a bit like a dried ink you can see a picture of that down here we've got this black electrode layer on one side you can see a little bit of the plastic layer on the side there where the gloved hand is holding it and on the other side we'd have another electrode there as well then everything that goes around that is to do with getting good distribution of gas being able to remove the product water and and minimizing any resistances that we have in the system so there's lots of elements that go into making a fuel cell you can see these in a bit more detail here on the right we have what's called a cross-sectional scanning electron microscopy image of a fuel cell electrode or an mea I should say a membrane electrode assembly and you can see here this gas diffusion layer formed of carbon fibers that gives that gives a really nice open pore structure for the gases to diffuse into the into the catalyst layer which you can see how thin this is here right so very little of the mea is actually this catalyst and that's because we want to try and minimize the amount of platinum that we use in these fuel cells to make them cheaper and make them more effective but the way in which you do that is really really important being able to make sure that all of the small amount of platinum that you put in the fuel cell is available for these electrochemical reactions is quite a difficult thing to do and so there's lots of different desirable properties that we want for these materials so the membrane or the electrolyte has to be a really good proton conductor remember that's what electrolytes do they allow ions to conduct through them but not electrons and so it must be it must be electrically insulated it's also got to be impermeable to gases because I think we've got we've got two different gases on either side of the fuel cell here hydrogen and oxygen and if they were to to mix together on the same catalyst layer we would actually instead of having an electrochemical reaction we would have a normal chemical reaction then I.e combustion essentially

and the the hydrogen would simply ignite and in some cases actually explode depending on how much of it you have there and and this actually can happen quite easily these are very active catalysts and they can catalyze that reaction very well remember what we want to do is split that reaction into two half electrochemical reactions so that instead of getting a big combustion a big explosion of hydrogen what we get is a release of oxy of of electrons on one side this ionic and electron transport being separated through the electrolyte and the circuit respectively and then combining with the oxidant on the other side to produce water okay and then we have all of these sort of engineering aspects outside of this as I say the motor of the fuel cell that's put or the engine put it that way the the membrane electrode assembly where the reactions happen gas diffusion layers we want to be porous we want them to have good electrical conductivity because remember the electrons have to travel all the way from here around the circuit and right back to the catalyst layer again sometimes we put what's called a microporous layer on that's just a layer of essentially the the same thing as the catalyst but without the platinum on it so just the carbon and that blocks some of the larger holes in these gas diffusion layers and makes a nice thin catalyst layer being able to be put on top of that in the fuel cell as I say the catalyst particularly for low temperature fuel cells we're talking about here with with these pem fuel cells about 80 degrees c operation is normally has to be platinum or some alloy of platinum because they're the most active catalyst for these particular electrochemical reactions which is a bit of a shame because obviously it's expensive and rare but we're working on trying to both reduce the amount of platinum that we use and also to use alternative catalysts catalyst research is a really massive area of fuel cell research in general both at UCL and of course across the world and they have to have good activity for these electrochemical reactions that are occurring in the fuel cell and then we have things like current collectors for example which obviously have to be electrically conductive but they also provide a lot of support mechanical support for the fuel cell itself remember the active part of the fuel cell is quite a quite a floppy sort of bit of plastic with some ink printed on it in a very thin layer so so it needs some mechanical support to make sure that everything is is working well and all of these materials have various different effects on the way that the fuel cell operates and so a fuel cell is an electrochemical device it has a it generates a voltage and it also generates a current and actually with these electrochemical devices we have a sort of something called an inherent voltage or an open circuit voltage this is the voltage that is defined by the various different electrochemical reactions that are happening and by the the catalyst that is on there on the surface as well and the temperature and and the concentration of gases and things like that as it turns out for a hydrogen fuel cell hydrogen combining with oxygen this gives us a voltage of around 1.2 volts depending on the temperature and the pressure of the gases but that's when there's no actual current flowing and of course that device wouldn't generate any power and wouldn't be able to power any of our electronics so for the for that to happen we need to actually start to conduct some electrochemical reactions at a reasonable rate and to start to draw current from our device as we draw current from our device unfortunately the voltage then decreases a little bit and it decreases for a variety of different reasons and these are all linked to these mechanical these material properties in the fuel cell the first of these is what we call an activation loss and this is essentially due to the catalyst and how easily it it activates the electrochemical reaction so if we had a very bad catalyst in there we would lose a lot of voltage based on the activation of the electrochemical reactions but we also have what's called ohmic losses and these are sort of more simple resistance losses in the in the cell so you might know the expression v equals ir voltage is current times resistance the larger the resistance in our fuel cell the larger the loss in voltage we will have for a particular current and this is often dictated by the actually the ionic resistance in the membrane it's not just the electrical resistances we need to think about it's the resistance of movements of ions through the electrode and in the case of hydrogen fuel cells these are these are protons going through that electrolyte and so we also have other losses associated with the inability to get the fuel to the surface of the catalyst so that could be being blocked by water generation for example or just bad engineering in terms of the flow fields that we're using and the gas diffusion layers etc so all of these losses add up to reduce the voltage of the fuel cell and effectively reduce the power the power is related to the voltage and the current that we're drawing from a fuel cell obviously we want things to be as efficient as possible and so the closer our voltage of our fuel cell is to what's called the open circuit voltage the higher the efficiency will be as I say as we draw current we're moving down this curve reducing voltage but of course we want a a practical current to come out of our device that we can power something and so often we'll be operating our fuel cells around here so we're not losing too much efficiency but we're generating a reasonably large current and so low temperature pem fuel cells such as this will often have an efficiency of around 60 or so depending on the operation of the fuel cell but also as I say depending on all of the amazing science and engineering that goes into making these things work really well you can see in a bit more detail the the origin of some of these activation losses here in the in the catalyst so it's a nice sort of 3d image of cartoon of what's going on when a fuel cell actually is working when the electrochemistry is happening okay remember we need these three things in any electrochemical cell to work well we need the electrode where the electron transfer happens where the electrons are either used or given up into the into the system we need ionic transport through the electrolyte medium and we need the reactants to be able to come to the surface of the catalyst for the whole reaction to occur in the case of fuel cells those reactants are gases and in the case of this cartoon here we've got hydrogen gas flowing through the the gas diffusion layer which is these sort of carbon fibers here reaching the surface of the catalyst where that electrochemical reaction occurs and in this case the hydrogen h2 is split into protons h plus and electrons e minus those electrons can travel back out through the electrical circuitry of the fuel cell itself and the protons can travel through the electrolyte material through this plastic called nafion over to the other side of the fuel cell but you can see that you need a bit of a network of ionic transport for that proton to get into the main bulk of the of the plastic and so this catalyst ink is often mixed with a little bit of that naphtha and material but the amount in which you use there is really key to how this works you can see for example some of these catalyst particles the the gray particles being the nanoparticles of platinum here aren't actually connected to the to the electrolyte membrane the shown in green okay so if if a hydrogen molecule was to reach this bit of catalyst for example the electron transport could occur but the ionic transport couldn't and therefore the electrochemical reaction can't happen on this bit of catalyst and that effectively is like wasting catalyst right so we've got very expensive platinum in our material if not all of it is both ionically and electrically connected to the to the fuel cell as a whole then those electrochemical reactions can't occur on the surface of that catalyst and so one way of remove of reducing the amount of catalysts that we put in fuel cells is making sure that what we do put in there is all being used as much as possible these catalysts are quite important in fuel cells I won't go into too much detail here but there's lots of degradation of these platinum catalysts that can occur and we can eventually lose surface area over time and that effectively means that the fuel cells become less efficient over time but generally because we've got a lack of moving parts in the fuel cell actually they're pretty stable devices and we can we can get a lot of use out of them over over time and and you know hopefully generate electricity for a long time they're also quite recyclable as well the small amounts of platinum used within fuel cells can be reused in other fuel cells when they come to the end of their life which is quite nice battery recycling for example lithium-ion batteries is quite tricky to do so we've looked at all the different parts of the fuel cell there's a huge amount of chemistry electrochemistry going on in there physics etc but there's also a huge amount of engineering that goes into the design of a fuel cell this is an example of what we call a stack lots of individual fuel cells so these meas the membrane electrode assemblies the the working part of the fuel cell the the engine of the fuel cell are all stacked together and put under compression so that they work very well but that means you've got to have gas flow that can go through each of these each of these fuel cells flowing through the whole stack these stacks can sometimes be very large depending on your depending on your your application and also when you have lots of fuel cells there because they're not 100 efficient they will be generating some waste heat and so the bigger the fuel cell is the more waste heat is being produced and you need some way of being able to get rid of that heat so often for larger fuel cell stacks or have some form of cooling in there perhaps water cooling or air cooling so there might be a water inlet that has to go through all of these different fuel cells as well we obviously need good electrical conductivity throughout the whole stack which is very difficult to do often that requires even compression over the stack as well so lots of lots of different engineering concepts going into making these fuel cells work well not just making sure that your electrochemical reaction is happening as best as possible but making sure that the whole thing the whole system is working well and that's not an easy thing to do but fuel cells do have quite a few different advantages as I say they're quite efficient particularly compared to for example combustion reactions generating electricity with we're directly generating electricity via an electrochemical reaction so we're skipping a lot of those steps that we normally use to generate electricity that means we can get an efficiency of somewhere between 50 and 60 in the fuel cell when operating on hydrogen there are no emissions at the point of operation so say just water that comes out of the exhaust pipe in a fuel cell and for example in inner city london where I’m giving this talk at the moment that can make a big difference to the quality of air which we know obviously has huge health impacts the the emissions and particulates that come out of vehicles so even if we were generating our hydrogen what's called a brown hydrogen which is taking fossil fuels and getting the hydrogen out of those which obviously produces co2 for example even if we were getting our hydrogen that way rather than green hydrogen the benefit of reducing the emissions at the point of operation still applies and so our city centres can be much more nice places to live and work let's say they're potentially highly reliable because they don't have moving parts like a combustion engine for example if you think about the the complexity of that having hundreds and thousands of little explosions going on all timed perfectly to move the the wheels in your car this is ostensibly a much much more simple system but as as we showed in the previous slides a lot of engineering aspects that need to go into it to work they're very flexible as well the amount of current you produce is directly related to the amount of electrochemical reaction that is occurring that in turn is related to the amount of surface area that you have in your fuel cell so the bigger the fuel cell you have the higher the surface area the more reactions per second can occur and therefore the higher current that you draw so you could make a fuel cell for just seeing if I've got one on my desk I don't seem to have one today I’m very we have these little demonstration fuel cells that can perhaps lighter led or something small like that right up to the fuel cell that's in that mirai car that we that we use sometimes for group activities at UCL so they're very scalable and flexible in that sense obviously there are engineering issues when you when you try to scale up but essentially the the working part of the fuel cell doesn't really change at scale which is great and we can have continuous operation as well which is perhaps one of the biggest aspects of or advantages over batteries in vehicles for example is that as long as you've got a fuel supply you can have continuous operation so for a stationary fuel cell for example if we had hydrogen on the grip on the gas grid instead of instead of methane we would have continuous supply of electricity from that hydrogen in a car we would need a hydrogen tank obviously but that tank is much quicker to fill up than than a battery is to charge which may take something like half an hour or an hour for example so for longer range driving then perhaps fuel cells have an advantage there because they have effectively low charge times but there are some disadvantages mainly around cost but particularly infrastructure as well where do you fill up your hydrogen currently if you have a hydrogen fuel cell car there are more and more of these hydrogen fueling stations being being put into the into the system but it's much harder thing to do than to just extend the electric grid for charging battery electric vehicles for example and there are still some reliability issues you know around around the catalyst degradation and things like that as well one thing that concerns a lot of people is sometimes safety hydrogen is a highly flammable and volatile gas and obviously there are some fairly high profile hydrogen disasters like the hindenburg disaster back in the day but there's a lot of safety engineering that goes into making fuel cell vehicles for example very safe this is a video from toyota who have fired a bullet which you might have just seen there I'll see if I can go back fired a bullet into one of their hydrogen canisters that that they use in the toyota mirai fuel cell car for example these are very highly reinforced high pressure canisters and that bullet you can see doesn't penetrate the canister even if it does or did penetrate the canister this test here was looking at the venting of a hydrogen from a car set on fire versus a gasoline vehicle for example and as I say hydrogen is very volatile but that means it actually dissipates quite quickly into the atmosphere we've got quite a spectacular flame coming out there but it burns away relatively quickly and actually doesn't affect the rest of the car whereas gasoline pulls around the bottom of the car and can cause quite a lot of issues there as well so we've learned how to make how to make gasoline cars petrol cars safe well I mean obviously they're not 100 safe but there are there are risks with all of these technologies and this is something that we need to mitigate there are also risks of battery electric vehicles as well and this is something that we study quite a lot in in our labs at UCL sorry let's get that to work there we are these batteries are very highly energy dense and can undergo explosions something called thermal runaway which we studied quite a lot with things like thermal imaging cameras and this which is an x-ray into the middle of the battery as it starts to degrade at very high speed and there are quite a few high-profile battery electric vehicle safety issues as well so safety is definitely a concern but it's something that is manageable and and something that we need to obviously pay a lot of attention for as we you know as we transition from cars that have been around for for you know decades petrol vehicles into electric vehicles be that battery or hydrogen safety is a key concern of these things I'll skip a little bit by the fuel cell research that goes on at UCL and perhaps we can go into that in the question session as I've sort of overrun a little bit from what I expected to to do here but suffice to say we do a lot of world leading fuel cell research in UCL we also do a lot of outreach as well we have a we have a mobile fuel cell unit which you can see in this small photo here and this can power things like performance stages or phone charging for example you can see us at a glastonbury festival way back in 2014 there and we we do science demonstrations and power events with our with our hydrogen fuel cell we've got this nice clear case so you can see all of the aspects of not just the fuel cell but something I haven't really touched on today all of the peripheral bits that go around the fuel cell the electronics the blowers the gas valves and in this case we've hybridized it with some lead acid batteries as well so if you've got more interest in that you can check out UCL's website there and see if there's any events coming up near you and go and see an actual working fuel cell which is great so I'll just finish with with this and say that hopefully I've shown that fuel cells have a place in our future greener electricity based future and that they're a multi-disciplinary problem across lots of different length scales obviously chemists quite and chemical engineers are quite quite prevalent in fuel cells but we have physicists as well mechanical engineers as I say electrical engineers materials scientists even biologists there are some fuel cells that use biological catalysts to to generate small amounts of electrical current and so they really are a fascinating area of study and hopefully something that you will hear more and more about in your everyday lives as we as we move forward and so with that I’m going gonna say thank you for your attention and please do put any questions in the q a box if you'd like me to elaborate on some of the stuff I've shown there today and also I'd like to thank the group at the electrochemical innovation lab the eil you can see again another photo of not all of us but most of us there a really great team doing lots and lots of excellent research and have provided a lot of the images and the content for this talk today and also to say if you want to reach out and learn more about fuel cells learn more about what we're doing here at UCL in chemical engineering around not just fuel cells but electrochemical devices in general about making our futures more green and electro and electricity-based then please do contact me and and I'll be very happy to discuss in the future so thank you very much so perhaps while we're having to think and sort of talk a little bit about a little bit more detail about batteries versus fuel cells I suppose lithium-ion batteries have obviously revolutionized our society in many different ways starting from consumer electronics with the sort of commercialization of the lithium-ion battery by sony for camcorders back in the 90s you might have seen a couple of years ago now that the the inventors of the lithium-ion battery won the nobel prize recently as well so they're very much in in the zeitgeist and they're great at what they do lithium-ion batteries have got excellent energy density they work really well we can charge and discharge them hundreds maybe even thousands of times before they start to fail depending on on what type of battery it is but there are still some key issues one of which being in the sort of projected amount of fuel of battery vehicles that that companies are planning to make in the next few years they actually have a real shortage of some key elements there lithium and nickel for example that are used in batteries and so there's going to be a bit of a sustainability issue there if we need to make all the batteries that we need to electrify transport and other sectors in in you know lives really and so there's a bit of an issue there so we need to think of some alternative battery materials for example and there's a lot of research going into that but also some alternative technologies and perhaps lithium-ion batteries aren't best suited for every single application that requires electricity they are often used for a lot of these applications because we've managed to make them very quickly very well and relatively cheaply as well so you know gigafactory is producing back you know multiple batteries per second it's really quite incredible feat of engineering manufacturing and this is why it's starting to transform our lives now and we're seeing much more battery electric vehicles on the road but for example for grid scale storage for heavy goods vehicles such as trucks they're not necessarily well suited batteries aren't particularly light as I say they have a lot of a lot of somewhat rare elements within them as well if we have larger vehicles that require much larger battery packs in order for them to to travel reasonable distances we're essentially wasting a lot of those elements in areas that perhaps we could have alternative technologies and that's where fuel cells I think sort of will come in I think that because of the infrastructure issues around hydrogen refuelling etc without a large government incentive to build that infrastructure and to make hydrogen cheaply and freely available it is going to be difficult to compete on a sort of consumer level let's say you know your your electric vehicles at home are probably likely to be battery electric vehicles but for larger ones for transporting goods for example which is a huge contributor to co2 emissions shipping for example then I think fuel cells are going to going to have to play a role there as well but fuel cells I didn't really touch on this either but fuel cells are in in fuel cell systems are often hybridized with batteries to some extent as well because of the way they operate because you get this change in voltage depending on what current you're using and they're actually not particularly well suited to large dynamic changes in in current and so often a fuel cell large or medium-sized fuel cell will be hybridized with a small battery to allow that sort of that rapid change in in current to occur and then the fuel cell is essentially charging the battery constantly with a you know with a supply of fuel and that may sound a bit strange you know combining these two technologies but it's actually actually really a sensible approach because it means that you can optimize the size of both of those things the fuel cell and the battery so that you can match the peak power that may require maybe required when you put your foot down and accelerate up a hill but that you don't need a huge you know a huge battery pack there for the for the range in your vehicle so hybridization is always going to be key batteries always going to go hand in hand with fuel cells and it's not just fuel cells as well that we need an increase in in hydrogen generation for hydrogen is a key chemical for lots of chemical industries it can be used for heating for example it could be used for aviation etc and so generating that hydrogen in a green and clean way is also really key and so we look into that a lot here at UCL via that process of electrolysis that I talked about at the start there the splitting of water into hydrogen and oxygen using electricity obviously if we use green electricity for that then then the hydrogen is essentially sustainably and greenly produced there is of course a slight inefficiency with doing that and then there's a slight inefficiency of converting that hydrogen back to electricity but what it does allow us to do is is to produce a sort of closed loop of fuel generation there right so instead of burning fossil fuels that have all the carbon encapsulated in them over millions of years of you know literally fossils on the order of you know minutes or hours or whatever we are using water as this kind of energy vector splitting it into hydrogen using electricity and then later on or somewhere else transporting that hydrogen somewhere and generating our electricity back and of course we take a an efficiency hit on that's not 100 efficient but it is pretty efficient and actually if we have enough supply of renewable energy then that's a really sensible way of doing things and actually that's referred to as the hydrogen economy that's where we take excess renewable electricity which you know is actually quite a problem for the grid as we've put more and more wind turbines and solar onto the grid not only do we have some periods where the generation from those things is is not enough and therefore we still have to use gas to generate our electricity but sometimes we actually have too much generation and the grid can't handle it and this is where you hear these sort of you know quite angry reports about wind turbines being paid to to be switched off and there's a reason of grid balancing in that okay and also you want to maximize the resources that that we're putting onto the grid the wind turbines etc and one way of doing that is to use that electric excess electricity for something useful for example generating hydrogen which can be stored and distributed elsewhere and used when needed to generate electricity via fuel cells another thing we can do of course is just to store that electricity in batteries for example as I mentioned lithium-ion batteries perhaps are not the best use for that kind of level of storage because their key benefit is how energy dense they are so they're best for portable applications but they are being used increasingly in grid scale storage solutions but we do a lot of research in UCL in something called redox flow batteries as well and there's a I think there's a example lecture up on youtube on the chemin's channel on youtube there from me that you can watch on flow batteries which are a really interesting grid scale energy storage solution as well so as we start to generate more green electricity with renewable sources we need to increasingly think about other technologies that help us harness that more effectively and help us get rid of the base load generation that comes from fossil fuels or nuclear as well and and actually move towards an entirely sustainable electricity economy basically and hydrogen can be a really key part of that okay not just through via fuel cells but as I say for you know replacing things like natural gas in in heat generation for example and also just as a commodity chemical for various different things so hopefully you can see that you know moving to obviously moving to a renewable electricity future is really key and that's obviously what's focused on a lot about when we're talking about reducing greenhouse gas emissions the electricity generation is just one is just one factor there we need to then electrify all of the other sectors that that use power or use or generate co2 and other greenhouse gases so transport being a key one obviously we're seeing some real excellent increases there with the uptake of electric vehicles but there's still more to be done and larger scale transport shipping etc is still is still tricky air travel is very tricky a huge contributor to to climate change and obviously we're you know trying to reduce that as much as possible but there are huge benefits from the world being more connected and as being able to travel around around the globe and so ideally we would like to be able to do that in a sustainable way that doesn't generate huge amounts of co2 so that's a big challenge electrifying the aviation sector or producing synthetic fuels from for example renewable electricity again that's an electrochemical problem and then also yeah domestic heating and things like that are a huge contributor as well to greenhouse gases I think boilers in the UK contribute something like 20 percent and don't quote me on that something like 20 of the greenhouse emissions of of the UK so a huge amount of a huge amount of work needs to be done to electrify multiple sectors and though we're doing we're doing that well there are some big challenges to to get across there often they involve electrochemistry and electrochemical engineering UCL is one of the best places to study electrochemical engineering if you want to do chemical engineering here with us at UCL as I say it's not just the chemistry we need to think about here but all of the stuff that goes into making that chemistry work the most efficient most effective way as possible and that's all about device engineering materials engineering and so I think the future of chemical engineering and other engineering disciplines is really going to be centered around things like batteries and fuel cells and grid scale storage we need to we need to do this or we're going to be you know in a lot of trouble very soon and so electrifying everything understanding and harnessing electrochemistry is going to be absolutely vital in the next few years and that's where I think chemical engineering and engineering in general needs to it needs to go thanks rhod myself and and mark have put a couple of links in the chat for people so if I hope everyone's enjoyed this there's just a question in them yeah about what options are there for studying fuel cells and electrochemistry at UCL so yeah that's a that's a really great question so so as I say I I think that electrochemistry electrochemical engineering is quite a kind of new aspect of chemical engineering and so a lot of chemical engineering courses across the country wouldn't really cover this at all and UCL's quite you know quite unique here in covering that and we do cover it to quite a large extent as well currently it's largely via final year options so this these would be sort of more advanced courses but I think it's quite important that we we start to think about including this into sort of basic introductory chemical engineering courses as well which is something we are working on currently I teach with with professor paul shearing a module called electrochemical engineering and power systems and that covers all of the fundamental electrochemistry that's required to understand these devices and then also how the devices work so as I say batteries fuel cells grid scale storage supercasters etc and that's a that's a module that you can do in your fourth year mn or msc at UCL chemical engineering there is also a course on energy systems and sustainability which takes perhaps a little bit of a wider view of all of these things again covers some of the electrochemical options here but also thinks about renewable generation wind turbines etc and puts things into more of a sort of global context of how these electrochemical devices fit into our grid our future generation options etc and we also have another module on advanced propulsion systems that's more look looking at transport aspects and this is linked with the soon to come online UCL east which is which is being well basically finished being built in the old olympic site in east london and there we will have something called the advanced propulsion lab where we'll be doing a lot more of our sort of large scale testing and research over there so things like whole battery packs fuel cell systems etc cars even vehicle bay testing but linked with that then there will be a new masters in in essentially energy materials and devices and so that's really exciting we're hoping to bring that online as soon as possible and that will really give a really sort of tailored and specific education for the battery and fuel cell engineers that we're going to need hundreds and thousands of in the next few years in fact I mean we've got a huge shortage at the moment of people who are trained in this currently as I say we have we have courses in the latter stage of chemical engineering degree and we have masters and soon to be a specific masters on this but you know back in my day when I did my phd it was really people coming into this completely fresh at a phd level learning all this stuff doing their phd and going on to be highly valued by electrochemical industries which are growing exponentially and so I think it's a really key area for education so yes so so we do have a real focus on it it's largely tends to be at more advanced later modules in the in the degree and that's something that's gradually changing as I say we hopefully have a specific masters project available for that masters stream available for energy materials and devices very shortly so hopefully that covers that a little bit but I think that if you have any sort of electrochemical engineering background in your undergraduate degree you'll be of great interest to many companies who are looking to make batteries and fuel cells a reality in the you know in the near future hopefully you've just been there absorbing everything as I say I'd be very happy to follow up via email or once this gets uploaded onto youtube for example via comments on there and yeah I hope that you've managed to see that fuel cells can be a vital part of our future energy mix and also that they require a lot of really key think

2022-06-24 03:21

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