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Hello, in this class we are going to disassemble fuel cell and reassemble it, and in the process, I am going to show you all the interior parts of single fuel cell and I will also explain to you what are you know possible options that people are looking at for these parts, what are they trying to do concerning all you know hardware design the design of the materials that go into the actual membrane electrode assembly and so on. So, we have seen them in the form of diagrams in some of our previous classes in this class we look at the actual hardware. I will also tell you that this is hardware that we use in the laboratory scale. So, there are some variations when you look at larger scale hardware, but still, the similarities are quite significant and I will also alert you to what changes you can expect when you look at a more industrial type of hardware for the same unit ok. So, with these introductory words, we will get into this looking at this fuel cell and taking it apart and then looking at its parts. So, we will begin by, of course, putting on some gloves here ok. (Refer Slide Time: 01:38) Okay so, we are ready here. I have with me the hardware the fuel cell hardware this is a single cell that I have here. It looks quite bulky quite heavy, as I said that’s because this is you know meant for laboratory testing we want to minimize any you know artefacts to the data coming from the hardware. So, we don’t compromise on the hardware in any manner we are not worried about the weight of the hardware because we just want to get the functioning of the hardware right. The weight is a consideration that’s looked at when this becomes a product ok. So, this is the hardware. So, I will show you even before I disassemble I will show you a few different aspects of this hardware and then when we disassemble it you will get a better sense of what those parts are. So, if you see here facing you see this is an endplate. So, maybe if you see it little closely you will see an endplate here and another end plate this side. So, you see one end plate here and one end plate here. So, these are two endplates and you will see a small hole that is visible here. So, this is the hole through which a heater is put inside this hardware. So, a cartridge heater it’s called a cartridge heater, it simply is you know heater in the form of a small rod that is put inside this hardware. That helps us heat this hardware so that we can run the fuel cell test at a fixed temperature at whatever temperature you want to run it at. So, if you if I want to run a controlled test with the hardware sitting at 60 degrees C then I can do that if I want to set it at 70 degrees C or 80 degrees C I can do that these are this kind of a cell is typically running below 100 degrees C. It’s a proton exchange membrane fuel cell test setup that I am showing you and so it runs below 100 degrees C. So, that is what you will see on that hardware. Now if I turn it the other way complete 180 degrees the other way, you are again seeing the same hardware from the other site same thing to end plates the same to end plates you are seeing from the other side. And you will see two tiny holes, one tiny hole here and another tiny hole here. So, that is there to simply insert 2 thermocouples. So, I can independently measure the temperature of this plate here and I can measure the temperature of this plate here. And that is essential for me for the experiment for us to you know keep track of whether the heater is working correctly or not or to give feedback to the heater because there is a controller which is going to decide whether the heater has to be switched on or switched off and that is based on the feedback that is that it is receiving from these thermocouples that are present at these 2 locations. And you can select which thermocouple you wish to use and in fact, you can also select to have two heaters if you wish on this cell this particular hardware has been set up with one heater, but you can potentially set this up with 2 heaters. So, that is the 2 aspects of the heating of the cell that I indicated in real hardware, for example, you would not be looking at external heat. There the problem is inverted the cell itself is generating a lot of heat and we are trying to manage the heat. So, there we send in coolants to remove the heat or at least to keep removing the heat at a rate which ensures that the cell remains at some temperature during the duration of that test. So, but why do we heat this hardware? We are heating this hardware because we have only had a single cell here. So, it is not a single cell is not generating and it’s a small cell I am going to open it and show you it is a very small cell. So, a single small cell does not generate enough heat to heat this entire hardware whereas, if it were several cells in series and they were large cells it would generate so much heat that the temperature of this hardware would keep on rising. So, therefore, those two situations are different. So, here in this test setup to run this test at some controlled temperature, we require an external heater to be attached to it and using that we run this test setup. I showed you that we can use a cartridge heater, you can also use flat plate heaters on either side different ways you can incorporate this heat into the system. So, that’s again an experimental variable that a lot of people in their labs will have the opportunity to explore and look at. But this is the one implementation of this hardware that I am showing you ok. (Refer Slide Time: 06:20) So, now we will look at this side of the hardware. You can see now there are two openings here one opening there and another opening out here. And this is the inlet the top one is the inlet and the bottom one is the outlet for one of the reactants it could be any of the reactants I mean we. So, one side of the cell will be receiving hydrogen and the other side will be receiving air or oxygen. So, if this were the hydrogen side you would have the hydrogen inlet typically this would be at the top, top inlet, top opening here and the bottom would be the outlet. Generally, we have the outlet at the bottom because you have liquid water being generated in the cell and therefore, you would like to use the assistance of gravity to get the water removed from the cell. So, that is the reason why we prefer to have the outlet at the bottom rather are rather than at the top ok. So, that’s the other aspect of it. You can see here a lot of bolts you can see there are, 3 plus 3, 6 plus 2, 8 bolts that are there in this hardware and these 8 bolts serve to hold the cell together in an in a proper you know uniformly compressed manner. So, there is uniform compression across this entire cell and that is ensured by using these bolts and that also ensures proper sealing through the cell. So, this is the reason you have so many bolts, bolts here ok. So, I am if I am I am just going to turn this hardware the other way around and you can see essentially the same kind of layout here similarly the same bolts are now, showing up on the other side the nut bolt arrangement is visible here you can see that how it has been implemented here and you also have or the inlet and outlet here the inlet on the top and the outlet at the bottom. So, that is also the same that you see as you saw on the other side. (Refer Slide Time: 07:53) You also see here two copper plates which again I will show you in a bit of a close up you can see these copper plates on top one, one that is here and you see another copper plate here there are 2 copper plates here which I will just rotate a little bit. So, you can see more clearly yes there are 2 copper plates there, 2 copper plates. They are the ones that are if I turn it around also you can see the orientation of the copper plate there, and those copper plates serve to current the current. So, when you correct connect this hardware to the external circuit this is where the current leads and voltage leads come and click they come and clip to this or they come and clip to this and that is how you create current into the external circuit. So, that is what is done and these bolts go otherwise they go right through all the bolts that you see here are going right across this hardware from this side to that side and that’s how they hold the hardware together. So, you may wonder that you know you are short-circuiting the cell because this bolt is actually coming from this endplate to this endplate and holding it all together. So, it looks like the hardware is short-circuited, but actually, that is not the case because the end the two endplates that you oversee here these two plates that you see here are not part of the electrical circuit. There is, there are gaskets which prevent them from being in the external circuit in the electrical circuit and as a result, they are actually not participating in the path of the current and therefore, it’s okay that they are in contact with each other. So, this is the basic hardware that is used in most experimental setups, this is what we have in our lab we sort of got this made to order we designed each part and got it made to order. But essentially you can get the same kind of hardware there are many commercial setups also which sell you these kinds of hardware we made this in our lab, you have to specify the dimensions and orientation of various things and people can get this made for you, you can machine it and get it. So, if you have good machining you know workshop in your university you can get one of these made its completely doable right. So, what I am going to do now is I am going to take apart this hardware, open it up and show you all the interior parts of it and then also discuss more about each of those parts. So, that’s what we are going to do now. So, we are going to now take apart this hardware, open it up completely and look at all the parts that are present inside it. And so to do that we are first going to lay it on its side and their areas you can see 8 bolts out here that we need to open and remove. So, we are just going to do that. So, this will take a couple of moments, but that’s part of the process. So, let’s do it and get to see what is on the inside. So, by keeping it lying down we also ensure that the materials that are inside are not disturbed and that that helps us if you were doing this on a tests condition that would allow us to open it up without disturbing the materials inside. And then you know doing some examination of those materials and then coming back and reassembling the cell so that you can continue with the test setup. So, this is normally done in all our laboratories we routinely open up these cells put in new materials inside, and then run the test and then partway into the test or after some of the testing has been done. If if you want to understand why the performance of the cell is a certain value or if we want to get a sense of what has you know maybe degraded inside the cell or you know some other thing that has happened inside the cell sometimes it becomes necessary to open the cells and then look at the hardware look at the interiors of the cell in greater detail. So, therefore, this is commonly done and its part of our activity in this fuel cell laboratory testing activities. So, there we are we have removed all the 8, we opened up all the oh we have one more here 8 nuts and bolts have been opened up and. So, I am now in a position to remove the top part of this hardware we do have the washer. So, I will remove them also otherwise they were all going to come tumbling down and so I will just do that so that it becomes easier to handle, all right. So, all the washers have now been removed and we are now in a position to start opening the cell and taking a look at what is inside. So, the first thing that is going to come off is this hardware on top that we are calling the endplate hardware and so that’s what I am going to remove here and that’s going to gently come right off of this structure. So, this is the endplate, and you can see you already saw the exterior of this end plate here and now I am just going to show you the interior. So, on the exterior side, you have these two connectors, these two connectors that are present here and they are you know different companies make these connectors you can get any connector that you are comfortable with that ensures a good seal and is a reliable connector. You have to attach a hose here and a hose here and those two should be supplying you know reactants to the cell. (Refer Slide Time: 13:58) So, therefore, you need this to be good connector reliable connector leak-free connector, so what you find commercially to do it you can purchase and fix up. So, now, if you turn it the other way around it’s flat. (Refer Slide Time: 14:31) It’s flat and this particular piece has been made out of aluminium, you can make it out of stainless steel typically for laboratory purposes those should work. They are; please keep in mind that this is not going to participate in the electrical circuit, this is not going to participate in the and none of them you know reactions are going to happen in direct contact with this surface. And therefore, the material is really what is whatever is convenient for you to use we just need something hard and rigid I mean at least in this scheme of activity within the scope of this activity. So, I mean any metal should in principle work fine. So, what we easily get is either aluminium or stainless steel would also mean it doesn’t corrode under you know the presence of water and so that’s something that you can consider. If you look at say the more industrial implementation of this hardware this particular piece of the hardware then people do look at you know some block of a thick block of plastic of different kinds that can be used instead of putting this you know a piece of metal there. But this piece of metal helps us in the test setup that we use mainly because as I said you can put in these connections here for putting the heater and you can heat the hardware which or which may not be which will be difficult to do if it were some kind of or plastic. So, you can put this heater here heat it and then that heat will get distributed through this hardware very well and that becomes easy to use. So, that is why we prefer to use this. In this side as I said other connections the connectors and on the other side you can see as I turn this around you have this heating element location, you also have a small hole for putting a thermocouple if you wish. So, all those elements are available on this hardware and this is a piece of hardware and that’s all it does this is the endplate. This is the exact thing that is also there at the bottom of this hardware, what you see at the bottom is also the same thing just another piece of it and when we get to the bottom of this hardware you will see it. (Refer Slide Time: 16:43) So, I am going to send this aside for the moment and I am going to show you the rest of the pieces one by one. And then after we disassemble the whole-cell we will reassemble it, so you will get a sense of what is involved in reassembling this hardware and it will be done bit slowly specifically, so you can see how it is done. And you also get a sense of you to know the just you know handling issues that are involved in putting such hardware together. So, that’s the purpose of what I am going to show you. So, that’s what you are going to see. So, I am going to set this aside for the moment we will get back to it in as necessary. So, just below that hardware that we removed is this gasket that you see that I am peeling I mean removing from this hardware and it is a silicone gasket. This is essentially a non-conducting material it does its electrically non-conducting. So, I am just going to first take it out here and it is specifically there to isolate that end hardware that I just removed from this cell from the rest of this hardware in terms of electrical contact. So, this gasket prevents the hardware that we just removed which is this one, it prevents this gasket here prevents this hardware from having any electrical contact with the fuel cell setup which is below this gasket right. So, if there is a fuel cell set up below this gasket and it insulates that set up from this hardware. And therefore, that’s how this hardware is no longer in the electrical circuit this entire block that you see here ok. So, I am going to set this aside and that as I said is the gasket; that gasket has you can see here there are 3 holes in it, 2 of these correspond to the fuel or is reactant inlet and outlet and the third one simply is one of the holes through which the bolt one of the bolts goes through this hole and that’s the reason there is a hole there. That I mean so that can vary from hardware to hardware. So, you can have hardware where the third hole is not necessary because maybe the bolt doesn’t go through this gasket. But in this hardware given the way the bolts are arranged one bolt goes through this gasket and therefore, you have 3 holes here. So, that’s what you will see. So, I am going to set this aside and then look at the next part of the hardware. So, we are just coming top-down, now one by one we are taking out. I just took out the end plate below that was this gasket. So, I am going to remove this gasket now. Below that gasket is the current collector. (Refer Slide Time: 19:25) So, this is the one. So, this is a copper current collector. So, I am just taking it out here this is the copper current collector. So, it’s made out of copper I just show you this current collector in different angles. So, that’s the current collector, and typically we clip on to it here to get it attached to the external circuit. So, that’s where we clip on to it and so that is the current collector you can see the same 3 holes in this as they were as you saw in the gasket and that’s because of the bolts that one through one hold the bolt goes through and that is this big this that is this hole here. So, this the bolt is going into the to the through the hardware and so that it holds the hardware together these other 2 holes that you see here are meant for the fuel or reactant in inlet and outlet. So, that is the next part of this hardware. So, this is the current collector ok. So, again I am going to set this aside. So, 3 pieces out now the end plate a gasket, a silicone gasket and this current collector. So, now since as you know as I said this is called the current collector it is very much part of the circuit, very much part of the circuit through which the current is being taken from this to the external circuit where you are using it for some particular purpose ok. So, therefore, this is very much part of the circuit and so we need to be aware of what is going on concerning this and to ensure that it is not accidentally in contact with the opposite side of the hardware. So, that is very important concerning this piece of the hardware. So, I am going to set this aside now ok. So, below the current collector comes the next piece of the hardware which is called the flow field or the flow channel and that is this graphite block ok. (Refer Slide Time: 21:12) So, this is a graphite block and it was phased down I have I am just showing you the backside that the side of it that was on the top that a face that was facing up is this. It is featureless on the top, you don’t see any features on it. What you will not see very if you watch carefully you will see two tiny holes here I am trying to position it so that that becomes visible to you yes that you now we will be able to see two tiny holes. So, I will point to them in just a moment. So, there’s you see one hole out here or at least one indication that there’s something there that said there is a tiny hole there right and at the diametrically opposite end there is a tiny hole. So, it is through this these are the two holes that line up with that inlet and outlet that you saw in the rest of the hardware and that is how the gas goes in and out of this hardware ok. So, this is called the flow channel, gas flow field and on the backside of it which is what you are currently seeing it is featureless and that’s and therefore, you will wonder what is you know where is the scope of anything flowing in it. But in the backside of it, there is no reason for anything to flow it simply goes into this hole that you see here and goes to the other side which is the front side of this flow channel and I am going to turn it around and show you the front side of the flow channel. So, the front side of the flow channel is the one that is facing the membrane electrode assembly which is where all the reactions are taking place, so the front side is where you need to have all the features. So, let me turn it around and show you the front side. (Refer Slide Time: 22:46) This is the front side of this flow channel you can see that it has some flow pattern in it let me change the position of it. So, you can get a better sense of it. There you get to see the flow channel. You will see here actually a set of the channel that goes up and down up and down up and down in a serpentine manner ok. So, it goes up and down up and down up and down in a serpentine manner, it's very narrowly spaced set of channels and so that’s you have to watch carefully to see it, but you can see that channel. So, what normally happens is the gas enters let’s say it enters here and then it is just going to go down and then come up and then go down and then come up etcetera and then come out finally, to the diagonally opposite end and at that point, it will come out through the backside of the flow channel and exit out the cell. Okay so, this is how the gas in this fuel cell is distributed through to the entire cell where the reaction is taking place and that that membrane electrode assembly is very close to this surface it is not in direct contact with the surface there is one more layer in between and so we are going to talk about that layer. But that is the first thing that distributes the gas is this gas flow field and that is what you are seeing out here at the moment. So, I am going to set this aside and then we look at the next few parts that are remaining in this hardware. So, right now once you come this far into this hardware there are you have to come very close to the fuel cell itself which is this layer that I am going to start taking out now we are just one sort of one layer away from the actual fuel cell or the membrane electrode assembly. But this new the layer we are currently dealing with has two parts in it, one is the gasket and the other is the gas diffusion layer. So, I am going to take out both of them and then show that to you. So, the first is this gasket, you can see that this is a square window of sorts. (Refer Slide Time: 25:06) And this is made out of Teflon as the material. It is there to ensure that first of all no gas leaks out of the cell. So, you don’t want gas leaking out of the cell and so, therefore, you need this gasket. And the second thing it does is the thickness of this gasket is an important parameter that decides how much the remaining parts of the cell which consists of the membrane electrode assembly and the gas diffusion layers, how much they get compressed is decided by the thickness of this gasket; because this gasket usually doesn’t compress a whole lot. And so when the hardware comes to a halt at this gasket the gas diffusion layer has been compressed to some degree. You don’t, you want the gas diffusion layer to be compressed to some degree because only then you will have good electrical contact to the gas diffusion layer if you just barely touch the gas diffusion layer if the current collector just barely touches the gas diffusion layer or if the I am sorry the gas flow channel I just badly touches the gas diffusion layer then you will not have good electrical contact you will lose electrical contact will have high contact resistance. So, you do need it to be compressed a little bit you want that compression to be there a little bit and so that you get good contact with the gas diffusion layer. But at the same time if you compress it too much the gas diffusion layer gets crushed and that is also not particularly good because that will destroy the gas diffusion characteristics of the gas diffusion layer. So, you want some compression, but not too much compression. So, that you know limited compression that you want is ensured by putting a gasket of some appropriate thickness this is not very thick it is relatively thin, but the measurement is decided based on that requires that you need sealing and you need some compression, but you don’t want the materials to be crushed that is the purpose of this gasket ok. So, that is there in this layer I am going to set that aside. And this layer that is just alongside the gasket is the gas diffusion layer. (Refer Slide Time: 27:12) So, this is the gas diffusion layer that I have that I am presently holding in my hand. This typically is a carbon cloth or a carbon paper and people are doing different kinds of you know research activities to see if there are alternatives to this in different ways in which you can implement this particular layer so that you can get the properties that it’s supposed to have or even improve on those properties that it has. But this is the gas diffusion layer gas goes through it and distributes across to the membrane all the active sites of the membrane electrode assembly It’s a porous carbon cloth or carbon paper sometimes it has a layer on top called the microlayer which has better conductivity, but those are all implemented various implementations of this gas diffusion layer and if you are doing active research in this area then those are kinds of parameters that you will focus on and try to make some variations on ok. So, that is what this gas diffusion layer is. So, that is one more part that I am just now going to set aside. And now we come to the most important part of the fuel cell which is the membrane electrode assembly and that is the layer that I am pulling out now ok. So, as I turn it around yes there you can see the reflection of the membrane all around. So, you can see that there is a larger membrane and there is in the centre you see the squarish electrodes, right. So, those electrodes are catalysts, catalyst layers that have been painted or you know deposited onto this membrane this clear relatively clear membrane that I am holding in my hand, clear transparent membrane that you see that’s the nature of the membranes used for this is activity and on that, you put this catalyst layer on either side. So, there is a layer on this side and if I turn it around carefully although you may not be able to see it properly there is a layer on the other side as well. So, both sides have the same layer and they are aligned on top of each other. So, and since the membrane is transparent you don’t I mean looking at it you will it looks like the same thing, but this site you are seeing one catalyst layer and as I turn it around you are seeing the other catalyst layer. So, these are the two catalyst layers. And depending on your test they may be the same you or you may have 3 different compositions on these two catalyst layers. So, you have the option of doing that, but then you also have this membrane, this membrane that is there. This membrane is the important thing in this setup in the sense that is the electrolyte and the two catalyst layers are the ones where the electricity is generated or the reactions occur rather. So, you have an electrochemical reaction occurring at the anode and another electrode chemical reaction and occurring at the cathode and so one of these layers is the anode and what is behind is the cathode. So, let’s say we can if we assume that this is the anode or if we have decided that this is the anode then this becomes the cathode layer behind becomes the cathode and in between the two layers is this membrane. So, this is the membrane electrode assembly ok. So, this is the membrane and electrode being assembled it’s called the membrane electrode assembly. And this is the central part of the fuel cell. On either side of this membrane electrode assembly is a gas diffusion layer then there are two gaskets there are flow channels and then there is a current collector one more gasket and then the end hardware. So, we have come to the centre of the fuel cell. So, what remains will be a replica of what we just took apart so far. So, I will just pull out those parts and show you that on the other half of the fuel cell also we have the same parts. So, just below it is one more gas diffusion layer and a gasket, so gas diffusion layer and a gasket and this will typically fit inside this will fit inside this regime there. So, you can see that it fits inside, you can pull it apart and then it comes off separately right. So, this comes apart and you can put it together that way. So, so that’s how they fit inside each other that’s how they are sized if you size it such that they do not overlap that they just about fit the gas diffusion layer just about fits inside the gasket layer that is provided, right. So, that’s the way we assemble it. So, these two are there. So, I am setting that aside and then below it is the next flow channel that you see here. Again you can see the serpentine flow channel, it’s called serpentine because it goes up and down and curves it is basically like a straight line that goes straight down then curves and comes right back then curves and goes down again and so on. And that’s called a single channel serpentine flow pattern. And that’s what is implemented in this hardware. You can have other forms of hardware where you can have different versions of this pa