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The current collector is in place and so is the first gasket layer. So, what I put there the silicone gasket layer as far as the current collector are all lined up correctly with the rest of the hardware. So, that was the purpose of those aligning pins, and you can see that now that the aligning pins are I mean because of those thin two thin wires that we had of the aligning pins we can do that quite effectively there is a pin here which I think you can see that maybe that you can probably see the pin here. So, that’s one pin and this is another pin that is out here that is that I am holding out here. So, that’s those are two pins that are sticking out and using that I have done this alignment. So, now, I am going to put it back in the flat position and then assemble the rest of the hardware and then we look at it ok. So, now, that we have these pieces in place our next part to put here is the flow field. So, the flow field I have in my hand. So, the flow field has to be an electrical contact with the current collector. So, therefore, we are not putting any silicone gasket between them It still, it has it also has alignment pins. So, we have to line up with the alignment pins and put them in. So, I am exactly what I am doing I put the alignment pin through it and another alignment pin here through it ok. So, it is all done goes neatly back down. So, that’s the flow channel you can see here now with the flow channel how the hardware looks. As I tilt it towards you and show it to you. So, this is with the flow channel in place you can see everything is in place and they are all lined up because of the alignment pins. So, the alignment pins are very critical for us I can hold it in one hand and show it to you because of the alignment pins and you can see all of them all of those layers are now one on top of the other. (Refer Slide Time: 42:32) The silicone gasket is not visible because it is behind the copper current collector and between the copper current collector and the endplate. So, that’s why it is not visible, but you see the endplate, you see the copper correct current collector and you also see the gas flow channel all 3 of them are visible. So, again we lay it back in the horizontal orientation, and we will stop now assemble the cell itself. So, to do that first thing we need is one more gasket that square gasket that we spoke about. So, that we will put here, yes, that side went through the aligning pin, now I got to get this side to go through the aligning pin. Yes, it’s through the aligning pin and it's down to the bottom, then I am going to put the gas diffusion layer that is just going to go and sit there. So, now, is those two are sitting there I cannot lift this well I can let me try to lift it and show you because I have to ensure that the bolts also don’t just fall right off, there you are you can see how this thing is oriented and all those units are there. So, I will just put it back down. I think I had one bolt come off, but that’s okay I can put it back there we got everything in more or less. Only one bolt is off we put that in just a moment. Yes, there we are we have got everything in and everything in place. So, now, the next thing that comes is the membrane electrode assembly that you have here membrane electrode assembly. So, that’s what I am going to put on top of the arrangement that we have so far that also has those two small tiny holes for the alignment pin. So, that helps us align in aligning it correctly. So, I got it through on one side, trying to get it through on the other side let’s see, yes, it is through. So, we have got the membrane electrode assembly also to go in. So, it is now sitting on the hardware with everything the way we just described and so that is in place. You can sort of seeing it even from that orientation as I rotate it along you can see that it is sitting in here, that’s the membrane electrode assembly. So, on top of this I am going to put the next GDL gas diffusion layer; so the gas diffusion layer that was put in the beginning the previous gas diffusion layer or someone side of the membrane electrode assembly. Now, I have put one more gas diffusion layer which is on the other side of the membrane electrode assembly and I am going to put this next gasket. So, that’s what this gasket is I am going to put it up here. Same thing we have the alignment pins I have to line it up and then put it through. Yes, it’s in, one aligning pin and almost in here not yet yes that’s it. So, I have got the second gasket also in. So, on both sides of the membrane electrode assembly, I now have a gas diffusion layer as well as the gasket on both sides. So, a peripheral gasket and in the centre, there is a gas diffusion layer. So, centrally there is a gas diffusion layer and on the periphery, you have this gas the gasket and this is there on both sides of the fuel cell. So, this is the peripheral gasket both sides of the membrane electrode assembly. So, we got several of the major parts in now I am going to on top of this the next part that needs to come is the other flow channel, flow channel on the other side of the cell. So, we have already seen one side of the cell we are seeing the other side of the cell. So, this flow channel needs to come on this side of the cell and so again we take the aligning pins and then line it up with this line up this part with the aligning pins and send it through. So, that it lines up correctly. So, I take that up here I see an aligning pin here. So, the hole for the lining pin; so I am going to send that it in yes that’s in on that side yes, it is it on this side as well right. So, it just goes straight down you can see it going down goes down down down down down and sits in perfect. So, we can see that you know this is now settled incorrectly we ensure that by just holding it down we don’t have any non-uniform I mean improperly aligned hardware we just ensure that you know its aligned properly and so the next piece of hardware that needs to come on top of this is the other current collector which is the copper current collector. So, I have one more of these here. So, that’s what we need to put here and so that’s what we are going to do. So, I am going to take it up here and you can see here again there’s an there are 3 holes in this. So, two are for the gas inlet and outlet that is this and this and this is where one of the bolts goes through as I mentioned that is just the design of this hardware that has this is a situation. So, now, I am going to do that and build it up. So, we will put this aligning pin here, yes it’s through the aligning pin and this other aligning pin is lined up there. Yes, it’s through. So, the two aligning pins are now through and it also goes through the bolt and it comes right down. So, that is our cell with the two current collectors that have been assembled. So, we just need to put one more gasket layer on top of this and put the rest of the end hardware and close the cell. So, that gasket layer is what I have here it consists of those same 3 holes that I mentioned, one for the inlet and outlet piece this spare is for the inlet and outlet this is the inlet this is the outlet and this is where the bolt will have to go through. So, same drill move it up here we line it up with the alignment pin, yes that went right through and this side I had to put it through the alignment pin, yes that’s also through. You can see it's now standing on those two alignment pins and as I slowly slide it down you see it goes through the bolt, I can slide it further down and it's now down. So, you can see how I will just tilt it up to tilt it over and then I will show you how it is all lined up there you are I managed to do it without having it all fall apart. But there you can see if I rotate it you can see the two holes and you can even see that the hole is going right through you can see you can see that hole of the current collector also lining up with this gasket. So, you need that because the gas has to go through, right. So, I am going to hold that together and make it all lye down. Yes, there we are. So, last part remaining here is the endplate that I am going to put on top which is the same as the end plate that you see at the bottom and with that, we can close the cell we can put the complete the nuts and bolts and that completes this cell hardware. So, that’s what I have here the hardware, the end hardware this side has to face the cell and this is the external side. So, I keep make sure that I don’t get that wrong and also the same orientation should be there for those two inlets and outlets with that in mind I take it up. Again there are the same two aligning pins are their holes are there for that. So, I have to make sure it goes through that, yes the first aligning pin went right through and let’s look at the second one. Yes, it went right through too. So, now, you have all the holes for the bolts and I just have to line them up. So, they all neatly go through their respective sockets. Yes, there you go then I just look and make sure it’s all sitting correctly and then I put all the washers. So, at first in any of these hardware builds that you make usually it’s all set up like this such that everything is sitting horizontal that way you can align things well. So, what you saw here, for example, was a single membrane electrode assembly in the middle and. So, it only had one pair of GDLs, and one pair of flow channels, one pair of electrodes. So, this is what we had one we had a single membrane pair of electrodes on either side which were already sort of you know attached to that membrane and then one pair of GDLs on either side of that and one pair of flow channels. Now, if you have a stack which we discussed in the class then you will have several such cells in series. And therefore, you need to assemble after you put the flow channel will then touch the flow channel of the next cell. So, the backside of the flow channel of one cell will touch the front side of the flow channel of the second cell. So, what they do is they have plates which are called bipolar plates they will have the flow pattern of the anode on one side and the flow pattern of the cathode on the other side so that one side becomes the anode of one cell and the other side becomes the cathode of the other cell. (Refer Slide Time: 53:58) So, when you do that you have to have everything horizontally located. So, you can put one cell, and then on top of it you can put the next cell, then the top of it you can put the next cell, and so on. So, you keep on building the cells and so in that process you stack it up steadily and. So, you will put one end plate at the bottom and then you instead of just one cell here you will put the second cell, third cell, fourth cell, fifth cell, whatever if it’s a 10 cell stack you will have 10 cells and only then the second hardware will come this second endplate will come on top of the tenth cell. Other cells will be attached connected in series. So, usually, you will have all these bolts standing vertically up and then all of these parts coming in one by one. So, you sit and assemble them one by one till you get all these 10 to line up correctly and then you put this bolts and then you tighten them up. So, in the I mean tighten them up. So, normally also we first you simply hand tight them the way I am just doing it right now. And so that’s the first stage of this build which is to hand tight everything. So, that they are you know firm they are not loose. So, if the hand tighten all of them and at that point, it's quite too for you to lift it and you can see the hardware it’s not going to fall apart it is going to stand on and so on its already you know tightened the way we want it to be tightened. What remains is simply based on this build the specification of the build we will look at we can you know specify a torque, torque value for each of this bolts. (Refer Slide Time: 55:25) And therefore, you can put a torque wrench and then you know to hold it on one side, so like this. So, you will hold it on one side and you will have a torque wrench on the other side and then you tighten it till you reach the correct torque. So, on each bolt, you can reach the correct torque and that way you ensure uniform compression of this hardware in all directions. So, right now I have only done hand tight on, hand tightening on all the bolts, but that’s for the first step of this build. You have to have a torque wrench with which you will apply a predetermined amount of torque and then at that point, you put the right kind of compression on this hardware so that it both seals as well as there is good electrical contact at various locations within this hardware. So, that’s how you would build this hardware. Of course, one last step remains once you are done with this complete hardware building you still have this aligning pins that are sitting in this hardware which I can slide out. So, I can show you here this is one aligning pin, and I can pull out this other aligning pin here which is sitting here. So, there are two aligning pins here there is one here and there is one here. So, if you see carefully you can see those aligning pins, one here and one here. So, I am just going to pull it out slowly. So, let me line it up here and then you can see it and begin to pull it out there you see the pin I am pulling it out. So, that’s the pin, pull it out, pull it out it comes right out there the pin has been removed the aligning pin has now been removed from the cell. So, one aligning pin was removed in that format and I am going to remove this other aligning pin here. Hopefully, you can see that, yeah there you can see the pin and I can just pull it right out it is being pulled out. So, both the aligning pins are out if they align aligning pin remains it does do some short circuit of the cell because it is going from one side of the hardware to the other side of the hardware it is connecting one current collector to the other current collector. So, it will do a short circuit of the cell. So, you cannot leave the aligning pin in while you still do the test at least not a metallic alignment pin. If you do have a plastic alignment pin you can do that that is not a problem or a non conducting align alignment pin. So, based on your hardware the exact details of each of these parts may vary, but or wherever you are working on this kind of activity, but broadly what I just showed you is what is there is a fuel cell hardware. Very broadly speaking this is what is there is a fuel cell hardware this is what we use in our lab to do our testing and so it’s a pretty good representation of what you can expect in a fuel cell test setup and also in a fuel cell hardware anywhere that you encounter it. At least you will be able to relate what we have seen here to any part that you see in the in any other hardware that you see you will see some variations on it you will see some variations on the pattern that is used in the flow channel, the sizing of the flow channels, sizing of the overall electrode area also. So, for example, the electrode area I just showed you were two and a half centimetres by two and a half centimetres. So, an active area of about 6.25-centimetre square, but that is just because it is a test cell that we want a controlled area over which across which we know what the test conditions are. But real hardware we may have 10 centimetres by 10 centimetres which is the 100-centimetre square active area. So, that will be much larger. So, you will have significantly large you know 10 centimetres by some 10 centimetre kind of situation and so, that that sized square you will have that is just the active area. As opposed to the small stamp-sized active area that we just saw in this test hardware. So, those kinds of variations you will have. Variations on the dimensions of this end hardware, variations in the way in which it is bolted together how many bolts you are using, what kind of bolts you are using there. You will also have to vary the thickness of those flow channels and as I said know is it a graphite flow channel, is it metallic flow channel, is it composite flow channel. So, we have a wide range of varieties like that. And the flow pattern inside it can be different. The gas diffusion layer material can be different, MEA can be different, but where whatever hardware you see I think you can pretty nicely relate it to them what you have seen here. I also showed you this hardware with flat gaskets. You may have gaskets that are circular in cross-section. And also because it’s a single cell we have some liberty in the sense that some advantages in the sense then I can comfortably set it up such that on one side I have the flow inlet and outlet for one gas and I can just turn it around and I have the inlet and outlet for the other gas right. And this I can do only because it happens to have only one cell inside it. If I have a series of cells inside it, a lot of cells inside it first cell, second cell, third cell, fourth cell and so on, then it is not easy for me to, I cannot just have one gas from coming from one end and another gas coming from the other end because it is not only there it has got more than two sides. So, you need gas hydrogen gas to go to the anode side of each cell. So, if I keep it like this if there is the first cell and then there is a second cell and a third cell let’s say, there are 3 cells here first, second and third. I need hydrogen gas to come to the anode side of the first cell, then not go to the cathode side but come to the anode side of the second cell not go to the cathode of the second call, but coming into the anode of the third cell and so on. So, similarly air, air would also have to come to the cathode of the first cell, skip the anode of this of the second cell, come to the cathode of the second cell, skip the anode of the third cell come to the cathode of the third cell. So, that is the kind of control I need to have on the path occupy travelled by the gas and so that is done based on a different layout of how the gas flows from cell to cell to cell. So, some, some changes like this you will see in the hardware, but I think what you saw today we will give you a much better perspective of any hardware that you get to see for a fuel cell activity. So, I think that was the purpose of this class. And I think you will find this information to you if you ever happen to look at fuel cell hardware. Thank you.