Fuel Cells and Hydrogen Economy

you 20 years ago there was a lot of talk about a hydrogen economy somehow instead of having gasoline filling stations dotted behind ways we'd have hydrogen stations and your cars would fill up with hydrogen the only waste products being water no pollution no environmental concerns wonderful until you realize that you can't just dig up hydrogen from the ground hydrogen has to be made and to make it it takes energy so you still need to use coal or natural gas or oil or nuclear power or some energy source to take water and split it apart into hydrogen then you could ship that hydrogen around store it places and use it in cars that use fuel cells well I don't think a hydrogen economy is going to happen plug-in hybrid cars electric vehicles are a much more sensible way to be able to substitute electricity for our transportation system but fuel cells do have a place first let me explain what a fuel cell is so one of the simplest fuel cells is the permeable membrane fuel cell and basically it has a membrane and this membrane is treated with some type of catalyst typically palladium and palladium is pretty wonderful stuff because if I take a hydrogen molecule and that hydrogen molecule wanders up here it splits in two hydrogen atoms which of course are just protons and on this surface you'd have a very large concentration of hydrogen palladium it turns out is transparent to hydrogen hydrogen goes right through it so you might think aha the whole thing is going to be filled with hydrogen well and I was moved when there was a gradient if there's a higher concentration on this side than that side indeed hydrogen will go through how do we create that gradient how do we take away the hydrogen on this side well if you add oxygen basically if you add air on this side as the hydrogen comes through you'll have the reaction of two hydrogen's plus an oxygen going to water you will have reconstituted this hydrogen gas into water and we will have a concentration gradient across this membrane forcing the hydrogen to go through as the hydrogen ion goes through the electron of course is siphoned off and you get a like mole or some other electric use this is the basic operation of a fuel cell the demo that you see here in class is one of using a hydrogen fuel cell and the first thing we have to do is create hydrogen and oxygen these cells can run backwards so if I take a battery and run the cell backward I will take water and turn it back into hydrogen and oxygen and that's what you see happening here in the demonstration once you can build off enough hydrogen and oxygen you can take the two electrodes from the membrane the fuel cell and connect them to an electric motor and voila the tires on the car move in this manner we are still quote burning hydrogen we're taking hydrogen combining it with oxygen and making water but there's no flame there's no explosion there's no rocket fuel going on here it's done in a solid device at room temperature in a very safe complete manner the problem with them of course is the hydrogen content in the first place we can imagine that this is your electric circuit you see fuel cells make electricity what happens is that you I gotta get my nut here all right all right that's coming up here is that if you add hydrogen on one side hydrogen if you recall is a proton right the nucleus with an electron going around it that's the nut now if you make this out of the right stuff like palladium right some type of precious metal that's really transparent to hydrogen the hydrogen comes in and the hydrogen can freely go back and forth through this piece of metal it's really amazing if you're ever trying to purify I've seen this in like James Bond movies okay when they're like oh I got to put the tritium and the nuclear bomb but the key is is that there's this metal palladium and hydrogen gas goes right through it's like not even there it's hard to believe because you know you can't walk through a wall but hydrogen walks through palladium so the question is is why would the hydrogen go through here's the key we establish a gradient on this side of the membrane we put a lot of hydrogen and on this side of the membrane we don't put any we actually would put air which has oxygen in it so because there's a higher concentration of hydrogen on one side the hydrogen molecule comes up palladium is a catalyst it splits the molecule into two hydrogen atoms the hydrogen atom goes right through the hole okay good and then it combines with oxygen on the other side making water but the electron doesn't the electron actually creates a voltage difference the electron is left behind so the electron can go through your circuit right light up your light bulb run your electric car power your office do the nice things that electrons do that's a tricity right and then the return wire returns it to the other end and when the hydrogen combines with the oxygen to make water on the other side you get the electron back to so basically a hydrogen atom is a proton with an electron going around it when you come up to the membrane the hydrogen atom goes through and the electron goes on the wire very cool system here's a picture of a hydrogen fuel cell of membrane hydrogen fuel cell very much like the one I had in class this one's hooked up to actually run a little fan if we look in this you can see the PM is the proton exchange membrane you've got the flow plates you've got a catalyst area cathode catalyst where you're actually taking apart the hydrogen or the water depending on what side of the direction you're running it these systems are nice but they're really toys you need pure hydrogen to start with which is a difficulty and the lifetime of these proton exchange membranes is not large the capital cost would be much higher than the energy gain that you would get from doing it let's look at the diagram again hydrogen in this case comes in the fuel the electrons go through the circuit the hydrogen's go through the polymer electrolyte combined with oxygen from the air and making water thing is you have to make that hydrogen what if you could do a fuel cell that instead of using hydrogen used natural gas so if I take natural gas methane coming in I now need something still that's going to split out this hydrogen to do that a proton exchange membrane will not work I'm going to need to do something that's at a much higher temperature there's a thing called a solid oxide fuel cell and this can take methane and it can split it up into the carbon and into the hydrogen's of course to be able to do that it needs some thermal energy these things are hot 800 degrees centigrade don't touch it I do this I can split up the methane as a fuel I can add air from the other side right of the oxygen and I can do the same reaction we do for burning methane methane plus oxygen going to carbon dioxide plus water this reaction will take place without burning no visible flames warm indeed but a solid oxide fuel cells can do the conversion all the way to electricity at 50% a natural gas power plant that just used a steam cycle would be at something like 33 percent a combined cycle natural gas system where first it runs a turbine that with the exhaust and that turbine turns a generator the excess heat boils water that turns another turbine which turns the generator that can get to 40% efficient this fuel cell with basically no moving parts just sits there sucks in methane and air puts out a little bit of carbon dioxide a little bit of water vapor in fact most of the water vapor is recycled can run at 50 percent the advantage of having a fuel cell energy system is that you have no moving parts no flame and it can be done in a manner such that Bloom Energy did where you don't even need any precious metal catalysts you just take many many of these stacks and they put on the electrodes with ink and they stack these things up seal them and they say they'll last for 10 years here's what they look like each of these units can make 100 kilowatts of electricity it's like a giant battery now you have to put in fuel you have to buy the natural gas still today that's actually quite economical so here we have a number of them in the lab so what about the economics how much does a Bloom Box cost it costs well over a million dollars unless you happen to be in a state that says hey people please buy these just like there are economic incentives to buy a hybrid car governments can decide that in certain locations particularly California in the United States the electric grid needs more power and it's been very difficult to build new power plants so many systems are designed to really subsidize people to put solar cells on their roofs or industries to buy fuel cell systems in California you can buy a 100 kilowatt electric unit that actually makes 100,000 watts for 750 thousand dollars is this a good deal well let's figure out how many cents per kilowatt hour this is one of the questions you always have to ask and we did this similarly when we trying to analyze a windmill is how long will it last how long before the fuel cell breaks they're saying 10 years so let's use 10 years because after all what we want is cents per kilowatt hour kilowatt time unit and energy unit we just need to do a little conversion one year is 8760 hours so years cancel this will now be dollars per kilowatt hour if I multiply this out it turns out to be 8 and a half cents per kilowatt hour of electricity that's the capital cost you still have to buy the methane at today's prices though and the amount of methane this needs is very small may be an additional penny per kilowatt hour in many places in the US the wholesale cost of electricity is still 3 or 4 cents per kilowatt hour in which case buying your own Bloom box probably would not make sense in places like California where the cheapest rate you can get is 12 cents per kilowatt hour these things are going like hotcakes fuel cells have the advantage that you are not part of the grid and just like anything else you could turn on or off there's some startup time the whole thing has to warm off after all it runs at 800 degrees centigrade but you can turn it off and not use it for a time period if that's your druthers otherwise you can use the system and it becomes quite economical so in some locations if the retail cost of electricity is very high and you still have a relatively low cost of natural gas making your own box your own Bloom Box makes a lot of economic sense that's what you need to know about fuel cells [Music]

Channel: Illinois EnergyProf

Views: 48,008

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Id: peoO8-_o6NM

Length: 15min 39sec (939 seconds)

Published: Mon May 13 2019