HydroScope
Mechanical
- Jul 23, 2003
- 72
This question also begins to ask is hydrogen the next fuel/energy carrier of the future? Let us ignore this debate as much we can, although when analysing risks to society from the fuels that run either a FC (fuel cell) or ICE (Internal Combustion engine) then it is impossible to ignore the added risks that might occur due to hydrogen storage and transport.
I would like peoples opinion on the race that seems to be on between FC & ICE for future low emission vehicles. I do not consider a FC vehicle a zero emission vehicle because of the extensive platinum they use. Platinum takes 6 months to refine and yields one ounce from 7-12 tonnes of ore?? What environmental benefit is there. Plus the emissions from the refinery process for over 6 months.
The DOE fuel cell durability target is 5000hrs equiv. to 10 – 15 years driving? Their finds found that hydrogen must have irreversible impurities less than 0.01 ppm to last that long, the market expected to do this latter this decade. With this in mind a Life Cycle Analysis would yield a large impact on the environment I’m sure.
The biggest argument that seems to be relevant over FC Vs ICE is that FC’s are highly efficient. So I question are they?
Above is a link to well known fuel cell page that states the mpg of some fuel cell prototype vehicles that have been built to date. It is relevant to note that the amount of energy in 1Kg of hydrogen = 1 gallon of gasoline on a HHV basis. Making it a convenient way of determining fuel efficiency compared to standard vehicle. You will notice that the best FC mileage vehicles come from the vehicles that only have a FC for power generation and not FC / battery hybrid’s making the regrating braking not worthwhile??. According to this chart the most impressive mileage of any FC only vehicle been built today is the GM’s Zafira mini-van at 80Mpg. This is not a practical vehicle as all FC have a start-up time of 3-4 mins.
It is easy to see that further development of the ICE are now leading towards the diesel engine or HCCI( homogeneous combustion compression ignition engines). Thus I will bring to your attention the latest TDI technology (turbo Diesel Direct Injected Engines) for sale today and near future
From a production car in place now 70-84 Mpg. The Volkswagen lupo.
how far can a diesel technology be pushed, answer 94Mpg for a speedster
what is the performance a TDI technology, compared to other production engine technology? this one won a production class rally, while running on part bio-diesel fuel.
Even Petrol/battery hybrid vehicles lack behind this type of technology, with both 2004 model honda insight and toyota prius showing 60- 65mpg. Where are the diesel electric hybrids? Or is it so that once you have a vehicle of decent mileage, adding weight via electric motor and battery hinders and not helps. I am aware that Fed express and eaton are joining forces to put in place diesel/electric hybrid trucks further applications can be made to garbage trucks etc.
They state they expect a huge 50 percent increase in mileage thus applying this to our 80mpg and 94mpg examples and you get, 160-188mpg. They also expect to put in place better pollution control on engine and get 95% reduction in pollution. A small hatch back with 3 cylinder TDI would not most likely not see the same results due to less energy in lighter weight vehicle when stopping and stopping not as frequent. I have seen Other quotes that an expected 20% rise in economy with diesel/electric vehicles, thus 96mpg-113mpg.
But the point remains that it seems Diesel/electric vehicle would easily exceed 100mpg on a EPA test. While FC “targets” remain at 100mpg, with not one prototype accomplishing it! With millions spent on each prototype, the diesel vehicle it seems would easily get further much further again.
An FC advocate would normal at this point say “FC are a new breed of technology, and the ICE has had over 100 years of advancement behind it, If FC had the same it would be so much better too”. Reminder that William grove invented the fuel cell in 1839. In 1807 Francois Isaac de Rivaz of Switzerland invented an internal combustion engine that used a mixture of hydrogen and oxygen for fuel. Rivaz designed a car for his engine - the first internal combustion powered automobile. However, this was a very unsuccessful vehicle. But for this it seems that both Fc and ICE have been worked on for about the same period of time and funny that hydrogen was actually one of the first fuels for use in a ICE.
This argument that Fc have not had time to develop doesn’t seem correct, as it also suggests that the people working on them do not understand their subject well. Does Ballard hire monkeys? Or do they employ the best material engineering experts with backgrounds in catalyst and polymer engineering research and development? I wonder?
So if the reason for FC development is not towards a vehicle that is leaps and bounds in front of conventional ICE economy, Then it must be because even with there reduced driving range that forces the driver to seek and deviate from original trip for a petrol station more often. They allow the vehicle to be safer on the road, now that toxic fuels such as petrol/diesel don’t need to be tanked around?
By the very name that I have given myself on this forum you can see I am a hydrogen fan!! And I will state that hydrogen is a safer outdoor transport fuel when stored and used correctly (disperses very fast). Which bring me directly to next dilemma facing FC, they are not fuel flexible. Thus this creates current FC vehicles to use high pressure purified hydrogen tanks (5000psi or 10000 psi) or cryogenic tanks of liquid hydrogen to store sufficient amounts of hydrogen for a driving range without the ridiculous weight penalty associated with metal hydride storage. Both high pressure and liquid hydrogen adds more risks to road users compared to driving a car carrying a liquid fuel stored at atmospheric temp and pressure, agree? Ignoring toxicity as there are liquid fuels that are non toxic.
Direct Methanol Fuel Cells (DMFC) which reform there hydrogen from methanol, are being researched with good efforts and results, but are lacking behind conventional PEMFC (polymer electrolyte membrane fuel cells) in power to weight ratio. Which is the whole reason for the PEMFC’s promotion towards vehicle applications in the first place as Ballard finally achieved a level where they could be considered to power a car.
So what is the future of hydrogen’s use assuming nobody wants 10 000psi tanks and cryogenic tanks with 1% hydrogen leak per day due to boil off? Either great advancements from physical and chemical adsorption techniques of hydrogen must become cheap (metal hydrides or carbon nanotubes) And/or onboard reformers must be used to minimising the total hydrogen needed to be stored.
Back to Fc vs ICE. The biggest difference I see in the point above is that FC will always need to have 100% of the onboard liquid fuel to be reformed, and as the above discussion shows it will need to be done to better than .01ppm a very costly process that will also add weight to the vehicle. ICE does not have to have all the fuel reformed it can be burnt in the ICE as well and is more likely to be completely burnt when hydrogen addition is used!! My area of interest!!
Thus the final reason contributing to fuel cells is that they are so much more environmentally friendly. If their energy conversion process is so much better why have they not produced prototype vehicles with better mileage than some of the more conventional ICE tech I pointed to earlier. Their weight? Will a FC vehicle that needs an air compressor and electric motor to drive the vehicle, Ever be smaller, lighter than conv ICE doing all those processes in one package.
The answer often given by FC advocates is, “ nanotechnolgy”, FC will benefit greatly, I think so too, but won’t ICE too, and How about cost!! Imagine having a small accident and your nano technology fc gets busted!! Suerly it cannot be fixed by local mechanic!!! Insurance price?? ICE will benifit from more precise injectors that atomise the liquid fuels to standards unseen before. Creation of the ultimate engine materials ( very low or zero heat convected away from the combustion process even when 3000oC are relevant) NO crevices between piston rings and piston top (major sources of unburned hydrocarbons adding further economy). Much lower rotating mass due to lightweight strong materials. No oil blow by/ passage.
Thus in this new technology scenario maybe the carnot cycle will finally show it’s limits and give way to the FC revolution. Carnot cycle efficiency is equal = 1- (T1/T2) where T1 and T2 are the temp of the working fluid’s high temp and low temp.
FC are not bounded by this and instead are bounded by the gibbs free energy law, how much free energy is available for the reaction H(g) + O(g) --> H2O (l). The total chemical energy available is 285.8 KJ/mole. The gibbs free energy available is 237.1 KJ/mole. Thus both the FC and the ICE will find it difficult to obtain the total chemical energy of hydrogen. The LHV of all fuels including hydrogen is generally seen as a representation of the amount of stored chemical energy that a carnot cycle engine if operating at 100% efficiency can obtain. We all know that is it impossible for any energy transfer system to reach 100% efficiency thus when the LHV of hydrogen is quoted at 240KJ / mole. Doesn’t that make the FC and ICE both aiming for approximately the same amount of energy / mole regardless of original fuel source? FC are held back via activation polarisation, ohmic polarisation, concentration polarisation. What does this mean?? FC efficiencies are almost opposite to ICE, It decrease as they approach their total power output,couple that with a electric motor of same trend?? Is that a good thing?? and they are hard to start up.
I think the most relivent point you can say about the fuel cell is that it can achieve its ideal cycle at room temp and pressure, the ICE obviously can not. It’s a shame that its fuel is one difficult to store at room temp and pressure. And operation at room temp and pressure puts added stress on the needed catalyst for the reaction. I can here a bunch of readers right now saying the carnot cycle will never get closer to 100% LHV than a FC could. those that do I ask you to take a closer look at the carnot cycle efficiency equation, and see what is really holding us back. If the working fluid is air then, the immediate restriction comes from T1 because it generally taken as ambient temp and pressure. What about charge cooling, but how? I find it interesting that all lower carbon chain fuels when stored as a liquid on board can be seen as a low temp reservoir (energy needed to liquify fuel can come from renewable source). If it was injected directly into the ICE as a liquid it would cool the incoming air, increasing air density, lowing T1, (the lower t1, the better the efficency and power density) enabling more power, torque, and HIGHER efficiency!! Check out the link below it has been done and was successful, this engine was throttled like all LPG. When coupled with a small amount of hydrogen injection the engine could then become un throtled lean operating like a diesel!! and higher efficiencies again (but from an engine with better power to weight ratio than diesel). It is a shame the emissions from the engine was not included in this report as I suspect this system might be able to avoid NOx emission, as they are related to cylinder high temp’s.
Yes I have contradicted myself now as this shows higher efficiency from a fuel that is not liquid at room temp and pressure. But LPG seems to well accepted as a alternative fuel by many countries and seems to have a good safety record despite that heat from engine getting into LPG fuel line can cause safety fears and problems. Advanced Technology may continue to raise the saftey in this regard.
The point I was trying to make is vast improvements can be made to all engines running on a carnot cycle and although FC’s are not bounded by this, they can not exceed the same amount of energy per /kg as a hydrogen ICE.
I personally don’t agree with the current trend of ICE to deal with pollution problems. That is to allow the engine to produce it and deal try and deal with it in the exhaust, when the engine is an economical one i.e diesel or HCCI engine then NOx reduction requires expensive un-efficient treatment processes!! If hydrogen was coupled with some an alcohol fuel or lower carbon chain fuel that posses 1. low flame temp and/or 2. ability to cool incoming charge. Then I’m sure we could have an engine with no/low hydrocarbon emissions and no/low Nox without after treatment!! I wonder if CO2 is really a concern? How many people breathing world wide??, maybe population control is a better measure, maybe outlawing the manufacture and sale of cigarettes would go further in reducing emissions that eliminating tailpipe emissions. Sorry that was a bit off track I not a smoker.
I wonder if the ultimate goal is to solve our energy conservation and environmental issues is via the highest technology route, or come from aiming for the cheapest route with all variables in mind meet with a sensible comprimise?? And low population, and no smoking!!
. . . .well I’m just a mere student engineer wondering what everones opinions on the future of FC and ICE are. . thanks
I would like peoples opinion on the race that seems to be on between FC & ICE for future low emission vehicles. I do not consider a FC vehicle a zero emission vehicle because of the extensive platinum they use. Platinum takes 6 months to refine and yields one ounce from 7-12 tonnes of ore?? What environmental benefit is there. Plus the emissions from the refinery process for over 6 months.
The DOE fuel cell durability target is 5000hrs equiv. to 10 – 15 years driving? Their finds found that hydrogen must have irreversible impurities less than 0.01 ppm to last that long, the market expected to do this latter this decade. With this in mind a Life Cycle Analysis would yield a large impact on the environment I’m sure.
The biggest argument that seems to be relevant over FC Vs ICE is that FC’s are highly efficient. So I question are they?
Above is a link to well known fuel cell page that states the mpg of some fuel cell prototype vehicles that have been built to date. It is relevant to note that the amount of energy in 1Kg of hydrogen = 1 gallon of gasoline on a HHV basis. Making it a convenient way of determining fuel efficiency compared to standard vehicle. You will notice that the best FC mileage vehicles come from the vehicles that only have a FC for power generation and not FC / battery hybrid’s making the regrating braking not worthwhile??. According to this chart the most impressive mileage of any FC only vehicle been built today is the GM’s Zafira mini-van at 80Mpg. This is not a practical vehicle as all FC have a start-up time of 3-4 mins.
It is easy to see that further development of the ICE are now leading towards the diesel engine or HCCI( homogeneous combustion compression ignition engines). Thus I will bring to your attention the latest TDI technology (turbo Diesel Direct Injected Engines) for sale today and near future
From a production car in place now 70-84 Mpg. The Volkswagen lupo.
how far can a diesel technology be pushed, answer 94Mpg for a speedster
what is the performance a TDI technology, compared to other production engine technology? this one won a production class rally, while running on part bio-diesel fuel.
Even Petrol/battery hybrid vehicles lack behind this type of technology, with both 2004 model honda insight and toyota prius showing 60- 65mpg. Where are the diesel electric hybrids? Or is it so that once you have a vehicle of decent mileage, adding weight via electric motor and battery hinders and not helps. I am aware that Fed express and eaton are joining forces to put in place diesel/electric hybrid trucks further applications can be made to garbage trucks etc.
They state they expect a huge 50 percent increase in mileage thus applying this to our 80mpg and 94mpg examples and you get, 160-188mpg. They also expect to put in place better pollution control on engine and get 95% reduction in pollution. A small hatch back with 3 cylinder TDI would not most likely not see the same results due to less energy in lighter weight vehicle when stopping and stopping not as frequent. I have seen Other quotes that an expected 20% rise in economy with diesel/electric vehicles, thus 96mpg-113mpg.
But the point remains that it seems Diesel/electric vehicle would easily exceed 100mpg on a EPA test. While FC “targets” remain at 100mpg, with not one prototype accomplishing it! With millions spent on each prototype, the diesel vehicle it seems would easily get further much further again.
An FC advocate would normal at this point say “FC are a new breed of technology, and the ICE has had over 100 years of advancement behind it, If FC had the same it would be so much better too”. Reminder that William grove invented the fuel cell in 1839. In 1807 Francois Isaac de Rivaz of Switzerland invented an internal combustion engine that used a mixture of hydrogen and oxygen for fuel. Rivaz designed a car for his engine - the first internal combustion powered automobile. However, this was a very unsuccessful vehicle. But for this it seems that both Fc and ICE have been worked on for about the same period of time and funny that hydrogen was actually one of the first fuels for use in a ICE.
This argument that Fc have not had time to develop doesn’t seem correct, as it also suggests that the people working on them do not understand their subject well. Does Ballard hire monkeys? Or do they employ the best material engineering experts with backgrounds in catalyst and polymer engineering research and development? I wonder?
So if the reason for FC development is not towards a vehicle that is leaps and bounds in front of conventional ICE economy, Then it must be because even with there reduced driving range that forces the driver to seek and deviate from original trip for a petrol station more often. They allow the vehicle to be safer on the road, now that toxic fuels such as petrol/diesel don’t need to be tanked around?
By the very name that I have given myself on this forum you can see I am a hydrogen fan!! And I will state that hydrogen is a safer outdoor transport fuel when stored and used correctly (disperses very fast). Which bring me directly to next dilemma facing FC, they are not fuel flexible. Thus this creates current FC vehicles to use high pressure purified hydrogen tanks (5000psi or 10000 psi) or cryogenic tanks of liquid hydrogen to store sufficient amounts of hydrogen for a driving range without the ridiculous weight penalty associated with metal hydride storage. Both high pressure and liquid hydrogen adds more risks to road users compared to driving a car carrying a liquid fuel stored at atmospheric temp and pressure, agree? Ignoring toxicity as there are liquid fuels that are non toxic.
Direct Methanol Fuel Cells (DMFC) which reform there hydrogen from methanol, are being researched with good efforts and results, but are lacking behind conventional PEMFC (polymer electrolyte membrane fuel cells) in power to weight ratio. Which is the whole reason for the PEMFC’s promotion towards vehicle applications in the first place as Ballard finally achieved a level where they could be considered to power a car.
So what is the future of hydrogen’s use assuming nobody wants 10 000psi tanks and cryogenic tanks with 1% hydrogen leak per day due to boil off? Either great advancements from physical and chemical adsorption techniques of hydrogen must become cheap (metal hydrides or carbon nanotubes) And/or onboard reformers must be used to minimising the total hydrogen needed to be stored.
Back to Fc vs ICE. The biggest difference I see in the point above is that FC will always need to have 100% of the onboard liquid fuel to be reformed, and as the above discussion shows it will need to be done to better than .01ppm a very costly process that will also add weight to the vehicle. ICE does not have to have all the fuel reformed it can be burnt in the ICE as well and is more likely to be completely burnt when hydrogen addition is used!! My area of interest!!
Thus the final reason contributing to fuel cells is that they are so much more environmentally friendly. If their energy conversion process is so much better why have they not produced prototype vehicles with better mileage than some of the more conventional ICE tech I pointed to earlier. Their weight? Will a FC vehicle that needs an air compressor and electric motor to drive the vehicle, Ever be smaller, lighter than conv ICE doing all those processes in one package.
The answer often given by FC advocates is, “ nanotechnolgy”, FC will benefit greatly, I think so too, but won’t ICE too, and How about cost!! Imagine having a small accident and your nano technology fc gets busted!! Suerly it cannot be fixed by local mechanic!!! Insurance price?? ICE will benifit from more precise injectors that atomise the liquid fuels to standards unseen before. Creation of the ultimate engine materials ( very low or zero heat convected away from the combustion process even when 3000oC are relevant) NO crevices between piston rings and piston top (major sources of unburned hydrocarbons adding further economy). Much lower rotating mass due to lightweight strong materials. No oil blow by/ passage.
Thus in this new technology scenario maybe the carnot cycle will finally show it’s limits and give way to the FC revolution. Carnot cycle efficiency is equal = 1- (T1/T2) where T1 and T2 are the temp of the working fluid’s high temp and low temp.
FC are not bounded by this and instead are bounded by the gibbs free energy law, how much free energy is available for the reaction H(g) + O(g) --> H2O (l). The total chemical energy available is 285.8 KJ/mole. The gibbs free energy available is 237.1 KJ/mole. Thus both the FC and the ICE will find it difficult to obtain the total chemical energy of hydrogen. The LHV of all fuels including hydrogen is generally seen as a representation of the amount of stored chemical energy that a carnot cycle engine if operating at 100% efficiency can obtain. We all know that is it impossible for any energy transfer system to reach 100% efficiency thus when the LHV of hydrogen is quoted at 240KJ / mole. Doesn’t that make the FC and ICE both aiming for approximately the same amount of energy / mole regardless of original fuel source? FC are held back via activation polarisation, ohmic polarisation, concentration polarisation. What does this mean?? FC efficiencies are almost opposite to ICE, It decrease as they approach their total power output,couple that with a electric motor of same trend?? Is that a good thing?? and they are hard to start up.
I think the most relivent point you can say about the fuel cell is that it can achieve its ideal cycle at room temp and pressure, the ICE obviously can not. It’s a shame that its fuel is one difficult to store at room temp and pressure. And operation at room temp and pressure puts added stress on the needed catalyst for the reaction. I can here a bunch of readers right now saying the carnot cycle will never get closer to 100% LHV than a FC could. those that do I ask you to take a closer look at the carnot cycle efficiency equation, and see what is really holding us back. If the working fluid is air then, the immediate restriction comes from T1 because it generally taken as ambient temp and pressure. What about charge cooling, but how? I find it interesting that all lower carbon chain fuels when stored as a liquid on board can be seen as a low temp reservoir (energy needed to liquify fuel can come from renewable source). If it was injected directly into the ICE as a liquid it would cool the incoming air, increasing air density, lowing T1, (the lower t1, the better the efficency and power density) enabling more power, torque, and HIGHER efficiency!! Check out the link below it has been done and was successful, this engine was throttled like all LPG. When coupled with a small amount of hydrogen injection the engine could then become un throtled lean operating like a diesel!! and higher efficiencies again (but from an engine with better power to weight ratio than diesel). It is a shame the emissions from the engine was not included in this report as I suspect this system might be able to avoid NOx emission, as they are related to cylinder high temp’s.
Yes I have contradicted myself now as this shows higher efficiency from a fuel that is not liquid at room temp and pressure. But LPG seems to well accepted as a alternative fuel by many countries and seems to have a good safety record despite that heat from engine getting into LPG fuel line can cause safety fears and problems. Advanced Technology may continue to raise the saftey in this regard.
The point I was trying to make is vast improvements can be made to all engines running on a carnot cycle and although FC’s are not bounded by this, they can not exceed the same amount of energy per /kg as a hydrogen ICE.
I personally don’t agree with the current trend of ICE to deal with pollution problems. That is to allow the engine to produce it and deal try and deal with it in the exhaust, when the engine is an economical one i.e diesel or HCCI engine then NOx reduction requires expensive un-efficient treatment processes!! If hydrogen was coupled with some an alcohol fuel or lower carbon chain fuel that posses 1. low flame temp and/or 2. ability to cool incoming charge. Then I’m sure we could have an engine with no/low hydrocarbon emissions and no/low Nox without after treatment!! I wonder if CO2 is really a concern? How many people breathing world wide??, maybe population control is a better measure, maybe outlawing the manufacture and sale of cigarettes would go further in reducing emissions that eliminating tailpipe emissions. Sorry that was a bit off track I not a smoker.
I wonder if the ultimate goal is to solve our energy conservation and environmental issues is via the highest technology route, or come from aiming for the cheapest route with all variables in mind meet with a sensible comprimise?? And low population, and no smoking!!
. . . .well I’m just a mere student engineer wondering what everones opinions on the future of FC and ICE are. . thanks
![[smile]](/data/assets/smilies/smile.gif "[smile] [smile]")
