Hydrogen fuel cell, good or bad idea? - Page 2 - Fuelly Forums

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Old 03-30-2008, 07:45 PM   #11
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Originally Posted by Ryland View Post
I'm suprized that the idea of fuel cells is still around, lithium batteries are cheaper, should last longer, and although they require exotic metals, the ones that they require are more common and cheaper.

A fuel cell car is just an electric car with a fuel cell battery, it's not magically turning the hydrogen in to motion.
The reason why fuel cells are still around is that they have one distinct advantage over ANY type of rechargeable battery: you don't have to wait HOURS for the battery to recharge. You just refuel and go, just like a conventional car. Recharging time has ALWAYS been the BIG downfall of battery electric vehicles. I myself could live perfectly FINE with a vehicle that can only go 150-200 miles before recharging/refueling (I don't know why people care SO much about not being able to go 400+ miles without refueling). But if it is going to require six hours of charging, this is a deal killer for ANYTHING but a commuter that can be charged overnight and/or at work. And unless that electric 'second car' is going to be cheap, it is just not going to be worth buying for MOST people.

As for the fuel cells themselves, their efficiency (at around 50-60%) leaves something to be desired. After all, this level of efficiency can be achieved by gas turbines. And gas turbines last a LONG time (compared to fuel cells and, for that matter, reciprocating engines). They can also burn a wide variety of fuels (including biodiesel and straight vegetable oil). But keep in mind a couple of things. First of all, this is really not much less than NiMH batteries. And NOBODY talks about how inefficient NiMH batteries are. And secondly, fuel cell technology is VERY much in its infancy (even compared to more advanced gas turbines). Efficiency has increased by quite a bit over even a few years ago. And I would suspect that it will imcrease further in the future.

Hydrogen production, on the other hand, is a BIGGER issue. Simply put, we really do not have a good way to make it. One way is from fossil fuels, either directly or by electrolysis of water using electricity made by burning fossil fuels. Neither of these methods are very efficient. And when combined with all the other losses in the entire hydrogen cycle, you are probably better off just burning the fossil fuels in a regular car like we do today. Another thing that few people consider is that if EVERYONE starts using grid power to make hydrogen, the grid will just not be able to handle it without large upgrades and additional power plants. So along with the greater inefficiency will come large infrastructure costs. You are beginning to see that this is not such a hot idea from the supply side.

So what about using wind and/or solar power to make hydrogen? In theory, it is an EXCELLENT idea. BUT, how much power is currently generated by wind and solar? I can't quote exact figures. But I believe it is well under 10%. In other words, we couldn't hope to make a dent in the current demand for energy to power vehicles with hydrogen made from wind and/or solar power (or other renewables, for that matter). And nothing short of a breakthrough in terms of drastically lowered cost of photovoltaics is going to change that. Now if we ever see photovoltaics at $.50 per watt, hydrogen will look ALOT more attractive. But I personally see higher fuel cell efficiency happening before THAT happens.
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Old 03-31-2008, 07:09 AM   #12
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As for the fuel cells themselves, their efficiency (at around 50-60%) leaves something to be desired. After all, this level of efficiency can be achieved by gas turbines.

I liked the thrust of your post, but I did want to amend the above statement.

Only extrememely large (Utility-sized) combined cycle gas turbine plants approach 60% efficiency. GE is the only company that claims to reach 60%, so far as I have seen.

Automotive size gas turbines only achieve ~30% efficiency, and this is when they are equipped with exhaust heat recuperators.

Simple Brayton cycle turbines under 500 HP usually have less than 20% efficiency.
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Old 03-31-2008, 07:44 AM   #13
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Actually there is a microturbine being used to generate electricity at the neighborhood level with the 300 degree exhaust heat used for building heating that approaches 90% efficency. The company is supposed to be in production of these generators right now.

http://www.microturbine.com/prodsol/products/index.asp
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Old 03-31-2008, 05:01 PM   #14
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I liked the thrust of your post, but I did want to amend the above statement.

Only extrememely large (Utility-sized) combined cycle gas turbine plants approach 60% efficiency. GE is the only company that claims to reach 60%, so far as I have seen.

Automotive size gas turbines only achieve ~30% efficiency, and this is when they are equipped with exhaust heat recuperators.

Simple Brayton cycle turbines under 500 HP usually have less than 20% efficiency.
Check out this microturbine:

http://www.wilsonturbopower.com/micro_overview.html

The efficiency of the genset is 50%, so the efficiency of the turbine itself is pobably closer to 55%. And this is WITHOUT taking congeneration into account. True, it is still somewhat in the developmental stage. But it looks promising.

What's interesting to note about this particular turbine is that it is largely an axial flow design. Only one stage of the four stage compressor is centrifugal. And the turbine is a three stage axial flow turbine. This contrasts with most small gas turbines (ie those that have been used experimentally for automotive use), which are typically single stage centrifugal designs on both the compressor and turbine - not an efficient design. Indeed, the fact that small gas turbines typically use this inefficient design is probably THE reason for the low efficiency typically seen in turbines producing under 500HP. For this reason, I am hopeful about this particular turbine. But whether it can be produced at a reasonable cost is another matter. After all, cost is probably the BIG reason why horribly inefficient designs are used for small gas turbines.
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Old 03-31-2008, 10:09 PM   #15
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The reason why fuel cells are still around is that they have one distinct advantage over ANY type of rechargeable battery: you don't have to wait HOURS for the battery to recharge. You just refuel and go, just like a conventional car. Recharging time has ALWAYS been the BIG downfall of battery electric vehicles. I myself could live perfectly FINE with a vehicle that can only go 150-200 miles before recharging/refueling (I don't know why people care SO much about not being able to go 400+ miles without refueling). But if it is going to require six hours of charging, this is a deal killer for ANYTHING but a commuter that can be charged overnight and/or at work. And unless that electric 'second car' is going to be cheap, it is just not going to be worth buying for MOST people.
Ah, yes, I forgot! you can just pour liquid hydrogen in to your 10,000psi storage tank... wait a minute! the other day when I was filling up a 20lb propane tank (about 5 gallons) and it took a good 5 minutes to fill, and that was with a lower pressure liquid gas that has much larger molecules, so it's easier to pump, easier to seal connections, and safer because it's at a lower pressure, although a leak can still flash freeze your skin!

Now I know that charging batteries takes time, but when you look at the specs for the newer batteries, a slow charge time of 45 minutes, and quick charge of 15 minutes, and I couldn't find the spec sheet but I know that those same cells were speced at being able to take a 5 minute 80% charge, so in the same amount of time that it takes you to fill your gasoline car, and less time then it would take you to fill your hydrogen car you could charge your electric car, if only to 80%, spend a few more minutes and depending on the car, battery pack, and so on, you could travle 100+ miles on a charge, and have to stop for 5 minutes every 80 miles after that to recharge, to me, that is reasonable, it's not 400 miles, but really, how far can a fuel cell car travle? 150 miles on a fill up? hydrogen takes up alot of space even when compressed to 10,000psi.
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Old 04-01-2008, 06:36 AM   #16
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Actually it takes me about 10 minutes to put a meer 10.5 gallons in my xB because the last gallon takes forever to go down the filler tube and all the mileage info I record. How many people take a 400 mile trip anyway? Mine are only 320 miles HA HA. BESIDES in most of our lifetimes there will NEVER be electric charging stations for our electric cars so don't worry about it.
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Old 05-19-2008, 09:28 AM   #17
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Originally Posted by StorminMatt View Post
The reason why fuel cells are still around is that they have one distinct advantage over ANY type of rechargeable battery: you don't have to wait HOURS for the battery to recharge. You just refuel and go, just like a conventional car.
Wrong. Only a handful of H2 stations, and there won't be more than that for a very long time, if ever. Takes 21 tanker trucks of H2 to deliver the energy of one tanker of gas
Quote:
Recharging time has ALWAYS been the BIG downfall of battery electric vehicles. I myself could live perfectly FINE with a vehicle that can only go 150-200 miles before recharging/refueling (I don't know why people care SO much about not being able to go 400+ miles without refueling). But if it is going to require six hours of charging, this is a deal killer for ANYTHING but a commuter that can be charged overnight and/or at work. And unless that electric 'second car' is going to be cheap, it is just not going to be worth buying for MOST people.

As for the fuel cells themselves, their efficiency (at around 50-60%) leaves something to be desired. After all, this level of efficiency can be achieved by gas turbines.
Wrong. No heat engine exceeds Carnot efficiency of ~40%, including gas turbines.
Quote:
And gas turbines last a LONG time (compared to fuel cells and, for that matter, reciprocating engines). They can also burn a wide variety of fuels (including biodiesel and straight vegetable oil). But keep in mind a couple of things. First of all, this is really not much less than NiMH batteries. And NOBODY talks about how inefficient NiMH batteries are. And secondly, fuel cell technology is VERY much in its infancy
Wrong
Quote:
(even compared to more advanced gas turbines). Efficiency has increased by quite a bit over even a few years ago. And I would suspect that it will imcrease further in the future.

Hydrogen production, on the other hand, is a BIGGER issue. Simply put, we really do not have a good way to make it. One way is from fossil fuels, either directly or by electrolysis of water using electricity made by burning fossil fuels. Neither of these methods are very efficient. And when combined with all the other losses in the entire hydrogen cycle, you are probably better off just burning the fossil fuels in a regular car like we do today. Another thing that few people consider is that if EVERYONE starts using grid power to make hydrogen, the grid will just not be able to handle it without large upgrades and additional power plants. So along with the greater inefficiency will come large infrastructure costs. You are beginning to see that this is not such a hot idea from the supply side.

So what about using wind and/or solar power to make hydrogen? In theory, it is an EXCELLENT idea. BUT, how much power is currently generated by wind and solar? I can't quote exact figures. But I believe it is well under 10%. In other words, we couldn't hope to make a dent in the current demand for energy to power vehicles with hydrogen made from wind and/or solar power (or other renewables, for that matter). And nothing short of a breakthrough in terms of drastically lowered cost of photovoltaics is going to change that. Now if we ever see photovoltaics at $.50 per watt, hydrogen will look ALOT more attractive. But I personally see higher fuel cell efficiency happening before THAT happens.
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