hydrogen fuel cell question

Darkstar · 02-13-2005, 09:36 PM

im sure SBN isnt the best place to ask this question but i know there are a lot of knowledgeable people on this board so why not...

anyway, how does a hydrogen fuel cell work? i know they are still trying to figure it out because of problems like storage and transportation. and compressing the gas requires energy, and compressed hydrogen contains far less energy than the same volume of gasoline. but its not like you would take your typical reciprocating engine and somehow pump some hydrogen in there, is it?

RayOSV · 02-13-2005, 10:08 PM

You're right in that you really can't beat good old gasoline for energy packed into a gallon.

Fuel cell vehicles have engines that are built to run on a mixture of gas (hydrogen usually) and oxygen. Think of a propane vehicle and it's close. The advantage is that the main combustion by-product from hydrgen is water. 4(H) + O2 = H2O basically. Very clean. The main disadvantages are that hydrogen is very combustible and volatile (think Hindenberg) and expensive per mile of travel. Of course the problems of production and distribution would also need to be solved, but volume would eventually cause some economies of scale.

It will be a while yet.

http://www.eere.energy.gov/hydrogenandfuelcells/

Hagios · 02-14-2005, 01:40 AM

It is notable that elemental H2 doesn't occur naturally--anywhere that we can gather it, at least. The only (Read: easiest and most efficient) way to create elemental hydrogen for fuel cells is to electrify water. This takes more energy than the hydrogen can produce in reaction with 2(O2) to create 2(H2O) due to the inherantly inefficient process. At best, with 100% efficiency with both the creation and use of H2, fuel cells would be a way to store energy without loss. As it is, they can store energy, with additional energy spent.

H2 will never replace gasoline. The most that you can expect to see, is that gasoline is used to power generators to break water into harvestable H2 and O2, and the H2 being sold to you--which would, in the long run, be worse for pocket books and for the environment than just using an internal combustion engine.

japbike · 02-14-2005, 09:38 AM

I'm assuimg this question is for a class of yours?! yea? anyway, here what I know..

Fuel cells use a chemical reaction, rather than combustion (burning a fuel), to produce electricity in a process that is the reverse of electrolysis. In electrolysis, and electric current applied to water produces hydrogen and oxygen. By reversing this process, hydrogen and oxygen are combined in the fuel cell to produce electricity and water.

hold on, I know I have a book on this someplace...*****tick toc***

ok.... here ya go: (also added a picture for ya if that helps)

Fuel cells are really a family of technologies; there are several major types of fuel cells, differentiated by the type of electrolyte they use. To illustrate how a fuel cell works, we will use the PEM fuel cell as an example.

Hydrogen (fuel) is fed into the anode of the fuel cell. Oxygen (from air) is fed into the cathode side. Encouraged by a catalyst, electrons are stripped from the hydrogen atom. Freed of the electrons, the protons pass through the electrolyte, while the electrons are forced to take a different path to the cathode. As the electrons travel their separate path, they create an electric current that can be utilized. At the cathode, another catalyst rejoins the hydrogen atom, which then combines with the oxygen to create a molecule of water.

Picture below..................

Darkstar · 02-14-2005, 05:15 PM

thanks for all the information so far!

jap-it's actually for my friend who said he was going to invent the first hydrogen rotary engine. and i told him he was retarded because they dont combust the hydrogen but i wasn't quite sure how it all happened so he pretty much dismissed what i knew and still thinks he is going to invent a rotary engine that will use hydrogen instead of gas

Hagios · 02-15-2005, 07:13 AM

Let him keep thinking that, Darkstar

pgansz · 02-15-2005, 01:56 PM

actually hydrogen fuel cells aren't a good invention at all...as stated before...hindenburg..

also note that IT REQUIRES TONS OF ENERGY to form this hydrogen in the fuel cells...therefore the energy required to make this clean fuel WILL EXPEND tons and tons of CO2 into the atmosphere....

the real problem lies in trying to find out exactly how beneficial this mode of transportation will be factoring in the CO2 used to produce the gas...

edit: we can currently use hydrogen as fuel for cars...i believe Mazda has a version of their Renisis engine that runs on hydrogen...

right now they have an RX-8 that is running on hydrogen...

the best thing we can do for the next 10 years is just to make everything a hybrid...cross between electric and gasoline...until we find a better way...IMO

what we should really focus on is trying to harness the energy used in the thinking process...

jim schmidt · 02-15-2005, 02:01 PM

I would think a rotary engine could be built to run on Hydrogen. It just wouldn't be a fuel cell. And it probably wouldn't make sense (although I can already tell others know a lot more about this than me!)

pgansz · 02-15-2005, 02:10 PM

it does run on hydrogen..thats what i'm saying

StormHawk · 02-15-2005, 03:34 PM

Arnold has a Hyrdrogen powered Hummer

Darkstar · 02-15-2005, 04:01 PM

Quote:

Originally Posted by pgansz

it does run on hydrogen..thats what i'm saying

so how does that work...they just pump it in and combust? how do they store the hydrogen?

hybrid · 02-15-2005, 04:19 PM

Dude japbike showed you how its done and no nobody uses an outright hydrogen gas as fuel for combustion. It wouldnt last very long. Propane is an example of that already.

You could make a propane rotary engine but why?

A tidbit for some of you....... Propane is for diesel like NO2 is for a gas engine

japbike · 02-15-2005, 05:38 PM

I can see where this is going....... here .............

Fuel cells are really a family of technologies containing five primary types, based on the type of "electrolyte" used. Each has specific characteristics that may make it better for some applications than others.

Polymer Electrolyte Fuel Cell (PEFC) or Proton Exchange Membrane Fuel Cell (PEMFC) - The electrolyte in this type of fuel cell is an ion exchange membrane made of some type of polymer that is a good conductor of protons. This type of fuel cell runs at low temperatures (usually around 80-degrees Celsius), with electrical efficiencies of about 45%, and is the primary candidate for automotive, small stationary, and portable power applications. PEMFCs require very pure hydrogen as the fuel.
Phosphoric Acid Fuel Cell (PAFC) - The electrolyte in this type of fuel cell is phosphoric acid, concentrated to 100%. PAFCs have an operating temperature of about 100-220 degrees Celsius, and achieve an electrical efficiency of about 37-42%. Buses and stationary applications currently use PAFCs.
Molten Carbonate Fuel Cell (MCFC) - The electrolyte in this type of fuel cell is usually a combination of alkali carbonates, retained in a ceramic matrix. The MCFC operates at 600-700 degrees Celsius. The high temperature enables the end user to utilize both the electricity and the thermal energy generated by the fuel cell, resulting in electrical efficiencies of more than 70 percent. MCFCs are well-suited to large-scale stationary applications, and are currently being demonstrated for powering buildings. High-temperature fuel cells can more easily use a wide range of fuels without using a "fuel reformer."
Solid Oxide Fuel Cell (SOFC) - The electrolyte in the SOFC is a solid, nonporous metal oxide. At temperatures over 650 degrees Celsius, the SOFC can utilize a hydrocarbon fuel directly, without reforming, similar to the MCFC. Also similar to the MCFC, the SOFC generates both electricity and usable thermal energy. High-temperature SOFCs are being demonstrated for stationary power applications, while low-temperature SOFCs are also being looked at for automotive applications.
Alkaline Fuel Cell (AFC) - This was one of the first modern fuel cells to be developed, and was used to provide on-board electric power for the Apollo space vehicle. The electrolyte in this fuel cell is Alkaline (KOH). AFCs require pure hydrogen and pure oxygen as the reactants. The operating temperature for this type of fuel cell is around 200 degrees Celsius.
Other Types of Fuel Cells - There are other types of fuel cells that are relatively newer to the family of fuel cells. The Direct Methanol Fuel Cell (DMFC) is very similar to the PEMFC, but it is able to directly utilize liquid methanol at the anode. There is also a Regenerative Fuel Cell, which contains a membrane that can both electrolyze water into hydrogen and oxygen and, with the flick of a switch, recombine the two elements, producing electricity and water. In a Metal Air Fuel Cell, zinc pellets and an alkaline electrolyte are circulated through the fuel cell stack and are combined with oxygen from air to create electricity, heat and zinc oxide (in a solution of potassium zincate). The zincate can be regenerated in a separate process into fresh zinc pellets.

hybrid · 02-15-2005, 05:46 PM

ouch!!!!!!

That made the little brains I had left hurt!!

Darkstar · 02-15-2005, 06:14 PM

Quote:

Originally Posted by hybrid

Dude japbike showed you how its done and no nobody uses an outright hydrogen gas as fuel for combustion....

pgansz said, in response to jim, that they do have a rx8 that runs on hydrogen and it is a rotary. i was asking how that worked. jap was very clear on how the hydrogen fuel cell works and i understand it.