Fuel Cells - What are they?

[T_Bohr]

Hi All!

 

Linus recently made a review video of a fuel cell recharged for smartphones and tablets. I think that it is a great excuse to shear my knowledge in this matter. I am an enthusiast in the fuel cell technology and I have devoted to both my BSc and MSc works to fuel cells. I also want to stress that I am not advocating for any fuel cell company, as I am not associated with any of them (yet).

 

If you are interested in fuel cells than keep reading and I hope you will find this post interesting and entertaining.

 

THE BEGINNING

I think it is important that I start with some historical background while in the same time describe what a fuel cell is. Fuel cell is an old concept it dates back to the times when a certain scientist "zapped" water with electricity. When he did so he got hydrogen and oxygen in a process of electrolysis. Now this process can be reversed. You can add hydrogen to oxygen and get things "moving" for example in rockets (rocket fuel is oxygen and hydrogen). Fuel cells use the same two ingredients, but in a more refined and controlled way. Inside of a fuel cell hydrogen is combined with oxygen, but flame and explosion part of this process is bypassed, instead you directly get electricity and some heat. The first attempts of building a working fuel cells date back to 1839, but materials available back then were not strong and resistant enough to withstand the reaction intermediate products. The first real world use for fuel cell was in the USA Gemini Space Program where they were used as the main power source for the spacecraft. Since the 1960's fuel cells are steadily getting more useful, efficient, long lasting, and cheaper. This why they are applied in more and more, down to earth, every-day scenarios.

 

THE INSIDE OF A FUEL CELL

Not getting into too much detail, there are three main components of a fuel cell. The first two are a cathode and an anode, connected by an external circuit - a wire. Both of these are in most cases made of different metals. Their role is to facilitate the reactions inside a fuel cell and to be a conduit for the electrons (the electrical current). The third essential component is the electrolyte. In a fuel cell an electrolyte separates the cathode from the anode preventing the transfer of electrons between them in any other way than through the external circuit mentioned before. Another very important property of the electrolyte is that it enables positively charged molecules to pass, right through it, from the anode to the cathode.

The whole process occurring in a fuel cell looks a bit like this - Hydrogen travels from a fuel tank to the surface of the anode. On that surface hydrogen splits into negatively charged electron and a positively charged proton. The proton feels an irresistible urge to travel to the cathode through the electrolyte. The electron left on the surface of the anode is compelled to return to the proton, but since it cannot go through the electrolyte it has to go through the external circuit to the cathode. In doing so it also powers any electrical device along that circuit. When both electron and proton meet on the cathode they are also joined by an oxygen molecule which is responsible for drawing them to the cathode in the first place. Now the oxygen can be easily taken from the air around the fuel cell and in return the fuel cell gives back water.

MORE DETAILED LOOK

Here is some additional information on fuel cell and its components for those who want to know a bit more.  

 

Electrolyte - This is definitely a defining element of the fuel cell, even different types of fuel cells are named after this element. The material of the electrolyte determines what kind of operational temperature is needed for the whole fuel cell to work and to produce electricity. This temperature can range from 1000 C to 60 C. What is more this determines what kind of materials can be used as an anode and a cathode. The temperature also determines the type of fuel (it doesn’t have to be hydrogen) and potential applications for that type of fuel cell.  

In low temperature fuel cells where the electrolyte is a polymer the fuel has to be hydrogen or methanol. In high temperature fuel cells you can feed the anode with a wide variety of liquids and gases.

Previously I have mentioned that the electrolyte has to be a barrier for electrons and it needs to conduct positively charged molecules and ions. There is a bit more to a good electrolyte thou. Below i will list just a few requirements that make an electrolyte suitable for the job.

• It has to be as little of a barrier for the positively charged molecules as possible (low resistance)
• It needs to be stable in the presence of very aggressive oxygen atoms present on the cathode.
• It cannot allow too much of fuel or oxygen to get through it, because then there are no electrons going through the external circuit and we get no electricity from the fuel cell.
• It needs to be cheap so that the production of a fuel cell is cost effective.

I will not get into more detail than that about the electrolyte.

 

Anode & Cathode - These seem as pretty straight forward elements. Just two slabs of metal connected by a wire. You see I thought so at the beginning, but there is much more to them than that. Especially the low temperature fuel cells need specialized anodes and cathodes, made from metals specially designed for the type of fuel - (platinum for hydrogen and a platinum-ruthenium mix for methanol). Extremely important is also the amount of surface area for both the anode and the cathode. More surface area is better and there is more electricity to get from a smaller fuel cell (in theory). It turns out there are quite ingenious ways to increase the surface area of an anode while at the same time decrease the amount of expensive metals used. Modern techniques can produce anodes which have only a few mg of metals for each square centimeter of surface area. 
 

I have attached a simple sketch of a basic components of a fuel cell and the way they come together.

 

 

WHAT IS IT FOR - FUEL CELL PROSPECTS

In my opinion you can divide fuel cells into three major size categories - stationary, transportation and mobile.

Large stationary fuel cells are deployed in industrial plants where hydrogen is a by product of some chemical reaction and can be used to power the fuel cell. They are also used as back-up power in hospitals and for cell towers. Another use of large fuel cells is to aide the electrical grid in times of high demand. In this case the excess energy in the grid is used to produce hydrogen from water during low demand (at night), and during electrical grid “rush hours” this hydrogen is converted back to energy via a fuel cell and feed to the grid. A bit closer to individual consumers are fuel cells for home - combined power and heat generation (check the Ene-Farm project:http://www.tokyo-gas.co.jp/techno/stp1/00h1_e.html). I think we will continue to see more and more fuel cells in the industry/services sector as the fossil fuel prices continue to rise.

Transportation sized fuel cells are an alternative for internal combustion engines and  battery powered vehicles. Almost every major car manufacturer has a fuel cell cars in their product lines. these type of cars combine the best from both world. They can be easily filled up just like a petrol/diesel/gas vehicle, but at the same time run on renewable, clean energy. The lack of a hydrogen infrastructure (fueling stations) is a pain though and the fuel cells are still more expensive than a traditional internal combustion engine.

Small mobile fuel cells are also a thing. One of the advantages of a fuel cell is that it can get as small as the transistors on your motherboard. This means you can easily fit them into a laptop and potentially a smartphone. I feel however this concept is a long way away for now and we will see many stand-alone fuel cell recharging stations like the one Linus reviewed before we will see it integrated into a portable electronic device.
 

THE END

I think I wrote too much, no one is going to read it all! However if there actually is anyone still interested I have plenty more information to shear on the subject of fuel cells. I am also open to any questions in this topic.

[Imaginaerum]

 I think that it is a great excuse to shear my knowledge in this matter. 

 

I also believe that if you think you wrote too much, it's a sign to go back and make it shorter. Either way, interesting read, it made me interested enough to Google some things. I want cars powered by water already.

[geforceftw]

Why is no one interested in this? Good explanation though

[rashdanml]

The biggest reason for the cost is the platinum. It's the rarest precious metal found on Earth, and fuel cells need to compete with the jewelry industry. Very few, if not none, of the alternatives that don't require platinum are good enough to replace it. 

[IPCharger]

This thing is longer than a PCper article... Still pretty interesting though.

[nicehat]

Birthday blood alcohol level too high....This isnt where I parked my car....

 

 

(article looks interesg...ill red it laer) good man

[Alex(PlayMedium)]

Could you please use the default/white font? It is nearly unreadable with the dark theme enabled