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  • Author Author: howroyd
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Hydrogen Fuel Cells!

howroyd

Hydrogen fuel cells (in particular PEMFCs) are an exciting technology which has been around for a while now. Unfortunately, they haven't really take off (excuse the pun) due to their high cost, poor lifetime and slow transient performance.

 

1. So why are people still interested?

 

Well, firstly you have the good old "clean & green" argument. In operation, the take in oxygen (from the air) and hydrogen (the fuel), and give out heat, water and electricity. No carbon dioxide, monoxide, sulfides and other nasty things.

Secondly, they're not dependent on fossil fuels to run, and are currently the most promising energy generation technology that is independent of the elements (wind, solar, etc).

Hydrogen has a superb energy density, meaning not much weight gives you a huge endurance.

Fuel cells tend to have no moving parts, unless the have a cooling fan or air supply fan, so they are mechanically very simple.


2. So why aren't we using them?

 

They require platinum as a catalyst so make the chemical reactions work. Platinum is incredibly expensive, and more annoyingly it tends to be washed away over time which reduces the fuel cells lifespan.

They are slow to respond, so cruising along at 10% power, then suddenly demanding a full 100% may take anything from seconds, to minutes, to hours, depending on the type of fuel cell. This proves a big challenge in mechanical transport, such as planes, and cars.

Hydrogen is a pain in the rear, generally. To produce the high quantities we need, we can only do it (cost-effectively) by burning fossil fuels. Of course it can be generated using renewables (wind, solar, etc), but this is far too expensive at the moment for the industry to consider.

Hydrogen also is a pain to store. Because there are so few molecules in such a large amount of space (low density), you have to store it at tremendous pressures to get a usable quantity, which requires huge storage tanks. Not particularly practical in transport applications. There are other methods, but cost and practicality is still a huge issue.

 

3. Where do I fit in?

 

To start I am not a chemical engineer. However, I am a PhD researcher for the Hydrogen Fuel Cells & their Applications Doctoral Training Centre (DTC) in the United Kingdom, so I know a fair amount about it. By trade I am a autonomous control engineer, specialising in unmanned aerial vehicles (UAVs).

Given all the problems outlined above, even the suggestion of putting a fuel cell on a small UAV, which is essentially a modified off the shelf remote controlled hobby plane, seems crazy. But it is do-able, and has been done. The advantages for flight aren't the clean & green approach currently dominating the selling point of fuel cells, but that key word "endurance". To fly for 10 hours, a UAV would have too many batteries to float, let alone fly, but with hydrogen's energy density this may well be possible. That's what I'm going to find out.

 

4. So that's nearly 500 words with no raspberryPi?

 

Haha, hopefully I have set the scene now. Let's talk about the electronics!

The fuel cell is a dumb system. It's just a contained and continuous chemical reaction. But it can be controlled through the hydrogen supply, the load and the temperature. I can overcome the poor transient performance if I know that "soon" I will need full power; I can simply crank the fuel cell up, dump the excess power, then when the time comes, 100% is there to give. Sounds wasteful, but it turns this fuel cell into something useful. To control the logic we need a computer. On a small UAV the raspberryPi is ideal, in terms of size, power (in & out), flexibility and functionality.

Running a Real Time Operating System (RTOS) is a seriously useful tool, which I could not do on my work last year (using Arduino). I can programme in any language, use other peoples software (eg the camera) and share my code with the world (and myself for backup!) on GitHub.

So far I am using several add-ons including the MATLAB/SIMULINK support (to help the academics!), rPi Camera, delta-sigma-pi I2C ADC, piFace SPI Digital IO, TMP102 I2C temperature sensors and have the whole lot connected to an onboard UAV autopilot.

 

At risk of making this essay any longer, I'll wrap up now. I hope this is something that tickles your interest, and keep tuned for some videos, pictures tutorials and demos in the coming weeks. In the meantime, if you are interested in the plane the check out my page on diydrones.

 

Simon

_________________________________

S HOWROYD MEng (Hons) RAFVR(T)

Academic Researcher

Fuel Cells in Unmanned Vehicles

Autonomous Systems Specialist

Aeronautical & Automotive Engineering

Loughborough University

 

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  • in reply to howroyd

    Hi Simon,

     

    You have the truth of it.

    Hydrogen is the cleanest fuel we could use.  Its widely abundant and actually safer to use than most of the hydro-carbon fuels currently in use.

    If we can get an economical fuel cell device, then we can get a lot of use out of Hydrogen without end.

     

    DAB

  • in reply to Former Member

    Interesting thoughts, thanks for your input.

     

    The rPi is certainly overkill for controlling a couple of switched and reading an ADC. But it does a lot more here, it acts as a webserver, datalogger and a bus controller. I could do it on a PIC, but the amount of effort it would take to build a circuit board, programme machine code etc etc.... Using an RTOS makes the timeframe shorter, and quite frankly, for £20 i'm really not bothered.

     

    Hydrogen can be turned into water and electricity at an instant, and the water converted back into hydrogen very fast. This is renewable by todays definition. Hydrocarbons are renewable, over thousands of years, and by then my car will be out of juice so I don't plan on waiting!

  • in reply to Former Member

    Hi Bud,

     

    You really need to read my new book, "I Killed Schrodinger's Cat!", when it comes out in a few months.

    I will explain to everyone what really happens in a sun as it creates things with fusion.

    One myth I will dispel is that an alpha particle is a helium nucleus.  It is not.

     

    By the way, I have discovered that most stars creates a lot of hydrogen.  The other myth I dispel is that the sun burns hydrogen to make helium.  It does not.

     

    The truth is out there and I will soon release a lot of truth and destroy a lot of myths.

     

    DAB

  • in reply to howroyd

    Petroleum is produced by holding a peat bog at a very critical temperature and pressure for a few million years. It is the "most" renewable fuel source in existence being formed daily under every Ocean and graveyard in the world.

     

    Hydrogen is the most abundant element in the universe -- we simply need a pipeline to the sun to recover it. We have one, it is called light and a green compound, chlorophyll, converts it to Adenosine-triphosphate (ATP).  While the ribose (sugar) portion of the ATP molecule is a hydrocarbon it is the reversible loss of its phosphorous tail that releases energy.  Since hydrogen for fuel is inefficiently produced by the combustion of formerly living things -- life is the source of all renewable energy, hydrocarbon fuel is renewable, Hydrogen is not.

     

    It seems intuitive that hydrogen is the perfect fuel for aircraft because it is lighter than air in storage but how do you land a zephyr -- normally you don't -- that is why the empire state building has a docking platform for them.   While the Pi could be used in your proposed project it is overkill, good for a prototype but not suited to production.  I don't see a clear problem statement but probably you want an opto-coupled triac driving a solenoid valve as the output of the Pi gpio.  Code written in 'C' should be fast enough to keep up with the mechanical components of the system.

     

    The Sun release photons created in its core as alpha particles when hydrogen atoms combine to form helium.  Helium-4 is the "clean" fuel and if Helium leaks it escapes our atmosphere -- "Dilution is the solution to pollution."  Helium is a higher smokestack.

  • in reply to DAB

    I believe our national gas infrastructure will only take a certain percentage hydrogen to natural gas. The number escapes me but I have 20% in the back of my head for some reason. Main point anyway is that it currently couldn't take 100% hydrogen.

    I guess this is down to the wholesale end where the pumps can't handle it, and the user end where the seals and valves can't hack it,

    Because H2 is such a small molecule  it fits through tiny gaps that methane cannot, so leaks spring up all the time with H2, which is a right pain!!

    Interestingly, look at the Autogas infrastructure that has popped up.This isn't being pumped in by the mains to the petrol stations. This is doing pretty well, which shows promise that hydrogen can do the same in the future.