Hi all,

 

The latest update on my project for the chemical engineering nerds out there, how to get a polarisation curve from my fuel cell using a raspberryPi controller.

 

Why a fuel cell; if you haven't followed my other posts, they can provide cruise power for hours, greatly increasing the endurance of a RC plane or UAV.

 

Unlike batteries, fuel cells do not lose voltage with time because you can keep feeding it fuel. Much like a car engine keeps working until the fuel is completely gone, whereas a battery has a gradual reduction in it's output with respect to it's state of charge (SOC). However, the voltage does vary with load, and this relationship is captured in a polarisation curve.

 

Hope you find the video interesting and inspiring, if so please click LIKE!

 

Regards,

 

Simon

Views: 2330

Comment by Quadzimodo on January 16, 2014 at 8:14pm
Great project. Hydrogen is such an exciting energy storage solution, with it's own set of unique challenges.
I am interested to know more about the vessel in which the hydrogen is contained. What is it's capacity, and under what pressure is the hydrogen stored. What is the total Ah capacity of the system, and what are the safety and compliancing implications of putting this type of system in the air.
Also, considering the less than fantastic power density, how do you see hydrogen playing a roll in aviation in the future?
Comment by Jack Crossfire on January 16, 2014 at 8:37pm

Dave Jones would go crazy over that dummy load.

Comment by Quadzimodo on January 16, 2014 at 10:34pm

Did somebody say dummy load?

I had this thing custom built for doing back to back load testing big monoblock car amplifiers.  It has 1, 2 and 4-ohm taps and is rated at about 10kW, more with a fan blowing a steady stream of air through.  Amazingly, it was great for the application, as it would give a nice faint hum (50Hz sine wave) and emit a harsh ticking sound at the onset of clipping. Also, great for heating the house in winter!

Comment by Simon Howroyd on January 17, 2014 at 2:05am

Thanks for the interest! I can answer a couple of the questions at this stage but not ass as it is still a fairly early prototype...

The H2 is currently being stored in a big 80kg tank outside. I have just got hold of some HydroStik canisters (click the link for all the details there) and will be trying those in the next couple of weeks to see if I can nail the portable storage solution.

In terms of safety, the only thing dangerous is the 1kg chunk of metal and it's inherent inertia, particularly on landing, so it may cause some fatigue on foamies where it is mounted, the hydrogen is safer than LiPo, glow fuel and kerosene.

Finaly the power density is the sticking point. When you launch you use all the capacity of your ESC. In my case 2kW. When I cruise I use about 100W. It makes sense to specify the fuel cell for the cruise (since it is going to be doing this for 10hrs say). This means you need something to give you a 2kW launch, eg a bungee, tow, or a small LiPo which just has enough capacity for a 20s burst. It is the latter, the hybrid with a LiPo I will look at first, then I would like to see how slow the take off run is at 100W and if it is possible with a long runway.

The long and short of it is, hydrogen has a much better energy density than any battery, meaning, for the same weight you can fly for longer (by lots!), but it doesn't tend to give you a lot of power, nor be any good at instantly changing the demand (unlike LiPo where you can go from zero to 100% throttle instantly).

A bit more research, and a lot of testing and I should have this giving some interesting results for RC and UAV!

Comment by Euan Ramsay on January 17, 2014 at 2:26am

Hydrogen has the most energy density of all the elements whether using chemically or nuclear, so this is great research by Simon.

Personally, I think a 1kg cell is "getting there", but there are many packaging problems to address before this can be used at the hobby level. And 1kg of metal will cause chaos with RF signals...and that's before we consider the fuel and storage. Lets say the propulsion system comes to 3kg - I think small, hand-launched non-glider foamies are ultimately impractical for "all day" endurance flight; CF frames, catapults and high lift wings are going to be needed.

I like the idea of a hybrid approach, maybe we can even use the FC to charge the Lipo when it's idle?

 

Comment by Simon Howroyd on January 17, 2014 at 2:33am

Euan, yep that is exactly the plan. Gives you that "get out of jail free" power when you need to do the inevitable go-around!

Interestingly, I didn't have any RF issues when I did my test flight with the fuel cell onboard but not plugged in, but this is something I will now look at a bit more closely, good point! Although I won't be doing any long distance stuff due to the UK regs.

I should point out that this fuel cell is not in any way (bar the controller I am designing) designed for airborne use. I just like the challenge! Horizon do do a more suited, 'twice the power, half the weight' fuel cell (Aeropak 200), which might be more suitable to get something working with less hassle. The sticking point here being cost at $15000.

Comment by Euan Ramsay on January 17, 2014 at 2:40am

Ah yes...just a couple of $zeros outside the hobby market then...:-)

Comment by Greg Dronsky on January 17, 2014 at 3:29am

Great post. H-CELL 2.0 by Horizon is in a better price but it only brings 30W. I subscribed to your YT channel and am waiting for more videos. Maybe some tutorial step by step?

Comment by Simon Howroyd on January 17, 2014 at 3:40am

Hi Greg. Thanks for the comments. 30W unfortunately would be too few, I think I am pushing my luck slightly with only 100W.

As for step-by-step. What sort of thing are you looking to do? I have a more in depth video here if it is of interest? I am certainly willing to do more videos if requested!

Comment by Quadzimodo on January 17, 2014 at 5:00am

I was not yet aware of a properly resolved, cost effective (reusable/reversable) and practical chemical storage solution.  I was under the impression that, while hydrogen promises to be the portable energy storage solution of the future, significant challenges were yet to be resolved before it could truly be made portable - both gravimetrically and volumetrically.

I can see that the power density of the Hydrostik is 0.13 Wh per gram (not including the associated fuel cell), which obviously renders it uncompetitive with existing technology, but the 0.65-0.80Wh per gram power density of the Aeropak is just outstanding!  Really exciting!

I look forward to future updates, info and results.

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