DLR.de developed fuel cell for e-cargo

[mark sutton]

Hi All,

Another 'could be the next big thing' style post from me. I've been speaking with the German Aerospace Center in recent weeks about a fuel cell they're developing.

Now this isn't necessarily an e-bike application, but for heavier e-cargo it fits the bill and has some good potential.

If you're interested, we've an interview with them here: https://cyclingindustry.news/german-aerospace-center-developing-fuel-cell-with-implications-for-big-business-cargo-bike-use/

Be interested to know thoughts,
Mark@cyclingindustry.news

 

[mike killay]

I think that improvements in battery technology are nearing their end. There is no holy grail, the chemistry is known and the theoretical possibilities are rather limited.
Efficient fuel cells offer a way forward, but the question must be asked, why a fuel cell?
Why not just burn the hydrogen in an internal combustion engine?

 

[Woosh]

Why not just burn the hydrogen in an internal combustion engine?

or burn something else easier to store as long as it's clean burn.

 

[Danidl]

I think that improvements in battery technology are nearing their end. There is no holy grail, the chemistry is known and the theoretical possibilities are rather limited.
Efficient fuel cells offer a way forward, but the question must be asked, why a fuel cell?
Why not just burn the hydrogen in an internal combustion engine?

... First
this use of magnesium hydrides is very interesting.. had not heard of it before, but is very exciting. Not a rechargable battery but presumably a remanufacturable product. Similar in possibilities to a domestic butane gas cylinder, where you replace the empties. The underlying material remains in the canister . If the factories remanufacture the containers, reusing the material and using renewable energies to do so it's a win win situation. We are not going to run out of magnesium....
Second
Why a fuel cell 2 reasons.
Electric production is more efficient, if the objective is the creation of electric power.
No extra pollution. Combustion in air will produce NOX
If the objective is /was to produce thrust, then a jet engine while being less efficient is simple in concept and nowadays highly reliable

 

[mike killay]

I thought that burning hydrogen in air only produced water?
I am not trolling, just not fully cognisant of all the science.

 

[flecc]

I thought that burning hydrogen in air only produced water?
I am not trolling, just not fully cognisant of all the science.

From Wikipedia:

In a flame of pure hydrogen gas, burning in air, the hydrogen (H2) reacts with oxygen (O2) to form water (H2O) and releases energy.

2H2(g) + O2(g) → 2H2O(g)
(If carried out in atmospheric air instead of pure oxygen (as is usually the case), hydrogen combustion may yield small amounts of nitrogen oxides, along with the water vapor.)
.

 

[Danidl]

I thought that burning hydrogen in air only produced water?
I am not trolling, just not fully cognisant of all the science.

.. flecc is correct. When the hydrogen burns or oxidises in air it will combine with the oxygen in the air to liberate a lot of heat and produce water vapour. The chemical reaction is as he has said. However there will be a lot more oxygen in the air than would be consumed by the limited amount of hydrogen. The most abundant gas in the atmosphere is nitrogen( 4 times more abundant than oxygen , ) and when it gets hot enough it can oxidise with free hydrogen. The resulting compounds are also gases which we call NOX .. N a nitrogen atom may bond with 2,3,4,5 oxygen atoms so the x in nox indicates indeterminate. The amount of nox formed depends on the temperature in the vicinity of the nitrogen, oxygen mix.

 

[Danidl]

Hi All,

Another 'could be the next big thing' style post from me. I've been speaking with the German Aerospace Center in recent weeks about a fuel cell they're developing.

Now this isn't necessarily an e-bike application, but for heavier e-cargo it fits the bill and has some good potential.

If you're interested, we've an interview with them here: https://cyclingindustry.news/german-aerospace-center-developing-fuel-cell-with-implications-for-big-business-cargo-bike-use/

Be interested to know thoughts,
Mark@cyclingindustry.news

.... I followed up on more of the posting on this very interesting product, and they will be presenting again in April in Hanover. From what I gather, there is a lot of interest in materials sciences circles about this and similar compounds. What this team have done is to add additional material and tweaked a manufacturing process, so that what would have been a slow reaction becomes very fast and predictable at low temperature. This recipe is being patented.
The magnesium hydride is in the form of a paste and is squirted by a pump into water, there is a chemical reaction liberating pure hydrogen , consuming water and creating a waste product .There is no requirement for the water to be clear or clean. They claim that the magnesium hydroxide , the waste product is safe. They are not interested in recycling the magnesium, but there are other groups working on efficient means of doing so. They suggest that the overall energy cycle of production to recovery is currently 20%.
The waste product is retained so in a mobile application there would need to be two containers and the waste material will be heavier...
They suggest that long term auxiliary power as a target market. I could envisages a role in aircraft power as the energy density is sufficient.

 

[Woosh]

I could envisages a role in aircraft power as the energy density is sufficient.

No chance for metal hydrides to fly an aeoplane.
There is a efficiency limit on systems based on metal hydrides and they still won't be able to compete against hydrocarbons or solar energy in the foreseeable future.
On the current scope, if the process produces a waste product then it's to be expected that the system has to be reprocessed, not dumped.
Lithium batteries for example do not contain dangerous substances and yet have to be recycled.
If you factor in the cost of reprocessing, I doubt that metal hydrides can compete against batteries.

 

[Danidl]

No chance for metal hydrides to fly an aeoplane.
There is a efficiency limit on systems based on metal hydrides and they still won't be able to compete against hydrocarbons or solar energy in the foreseeable future.
On the current scope, if the process produces a waste product then it's to be expected that the system has to be reprocessed, not dumped.
Lithium batteries for example do not contain dangerous substances and yet have to be recycled.
If you factor in the cost of reprocessing, I doubt that metal hydrides can compete against batteries.

.. according to the figures provided by the Fraunhofer institute, the energy density of the magnesium hydride powerpaste is the same as hydrocarbons. So they would not be competing in the same space as rechargeable cells. The waste product would be a laxative, milk of magnesia!!! And could be dumped at sea with no ill effects .The advantage of recycling would be to recover the magnesium, at presumably less cost than its extraction from the sea. The lithium battery packs do contain organic solvents, aluminium foil, carbon materials and assorted plastics specialist activators.
The concept would be that solar energy be used to create the hydride and then use it as a secondary energy store. Once the hydride is formed it can be stored indefinitely and only comes to life when mixed with water producing it's hydrogen.

 

[Woosh]

I am not sure they compare like with like. MgH2 is made from H2 and powdered magnesium under high pressure and temperature. MgH2 reacts with water to release hydrogen and Mg(OH)2. Yes, you can dump the waste at sea but if you look at the energetic contents of MgH2 which comes entirely from using the released hydrogren and not burning the magnesium, against hydrocarbons even on the less energetic CnH2n+2, on weight of carburant or system weight, or even on volume, it's a no brainer, even before you consider the material cost (as you dump the milk of magnesia into the sea).

 

[flecc]

The waste product would be a laxative, milk of magnesia!!! And could be dumped at sea with no ill effects .

Given the huge number of transatlantic flights, ships helmsmen could ignore their compasses and just follow the white line on the sea.

We'd need to agree with the USA whether we flew on the left or the right.
.

 

[FoxZulu]

Given the huge number of transatlantic flights, ships helmsmen could ignore their compasses and just follow the white line on the sea.

We'd need to agree with the USA whether we flew on the left or the right.
.

We already have such an agreement. Everyone flies on the right

 

[Woosh]

but that may change after brexit, we may fly any way we like!

 

[Danidl]

I am not sure they compare like with like. MgH2 is made from H2 and powdered magnesium under high pressure and temperature. MgH2 reacts with water to release hydrogen and Mg(OH)2. Yes, you can dump the waste at sea but if you look at the energetic contents of MgH2 which comes entirely from using the released hydrogren and not burning the magnesium, against hydrocarbons even on the less energetic CnH2n+2, on weight of carburant or system weight, or even on volume, it's a no brainer, even before you consider the material cost (as you dump the milk of magnesia into the sea).

.. in their presentation, they quote the production of electricity as their benchmark. Using fuel cells they get more energy from the conversation of the hydrogen than from the thermal processes involved in converting a hydrocarbon into electricity.They do not consider burning the magnesium.
In the Q and A section he referred to a 20% overall energy budget. Eg recycling the waste products back into useful product cost 80% . , I would assume that would have included the energy costs of high pressure and temperature forming and the electrolysis of the hydroxide.

 

[mike killay]

Given the huge number of transatlantic flights, ships helmsmen could ignore their compasses and just follow the white line on the sea.

We'd need to agree with the USA whether we flew on the left or the right.
.

At least, constipation would be a thing of the past!

 

[Woosh]

before we get all excited about this, it's nothing new. The molar mass for MgH2 is 26g/mole. If you combine the H2 with the oxygen from the air, you will get at most 286 kJ/mole, or 11MJ/kg (specific energy rating) for MgH2. Jet fuel: 42.8MJ/kg.
The price of pure magnesium powder, hydrogen storage grade is about £20 a kg. Jet fuel costs less than £1 a kg.
Fraunhofer make and sell magnesium powder, it's no surprise that they try to push consumption.

 

[Danidl]

before we get all excited about this, it's nothing new. The molar mass for MgH2 is 26g/mole. If you combine the H2 with the oxygen from the air, you will get at most 286 kJ/mole, or 11MJ/kg (specific energy rating) for MgH2. Jet fuel: 42.8MJ/kg.
The price of pure magnesium powder, hydrogen storage grade is about £20 a kg. Jet fuel costs less than £1 a kg.
Fraunhofer make and sell magnesium powder, it's no surprise that they try to push consumption.

I suspect that the price of magnesium you are referring to to would be lab reagent spec. The same interview i referred to earlier had the Fraunhofer representative quoting 2 euro per kilo. Which is why he was dismissive about needing to recover it.
The energy levels you quote are consistent with his graphic. In a sense he egged the pudding by equating it to electricity production not the raw chemical energy in the respective materials. He was, if memory serves, suggesting a conversation efficiency of 20% for hydrocarbons and 50% for hydrogen in a fuel cell.
While this chemistry might have been familiar to you, I must admit it was new to me.