I was looking into fuel cells running on wood because of the silent operation and efficiency. I came across this interesting research paper:
A simple high-performance matrix-free biomass molten carbonate fuel cell without CO2 recirculation
They tried two different fuels: charcoal and just straight up wood. the way they designed it is just by putting the wood right into a molten salt with an anode also in there. They call these type of fuel cells direct carbon fuel cells because it uses the carbon directly. They made this much more simple in this design compared to every other design I’ve seen. They also said that using straight wood was good because,
“The combustion of this produced biogas in the air can provide heat to maintain the high operating temperature. Therefore, directly using biomass such as wood as the fuel in an MCFC can maximize energy utilization. Therefore, wood, which is a typical biomass, was directly used as fuel for the newly designed MCFC.”
It also worked out that the molten electrolyte bonded with different impurities in the wood that would usually poison the cell, and could be cleaned out fairly easily.
“From this point of view, MCFC has a high impurity tolerant limit, and the contamination is regenerative, which is particularly suitable for fuels containing high impurity, such as biomass.”
Anyways, if you are interested in fuel cells I would definitely read this and I would like to hear what other people think even though it’s just a lab study. I think that this could be really useful because the wood does not have to get turned into gas, cleaned, and then fed to the cell. It all just kind of gets burnt up in the molten electrolyte where the energy is also produced.
Very cool stuff. Fuel cells can have higher efficiency than combustion engines and have no or few moving parts. Power density tends to be low though. And some combination of high heat, highly corrosive liquids or both tends to make for a materials challenge.
This design is simple enough to be DIY’able for the most part and eliminates some of the materials challenges, but not all. Seeing a maximum power density of around 400mW/cm2. For a 4kw fuel cell that is a square meter of surface area - quite a bit even in a stacked configuration.
The power density wouldn’t matter too much because the generator could be running almost 24/7 since it is silent. I’m thinking that if this was a stationary power supply for a house then it could just be making power at all hours and have a slow consumption of fuel.
At that type of temperature and that type of energy density I dont see it as a DIY option. The tech looks cool though. On a home scale you would be further ahead doing a woodstove and a thermo electric setup. Less complexity less oh shit possibilities.
I agree that density isn’t a big deal for stationary power but the low density does create cost pressure. Larger devices need more stainless steel and specialized coatings, etc than small ones. Lower power devices need to run longer to generate the same amount of kwatt hours, thereby using up their useful life faster.
The linked article is great progress for fuel cells but more is needed to displace combined cycle turbine and piston driven generators.
Definitely too complex for diy compared to a gasifier with an internal combustion engine, but I think that it could be a useful alternative for more localized power generation. One thing that I didn’t notice before that complicates the whole thing a lot is it looks like you might have to purge all the oxygen out of the hopper area with nitrogen. That would definitely make it less simple to make and operate. All in all, I think that the system has its benefits to most other fuel cell from biomass systems I have seen. Maybe exhaust from somewhere could be used to purge out the oxygen. Not sure what I think about that now