Aircraft retrofitted with hydrogen fuel cells could slash CO2 emissions from small planes — and potentially pave the way for hydrogen jets, new study shows.
The first hydrogen-powered planes are taking flight::undefined
Someone do the math on the net CO2 impact between jet fuel and natural gas reforming, including emissions to build that infrastructure, natural gas leaks (there’s a lot here), and transporting the hydrogen
I can’t include emissions for building infrastructure or natural gas leaks, but I think it’s a fair assumption that those costs are the same order of magnitude whether you use the gas directly or convert it to hydrogen + CO2, and then use the hydrogen. I mention transportation a bit further down.
Someone do the math on the net CO2 impact between jet fuel and natural gas reforming
Ask and thou shalt receive.
When we burn hydrocarbons, the overall reaction going on (neglecting byproducts) is
2 CnH2n+2 + (3n + 1) O2 => 2nCO2 + (2n + 2)H2O
When we steam-reform hydrocarbons, we use the reaction
4n H2O + 2 CnH2n+2 => 2 nCO2 + 2 (3n + 1)H2
Such that the CO2 emissions from the consumption of the hydrocarbons is exactly equal. Now, the question is about efficiency. Steam reforming has an efficiency of about 65-75 %, which means we need (very roughly) 253 kJ of energy as input per mol steam-reformed hydrocarbon (assuming 65 % efficiency).
The (ideal) energy output from the corresponding consumption of 4 moles of hydrogen is approximately 1140 kJ. Hydrogen fuel cells typically have an efficiency of about 40-60%, so the true output is about 456 kJ (assuming efficiency of 40 %). This gives a net energy output of 203 kJ per mole gas consumed by steam reforming, and consecutive hydrogen consumption.
For comparison: Internal combustion engines typically have efficiencies around 20-35%. If the same gas is consumed in a gas turbine, we thus get an energy output of about 280 kJ (assuming efficiency of 35%).
The comparison in total:
Assuming lower end efficiencies for steam reforming + fuel cell: 203 kJ / mol gas
Assuming higher end efficiencies for steam reforming + fuel cell: 464 kJ / mol gas
Assuming lower end efficiency for gas turbine: 160 kJ / mol gas
Assuming higher end efficiency for gas turbine: 280 kJ / mol gas
So, the only case in which the gas turbine beats steam reforming + hydrogen on efficiency is when we assume higher-end efficiency for gas turbines, and lower-end efficiencies for steam reforming and fuel cells.
It should also be added that combustion engines have a theoretical maximum efficiency of about 58 %, while hydrogen fuel cells have a theoretical maximum close to 100 %. In addition, combustion engines have a huge head start on fuel cells regarding development. We can expect steam-reforming + fuel cells to improve a lot in efficiency the coming years, the same is not the case for combustion.
I have also not mentioned yet that hydrogen has a higher energy density (by mass) than gas, making the transportation cost and emissions (per joule transported fuel) lower.
Shortly speaking: The numbers say that steam-reforming + fuel cells is already a competitive option when looking at energy waste and emissions per joule produced. It can be expected to get even better in coming years.
Now for some more points I haven’t mentioned yet:
Using steam-reformed hydrogen makes hydrogen cheap, which helps incentivise building things that use hydrogen, rather than combustion, which further increases demand for hydrogen. This helps lay the ground work for future, green, hydrogen infrastructure.
Maybe most importantly of all: When hydrogen is produced by steam reforming, all the CO2 is produced in one place, which can make CO2-capture viable. When the gas is burned as fuel in a bunch of different places, CO2-capture becomes less viable, as current technology heavily favours large, centralised capture operations.
I am no fan of Hydrogen as a fuel. At least not for cars. It takes more to make it and it can offer up as a fuel. All the proponents of hydrogen cars usually have ulterior motives.
BUT… I think that changes for the the aviation industry. The fact remains that batteries are incredibly heavy and expensive and they simply are not power-dense enough. Those are all issues for a car, but even more so for a vehicle that flies. Hydrogen could very well be a reasonable alternative for the aviation industry. Hydrogen isn’t particularly “green” to produce now, but there have been advances to make it much more so in recent years. I could see that being the fuel of the future for planes.
I definitely think hydrogen and batteries solve different problems, and we’re going to need both. Batteries have lower energy waste when recharging, and can handle power fluctuations better, while hydrogen has a far higher energy density, and scales much better to large scale storage. In addition, hydrogen tanks don’t wear out the same way as batteries after many empty-full cycles.
This makes hydrogen very good for large scale applications, where the power requirements don’t fluctuate much.
Hydrogen has a whole host of problems of it’s own. The absolute lack of infrastrucure is a massive, massive, massive hurdle, but if you limit that infrastructure to just large scale applications (like airports) then it becomes much less of a problem. Still hydrogen storage is extremely tricky simply because the gas is so tiny. On an atomic level, it is hard to keep it contained. That seems trivial, but is really isn’t. But ultimately if hydrogen is just one part of a wider energy solution, then things can get worked out.
Hydrogen storage is definitely something we need to do more research on. Cooling as well turns out to be quite a bit more complex than for most other fluids because of the quantum effects that become relevant once you close in on the critical temperature (which is very relevant if you want to store liquid hydrogen). It’s not only a problem that hydrogen escapes when diffusing through a container, but it usually degrades the material the container is made of in the process, reducing the life time of the containers.
We’re currently looking into using various materials that can adsorb and desorb hydrogen in a controlled manner for large scale storage applications, that’s one of the possible solutions to the fact that hydrogen can diffuse through pretty much anything.
Hydrogen would also work well for ships, trains, and to some extent trucks. Basically anywhere that requires long distance travel without infrastructure in between where batteries just don’t have the range or power to weight ratio to reach - at least not efficiently. And hydrogen is also specifically better for things connecting to a central transport hub, where the hydrogen production and storage and refueling can be centralized to minimize the infrastructure buildup and maximize production and storage efficiency. These would include ports, airports, trainyards, warehouses, sufficiently large bus terminals, basically everything except cars. And as a bonus it doesn’t require stripping the earth or rare metals, sometimes mined by slave and child labor.
I understand the advantages of hydrogen since burning it doesn’t produce greenhouse gasses, but being around that much hydrogen makes me uneasy from everything I’ve read about how explody it is. I am sure the engineers responsible know what they’re doing though
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Cool story bro.
So where’d that hydrogen fuel come from?
Today 95% of the hydrogen produced in the United States is made by natural gas reforming in large central plants.
https://www.energy.gov/eere/fuelcells/hydrogen-resources
Someone do the math on the net CO2 impact between jet fuel and natural gas reforming, including emissions to build that infrastructure, natural gas leaks (there’s a lot here), and transporting the hydrogen
It is horrible today. The only hope is to use solar energy to split water.
Given our tendency to overdo everything, this would concern me that we could actually use up all our water
I can’t include emissions for building infrastructure or natural gas leaks, but I think it’s a fair assumption that those costs are the same order of magnitude whether you use the gas directly or convert it to hydrogen + CO2, and then use the hydrogen. I mention transportation a bit further down.
When we burn hydrocarbons, the overall reaction going on (neglecting byproducts) is
2 CnH2n + 2 + (3n + 1) O2 => 2nCO2 + (2n + 2)H2O
When we steam-reform hydrocarbons, we use the reaction
4n H2O + 2 CnH2n+2 => 2 nCO2 + 2 (3n + 1)H2
Such that the CO2 emissions from the consumption of the hydrocarbons is exactly equal. Now, the question is about efficiency. Steam reforming has an efficiency of about 65-75 %, which means we need (very roughly) 253 kJ of energy as input per mol steam-reformed hydrocarbon (assuming 65 % efficiency).
The (ideal) energy output from the corresponding consumption of 4 moles of hydrogen is approximately 1140 kJ. Hydrogen fuel cells typically have an efficiency of about 40-60%, so the true output is about 456 kJ (assuming efficiency of 40 %). This gives a net energy output of 203 kJ per mole gas consumed by steam reforming, and consecutive hydrogen consumption.
For comparison: Internal combustion engines typically have efficiencies around 20-35%. If the same gas is consumed in a gas turbine, we thus get an energy output of about 280 kJ (assuming efficiency of 35%).
The comparison in total:
So, the only case in which the gas turbine beats steam reforming + hydrogen on efficiency is when we assume higher-end efficiency for gas turbines, and lower-end efficiencies for steam reforming and fuel cells.
It should also be added that combustion engines have a theoretical maximum efficiency of about 58 %, while hydrogen fuel cells have a theoretical maximum close to 100 %. In addition, combustion engines have a huge head start on fuel cells regarding development. We can expect steam-reforming + fuel cells to improve a lot in efficiency the coming years, the same is not the case for combustion.
I have also not mentioned yet that hydrogen has a higher energy density (by mass) than gas, making the transportation cost and emissions (per joule transported fuel) lower.
Shortly speaking: The numbers say that steam-reforming + fuel cells is already a competitive option when looking at energy waste and emissions per joule produced. It can be expected to get even better in coming years.
Now for some more points I haven’t mentioned yet:
Using steam-reformed hydrogen makes hydrogen cheap, which helps incentivise building things that use hydrogen, rather than combustion, which further increases demand for hydrogen. This helps lay the ground work for future, green, hydrogen infrastructure.
Maybe most importantly of all: When hydrogen is produced by steam reforming, all the CO2 is produced in one place, which can make CO2-capture viable. When the gas is burned as fuel in a bunch of different places, CO2-capture becomes less viable, as current technology heavily favours large, centralised capture operations.
Awesome, thanks love.
*ucking wonderful! Even more rain, even more white out sky’s.
Do you know what you get when you burn hydrocarbons? The carbon becomes carbon dioxide, and the hydrogen… I’ll wait.
removed by mod
I am no fan of Hydrogen as a fuel. At least not for cars. It takes more to make it and it can offer up as a fuel. All the proponents of hydrogen cars usually have ulterior motives.
BUT… I think that changes for the the aviation industry. The fact remains that batteries are incredibly heavy and expensive and they simply are not power-dense enough. Those are all issues for a car, but even more so for a vehicle that flies. Hydrogen could very well be a reasonable alternative for the aviation industry. Hydrogen isn’t particularly “green” to produce now, but there have been advances to make it much more so in recent years. I could see that being the fuel of the future for planes.
deleted by creator
I definitely think hydrogen and batteries solve different problems, and we’re going to need both. Batteries have lower energy waste when recharging, and can handle power fluctuations better, while hydrogen has a far higher energy density, and scales much better to large scale storage. In addition, hydrogen tanks don’t wear out the same way as batteries after many empty-full cycles.
This makes hydrogen very good for large scale applications, where the power requirements don’t fluctuate much.
Hydrogen has a whole host of problems of it’s own. The absolute lack of infrastrucure is a massive, massive, massive hurdle, but if you limit that infrastructure to just large scale applications (like airports) then it becomes much less of a problem. Still hydrogen storage is extremely tricky simply because the gas is so tiny. On an atomic level, it is hard to keep it contained. That seems trivial, but is really isn’t. But ultimately if hydrogen is just one part of a wider energy solution, then things can get worked out.
Hydrogen storage is definitely something we need to do more research on. Cooling as well turns out to be quite a bit more complex than for most other fluids because of the quantum effects that become relevant once you close in on the critical temperature (which is very relevant if you want to store liquid hydrogen). It’s not only a problem that hydrogen escapes when diffusing through a container, but it usually degrades the material the container is made of in the process, reducing the life time of the containers.
We’re currently looking into using various materials that can adsorb and desorb hydrogen in a controlled manner for large scale storage applications, that’s one of the possible solutions to the fact that hydrogen can diffuse through pretty much anything.
Hydrogen would also work well for ships, trains, and to some extent trucks. Basically anywhere that requires long distance travel without infrastructure in between where batteries just don’t have the range or power to weight ratio to reach - at least not efficiently. And hydrogen is also specifically better for things connecting to a central transport hub, where the hydrogen production and storage and refueling can be centralized to minimize the infrastructure buildup and maximize production and storage efficiency. These would include ports, airports, trainyards, warehouses, sufficiently large bus terminals, basically everything except cars. And as a bonus it doesn’t require stripping the earth or rare metals, sometimes mined by slave and child labor.
I understand the advantages of hydrogen since burning it doesn’t produce greenhouse gasses, but being around that much hydrogen makes me uneasy from everything I’ve read about how explody it is. I am sure the engineers responsible know what they’re doing though