New Energy Vehicles (NEVs) in China


Nutrient

Junior Member
Registered Member
I think Hydrogen is a dead end. Maybe its because I have watched so many engineers say that, that it has many disadvantages compared to electric.

Hydrogen needs to be taken from natural gas.
It consumes energy to convert natural gas to hydrogen.


No, natural gas is not an absolute necessity for making hydrogen -- it is just the currently most convenient method, as the gas pipelines have already been built.

You can also get hydrogen by electrolyzing water, using electricty from solar panels. Yes, as Elon Musk says, this is less efficient than putting the electricity directly into batteries, but solar farms can generate so much energy during the day that we can afford to waste some.

Hydrogen is portable energy, far more portable than batteries. The best Lithium batteries are at 250 watts/kg, and Hydrogen is like 38,000 watts/kg, over 100 times better. So hydrogen is great for larger vehicles like trucks, ships, airplanes, and so on.

Note that I said "larger". Hydrogen's biggest problem is its very low density: it liquifies at ultra-low temperatures (-269 C), which makes liquid hydrogen impractical for everyday use (it's great for rockets though). You could combine the hydrogen with something else to make a liquid (like methanol), but then you would have to get the hydrogen out again, and that wastes energy. So you need a large tank to hold the gas, which means large vehicles like trucks, ships, etc.

Or you could compress the hydrogen for use in passenger cars. The Toyota Mirai, for example, uses tanks containing 700 atmospheres. That makes me nervous: so much pressure is like a bomb waiting to explode. Toyota reassures everyone that their tanks are strong enough, but I am not so sure.

So for the moment, hydrogen is for the larger vehicles like trucks or ships, or maybe even airplanes.
 

FairAndUnbiased

Junior Member
Registered Member
No, natural gas is not an absolute necessity for making hydrogen -- it is just the currently most convenient method, as the gas pipelines have already been built.

You can also get hydrogen by electrolyzing water, using electricty from solar panels. Yes, as Elon Musk says, this is less efficient than putting the electricity directly into batteries, but solar farms can generate so much energy during the day that we can afford to waste some.

Hydrogen is portable energy, far more portable than batteries. The best Lithium batteries are at 250 watts/kg, and Hydrogen is like 38,000 watts/kg, over 100 times better. So hydrogen is great for larger vehicles like trucks, ships, airplanes, and so on.

Note that I said "larger". Hydrogen's biggest problem is its very low density: it liquifies at ultra-low temperatures (-269 C), which makes liquid hydrogen impractical for everyday use (it's great for rockets though). You could combine the hydrogen with something else to make a liquid (like methanol), but then you would have to get the hydrogen out again, and that wastes energy. So you need a large tank to hold the gas, which means large vehicles like trucks, ships, etc.

Or you could compress the hydrogen for use in passenger cars. The Toyota Mirai, for example, uses tanks containing 700 atmospheres. That makes me nervous: so much pressure is like a bomb waiting to explode. Toyota reassures everyone that their tanks are strong enough, but I am not so sure.

So for the moment, hydrogen is for the larger vehicles like trucks or ships, or maybe even airplanes.
You don't need to get hydrogen out of methanol. You can burn it directly. You can also reform hydrogen into natural gas if the hydrogen is obtained from renewables.
 

AssassinsMace

Lieutenant General
What changes the game for hydrogen cars is when you can fill up your tank with water is where you get the hydrogen from. I remember long ago that was the pitch for hydrogen cars. I don't know if that was unrealistic but by watching that video they aren't even anywhere close to that.
 

Nutrient

Junior Member
Registered Member
You don't need to get hydrogen out of methanol. You can burn it directly.
Yes, you could burn the methanol directly. But methanol (CH3-OH) has carbon in it. Are there any scalable sources of renewable carbon? (There's a reason the English switched to coal: they probably preferred to burn wood, but their forests were almost gone.) Getting carbon from the atmosphere is impractically slow: I believe I said upthread that carbon dioxide is 0.04% of air.


You can also reform hydrogen into natural gas if the hydrogen is obtained from renewables.
Natural gas is methane (CH4). So it's the same problem: a scalable source of renewable carbon.
 
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FairAndUnbiased

Junior Member
Registered Member
Yes, you could burn the methanol directly. But methanol (CH3-OH) has carbon in it. Are there any scalable sources of renewable carbon? (There's a reason the English switched to coal: they probably preferred to burn wood, but their forests were almost gone.) Getting carbon from the atmosphere is impractically slow: I believe I said upthread that carbon dioxide is 0.04% of air.



Natural gas is methane (CH4). So it's the same problem: a scalable source of renewable carbon.

You can produce carbon and carbon monoxide from biomass in a charcoal process. Biomass sequesters carbon.

From charcoal carbon use the syngas reaction to produce more hydrogen and carbon monoxide:

C + H2O -> CO + H2

The energy for this is supplied with renewable electricity.

Your final product stream is solely hydrogen, carbon monoxide and carbon dioxide from the charcoal process. Now you can use the ICI process to produce methanol with leftover hydrogen:

CO+2H2 -> CH3-OH. Again this is renewable powered.

Then use captured CO2 in the Sabatier process:

CO2 + 3H2 -> CH3-OH + H2O.

End result is renewable electricity + biomass -> liquid fuel. The advantage of hydrogen here vs direct biomass utilization is to reduce the carbon monoxide and carbon dioxide to a hydrogenated form with more chemical energy content per carbon atom, and to produce a common chemical feedstock.
 

Nutrient

Junior Member
Registered Member
You can produce carbon and carbon monoxide from biomass in a charcoal process. Biomass sequesters carbon.

From charcoal carbon use the syngas reaction to produce more hydrogen and carbon monoxide:

C + H2O -> CO + H2

The energy for this is supplied with renewable electricity.

Your final product stream is solely hydrogen, carbon monoxide and carbon dioxide from the charcoal process. Now you can use the ICI process to produce methanol with leftover hydrogen:

CO+2H2 -> CH3-OH. Again this is renewable powered.

Then use captured CO2 in the Sabatier process:

CO2 + 3H2 -> CH3-OH + H2O.

End result is renewable electricity + biomass -> liquid fuel. The advantage of hydrogen here vs direct biomass utilization is to reduce the carbon monoxide and carbon dioxide to a hydrogenated form with more chemical energy content per carbon atom, and to produce a common chemical feedstock.

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, in order to produce a gallon of gasoline, you need the biomass from 40 acres of wheat.

The US consumes 19 million barrels of crude oil per day, or about 7 billion barrels per year. Gasoline refining is about 50% efficient, so the 7 billion barrels of crude translates to 3.5 billion barrels of gasoline, or 1.5e11 gallons.

So just to satisfy the US's appetite for gasoline, we would need

1.5e11 gallons * 40 acres/gallon = 24 billion square km of land

or 2400 times the total area of the US (the total area of the US is about 10 million km^2; this includes Alaska, I think).

Perhaps other crops can make more biomass/acre than wheat, but I doubt they are 2400 times more efficient. Biomass is not a scalable option.
 

ZeEa5KPul

Senior Member
Registered Member
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, in order to produce a gallon of gasoline, you need the biomass from 40 acres of wheat.

The US consumes 19 million barrels of crude oil per day, or about 7 billion barrels per year. Gasoline refining is about 50% efficient, so the 7 billion barrels of crude translates to 3.5 billion barrels of gasoline, or 1.5e11 gallons.

So just to satisfy the US's appetite for gasoline, we would need

1.5e11 gallons * 40 acres/gallon = 24 billion square km of land

or 2400 times the total area of the US (the total area of the US is about 10 million km^2; this includes Alaska, I think).

Perhaps other crops can make more biomass/acre than wheat, but I doubt they are 2400 times more efficient. Biomass is not a scalable option.
Read the article carefully. It needs 40 acres if you're doing it like Earth did it over geological timescales. That's very inefficient. This isn't about converting biomass to a liquid fuel in any sane way.
 

FairAndUnbiased

Junior Member
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, in order to produce a gallon of gasoline, you need the biomass from 40 acres of wheat.

The US consumes 19 million barrels of crude oil per day, or about 7 billion barrels per year. Gasoline refining is about 50% efficient, so the 7 billion barrels of crude translates to 3.5 billion barrels of gasoline, or 1.5e11 gallons.

So just to satisfy the US's appetite for gasoline, we would need

1.5e11 gallons * 40 acres/gallon = 24 billion square km of land

or 2400 times the total area of the US (the total area of the US is about 10 million km^2; this includes Alaska, I think).

Perhaps other crops can make more biomass/acre than wheat, but I doubt they are 2400 times more efficient. Biomass is not a scalable option.
Biodiesel from biomass is a totally different process than biomass to syngas to methanol.

Biodiesel process feedstock is only triglycerides, which is a tiny portions of plants. biomass to syngas to methanol can use the whole plant (only needs a carbon source, ANY carbon) and hydrogen.
 

Nutrient

Junior Member
Registered Member
Read the article carefully. It needs 40 acres if you're doing it like Earth did it over geological timescales. That's very inefficient. This isn't about converting biomass to a liquid fuel in any sane way.

Yes, you're right. The "40 acres of wheat per gallon of gasoline" was sensational enough that I stopped there. However, my conclusion stands: biomass is not a scalable option for renewable energy.


Biodiesel from biomass is a totally different process than biomass to syngas to methanol.

Biodiesel process feedstock is only triglycerides, which is a tiny portions of plants. biomass to syngas to methanol can use the whole plant (only needs a carbon source, ANY carbon) and hydrogen.

The article goes on to say, "we would need to harvest 22 percent of all land plants just to equal the fossil fuel energy used in 1997". This calculation is for using plant material directly, not as prehistoric biomass.

The 22% is roughly the fraction of arable land in the US -- and that assumes the US only uses energy at the average global rate, which we know isn't true. The US uses far more. So to produce the necessary biomass, the Americans would have to use up more than all the arable and farmable land they have, leaving nothing left for trivial things like growing food.

Only 7% of China's land is arable, so using valuable farmland to grow biomass is even less feasible. What's more, China's energy needs will probably grow four or five times in the next century. This makes biomass utterly insufficient.

Conclusion: biomass is not a scalable option for renewable energy.

Solar power is enough for Earth, many times over, if we use solar power satellites (SPSs). However, the satellites are probably several decades in the future. If we're stuck on terra firma, we need to store the solar energy for nighttime, which means either batteries or hydrogen. Batteries have a problem: there may not be enough resources to make enough batteries for terawatts of power storage. That leaves us with hydrogen, which should work.
 

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