Darwin Strikes Again....

[Aristides]

3 hours ago, herbie said:

Just finished reading about how H2 can be chemically produced using the waste heat from nuclear reactors without electrolysis. Theoretically it could be produced with high temperature geothermal as well.

Also worth noting, H2 has almost triple the energy content of LNG per kilogram.

But only 1/4 by volume of gasoline.

[Rebound]

5 minutes ago, Aristides said:

But only 1/4 by volume of gasoline.

What does that mean, since one is liquid and the other is a gas?

[Aristides]

34 minutes ago, Rebound said:

What does that mean, since one is liquid and the other is a gas?

No, I mean liquid hydrogen only has 1/4 the energy density by volume of gasoline or diesel. It has about three times the density by weight. It must also be kept at minus 252 degrees C to remain liquid.

Edited September 29, 2022 by Aristides

[Rebound]

14 hours ago, Aristides said:

No, I mean liquid hydrogen only has 1/4 the energy density by volume of gasoline or diesel. It has about three times the density by weight. It must also be kept at minus 252 degrees C to remain liquid.

I‘m not an expert at these things and I’m not a fan of HFC’s, but I did run across this:

”Another advantage is hydrogen’s energy density. Diesel has an energy density of 45.5 megajoules per kilogram (MJ/kg), slightly lower than gasoline, which has an energy density of 45.8 MJ/kg. By contrast, hydrogen has an energy density of approximately 120 MJ/kg, almost three times more than diesel or gasoline. In electrical terms, the energy density of hydrogen is equal to 33.6 kWh of usable energy per kg, versus diesel which only holds about 12–14 kWh per kg. What this really means is that 1 kg of hydrogen, used in a fuel cell to power an electric motor, contains approximately the same energy as a gallon of diesel. ”

 

https://rmi.org/run-on-less-with-hydrogen-fuel-cells/

[Aristides]

You are quoting energy density by weight which is true. Liquid hydrogen has an energy density by volume a quarter of gas or diesel. If liquid hydrogen has three times the energy density by weight, you would still need tanks that are 25% larger to hold it. A kilo of gaseous hydrogen would take up a huge volume. 

I think hydrogen will be part of reducing dependence on fossil fuels but there is no single silver bullet that will replace all the applications using fossil fuels.

 

[Rebound]

1 hour ago, Aristides said:

You are quoting energy density by weight which is true. Liquid hydrogen has an energy density by volume a quarter of gas or diesel. If liquid hydrogen has three times the energy density by weight, you would still need tanks that are 25% larger to hold it. A kilo of gaseous hydrogen would take up a huge volume. 

I think hydrogen will be part of reducing dependence on fossil fuels but there is no single silver bullet that will replace all the applications using fossil fuels.

 

I think hydrogen’s problem is that it takes energy to produce it. Yes, the hydrogen reaction inside the car is “free”  and it is perfectly clean-burning, but it takes tremendous energy to produce that hydrogen. But I admit I haven’t studied the chemistry to the extent I can calculate how many kW of energy is needed to product store and transport the hydrogen needed to create that many kW of electricity inside the car.