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Archive:000/Hydrogen gas: Difference between revisions
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{{pn|TODO: Add calculation: Knowing the losses, is there still enough [[land]] for wind-generated hydrogen gas were to directly replace all fossil fuels, in principle?}} | {{pn|TODO: Add calculation: Knowing the losses, is there still enough [[land]] for wind-generated hydrogen gas were to directly replace all fossil fuels, in principle?}} | ||
{{dp | |||
|<nowiki>hydrogen_gas.specific_energy</nowiki> | |||
|<nowiki>120 MJ/kg</nowiki> | |||
|<nowiki></nowiki> | |||
|<nowiki>"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."</nowiki><br /><nowiki> | |||
Oct 2, 2019</nowiki><br /><nowiki> | |||
Run on Less with Hydrogen Fuel Cells - RMI</nowiki><br /><nowiki> | |||
rmi.org › Blog </nowiki> | |||
}} | |||
{{dp | |||
|<nowiki>water.hydrogen_by_mass</nowiki> | |||
|<nowiki>hydrogen*2 / (hydrogen*2 + oxygen)</nowiki> | |||
|<nowiki>What percent of water's mass is hydrogen atoms</nowiki> | |||
|<nowiki>It's about 11%. Expressed using the calculator's built-in chemistry constants (atomic masses).</nowiki> | |||
}} | |||
{{dp | |||
|<nowiki>electrolysis.efficiency</nowiki> | |||
|<nowiki>80%</nowiki> | |||
|<nowiki>Energy efficiency of producing hydrogen & oxygen gases from water</nowiki> | |||
|<nowiki>Hydrogen made by the electrolysis of water is now cost-competitive ...</nowiki><br /><nowiki> | |||
www.carboncommentary.com › blog › hydrogen-made-by-the-electrolysis... </nowiki> | |||
}} | |||
In cases where electrolysis is done in weather below 0°C, such as beside wind turbines in cold parts of the world during winter, losses may be somewhat worse. {{x|The water has to be liquid (not frozen) while it's being electrolyzed to become hydrogen and oxygen. Heating takes energy; then again, maybe the waste heat of electrolysis would already be enough to keep the water liquid. In theory it can: For any amount of H<sub>2</sub>O electrolyzed, the waste heat is 8 times more than what it takes to melt that amount of ice: {{p2|'''[See calculation]'''|{{calc|hydrogen_gas.specific_energy * water.hydrogen_by_mass * (100% - electrolysis.efficiency)|water_fusion_heat}} {{pn|Maybe this belongs on a separate page called "hydrogen gas production in winter weather"?}} }}. For this to work, the hydrogen production system would have to be well-insulated from the weather. }} {{npn}} | |||
==Shelf life== | ==Shelf life== | ||