2006-07-10 09:59:54 · 2 answers · asked by danny m 1 in Science & Mathematics ➔ Chemistry
"A cubic meter (35.3 cubic feet) of hydrogen gas takes
about 5.9 hours to produce in this electrolyzer, when
operated at its rated input power of 1000 Watts. This
means the energy required to produce a cubic meter of
hydrogen and 0.5 cubic meter of oxygen is about 5.9
kW-hr. This translates to an efficiency of 51%, where 3
kW-hr/m3 equals 100% efficiency at 20°C. Typical
industrial scale plants operate at about 4.5 kW-hr/m3 or
67% efficiency at high current density. The efficiency is
better at lower current density." See Reference 1.
Electricity in your area probably runs about 8-10 cents per kilowatt hour, delivered. So, a cubic meter of hydrogen + 1/2 cubic meter of oxygen requires about 48-59 cents of electricity, depending upon your location. Production on a larger scale is more efficient.
2006-07-10 10:09:55 · answer #1 · answered by Anonymous · 1⤊ 0⤋
It takes 918 KJ/mole to completely disassocciate the water molecule.
http://en.wikipedia.org/wiki/Bond_dissociation_energy
This is similar to (but lower than) the actual energy it would take to evolve hydrogen from water with electrolysis.
Another way to look at it is the energy of the opposite reaction. How much energy is evolved, when oxygen and hydrogen are combined (by burning). Again, the number is similar.
the energy for splitting the molecule is always slightly higher than the energy you can generate by forming it
2006-07-10 10:12:00 · answer #2 · answered by enginerd 6 · 0⤊ 0⤋