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smallscaleH2 · 07-21-2017, 12:49 PM

According to this site,
hydrogen has 50,000 Btu's per pound whereas Brown's gas has about 66,000 Btus per pound. So, that means it would (presumably) be 32% more energetic
(66 000 - 50 000 = 16 000 / 50 000 = 0,32 x 100 = 32 )

If so, than it would have 0,00396 kWh/l
(0,003 kWh for hydrogen x 1,32 = 0,00396 )

The same site also mentioned that you could generate 340 litres of Brown's gas (13.6 cu. ft.) per kilowatt-hour. If so, than the amount of energy you could generate per 1 kWh battery would be 1,3464 kWh
(340l x 0,00396 kWh/l) so that would be even more energy than the energy in the battery itself.

This doesn't seem right. I guess there are probably some incorrect figures here, so let's calculate it out another way.

At wikipedia we read at the Brown's gas page:
"Theoretically, a ratio of 2:1 hydrogen/oxygen is enough to achieve maximum efficiency; in practice a ratio 4:1 or 5:1 is needed to avoid an oxidizing flame."

So if we consider that oxygen does not add any energy, and only the hydrogen in the HHO adds energy, then HHO could be
- 50% less energetic then hydrogen (2:1 H2-02 ratio)
- 25% or 20% less energetic then hydrogen (4:1 or 5:1 H2-02 ratio)

Depending on this, it could have:
- 0,0015 kWh/l
(0,003 kWh for hydrogen x 0,5 = 0,0015 )
- 0,00225 kWh/l or 0,0024 kWh/l
(0,003 x 0,75 = 00225 ; 0,003 x 0,8 = 0,0024 )

Regarding the amount of energy you could generate with it:
I could not find any data on the efficiency of HHO electrolysers, but there is data of the efficiency of hydrogen electrolysers (which granted, work at a different way). But still, it gives an idea. Anyway, PEM electrolysers are 94% efficient, alkaline electrolysers are 43-67% efficient. So let's say the HHo electrolysers are 50% efficient. Then how much liter of gas could they generate ?

Calculation:
A 1 kWh battery could then generate 0,5 kWh on HHO gas.
The HHO gas has an energy of (and now we use a range of found data above): 0,00396 kWh/l or 0,0015 kWh/l or 0,00225 kWh/l or 0,0024 kWh/l
So:
0,5 kWh /0,00396 kWh/l = 126 liter
0,5 kWh /0,0015 kWh/l = 333 liter
0,5 kWh /0,00225 kWh/l = 222 liter
0,5 kWh /0,0024 kWh/l = 208 liter

07-21-2017, 12:49 PM	#4 (permalink)
smallscaleH2 EcoModding Lurker Join Date: Jul 2017 Location: Planet Earth Posts: 43 Thanks: 3 Thanked 0 Times in 0 Posts	According to this site, hydrogen has 50,000 Btu's per pound whereas Brown's gas has about 66,000 Btus per pound. So, that means it would (presumably) be 32% more energetic (66 000 - 50 000 = 16 000 / 50 000 = 0,32 x 100 = 32 ) If so, than it would have 0,00396 kWh/l (0,003 kWh for hydrogen x 1,32 = 0,00396 ) The same site also mentioned that you could generate 340 litres of Brown's gas (13.6 cu. ft.) per kilowatt-hour. If so, than the amount of energy you could generate per 1 kWh battery would be 1,3464 kWh (340l x 0,00396 kWh/l) so that would be even more energy than the energy in the battery itself. This doesn't seem right. I guess there are probably some incorrect figures here, so let's calculate it out another way. At wikipedia we read at the Brown's gas page: "Theoretically, a ratio of 2:1 hydrogen/oxygen is enough to achieve maximum efficiency; in practice a ratio 4:1 or 5:1 is needed to avoid an oxidizing flame." So if we consider that oxygen does not add any energy, and only the hydrogen in the HHO adds energy, then HHO could be - 50% less energetic then hydrogen (2:1 H2-02 ratio) - 25% or 20% less energetic then hydrogen (4:1 or 5:1 H2-02 ratio) Depending on this, it could have: - 0,0015 kWh/l (0,003 kWh for hydrogen x 0,5 = 0,0015 ) - 0,00225 kWh/l or 0,0024 kWh/l (0,003 x 0,75 = 00225 ; 0,003 x 0,8 = 0,0024 ) Regarding the amount of energy you could generate with it: I could not find any data on the efficiency of HHO electrolysers, but there is data of the efficiency of hydrogen electrolysers (which granted, work at a different way). But still, it gives an idea. Anyway, PEM electrolysers are 94% efficient, alkaline electrolysers are 43-67% efficient. So let's say the HHo electrolysers are 50% efficient. Then how much liter of gas could they generate ? Calculation: A 1 kWh battery could then generate 0,5 kWh on HHO gas. The HHO gas has an energy of (and now we use a range of found data above): 0,00396 kWh/l or 0,0015 kWh/l or 0,00225 kWh/l or 0,0024 kWh/l So: 0,5 kWh /0,00396 kWh/l = 126 liter 0,5 kWh /0,0015 kWh/l = 333 liter 0,5 kWh /0,00225 kWh/l = 222 liter 0,5 kWh /0,0024 kWh/l = 208 liter Last edited by smallscaleH2; 07-21-2017 at 01:11 PM..