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48 comments on Thursday afternoon at Clean Tech 2007

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Murray on June 24, 2007 - 10:36am

The round trip efficiency of electricity to hydrogen to electricity is 7%.
Where on earth do you get this number.? Using currently available commercial technology it is easily 30%, and best available technology is >50%.

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robert2734 on June 24, 2007 - 2:58pm

http://www.siei.org/efficiency.html

This is where the 7% number came from. I'm not surprised the best available commercial technology can do better but it was the only number I knew.

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Engineer-Poet on June 24, 2007 - 8:02pm

70% is a more reasonable efficiency for an electrolyzer. Vehicular use requires considerable energy for compression; I recall a figure around 20% for this, so the total production efficiency of compressed hydrogen is (.7/1.2)=58%. A 40%-efficient PEM FC yields throughput of about 23%. Power conditioning will cut the yield from the AC line further.

Li-ion batteries are about 90% efficient, so they can yield about 4 times as much useful work per unit of input as a hydrogen system; on top of that, we already have all the infrastructure we'll need for years. Hydrogen is a boondoggle.

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marcosdumay on June 25, 2007 - 1:14pm

We just need the litium...

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