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Old 04-15-2011, 06:46 AM   #22 (permalink)
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Originally Posted by erichans View Post
There's the opinion that there are other fringe benefits. Eg., that there is a drastic reduction in CO2 emissions (NOx, too) and a cleaning effect of the carbon in the engine. Just wondered if that alone is sufficient justification for installing a system---leave out the controversial MPG gains!
If the MPG gains are controversial - then so are the CO2 emissions (in pretty much all cases).
Case 1: You 'make' the H2 on-board via electrical (& ultimately mechanical) load on the alternator. Even if this helps stabilise the burn for some HCCI configurations, the energy gains of the 'stabilisation' are outweighed by the 50%+ loss incurred through extra mechanical load on the engine.
Case 2: A large tank of H2 is stored onboard. The H2 is generated via - most probably - NG or some other FF. Still plenty of CO2 involved here.
Case 3: Like case 2, but H2 is from renewable electricity. The electricity is 'clean' yes, but electricity is highly valuable in it's own right.

In all three scenarios the amount of CO2 offset by any renewables in the entire system (including the demand for non-transport electricity) is lessened compared with the renewable electricity being used directly.
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