Vehicle conversion FAQ
Compressed air and hydrogen (used as fuel on itself -so not as a booster) are not mentioned at opengarages. Why is that ?
Let's start with hydrogen: Hydrogen is often hyped as the fuel of the future, but it still has many problems making its use in vehicles today impractical and not at all ecologic. The main problem is the storage of the fuel itself: to store hydrogen we need either extreme pressure (5000-10000 psi) or extreme cooling (to − 252.87 °C).
So, when applying the cooling technique, we need to have a refrigeration system on-board the vehicle that can cool it to this temperature. This hence requires huge amounts of electricity, which itself needs to be derived from the power the engine (running on hydrogen) needs to provide. If we consider that the efficiency of the engine itself isn't all that great (35% when using the hydrogen in an internal combustion engine), it quickly becomes clear the whole thing is very inefficient (and not to mention costly, as such extreme coolers can't be acquired cheaply).
When applying extreme pressure, it may be possible to use it in a internal combustion engine effectively, but tanks that can withstand that kind of pressure can't be obtained easily, and are again, very costly even if you do find them.
If hydrogen tanks do become cheap enough, we also need to consider that you might still emit some CO² per kWh. This, depending on where the electricity you use to recharge your batteries came from: If coal was used to generate the electricity: you'll emit 1 kg CO² per consumed kWh. If it came from PV solar panels, you'll emit 0,1 kg CO² per consumed kWh. If it came from nuclear power plants, you'll emit 0,006 kg CO² per consumed kWh.
Now for compressed air: Air, compressed at 30 MPa (4,500 psi) contains but a mere 0,050 kWh of energy per liter, whereas say gasoline has 8,9 kWh per liter. So, a vehicle that could drive say 700 km with its given gasoline tank (most have about a 50 liter tank (1) -and a consumption of about 15 to 21 km/liter (2)-), could drive only 3,9 km.
Ethanol is listed as a useful fuel, but what about methanol ? This too is a biofuel, and it's practical. However it is very toxic and can be absorbed by the skin. If absorbed, it could cause blindness. So, we rather avoid it.
What's the difference between CNG and the "biogas" you keep mentioning ? CNG is a compressed gas. More importantly, it is "natural gas", meaning gas that is derived from cavities under the the soil where it has been locked away for millions of years. It is as such a fossil fuel and contributes to global warming (quite considerably even, it contains 0,6 kg CO²/liter). Biogas is created artificially, using anaerobic digesters, and contains 0 kg CO²/liter.
Hybrid vehicles aren not mentioned neither ? Only provide better mpg if the vehicle needs to stop and start
1: a 50 liter tank is about a 13 gallon tank 2: 15 to 21 km/liter is about 35-50 mpg;