The "Hydrogen" engine
An abuse of language wants that we call hydrogen engine the engines based on a Fuel Cell. However, some details are necessary:
1) A conventional heat engine (with positive ignition) is capable of burning pure hydrogen with a few modifications for better efficiency and reliability (materials of the chamber, seats and valves, of the piston, adaptation of the ignition, etc. …). The main difficulty residing in the storage of hydrogen (gas 27 times lighter than air and so small that it diffuses in most materials)This type of engine could obviously be called a Hydrogen Engine.
2) The "hydrogen" engines currently being talked about in the media are in fact based on a Fuel Cell (see the specific pages on this technology for more information) which will "transform" the hydrogen (and oxygen from air) into electricity and water (liquid or vapor).
So there is only liquid water and vapor that will come out of the exhaust.
The still big possible confusion with the "water engine" (which does not officially exist) because it is not because we reject water that it is what we consume. Is a gasoline engine called a CO2 engine? No of course!
3) Hydrogen is only an energy vector and in no way a source of energy (considering that we are not talking about thermonuclear fusion of course). Because as it is not (or very little) present on earth in a simple state, it has to be transformed from other chemical elements, conditioned, transported and stored. All these stages consume energy which must obviously be taken into account in the performance and emissions of one technology or another. This is exactly what an MIT team did.
The results are unfortunately (for its defenders…) not in favor of the fuel cell.
This extract from a Science & Avenir comes from a study carried out by MIT and compares, in 2020, the different propulsion technologies used:
- Hybrid Gasoline
- Hybrid Diesel
- Hydrogen with fixed reformer
- Hydrogen with on-board reformer
The author presents the environmental impact for each of these technologies: energy consumption per Kilometer traveled (in Mj / km) and CO2 emissions (in grams of carbon / km).
He deduces that environmentally, the diesel hybrid can compete strongly with the fuel cell car (more econological in all cases than a heat pump with onboard reformer). Economically there is a good chance that the diesel hybrid is much cheaper than vehicles with heat pump (especially with on-board reformer). The diesel hybrid is therefore the most environmentally friendly vehicle currently available.
Especially since the cost and technological development of diesel hybrids is already developed, which is far from being the case with heat pumps! These are only macroeconomic notions that hamper its launch on the market.
The results :
Click on the image to enlarge.
This page is an extract from Science & Avenir 676 of June 2003. The official website
The 7 modes of hydrogen production.
Here are the 7 possible means of producing energetic hydrogen:
- Steam reforming of heavy hydrocarbons
- Reforming of light hydrocarbons
- Biomass gasification
- Carbon to water gasification
- electrolysis nuclear
- renewable electrolysis