I see chilihed answered my combustion questions on the first page, in spades!

I have also read that hydrogen engines are capable of higher efficiencies.

I suspect it has to do with the temperature of the exhaust being lower.

I have also read that they produce less power for the same sized engine, but this would be a bonus if you wanted to convert an engine that you considered to be inefficient because it was overpowered to begine with.

 

The storage of hydrogen is a problem, but less of a problem at low speeds and over short distances. A hydrogen car is potentially more efficient than an electric vehicle, unless the electric vehicle is connected to the grid, like an electric train or street car. Such a vehicle could then be powered from a combined heat and power source, or wind energy etc. An interesting idea would be to have a tank of compressed hydrogen which is refueled at home from your otherwise oversized wind turbine. The wind turbine could be 5kw and generate power for your home when generating 1kw or less, but produce hydrogen and store it into a tank when generating more than 1kw. In addition to your commuter having a small hydrogen tank refilled at home each night, it would have a compressed air tank which is resupplied by dynamic braking. In this way your engine would not have to do any compression, but would only have to do combustion and expansion. The exhaust gas would be cooler as a result also, for more efficiency. The engine would essentially be a steam engine, or perhaps something sort of half way between a steam engine and a diesel. Efficiency could easily be 25%, perhaps 40%, but considerably better than 15-20% of gas engines.

 

Electrical cars are surprisingly inefficient due to the charging losses, discharging losses, inverter losses, and the losses associated with having to carry around all that extra payload. They are potentially very efficient for neighbourhood vehicles, but so are bicycles. They do have there place. There should be more of them.

At higher temperatures (for higher efficiency) hydrogen engines will produce more NOx. This could be avoided by not having Nitrogen in the air, but it would be more practical to reduce efficiency somewhat to some happy compromise. At home you could run a hydrogen powered generator in a combined heat and power operation for your heat and hot water when the wind is not blowing.

Hi there:

 

Fuel cell has a higher efficiency because fuel cell is not a heat engine -- there is not temperature limitation on the cycle efficiency.

 

Thanks,

 

Gordan

Intuition says "hydrogen is light" and therefore we get less energy per unit gas volume (not weight). This was nagging at me until reading on the first page that compression can go way up if we deal with nitrogen oxides.