Bivalent (engine)

[citation needed] Engines that can use either alcohol (often produced as a biofuel) or standard gasoline are variants of flex fuel vehicles.

Still, CNG at typical pressures requires more frequent refueling because it contains only a quarter of the energy per unit volume of gasoline,[1] whereas LNG contains only 80%.

[4] Reduction of greenhouse gas emissions and preservation of natural resources are becoming increasingly important to people worldwide.

[citation needed] Hydrogen can be used and created in fuel cells to power electric motors or burnt directly in combustion engines.

BMW has developed a bivalent internal combustion engine that can switch between petroleum and liquid hydrogen fuels.

The safety of the hydrogen storage tanks in the event of an accident has been investigated, and various tests show that they do not present any problems.

These properties allow hydrogen to be burned using a wide range of air-fuel mixtures, but problems arise with premature ignition.

Proper ventilation is needed to prevent ignition in the crankcase and the formation of water in the engine oil.

[6] Hydrogen and natural gas are very similar fuels, so the differences between the components needed to burn them are trivial, and interoperable systems are easily made.

Many of the processes commonly used in creating the fuel give off greenhouse gases, and the hydrogen produced is usually derived from finite resources.

Release valves are installed in these vehicles so that the pressure in the tank does not get too high, but a small amount of fuel is lost.