Hydrogen Safety As A Fuel

Hydrogen is a medium for storing energy, otherwise known as an energy carrier. All energy carriers and fuels, such as gasoline and natural gas, have the characteristic of being volatile (containing potential energy). Hydrogen’s benefits and disadvantages differ from the fossil fuels commonplace in an advanced energy utilizing society such as in the United States.

In order to have a clear picture of hydrogen’s advantages and disadvantages, the following paragraph contains the facts surrounding hydrogen.

Hydrogen is an odorless and colorless gas, due to its boiling point of -252.77o C.  Its density of 0.0899 grams/liter make it lighter than the surrounding air and bestows the ability to rapidly dissipate if released into the atmosphere or spilled onto the ground. According to “Hydrogen in the Energy Sector” by Dr. Zittel; et al., when comparing energy density by weight, “hydrogen has the highest energy to weight ratio of all fuels. 1 kg of hydrogen contains the same amount of energy as 2.1 kg of natural gas or 2.8 kg of gasoline.” To clarify a point, hydrogen ranks last when
the comparing energy density by volume. Hydrogen possesses 2.36 kWh/liter as a liquid, natural gas contains 5.8 kWh/liter and gasoline registers at 8.76 kWh/liter. These facts are relevant to the analogy of the size of a hydrogen tank and the size of a comparable gasoline tank as well as the explosion hazard associated with the fuels.

• Hydrogen is non-toxic

Gasoline and oil are extremely toxic and poisonous to humans and wildlife alike when unintentionally released into the environment. If a hydrogen spill occurred, the hydrogen would evaporate almost immediately leaving only water behind. Oil and gasoline, on the other hand, require immense clean up efforts with the result being that most of the spilled toxic gasoline or oil seeps into the surrounding ecosystem wreaking irreparable harm.

• In order to burn, hydrogen requires a higher concentration in the atmosphere than other fuels

When hydrogen approaches levels of 4% concentration in the atmosphere, the possibility of it igniting increases greatly.  A concentration level of 4% for hydrogen does not seem that high, but when compared to gasoline, which is 1%, hydrogen offers a significantly lower risk of explosion. Gasoline becomes volatile at a concentration 4 times lower than that of hydrogen.

• Hydrogen’s Properties vs. Other Fuels

The properties that are characteristic of hydrogen allow hydrogen to have many advantages over fossil fuels in terms of safety. Hydrogen’s low density and ability to rapidly disperse allows it to escape to the atmosphere if a leak occurred. Propane and gasoline, with their high densities and slow dispersal allow the fuels to congregate near the ground increasing a risk of explosion.

Hydrogen has to reach a concentration of 4% in the surrounding atmosphere before hydrogen poses a danger. Gasoline’s concentration only has to reach 1% before the danger of ignition is apparent. The chart below contains the characteristics of gasoline, methane and hydrogen relating to ignition and explosion hazards.