Renewable Energy problem Several fuels methane CH4 propane C

Renewable Energy problem

Several fuels methane (CH_4), propane (C_3H_8), methanol (CH_3OH), ethanol (CH_3-CH_2-OH)-may be combusted in oxygen to get heat. Please compare the energy density of these types of fuels. Energy density here is defined as the energy from the combustion of per kilogram of the fuel. Assume the reactants and combustion products of the fuels are all in a state of 25 degree C and 1.0atm. The product of combustion for hydrocarbons is H_2O and CO_2.

Solution

Energy density is the energy per unit volume of a fuel.

E_d = E / V

Methane (CH₄) - 23,529 MJ/m³

Propane (C₃H₈) - 29,449 MJ/m³

Methanol (CH₃OH) - 17,855 MJ/m³

Ethanol (CH₃-CH₂-OH) - 23,278 MJ/m³

Here is a correction that,

Specific energy is the energy per unit mass of a fuel.

E_s = E / m

In the simple sense, Energy density shows that for a how much energy you can get from a specific amount say 1 m³ of volume.

From the above data we can get highest energy from propane and lowest energy we can get from methanol for a specific volume of 1 m^3.

This is helpful in desiging of fuel tank because it can defined how much volume you will need to get a specific amount of energy and thus how far you can go with that. If we will use Low energy density fuel then we have to take a large amount of fuel with is and vice versa.