How to store energy -4

2022/12/13 2023/01/03

lenemas

This post is 4th of a series "how to store energy" (see previous posts of first, second, third in the series). Centered around "hydrogen", the posts have discussed the volmetric density of hydrogen carrier.

This post also compares values of energy density with taking some specific examples.

What is the energy density of gasoline?

The substance that has high energy density and is easy to handle.... would be gasoline. Taking the gasoline as an example, we will see some energy density values of energy caeeir.

The energy density of gasoline was 6.0 [kcal g^-1] (see （Hydrogen as an energy carrier?),^[1] which corresponds to 33.36 [MJ L^-1] on a volmetric energy density basis.^[1] The energy filling a 50-L gasoline tank of a vehicle is calculated to amount to 1.7 [GJ] (= 33.36 [MJ L^-1] * 50 [L]). With a density value of 0.74 [g mL^-1],^[1] this quantity weights approximately 37 [kg] (= 50 [L] * 0.74 [g mL^-1]).

Overall, 50 [L] and 37 [kg] of gasoline contains 1.7 [GJ]

Comparison of gasoline with other energy carriers

Referencing to this value as a figure of merit, gasoline shall now be compared with other representative energy carriers.
The next figure illustrates energy carriers with a focus on the volumetric energy density (drawn with referring to a reference[2])

comparison-of-energy-densities-of-carriers

* Sorry that the figure is in Japanese, but will be translated into English.
From the top to bottome, ガソリン is gasoline, 液化アンモニア is liquid ammonia, 有機ハイドライド is organic hydride, 高圧水素 is high-pressure hydrogen, リチウムイオン電池 is lithium-ion battery, 水素 is hydrogen

To achieve the same ammount of energies with gasoline in 37 [kg] and 50 [L],
- liquid ammonia of 96 [L], or
- chemical hydrogen (=methyl-cyclohexane) of 210 [L], or
- compressed hydrogen of 190 [L]
are needed, which corresponds to 140,000 [L] of gaseous hydrogen. Among carrierse considred, the volumetric energy density of liquid ammoia is the highest.

The same figure also illustrates the case with lithium-ion battery. Its volume of 770 [L] is shocking, but the more amazing would be its weight of 1,900 [kg]. When a vehicle is considered to be equipped with an energy carrier, gasoline requires just 37 [kg] while lithium-ion battery does around 2 [ton]. For your information, the weight of a vehicle is around 1 [ton]. The low energy density of battery is a quite important point of consideration in the context of the electric vehicle.