highenergydensity

High energy density refers to the amount of energy stored in a material or device relative to its mass or its volume. It is typically described using gravimetric energy density (measured in watt-hours per kilogram, Wh/kg, or megajoules per kilogram, MJ/kg) and volumetric energy density (measured in watt-hours per liter, Wh/L, or MJ/L). These metrics help compare how much usable energy can be carried or stored in different systems.

In fuels, energy density is a key performance factor for transportation and power generation. Hydrocarbon liquids often exhibit high volumetric energy density, meaning they store a large amount of energy per liter. Gasoline, for example, has a very high energy per liter and also a substantial energy per kilogram. Hydrogen has a high energy per kilogram but much lower volumetric density when stored as a gas at ambient conditions; its volumetric density improves with compression or liquefaction. Batteries and other electrochemical storage devices typically provide hundreds of Wh per kilogram (gravimetric) and several hundred Wh per liter (volumetric), depending on chemistry and design. Supercapacitors offer higher power density but generally lower energy density.

Applications of high energy density include longer-range electric vehicles, portable electronics, aerospace, and grid storage. Trade-offs exist among energy density, power density, safety, cost, and durability. Ongoing research seeks higher energy density while improving safety and longevity, through advances in solid-state batteries, lithium-sulfur and other chemistries, and in alternative energy carriers such as advanced fuels and hydrogen storage. Lifecycle, environmental impact, and manufacturability are also integral considerations.