Density of Hydrogen

Hydrogen is the most abundant element in the universe. Present since the very birth of space and time, life as we know it would be impossible without it. So, it only stands to reason that mankind has always looked to harness the power of hydrogen. The density of hydrogen plays a crucial role in this respect. Technology has advanced in leaps and bounds over the past few decades; allowing this gas to represent the next potential leap forward in power generation.

However, hydrogen energy density (whether mass per volume, energy per volume or energy per weight) is only one part of the puzzle. It is still a good idea to review the basics in order to understand the associated benefits and even some possible drawbacks. We will begin by discussing the density of hydrogen, why this characteristic is important, as well as some other relevant information.

What is the Density of Hydrogen?

When speaking of the density of hydrogen, scientists will often use the term standard temperature and pressure (STP). This equates to a temperature of 0º C at 1 bar of pressure (the air pressure at sea level). The density of hydrogen under these circumstances is 0.08375 kilograms per cubic metre.^[1] Why is the density of hydrogen important when discussing the generation of power?

Hydrogen energy density essentially equates to how much energy a specific volume (volumetric energy density) or weight (gravimetric energy density) of this gas is able to produce when compared to other materials. An example will better illustrate how the density of hydrogen can impact its usefulness.

The energy density of hydrogen is 2.5 times greater than methane (a typical gas used to produce heat)] I.e. hydrogen contains 33.3 kWh/kg, while methane gas only contains 13.9 kWh/kg. However, we also need to take into account volume in relation to the density of hydrogen. Hydrogen gas is extremely low in density.^[2] It will therefore require nearly three times as much hydrogen (by volume) in order to produce the same amount of energy. Simply stated, the density of hydrogen is a lot less when compared to other gases.

Although the density of hydrogen might appear to be a disadvantage at first glance, this is not necessarily the case. Let us now examine some of its other core characteristics, as well as why cutting-edge technology such as hydrogen fuel cells have already begun to transform the energy sector.

Is Hydrogen a Safe Fuel?

The density of hydrogen naturally dictates that this gas is lighter than air. While it is a flammable gas, it will also disperse rapidly when released. This makes the likelihood of a fire much less likely. Although hydrogen is non-toxic and disperses quickly, it is still highly flammable and requires specific safety measures, particularly when stored under pressure.^[3] It should be handled by trained personnel.

Hydrogen Storage at a Glance: Challenges Associated with the Density of Hydrogen Under Pressure

Due to the density of hydrogen mentioned earlier, this gas is stored under pressure. Note that hydrogen is typically stored as a gas or, less commonly, as a liquid under extremely low temperatures. Still, the most common way to store hydrogen is as a pressurised gas. Some storage tanks exert pressures of up to 1,000 bar.^[4] The high pressure significantly increases the density of hydrogen, allowing larger amounts to be stored in a relatively small space; providing an effective way to power related components such as a fuel cell.

Still, there are some concerns about the density of hydrogen under these conditions to highlight before moving on. The density of hydrogen while being stored under pressure may present some challenges. Tanks that develop a leak may be prone to spontaneous combustion, but the risk is more of a theoretical one.^[4] Storage devices must nevertheless be handled with care and examined for defects on a regular basis. Once released into the environment, the low density of hydrogen will nonetheless cause it to quickly disperse.

Additional Characteristics of Hydrogen

There is little doubt that the density of hydrogen is one of its most relevant qualities in terms of efficient energy generation; specifically when referring to how this gas is stored under pressure. What other unique features can be attributed to this gas?

Due in part to the density of hydrogen, it emits a nearly colourless flame when ignited. This might require the use of a flame detector, as the risk of a conflagration is very real if even the smallest of flames is not extinguished.^[5] However, hydrogen may also emit a bluish flame under certain conditions.

There are also different types of hydrogen which can be used in the energy sector. These are often denoted by colours. For example, grey hydrogen is produced by combining natural gas and water. This is known as steam reforming and a significant amount of carbon dioxide is produced as a result. On the contrary, green hydrogen is created by electrolysis and the only by-products are heat and water, making it a more environmentally friendly option when renewable energy is used for the electricity. Blue hydrogen is hydrogen produced from natural gas with a process of steam methane reforming, where natural gas is mixed with very hot steam and a catalyst

From a larger perspective (and thanks to the low density of hydrogen), this element is thought to comprise more than 75 per cent of all matter found throughout the universe. All the stars within the night sky use hydrogen to produce light (a process known as fusion).

The Future of Energy Production and Storage?

The density of hydrogen is only one of the many characteristics of this essential gas. When employed with environmentally friendly production and storage strategies, hydrogen could represent a significant step forward in the global transition to sustainable energy.

The future of energy production and storage will be significantly shaped by innovative technologies and sustainable solutions. Hydrogen plays a central role in this context, particularly due to its high-energy density and ability to store and transport large amounts of energy efficiently. Despite current challenges in production and storage, research is advancing to develop new materials and processes that make these procedures safer and more cost-effective. With ongoing technological progress and supportive political initiatives, hydrogen is set to become a key component of the global energy transition. In the long term, its use could contribute to the decarbonization of various sectors, marking an important step toward a sustainable energy supply and emission-free future.