Coal: A renewable resource? Unlocking hydrogen storage possibilities

Coal has been discovered as a potential hydrogen storage medium, offering a clean energy solution with existing infrastructure and economic opportunities.
Kavita Verma
Large lump of coal is being held by a Penn State researcher.
Large lump of coal is being held by a Penn State researcher.

Penn State 

Scientists from Penn State University have made an unexpected discovery while working to produce hydrogen as a renewable energy source that lessens our dependency on fossil fuels. Researchers have discovered that coal, which is frequently connected to traditional energy production, may be used to store hydrogen gas. 

It has proven challenging to store hydrogen efficiently and economically, which poses a significant barrier to developing a sustainable energy supply chain. This innovation may solve that problem.

Lead researcher Shimin Liu, associate professor of energy and mineral engineering at Penn State, explains, "We found that coal can be this geological hydrogen battery. You could inject and store the hydrogen energy and have it there when you need to use it." This revelation opens up possibilities for coal to play a pivotal role in the future of clean energy.

Coal's potential as a hydrogen storage solution

With its reputation for being clean-burning, hydrogen shows potential for supplying the energy needs of high-consumption industries, including transportation, power generation, and manufacturing. 

Creating a hydrogen infrastructure, including practical storage solutions, is still a major obstacle. To handle variations in energy demand, geologic formations have become a promising possibility for extensive hydrogen storage.

Coal is suitable for geological hydrogen storage since it is widely accessible and has a built-in infrastructure. Researchers examined eight kinds of coal and determined that low-volatile bituminous coal from eastern Virginia and anthracite coal from east Pennsylvania were the best. 

Like methane adsorption to coal, depleted coalbed methane deposits could store hydrogen. These formations serve as seals and are frequently covered with shale or mudstone layers. 

The specific hydrogen affinity of coal is overcome by specialized machinery developed through trial and error. This discovery creates opportunities to revitalize coal mining towns and build a hydrogen infrastructure. The ability of coal to store gas makes a clean energy future more and more conceivable.

Hydrogen injection and economic opportunities

To calculate the pace at which hydrogen can be injected into and recovered from coal in the future, researchers plan to investigate dynamic diffusivity and permeability. They also emphasize the economic opportunities that coal mining areas may have, as the energy change has greatly impacted these communities. 

By reusing these areas, building hydrogen storage infrastructure could open up new possibilities while utilizing the energy engineers' already-existing skills.

Penn State is perfectly situated to lead this research and contribute to the nation's hydrogen infrastructure thanks to its abundant natural gas and coal supplies and the essential engineering and business experience. The possibility of a cleaner and more sustainable energy future becomes more and more conceivable with coal acting as a geological hydrogen battery.

Study Abstract:

A full-scale hydrogen economy requires a bulk energy storage system to store the excess energy as a buffer and to fulfill the demand constantly. Hydrogen sorption capacity and diffusion behavior in coal quantify its potential to become a well storage candidate from geological formations. In this study, the sorption and diffusion behaviors of eight coals across the major coalfields in the United States in terms of their ranks, fixed carbon content, vitrinite reflectance, vitrinite or huminite content, O/C ratio, and H/C ratio were measured and analyzed. The sorption data shown that all eight coals have considerable sorption capacities, among which the LvB coal has the maximum adsorption capacity of ∼ 1.17 mmol/g, followed by An coal with the maximum hydrogen adsorption capacity of ∼ 0.95 mmol/g and the SemiAn coal of approximately 0.82 mmol/g. The fixed carbon content and typically the O/C ratio are obviously correlated with the maximum hydrogen adsorption capacity in coals, which may be attributed to the oxygen-containing functional groups. Hydrogen has superior diffusive gas deliverability defined by hydrogen effective diffusivity. The effective diffusivities of hydrogen in SemiAn coal decreases from ∼ 0.00156 to ∼ 9.26 ×10^4 1/s with pressure increases from ∼ 2.45 MPa to ∼ 10.07 MPa, among which the lowest diffusivity at ∼ 10.07 MPa is even ∼ 4 times higher than that of CH4 at equivalent pressure. This is a vantage for a promising field candidate of hydrogen storage in coal with maximized injectivity. The results reveal that the sorption and diffusion behaviors of hydrogen in different rank coals towards the depleted coalbed methane formation with injected hydrogen can serve as a geological “H2-Battery”.

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