Hydrogen is often seen as a key fuel for a cleaner future because it burns without producing carbon dioxide.
However, storing and transporting hydrogen is not easy. It usually requires very high-pressure tanks or extremely cold temperatures, both of which are expensive and technically challenging.
Researchers at King Abdullah University of Science and Technology have been exploring a simpler and more practical solution.
Instead of storing hydrogen as a gas, they suggest storing it inside special liquid chemicals known as Liquid Organic Hydrogen Carriers, or LOHCs.
These liquids can safely hold hydrogen and release it when needed, making them much easier to handle.
LOHCs work through a chemical process. At the surface, hydrogen is added to a liquid molecule using a catalyst, creating a hydrogen-rich liquid.
This liquid can then be transported or stored like regular fuel. Later, another reaction removes the hydrogen, allowing it to be used while the original liquid is reused.
One major advantage of this method is that it can use existing oil and gas infrastructure, such as pipelines and storage tanks.
This avoids the need to build entirely new systems for hydrogen, which is one of the biggest barriers to using it on a large scale.
In their study, published in the journal Fuel, the researchers explored whether depleted oil fields could serve as underground storage sites for these hydrogen-rich liquids.
They used computer simulations to test how the system would work in a typical sandstone reservoir about 2,200 meters underground.
The team focused on a well-known LOHC system that combines hydrogen with a chemical called toluene to produce methylcyclohexane.
This liquid flows easily underground and can store a useful amount of hydrogen. In the simulation, the liquid was injected into the reservoir, left there for a short period, and then pumped back out. This cycle was repeated many times.
The results were promising. About three-quarters of the liquid could be recovered after each cycle, and over time, the process also helped extract more than half of the leftover oil trapped in the field.
This extra oil could help cover the costs of the storage system, making the whole approach economically attractive. The researchers estimate the project could generate significant financial value beyond its costs.
They also tested another type of LOHC that could store more hydrogen per molecule, but it did not perform as well because it was thicker and harder to move through the underground rock.
Although extracting leftover oil would still produce some emissions, the researchers believe these are small compared to the environmental benefits of using hydrogen as a clean fuel. They see this approach as a practical step toward making hydrogen energy more widely available, using resources that already exist.
In the future, the team plans to study how this system would work on a larger scale, with multiple wells operating at the same time across an entire oil field.
Source: KSR.
