Summary
- Hydrogen’s high energy density by mass is often misunderstood and misleading when considered for energy storage and transportation.
- Storing hydrogen is challenging due to its low volumetric energy density, requiring compression, liquefaction, or chemical carriers, all of which decrease overall efficiency.
- Hydrogen’s round-trip efficiency, from production to final conversion back to electricity, can be as low as 25-35%, compared to lithium-ion batteries with efficiencies of 85-95%.
- Hydrogen’s infrastructure costs and complexity make it less competitive than direct electrification for transportation and energy storage applications.
- The gravimetric energy density of hydrogen is misleading, as it overlooks the practical challenges of storage, transportation, and utilization, making it not viable as an energy carrier for widespread deployment.
Article
Hydrogen is often touted for its high energy density by mass, but the practical challenges associated with its volumetric energy density, storage requirements, and overall system efficiency make it less suitable for real-world energy storage and transportation. Storing hydrogen is like trying to squeeze a watermelon into a soda can, as it has a very low energy density by volume compared to gasoline and requires compression, liquefaction, or chemical binding in carriers to be stored in usable quantities. Each storage method introduces significant energy penalties and complexity, leading to lower system-level energy efficiency.
Compression to 700 bar and liquefaction, both commonly used methods for storing hydrogen, require a significant amount of energy consumption, reducing overall efficiency. Chemical carriers introduce additional conversion and reconversion steps, further decreasing efficiency. Studies have shown that hydrogen’s round-trip efficiency, factoring in production, storage, transport, and conversion back to electricity, can be as low as 25-35%. In comparison, lithium-ion batteries achieve higher round-trip efficiencies and do not require high-pressure or cryogenic infrastructure, making them more energy-efficient for transportation applications.
When considering infrastructure costs and complexity, hydrogen faces additional challenges compared to direct electrification. The need for specialized pipelines or expensive transport methods further reduces hydrogen’s competitiveness as an energy carrier. The gravimetric energy density of hydrogen, often used as a headline figure for its capabilities, can be misleading as it does not account for the practical difficulties of storing, transporting, and utilizing hydrogen. It has been argued that hydrogen is not an energy source but a synthetic energy carrier with fundamental disadvantages.
While hydrogen remains essential as an industrial feedstock, its low volumetric energy density and high infrastructure demands present barriers to its widespread deployment for transportation, heat, and energy storage applications. The energy content of a fuel by mass is only one aspect to consider, as volume, efficiency, infrastructure requirements, and lifecycle costs play crucial roles in determining the viability of an energy carrier. In the case of hydrogen, these practical challenges overshadow its high energy density by mass, making it less favorable compared to alternatives such as lithium-ion batteries for certain applications.
Overall, the practical challenges of storing, transporting, and utilizing hydrogen for energy storage and transportation highlight its limitations as an energy carrier. While it has high energy density by mass, the issues related to volumetric energy density, infrastructure requirements, and overall system efficiency make hydrogen less viable for real-world applications. To accelerate the cleantech revolution, it is important to consider these factors when evaluating different energy storage options and focus on solutions that offer higher efficiency and lower infrastructure demands.
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