Debunking The Fantasy: Hydrogen’s Excessive Vitality Density By Mass Is Trumped By Low Density By Quantity

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Hydrogen is usually cited for its excessive power density by mass — roughly 120 MJ/kg — making it look like an excellent power service. Nevertheless, this determine is often misunderstood or introduced out of context, resulting in deceptive conclusions about hydrogen’s suitability for real-world power storage and transportation. The problem lies not in its theoretical mass-based power content material however within the sensible challenges related to its volumetric power density, storage necessities, and general system effectivity.

This can be a companion article to the Cranky Stepdad vs Hydrogen for Vitality materials. In the same method to John Cook dinner’s Skeptical Science, the intent is a speedy and catchy debunk, a second stage of element within the Companion to Cranky Stepdad vs Hydrogen for Vitality, after which a fuller article because the third stage of element.

Hydrogen might weigh much less, however storing it’s like making an attempt to squeeze a watermelon right into a soda can.

Beneath commonplace atmospheric situations, hydrogen is a really mild gasoline with extraordinarily low power density by quantity — about 0.01 MJ/L in comparison with gasoline’s 34.2 MJ/L. To be saved in usable portions, hydrogen have to be both compressed to extraordinarily excessive pressures (usually 350 to 700 bar), liquefied at cryogenic temperatures (−253°C), or chemically sure in carriers comparable to ammonia or steel hydrides. Every of those choices introduces important power penalties and complexity.

Compression to 700 bar — the strain utilized in most hydrogen gasoline cell automobile tanks — requires about 10–15% of the power content material of the hydrogen itself only for the compression course of (U.S. Division of Vitality, 2023). Liquefaction is much more energy-intensive, consuming between 30–40% of hydrogen’s power content material (Worldwide Vitality Company [IEA], 2021). Chemical carriers introduce conversion and reconversion steps, additional lowering general effectivity.

These storage and transport challenges lead to a considerably decrease system-level power effectivity for hydrogen than is usually acknowledged. Bertuccioli et al. (2014) emphasize that whereas hydrogen can theoretically retailer power effectively by mass, real-world purposes contain infrastructure that considerably erodes these good points. Lifecycle assessments present hydrogen’s round-trip effectivity — factoring in manufacturing by way of electrolysis, compression or liquefaction, transport, and remaining conversion again to electrical energy — could be as little as 25–35% (Qiu et al., 2021).

In distinction, lithium-ion batteries, whereas heavier, obtain round-trip efficiencies of 85–95% and don’t require high-pressure or cryogenic infrastructure. Electrical automobile (EV) drivetrains utilizing batteries are usually over twice as power environment friendly as these counting on hydrogen gasoline cells when measured from supply to wheel (European Fee, 2022).

This situation is compounded when evaluating infrastructure prices and complexity. Hydrogen requires pipelines designed to deal with excessive diffusivity and embrittlement, or alternatively, costly overland transport by way of cryogenic vans or pressurized containers. These distribution challenges additional scale back hydrogen’s competitiveness relative to direct electrification.

The widespread use of gravimetric power density as a headline determine for hydrogen’s capabilities is due to this fact deceptive — a textbook case of the deceptive statistics fallacy. Whereas technically appropriate, this single metric is divorced from the realities of how hydrogen have to be saved, transported, and utilized. Bossel (2006) was among the many first to comprehensively spotlight this situation, arguing that hydrogen is “not an power supply, however an artificial power service with elementary disadvantages.”

Hydrogen is important as an industrial feedstock, for instance within the manufacturing of ammonia fertilizers. Nevertheless, for transportation, warmth and power storage purposes, its low volumetric power density and excessive infrastructure calls for current main limitations to widespread deployment.

The power content material of a gasoline by mass is just one piece of the puzzle. When quantity, effectivity, infrastructure necessities, and lifecycle prices are included within the evaluation, hydrogen isn’t viable as an power service.

References:

Bertuccioli, L., Chan, A., Hart, D., Lehner, F., Madden, B., & Standen, E. (2014). The constraints of hydrogen as an power storage medium. Worldwide Journal of Hydrogen Vitality, 39(36), 21647–21662.

Bossel, U. (2006). Does a hydrogen economic system make sense? Proceedings of the IEEE, 94(10), 1826–1837.

European Fee. (2022). Hydrogen Storage and Transport: Technical and Financial Boundaries. Brussels: European Union.

Worldwide Vitality Company. (2021). The Way forward for Hydrogen: Storage and Transport Challenges. Paris: IEA.

Qiu, Y., Wang, L., Zhang, X., & Ding, Y. (2021). Evaluating hydrogen storage with various power carriers: A lifecycle effectivity evaluation. Vitality Experiences, 7, 3950–3962.

U.S. Division of Vitality. (2023). Hydrogen Storage and Distribution: Assessing Effectivity and Prices. Washington, DC: DOE.

Hume, N. (2021, October 4). Hydrogen’s power density downside: Why storage and transport stay key obstacles. Monetary Instances.