Moreover, NH 3 is safe and easy to store and transport because of its low vapor pressure and high boiling point. (21,22) Compared to LH 2, NH 3 can be easily liquefied either by increasing the pressure to ∼10 bar at room temperature or by cooling down to −33 ☌ under 1 atm. as well as ammonia (NH 3) have been recommended as more technically viable options, certainly because of their desired properties ( Table 1).
(18) To circumvent the inherent issues with LH 2 storage and transport, several other carbon-based fuels such as methanol (CH 3OH), methylcyclohexane (MCH), etc. (19,20) The necessary storage and shipping infrastructures for long distances are yet to be developed. (16−18) Although liquid H 2 (LH 2) offers advantages for easy conversion into gaseous H 2, the liquefaction step consumes almost 30–40% of the energy content of H 2 in addition to boil-off losses during transportation. (14,15) In this regard, hydrogen (H 2) is a promising energy vector for its efficient utilization in fuel cells (FCs). Storing RE in the form of chemical fuels has been considered logical for both short- and long-term storage, particularly for use in the transportation sector. (13) The choice of the storage system is highly application dependent, based on the type (stationary or mobile), scale, time, cost, safety, etc. One of the most critical enabling factors for the RE future is a means of storing and transporting RE at a multi-EJ scale to manage the energy system by peak shaving and valley filling, to overcome the issues of intermittency of solar and wind energies, etc., and to serve regions where RE is difficult to produce due to economic and environmental constraints. (9−11) Thus, this energy transition is no longer a matter of technical feasibility or economic viability, but political will. (6−8) Despite a moderate increase in the overall share of RE in the current energy landscape, recent studies indeed indicated that a full transition to 100% RE is attainable within the next 3 decades or so with a cost-efficient vision of deep electrification of heat and transportation sectors around the globe.
(1,2,5) To meet such needs while minimizing the environmental impacts by curtailing anthropogenic CO 2 emissions, large-scale deployment of low-carbon renewable energy (RE) is necessary. (3,4) Considering the current rate of population growth and associated increases in energy consumption, it has been projected that the corresponding global energy demand will be increased by at least 50% before 2050. (1,2) Transportation that provides mobility to passengers and freight is responsible for approximately 25% of the overall CO 2 emission. Annual global carbon dioxide (CO 2) emissions reached 34.2 gigatonnes (Gt) in 2019 as a result of extensive and unrestricted use of fossil fuels to fulfill ∼80% of society’s energy needs at the current level of ∼585 exajoules (EJ)/year.
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