The International Renewable Energy Agency (IRENA) has released a new report series on global hydrogen, showing the importance of its commercial transport and trade for the establishment of a more diversified and sustainable energy system as well as CO2 emissions reduction.
Hydrogen is the most important component of a zero-energy energy system. Currently about 95% of hydrogen is produced using the steam methane reforming process generating carbon emissions. So-called green hydrogen, i.e. electrolytic hydrogen produced with renewable energy sources, is the most promising production technology, given the global hydrogen trade targets under the 1.5°C scenario in 2050. However, there are a number of challenges to the deployment of green hydrogen. One major problem is its higher cost compared to fossil fuels and other alternative low-carbon technologies. Thanks to technological innovations to improve performance, the introduction of technologies to increase global scale, the increasing size of electrolysis plants and the continuous reduction of the cost of renewable energy, which is a major cost factor, green hydrogen is expected to be comparable in cost to hydrogen from fossil fuels within the next decade.
In contrast to fossil fuels, whose large reserves are concentrated in certain regions, renewable energy sources are available to varying degrees in every country. Apart from production costs, however, the challenge is a cost-effective way to transport renewable electricity over long distances to connect places of production with centers of demand. Using hydrogen as an energy carrier could be a solution, allowing renewable energy to be traded across borders in the form of molecules or commodities, such as ammonia. IRENA presents an overview of main technologies for transporting hydrogen highlighting the advantages and disadvantages of each potential pathway.
Hydrogen can be transported in large quantities by pipiline or by ship as ammonia, in liquid form, as a liquid organic hydrogen carriers (LOHC). The figure above represets the total cost of transport for the three shipping pathways showing a relatively wide range of cost given both the optimistic and pessimistic development scenarios. When comparing these technology options, ammonia ships are the most attractive because shipping costs are relatively low and long distances have a limited effect on the overall cost, making it more attractive as distance increases. In addition, ammonia is already produced, stored and sold on a large scale today. A major limitation is the conversion of ammonia to hydrogen (called cracking), which can consume the equivalent of 13-34% of the energy contained in hydrogen. The next hydrogen carrier, namely liquefaction, is already being commercialized today, but only on a very limited scale. A key obstacle to this path is the low temperatures required for liquefaction (-253°C), which demands more expensive equipment to reduce heat losses and withstand cryogenic temperatures. LOHCs are compounds that react with hydrogen and can be used repeatedly. One advantage of this pathway is that LOHCs have similar properties to diesel fuel and can be transported in liquid form by different means (e.g. ship, rail and then truck), which means low losses in the transportation phase. The main limitation is the energy consumption during reconversion (called dehydrogenation), which can consume the equivalent of 25-35% of the energy contained in hydrogen. Transporting hydrogen by pipeline is the cheapest option for short distances up to 3,000 km and existing networks can be repurposed for hydrogen. However, energy consumption for transportation is higher than for natural gas and not all pipeline materials are suitable for hydrogen.
According to IRENA, considering all factors from a cost perspective, ammonia seems to be the most attractive carrier which is also depicted in the Figure below that shows total capital cost breakdown. However, the absolute costs are mainly determined by two factors: the size of the project, which affects the economies of scale for all equipment, and the distance between the two ports, and here each technology has its pros and cons.
Experts state that there is uncertainty about the effectiveness of hydrogen production und transporting technologies by 2050. The specific values to be achieved in the next 30 years will depend strongly on specific actions to choose and develop the pathways described. The realization of the optimistic scenario requires maximum efforts and coordinated actions at all levels involved and needs to be pursued without delay.