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■ Date: April 20, 2021
【What is next for China’s hydrogen supply chain (2) --- Storage and Transport】
In last article What is next for China’s hydrogen supply chain (1) --- Production, we have introduced three development phases of hydrogen production by 2050, transitioning from blue and grey hydrogen to green hydrogen. Following the green transition, this article is about to explore the bridge between supply and demand, namely hydrogen storage and transport, based on which future hydrogen delivery system is discussed.
Overview of hydrogen storage and transport in China
Broadly speaking, hydrogen can be stored and transported in three different forms, compressed gaseous hydrogen, cryogenic liquid hydrogen and hydrogen carriers.【Details of storage technologies please go to Overview of Hydrogen Storage Technology in China】Compressed gas delivery is ideal for short-distance and small-scale demand, transporting either by tube trailers or through pipelines. Cryogenic liquid hydrogen is suitable for long-distance delivery and high-volume demand, transporting by liquid tankers, where gaseous hydrogen is liquefied and stored in large insulated tanks. As for hydrogen carriers, liquid organic hydrogen carrier (LOHC) is preferable for long-term storage and long-distance delivery than cryogenic liquid hydrogen thanks to its chemically stable in storage and very minor boil-off losses during transportation. Metallic hydride such as Mg-based hydride possesses good-quality functional properties, such as heat-resistance, vibration absorbing, reversibility and recyclability. Currently, both LOHC and metallic hydride are in the early stage of R&D and have not been commercialized yet. Applying such new carriers, however, would constitute a significant departure from the way hydrogen is delivered today (Fig 1).
Fig 1.
Three development phases of hydrogen storage and transportation
According to China Hydrogen Alliance, along with the green transition of hydrogen production, the development of hydrogen storage and transportation is also assumed to experience three phases by 2050, diversifying hydrogen storage and transportation methods for the advancement of hydrogen and fuel cell technologies (shown in Fig 2).
Fig 2.
By 2025, based on Integral estimation, total hydrogen demand of FCEV is expected to reach 0.89 million tons/year, mainly from the Yangtze River Delta Area, Jing-Jin-Ji Region, and Pearl River Delta Area, where by-product hydrogen is the major supply with an estimated capacity of more than 1.2 million tons/year in 2022 (shown in Fig 3).
Fig 3.
As the local by-product supply could entirely meet the hydrogen demand (shown in Fig 4), tube trailer is the most economical tool for small-scale and short-distance delivery.
Fig 4.
Although it is a preferable solution for now, tube trailers still hold certain drawbacks. For instance, the storage capacity of tube trailers is quite low (around 1.1wt%) compared to other methods. Moreover, the transportation costs of tube trailers is distance-sensitive, which would be uneconomical when the transport radius exceeds around 300km.
In the mid-term (2026-2035), based on Integral estimation, total demand of FCEV in China is projected to reach 4.3 million tons/year. While the FCEV market keeps growing, industrial by-product and renewables continue to supply the most hydrogen fuel nation-wide, complemented by coal with CCS technology. Two issues may be raised for inter-provincial hydrogen storage and transportation. One is that local hydrogen demand cannot be met by local by-product hydrogen supply. The second is the geographical differences between renewable energy areas and the major hydrogen consumption markets (shown in Fig 5).
Fig 5.
In this case, tube trailer will no longer be an optimal solution due to its distance-sensitive cost and low storage capacity. That's where cryogenic liquid hydrogen tanker and LOHC come in.
With higher storage density (about 14%) and hydrogen purity, cryogenic liquid hydrogen would be a more economical option for high-volume and long-distance transport. Several challenges with cryogenic liquid transportation include the potential for boil-off (the boil-off rate is around 0.6-1% per day), the energy-consuming and expensive liquefaction process.
Compared to cryogenic liquid hydrogen, LOHC is safer and less energy-consuming as it can be transported at room temperature and atmospheric pressure. Without leakage and explosion risks, LOHC is more suitable for long-term storage and long-distance transport than cryogenic liquid hydrogen. Future operation of central LOHC hydrogenation plants is possible at the production sites where a large amount of curtailed RE-generated hydrogen is produced and stored. However, high-purity hydrogen is difficult to guarantee due to the unstable (de)hydrogenation process of LOHC.
Except for trucks, hydrogen could also be transported through pipelines much the way natural gas is today, particularly for large-scale transport. Currently in China, hydrogen pipeline is under the stage to be expanded due to various factors, including its high initial investment, the special steel materials required to avoid hydrogen embrittlement (HE), and government supports. Another solution is hydrogen compressed natural gas, which might have a huge potential to scale leveraging existing natural gas pipelines, reduce emission and save energy. Demonstration projects of hydrogen compression natural gas have started in Europe, whereas only one demonstration project is under operation in China. Some key challenges need to be resolved include optimizing H2/ NG blending ratio and reducing risks of leakage and explosion.
In the long-term (2036-2050), renewable energy is expected to be the main supply for hydrogen production, deepening the gap between renewable resource areas and major hydrogen demand markets (shown in Fig 6). In this case, diversified transportation technologies would co-exist to meet different hydrogen demands and cross-province delivery.
Fig 6.
New hydrogen carriers would be commercialized for long-distance delivery, thanks to their convenience and safety in transportation. Some bottlenecks of new hydrogen carriers include short life span, low storage capacity, low economical competitiveness and high-temperature requirements of (de)hydrogenation process. In addition, cryogenic liquid hydrogen and hydrogen carriers transported by rail or ship would be developed to export hydrogen from China to other countries.
Vision of hydrogen supply chain
From 2035 onward, China’s hydrogen supply chain would consist of different hydrogen storage and transport tools, as well as ultra-high-voltage (UHV) power transmission grid, which is another solution to bridge the geographical gap between renewable resource areas and major hydrogen demand markets (Fig 7).
Fig 7.
Under this vision, hydrogen production site would be possible to extend from renewable resource areas to hydrogen demand areas on conditions of reduced electricity price and completed UHV power grid (Fig 8). UHV grid allows green electricity to be transmitted from renewable resource areas to hydrogen demand areas at low loss rate and high capacity. For example, average loss rate of a ±1100kV/12GW UHV line is 1.5%/1000 km, 5.4% lower than a common ±500kV/3GW transmission line. 【Details of UHV can be found in Smart Grid, A Game Changer】To compare, the ideal boil-off loss of cryogenic liquid hydrogen delivery for a 2000 kg/day station is around 1.2-2%/1000 km, similar to UHV line. However, UHV grid has an edge in transmission costs ranging from 5.5 to 12 Yuan/kg H2, less than the transportation cost of cryogenic liquid hydrogen, at around 13~15 Yuan/kg H2.
Fig 8.
Three major scenarios are assumed to co-exist for hydrogen distribution domestically and internationally (Fig 9).
Fig 9.
Scenario one refers to hydrogen produced at centralized renewable power plants in North and Southwest China with high-volume storage, and transported to demand areas via tankers, ships and trains. In the medium term, hydrogen would continue to be produced by renewable power generators to reduce curtailed power amount led by expanding installment of renewable energy, as practiced in current power-to-gas demonstration projects. In this scenario, large-capacity storage, like hydrogen carrier, is needed for hydrogen produced, given part of hydrogen would be reused for power generation during peak demand time and the rest can be sold to hydrogen consumers. Transport tools, like liquid tankers and ships, would be used for inter-provincial/regional and even international delivery.
Scenario two refers to hydrogen produced at demand sites using on-grid power transmitted via UHV grid from renewable resource areas, like hydrogen refueling stations, factories and buildings. Hydrogen produced in this scenario is majorly for self-consumption. It is worth to notice that three prerequisites of this scenario are the reduced on-grid electricity price, reduced hydrogen production CAPEX and well-developed UHV grid. Ideally, hydrogen could be produced on site based on individual hydrogen demand with zero transportation cost. Stationary gas cylinders would be required for small-scale storage.
Scenario three refers to hydrogen produced at centralized hydrogen plants using excessive on-grid power generated during off-peak demand time. Such hydrogen plants have flexible locations based on actual hydrogen demand and transportation costs. To meet increasingly growing demand, large-amount hydrogen would be produced from off peak on-grid power. A possible case is that power generators partnered with state-owned grid enterprises invest in hydrogen plants on demand side to produce hydrogen during off-peak time. Hydrogen produced in this way can be sold at a cheaper price because of low transportation cost of UHV grid. Hydrogen carriers would be used for high-volume storage. Tube trailers and pipelines would be used for last-mile delivery to demand sites within provinces. In case of exporting businesses, long-distance transport means, like liquid tankers and ships, would be used for delivery to other countries.
Conclusion
In the next three decades, diversified hydrogen storage and transport tools combined with UHV grid would coexist to constitute a well-rounded hydrogen delivery system in China. We assume that, in medium term (2026-2035), scenario one would be the mainstream supply considering rising power curtailment issue and scale economy. Long-term hydrogen supply contract is the key to secure stable downstream markets and reasonable returns on investment. In the long term (2036-2050), with the curtailed issue resolved and UHV grid completed, scenario two and three could be expected to emerge and co-exist with scenario one. Large-capacity, long-distance storage and transport tools, as well as UHV grid infrastructure, are pivotal to domestical and international delivery systems.
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