HydroTransformer, a Chinese hydrogen energy startup founded in 2021, develops liquid organic hydrogen carrier (LOHC) technologies to store and transport hydrogen gas without the need for cryogenics or high pressure.
Challenges:Â hydrogen storage
As we move toward a cleaner energy future, hydrogen's versatility and sustainability make it an increasingly attractive option. This clean energy carrier offers several advantages, including the potential for production from renewable resources, zero-emission combustion, and high energy density. Applications for this highly portable energy source range from generating electricity through fuel cells to producing heat through combustion, all while minimizing greenhouse gas emissions. Its flexibility and eco-friendly nature position hydrogen as a key player in the evolving energy landscape.
Traditionally, the world has relied heavily on steam methane reforming (SMR) to produce over 60 million tons of hydrogen annually. However, this method comes with a significant environmental cost. It's an energy-intensive process that contributes approximately 2% to global carbon dioxide (COâ‚‚) emissions, releasing between 5 and 9 tons of COâ‚‚ for every ton of hydrogen it generates.
There are cleaner paths to producing hydrogen, such as water electrolysis and methane pyrolysis.
After production, transporting hydrogen to end users is essential. However, this process is challenging due to hydrogen's unique chemical and physical properties. Safety concerns arise from hydrogen's potential to cause material embrittlement and its propensity to escape from containment. Additionally, hydrogen's wide flammability range and low ignition energy present significant risks. These factors pose substantial challenges to the widespread and safe adoption of hydrogen as an energy carrier.
Several solutions have been developed for hydrogen transportation, each with its own set of limitations:
- High-pressure/compressed hydrogen
This method utilizes bulk storage vehicles like tube trailers. However, it faces constraints in transport volume and experiences hydrogen losses, reducing efficiency over long distances. Compressed hydrogen storage and transportation can consume up to 20% of the fuel's energy content.
- Liquid cryogenic hydrogen
This approach is favored for high-volume transport, especially in the absence of pipelines. The process involves cooling hydrogen to below 20K through liquefaction and transporting it in liquid tankers with onboard cooling systems. While effective for large volumes, this method is energy-intensive, potentially using up to 40% of the hydrogen's energy content.
- Adsorption materials
Metal hydrides, which are formed by the chemical reaction of metals and hydrogen gas, provide a highly compact method of storing hydrogen. They are denser than liquid hydrogen and can be stored at normal temperatures and pressures. However, metal hydrides have a relatively low hydrogen storage capacity, ranging from 1-5% by weight. Furthermore, metal hydrides are unsuitable for flow-based transportation methods like pipelines. Metal hydrides are primarily used in stationary applications due to their high energy demand and slow kinetics associated with hydrogen absorption and release.
- Liquid Organic Hydrogen Carriers (LOHCs)
LOHCs are an innovative solution for hydrogen storage and transport. This technology involves hydrogenating an unsaturated organic compound, such as toluene, to form a hydrogen-rich liquid, like methylcyclohexane, which can be stored and transported under ambient conditions without the need for high pressures or low temperatures. When hydrogen is needed, methylcyclohexane undergoes dehydrogenation, releasing hydrogen for use. This process is facilitated by catalysts and can be integrated into existing fuel infrastructure, making LOHCs a practical and cost-effective alternative to traditional hydrogen storage methods.
HydroTransformer Technology
HydroTransformer develops LOHC technologies that use carbazole as hydrogen storage carriers, allowing for efficient hydrogen storage and release through advanced hydrogenation and dehydrogenation systems.
Carbazole and its derivatives, especially N-ethylcarbazole, offer high hydrogen storage densities and reversible hydrogenation/dehydrogenation capabilities, making them suitable for hydrogen storage and transport applications. N-ethylcarbazole can be fully hydrogenated to dodecahydro-N-ethylcarbazole, which has a high hydrogen storage capacity of approximately 5.8 wt%. The hydrogenation and dehydrogenation processes are facilitated by various catalysts, including Pd, Rh, and Ru with Al₂O₃ support showing particularly effective catalytic performance.
How HydroTransformer dehydrogenates LOHCs
The diagram below depicts HydroTransformer’s conical rotating packed bed dehydrogenation reactor for the dehydrogenation of dodecahydro-N-ethylcarbazole, which generates hydrogen gas and N-ethylcarbazole.