Returning Airships to the Skies

The researchers postulate that the reintroduction of airships into the transport sector could also offer an alternative for the transport of hydrogen. Hydrogen is a good energy carrier and a valuable energy storage alternative. Given that renewable electricity, for example, excess wind power, can be transformed into hydrogen, there is optimism that the hydrogen economy will form a fundamental part of a clean and sustainable future. One of the challenges to implementing a hydrogen-based economy is cooling the hydrogen to below -253°C to liquefy it. The process consumes almost 30 percent of the embodied energy, with further energy of around 3 percent required to transport the liquefied hydrogen. In their study, the authors however propose that instead of using energy in liquefaction, hydrogen in gaseous form could be carried inside the airship or balloon and transported by the jet stream with a lower fuel requirement. Once the airship or balloon reaches its destination, the cargo can be unloaded removing around 60 percent or 80 percent of the hydrogen used for lift, and leaving 40 percent or 20 percent, of the hydrogen inside the airship or balloon to provide enough buoyancy for the return trip without cargo. To address the risk of combustion of the hydrogen in the airship, the authors suggest automating the operation, loading, and unloading of hydrogen airships and designing flightpaths that avoid cities to reduce the risk of fatalities in the event of an accident.

According to study lead-author Julian Hunt, an IIASA post-doctoral fellow, a further interesting aspect unveiled in this study is the possibility that airships and balloons can also be used to improve the efficiency of liquefying hydrogen. As the temperature of the stratosphere (where the airships will be flying to utilize the jet stream) varies between -50°C to -80°C, it means that less energy will be required to meet the -253°C mark if the process happens onboard the airship. The energy required for the additional cooling needed can be generated using the hydrogen in the airship.

Hunt says that this process also presents a number of additional possibilities: The process of generating energy from hydrogen produces water – one ton of hydrogen produces nine tons of water. This water could be used to increase the weight of the airship and further save energy in its descending trajectory. Another possible application for the water produced is rainmaking, which involves releasing the water produced from the stratosphere at a height where it will freeze before entering the troposphere where it would then melt again. This reduces the temperature and increases the relative humidity of the troposphere until it saturates and starts raining. The rain will in turn initiate a convection rain pattern, thus feeding even more humidity and rain into the system. This process could be used to alleviate water stress in regions suffering from shortages.

“Airships have been used in the past and provided great services to society. Due to current needs, airships should be reconsidered and returned to the skies. Our paper presents results and arguments in favor of this. The development of an airship industry will reduce the costs of fast delivery cargo shipping, particularly in regions far from the coast. The possibility to transport hydrogen without the need to liquefy it would reduce the costs for the development of a sustainable and hydrogen-based economy, ultimately increasing the feasibility of a 100 percent renewable world,” concludes Hunt.