Leiden University Professor argues that hydrogen-powered flight could be a viable route decarbonising transport
Transport makes up around 20% of global energy use around the world, according to the International Energy Agency (IEA). As governments and industry look to more sustainable solutions, a new study published by physicist Jo Hermans in MRS Energy and Sustainability–A Review Journal (MRS E&S) examines the energy efficiency of current modes of transport.
Covering bicycles to buses, from air transport to cruise ships, Hermans concludes that liquid hydrogen seems to be a realistic option for what is probably the most problematic of transportation modes in terms of sustainability: future air travel.
Professor Hermans from the Leiden University Huygen Laboratory acknowledges that oil-based liquid fuels such as gasoline, diesel and kerosene will be hard to beat when it comes to how much energy they pack in relation to their volume and weight – not to mention the sheer convenience of using them to get from A to B. Although this convenience poses a challenge, liquid hydrogen could offer a potential solution. “Given the severe weight limitations for fuel in aircraft, liquid hydrogen may be a viable alternative in the long run,” Hermans says.
He identifies three key areas. First, that handling of liquid hydrogen would be carried out by professionals, which reduces the safety issues involved with liquid hydrogen to the same level of risk involved in handling kerosene. Second, liquid hydrogen itself is very light (obviously a gaseous state at ordinary temperatures), which is an important advantage for air travel.
Third, the disadvantages of “boil off” (created by the low boiling point of liquid hydrogen) would be reduced in air travel because of the low outside temperature at cruising altitudes.
Hermans discounts the use of solar power for air travel without revolutionary changes in the airplane concept, but concludes that it seems wise to extend the availability of oil products as long as possible. However, he argues that the low cost of kerosene is a huge disincentive in this respect: “It is a defect that kerosene is so irrationally cheap, which triggers much unnecessary air travel,” he writes. “A worldwide tax on kerosene – if at all politically possible – should be something to pursue.”
For road transport, Hermans argues that liquid hydrogen is not a viable option owing to the safety issues around handling it. He finds that electric vehicles offer the most promising solution. However, the challenge here is in improving the performance of batteries to prolong the driving time for electric cars, as well as improving the performance of supercapacitors for more rapid charging of the batteries, he argues.
Alternatively, Hermans writes, the most efficient way for us to reduce energy use in future is to reduce our mobility, for example, by having shorter distances between the workplace and home. “In other words, urban planning provides an important key,” he concludes.
Source: MRS Energy