Will Future Aircraft Run on Hydrogen Fuel Cells or Batteries?
By: Vern Scott
Tags: Aircraft, Hydrogen Fuel, Global Warming, Renewable Energy, Lithium Ion Battery

Aircraft is already being designed and tested to run on hydrogen fuel-cells or batteries. They work for small aircraft, but can they work for jets?

Can aircraft run on hydrogen fuel cells or lithium ion batteries, like cars? Well yes and maybe. Yes, hydrogen fuel cells and lithium ion batteries are already being used to power lighter aircraft, but commercial jetliners may have to wait for a few advances, most likely “hybrids” initially (planes that take off using traditional fuels, but then “cruise” using battery or hydrogen fuel cell power). If hydrogen/hydrogen fuel cells could be cheaper, then they may be the dominant power-provider for jetliners, given their superior energy densities and energy to weight ratios. Lithium ion/Lithium metal batteries may be able to power lighter aircraft, as weight ratios are not as critical in that realm, plus they are currently cheaper technologies.

Hydrogen has an energy density per unit mass that is three times greater than jet fuel (either unleaded kerosene, Jet A, or naphtha-kerosene blend, Jet B). However, jet fuel has four times the energy per unit volume, so a jet would have to carry significantly larger fuel tanks to run on hydrogen fuel. Since hydrogen fuel is more volatile (combustible), most designers do not think it can be carried in the wings, where jet fuel is currently stored. Instead, a larger fuselage is envisioned, where the larger hydrogen fuel tanks can be safely stored. This in turn would increase the size and drag coefficient of the fuselage, but since the overall weight of the hydrogen fuel would be significantly less, the performance of the jet would not be negatively affected.

There are several hydrogen powered aircraft prototypes. The first ever built was the Russian TU155, which made its first flight in 1989, using liquid hydrogen. After test flights, no commercial version was built. Boeing Research and Technology Europe (BRTE) made a hydrogen fuel cell powered two seater called the DA20 in 2008, but this aircraft was extremely light and needed very little energy for take off. In 2010, Rapid 200-FC made an aircraft that ran on gaseous hydrogen, and recorded six test flights. In 2016, the HY4 became the first passenger aircraft to run on hydrogen fuel cells. (Hawkins,2019),(Robertson,Maniaci,Segal,Scholz,Tidey,et al, n.d.)

The first electrically powered aircraft flight was the MB-E1 in 1971. Famously, the Solar Impulse 2 flew around the world using only solar powered electricity, and is now being considered for some commercial applications (mostly non-passenger oriented, due to the limitations of lithium battery technology). Due to weight considerations, batteries are currently limited for lighter aircraft, and range is modest (does this sound similar to electric car technology?). It is thought that a 20-fold increase in energy density will be needed to make batteries capable of making the jump to commercial passenger aircraft. The NASA X-57 Maxwell is another recent entry into electric aircraft, with a 4-seater designed to reduce fuel use, emissions, and noise.

A hybrid concept has been proposed for commercial aircraft, and several start ups are working on the concept, including Zunum Aero, General Electric, Volt Aero, Ampaire, Cranfield Aerospace, and the Berlin Brandenburg Aerospace Alliance. Generally speaking, the batteries are used for take off and landing, while an engine is used during flight for cruising speeds, and to recharge the batteries (just like an auto hybrid). (Guy,2020)

The potential “hydrogen-izing” of aircraft is held back by some of the same factors that inhibit implementation in cars and trucks. Though hydrogen fuel itself is currently comparable in price to fossil-fuel (and getting cheaper), fuel cells are currently expensive, but look to lower costs with increased productivity. There are also few hydrogen fueling stations at present, which limit a traveler’s options. Hydrogen fuel choices vary between CO2-free “green” varieties (typically produced by renewable-powered electrolysis and more expensive) and “grey” types (typically produced by steam-reforming natural gas, cheaper but with CO2 byproduct). (Van Hulst,2019)

Obviously, advances in aircraft electrification are quite dependent on better (lighter) battery technology and commercialization of hydrogen technologies, plus economy of scale pricing. It would seem that government subsidies would be in order, as these technological advances would not only improve aircraft, but other tech sectors such as auto and rail transportation.

Like this article? Read more in Vern Scott’s new book “Civil (Engineering) Disobedience”, available on Amazon.com