A session on hydrogen and electric power explored the opportunities and challenges these advanced power sources represent. Looking ahead, a basic big picture sees electric power being used for small, short-haul flights, hydrogen used for regional flights and sustainable aviation fuels (SAF) for widebody, long-haul flights.

But this picture, examined by a panel at the World Sustainability Symposium, has a multitude of challenges. Although SAF is proven, electric and hydrogen power would be completely new to aviation.

Electric doesn’t have the energy density to power big aircraft. A large, 900kw battery, needed for a 9-seater aircraft, weighs some 2,000lb and is therefore impracticable. There are other challenges too that include charging the batteries. Aside from the critical question of where the charge is coming from, the charging time would be too long, and turnarounds times would be extremely lengthy.

The way forward is hybrid power where a combustion engine powers the charge. In tests, Ampaire have reduced fuel use—and hence emissions—by 70%.

If anything, hydrogen has bigger infrastructure issues. It needs to be in liquid form, cooled, and its volume means aircraft will need to be redesigned for larger tanks. Ideally, it will also need to be “green”, meaning it is produced using non-CO2 generating technologies. But again, if the issues are solved, airlines could get a carbon-free, high-energy fuel.

Certification will be an issue for both electric and hydrogen. Authorities are understandably cautious and there is enormous demand on their resources as so many new technologies being developed. The tests that have been conducted to date have had huge amounts of redundancy and in-built redundancy will help with certification going forward. In addition, lessons are being learned every day and this is accelerating the certification curve.

Other issues include how a mid-sized airport might cope. Can it accommodate electric, hydrogen, and conventional, SAF-powered aircraft? What would that to do to airfield design? And because new skills will be required, new training standards will be essential. An electric aircraft would be high voltage, for example.

Also, though being carbon free is the main goal, the non-CO2 impact of these technologies has to be considered and this is still a developing field. NOx and noise are just two of the considerations.

The panel noted that successful tests are already being conducted and hybrid-electric engines could be available on small aircraft in the next few years. They called for airlines to get involved even if small aircraft will never be part of their network. The lessons learned would be enormous and help develop the technology for larger models.

The point is that manufacturers and technology specialists will not be able to come up with an electric or hydrogen aircraft that looks and behaves like a kerosene-powered aircraft. Airlines therefore must feed into development and their partners what will work.

In this sense, it is economics—and not technology—that will drive development. And to ensure economic viability will require partnerships across the aviation value chain. The aim must be to start small, get certified, learn, and scale up.

Article Source: Getting ready for electric and hydrogen aircraft