Sustainable aviation requires the availability of a fuel which either emits no carbon dioxide during combustion or, at the very least, is carbon neutral in the sense that any emitted carbon dioxide is recovered in some way. These objectives can be met by battery-powered electric aircraft, by hydrogen-fueled aircraft or by conventionally-fueled aircraft whose carbon-dioxide emissions are recovered. Battery-powered electric aircraft require renewably produced electricity, hydrogen-fueled aircraft require renewably produced hydrogen, and conventionally fueled aircraft require a mechanism to recover the emitted carbon dioxide.

In this lecture Prof. Platzer will review the progress achieved in the past few years in the development of the "energy ship concept" he developed in collaboration with faculty and students at the University of California Davis, Royal Institute of Technology Stockholm, and the Technical Universities of Graz, Austria, and Darmstadt, Germany. He will show that large sailing ships equipped with hydro turbines, electrolysers and compressors, operating in wind-rich ocean areas, can be used to convert the sea water into compressed hydrogen which then is shipped back to shore for re-conversion into electricity or directly used for transportation purposes. An additional use of these sailing ships is to extract not only hydrogen but also carbon dioxide from the sea water by means of bipolar membrane electrodialysis. The hydrogen and carbon dioxide then are converted into synthetic jet fuel by means of the Fischer-Tropsch process.

Prof. Platzer will describe the major design and operating features of this energy ship concept. A major advantage of this concept is the much higher capacity factor available to sailing ships operating in wind-rich ocean areas as compared to the capacity factors available to land or off-shore based wind turbines. A further advantage is the ability to operate the energy ships in international waters. As a result a new supply of renewably generated hydrogen becomes available for use in hydrogen fuel-cell powered aircraft, as presently being developed by DLR in Germany. A further result is the supply of synthetic jet fuel to the global aviation community, making possible carbon-neutral aviation without changes in jet engine and aircraft design or general aviation infrastructure.