Session: 17-01: Symposium Steinfeld - Solar Energy Perspectives

Paper Number: 142278

142278 - Perspectives of Sustainable Aviation Fuels From the Solar-Thermochemical Production Pathway 

Abstract: 

The target of climate neutrality for aviation presents a strong technology pull factor for innovative solutions for sustainable energy and carbon capture, aircraft and operational efficiency, and for non-CO2 climate impact mitigation. A major lever is the transition to 100% renewable energy with high-energy-dense liquid fuels that meet the challenge of sustainable production volumes with greenhouse gas (GHG) savings beyond 80% compared to conventional aviation fuel. This raises the question, which production processes promise the required production volumes at acceptable production cost, and are sustainable not only with their potential for deep decarbonisation with significant climate impact reduction, but also in the context of land use and water footprint. The substitution of fossil kerosene by sustainable aviation fuel requires an in-depth analysis of these potentials of specific fuel production pathways. The production of solar-thermochemical fuels has the advantage of requiring only water and renewable CO₂ (for instance through direct air capture) as feedstock, and direct sunlight as a source of renewable energy. It is thus obvious that arid non-arable land locations with high solar irradiation are particularly suited where there is no competition with food and feed production.

For deep decarbonisation, both the energy and carbon source must be renewable. Detailed life-cycle analyses (LCA) for various locations and for combinations of carbon feedstock and auxiliary power sources confirm the potential for more than 80% GHG reduction and low water footprint compared to biofuel pathways.

A detailed location-specific techno-economic analysis (TEA) for various locations, combining the physio-geographic (here, mainly direct normal irradiation) and macroeconomic (here, mainly financing cost in terms of weighted average cost of capital (WACC)) aspects was performed for all relevant world regions (e.g. the Mediterranean, the United States, the Andes region, Australia, and southern Africa). All these regions hold suitable locations for the production of solar thermochemical fuels with high solar irradiation. Yet, production sites with high irradiance can lose their attractiveness through high financing cost. Due to the strong relationship between financing cost and fuel cost, locations with relatively lower solar irradiance can become interesting if financing cost are very low. This shows the importance of taking into account both physio-geographic and macroeconomic aspects when evaluating production locations.

It turns out that the technical production potential far beyond global aviation’s fuel demand can be met in several regions of the world. The fuel cost in suitable locations is strongly determined by reactor efficiency – which has great leverage of reducing the cost for the heliostat field - by cost of CO2, and cost of capital. A solar-to-syngas reactor energy efficiency of around 20% and a lower cost of capital by reducing the investment risk with strategic producer-user partnerships are the key to economic viability. To this end, and to advance the technology readiness and scale, a series of research and innovation actions, the projects SOLAR-JET (2011-2015), SUN-to-LIQUID (2016-2019) and SUN-to-LIQUID II (2023-2027) were and currently are funded by the European Union and Switzerland, building on several generations of the ceria-based reactor technology developed and refined by Prof. Aldo Steinfeld and his team at ETH.

In summary, providing future aviation with renewable, climate neutral fuels is challenging in terms of sustainability, scalability, and economic viability. Synthetic solar-thermochemical jet fuel is a promising solution in technical, environmental and economic terms, and is expected to bring socio-economic benefits to vast areas of arid non-arable land: The construction of large-scale production facilities could therefore bring employment and wealth to economically challenged regions.

Presenting Author: Andreas Sizmann Bauhaus Luftfahrt e.V.

Presenting Author Biography: Dr. Andreas Sizmann is Head of Future Technologies and Ecology of Aviation at Bauhaus Luftfahrt where he established a future technology analysis methodology for the assessment of innovation potentials in aviation based on latest advancements in science and technology. He is coordinator of the Horizon Europe Project “SUN-to-LIQUID II” (2023-2027) and of its predecessor projects “SUN-to-LIQUID” and “SOLAR-JET” that pioneered solar-thermochemical hydrocarbon fuel production. Since 2011 he also serves as member of the Working Group “Protecting the Environment and the Energy Supply” of the Advisory Council for Aviation Research and Innovation in Europe (ACARE).

Authors:

Andreas Sizmann Bauhaus Luftfahrt e.V.
Christoph Falter Synhelion SA
Valentin Batteiger Bauhaus Luftfahrt e.V.