Technical, economic and environmental analysis of solar thermochemical production of drop-in fuels

Christian Moretti; Vikas Patil; Christoph Falter; Lukas Geissbühler; Anthony Patt; Aldo Steinfeld

doi:10.1016/j.scitotenv.2023.166005

Technical, economic and environmental analysis of solar thermochemical production of drop-in fuels

Sci Total Environ. 2023 Nov 25:901:166005. doi: 10.1016/j.scitotenv.2023.166005. Epub 2023 Aug 2.

Authors

Christian Moretti¹, Vikas Patil², Christoph Falter³, Lukas Geissbühler³, Anthony Patt⁴, Aldo Steinfeld²

Affiliations

¹ ETH Zurich, Department of Environmental Systems Science, 8092 Zürich, Switzerland. Electronic address: christian.moretti@usys.ethz.ch.
² ETH Zurich, Department of Mechanical and Process Engineering, 8092 Zurich, Switzerland.
³ Synhelion SA, Lugano, Switzerland.
⁴ ETH Zurich, Department of Environmental Systems Science, 8092 Zürich, Switzerland.

PMID: 37541501
DOI: 10.1016/j.scitotenv.2023.166005

Abstract

This study analyzes the technical performance, costs and life-cycle greenhouse gas (GHG) emissions of the production of various fuels using air-captured water and CO₂, and concentrated solar energy as the source of high-temperature process heat. The solar thermochemical fuel production pathway utilizes a ceria-based redox cycle for splitting water and CO₂ to syngas - a tailored mixture of H₂ and CO - which in turn is further converted to liquid hydrocarbon fuels. The cycle is driven by concentrated solar heat and supplemented by a high-temperature thermal energy storage for round-the-clock continuous operation. The study examines three locations with high direct normal irradiation using a baseline heliostat field reflective area of 1 km² for the production of six fuels, i.e. jet fuel and diesel via Fischer-Tropsch, methanol, gasoline via methanol, dimethyl ether, and hydrogen. Two scenarios are considered: near-term future by the year 2030 and long-term future beyond 2030. In the near-term future in Sierra Gorda (Chile), the minimum fuel selling price is estimated at around 76 €/GJ (2.5 €/L) for jet fuel and diesel, 65 €/GJ for methanol, gasoline (via methanol) and dimethyl ether (DME), and 42 €/GJ for hydrogen (excluding liquefaction). In the long-term future, with advancements in solar receiver, redox reactor, high-temperature heat recovery and direct air capture technologies, the industrial-scale plant could achieve a solar-to-fuel efficiency up to 13-19 %, depending on the target fuel, resulting in a minimum fuel selling price of 16-38 €/GJ (0.6-1.3 €/L) for jet fuel and diesel, and 14-32 €/GJ for methanol, gasoline, and DME, making these fuels synthesized from sunlight and air cost-competitive vis-à-vis e-fuels. To produce the same fuels in Tabernas (Spain) and Ouarzazate (Morocco) as in Sierra Gorda, the production cost would increase by 22-33 %. Greenhouse gas savings can be over 80 % already in the near-term future.

Keywords: Direct air capture; LCA; Minimum selling price; Renewable fuels; Solar redox.