The primary objective of SUN-to-LIQUID II is to increase the solar reactor energy efficiency to >15% by improving the effective radiative absorption using 3D printed redox materials with optimized structure and reducing sensible heat losses during the temperature swing redox process.

  • A gas-to-liquid plant will be integrated further downstream to convert the solar syngas to fuels. Thereby SUN-to-LIQUID II will advance the European scientific basis and global technological leadership in the area of solar thermochemical fuel conversion.
  • Improving the energy conversion efficiency of the key solar energy conversion step will reduce cost and GHG emissions of solar fuel production in the long-term.
  • The 3D printed structures will be scaled-up from a 5-kW setup in the laboratory to 50 kW in the existing experimental solar facility in Móstoles, Spain, where the complete integrated fuel production chain to solar liquid hydrocarbon fuels from H2O, CO2 and solar energy will be demonstrated.
  • The maturity target of the SUN-to-LIQUID II is to demonstrate the innovative fuel production process up to validation in relevant environment. This goal will be achieved by the following specific objectives:

Specific objectives:

Optimization and enhancement of a high-flux solar concentrating heliostat and tower system
  • Optical optimization of solar system and reactor design: Enhancement of pointing accuracy, stability and focus of ultra-modular high-flux concentrating system to deliver on average onto receiver aperture 1,500-2,000 kW/m2. This increases the contribution of the renewable solar resource, the number of hours of robust and stable operation of the reactor, decreases heat losses and enhances the amount of redox material undergoing reduction and, consequently, the specific yield.

Demonstration of enhanced yield from novel 3D structured chemically active redox materials
  • Advanced computer-aided-designed redox structures overcome the inhomogeneous radiative absorption and temperature distribution during the heated-up phase in the reduction step. To reach a higher yield of high-quality fuel, SUN-to-LIQUID II introduces novel 3D-printed hierarchically structured redox materials with optimized porosity gradient for thermochemical cycling.

Advanced solar reactor with integrated high-temperature heat recovery achieving record-high solar thermochemical reactor efficiency
  • An advanced solar reactor concept will foster the development of the technological pathway, with integrated heat recuperation to be designed, constructed and tested in field at the research facility in Móstoles. The new solar reactor will apply novel 3D structured reactants (Objective 2) with increased specific yield, regenerating heat from the solid redox material by integrating a heat recovery system, and reduce heat losses with an aperture cover during cool down and oxidation.

Preparing commercial exploitation of solar thermochemical fuels
  • Integrating a Fischer-Tropsch plant demonstrates the entire path from sunlight, water and CO2 to hydrocarbon fuel, and especially jet fuel, delivering technology for longer-term needs for renewable fuels in energy and transport. In addition, scale-up modeling of a multi-megawatt plant and system-level analyses provide decision support for commercial exploitation. The analyses identify cost and emission reduction potentials, systemic constraints as well as risks towards attaining selected SDGs with a sustainable, secure and competitive hydrocarbon fuel supply.