In Austria alone, the transport sector requires more than 400 PJ of energy per year. This sector thus accounts for about 36 % of final energy demand. Since many of the means of transport used have not yet reached the end of their lifetime, a reasonable strategy for decarbonization is essential. Climate-neutral and synthetically produced fuels, so-called eFuels, make it possible to use existing transport means until the end of their lifetime. Due to the lack of electrification options, climate-neutral eFuels will continue to be in high demand for areas such as aviation or shipping.

In the Innovation Flüssige Energie - IFE project, a power-to-liquid (PtL) plant will be designed for the highly efficient production of CO2-neutral synthetic fuels. The PtL plant will produce synthetic diesel, naphtha and waxes from water, CO2 and renewable electricity. A solid oxide co-electrolysis (Co-SOEC) will be combined with an efficient CO2 extraction and Fischer-Tropsch (FT) process. The SOEC is operated as a co-electrolysis and thus produces H2 and CO in one process step. By thermally coupling the Co-SOEC with the FT process, significantly higher efficiency can be achieved compared to conventional approaches.

Demo plant function diagram


Heat exchanger network


The PtL plant will be used for a nominal electrical input power of 200 kW, which allows the production of approx. 115,000 liters/year synthetic fuel. However, the plant should also operate in a flexible load range, since when operating with electricity from renewable sources (e.g. wind, solar, hydropower), the available electrical power can fluctuate considerably. After a subsequent industrialization phase, the developed technology will be produced in Austria and integrated into the Austrian energy system. This should lead to positive economic and ecological effects in Austria. The goal is to produce synthetic fuel from € 1/liter to € 1.5/liter.

The IFE project aims to maximize system efficiency in the range of 55 %. Comparable state-of-the-art systems have an efficiency of about 43 %. Heat integration of the process streams is crucial in achieving system efficiency. Within the framework of this research project, innovative methods in the field of mathematical optimization are being developed by the research department Industrial Energy Systems of the TU Wien. In contrast to already established methods, not only given process flows can be optimized, but also the operating point of individual plants can be considered. Thus, a holistic process consideration can guarantee optimal results.

  1. F. Birkelbach, D. Huber und R. Hofmann, Piecewise Models for MILP unpublished - Computers and Chemical Engineering, 2022.
  2. Huber, D., Birkelbach, F., & Hofmann, R. (2023). HENS Unchained: MILP Implementation of Multi-Stage Utilities with Stream Splits, Variable Temperatures and Flow Capacities. Energies, 16(12), Article 4732.
  3. S. Pratschner, M. Hammerschmid, F. J. Müller, S. Müller und F. Winter, Simulation of a Pilot Scale Power-to-Liquid Plant Producing Synthetic Fuel and Wax by Combining Fischer – Tropsch Synthesis and SOEC Energies, Bd. 15, Nr. 11, p. 4134, 2022.
  4. Huber, D., Birkelbach, F., & Hofmann, R. (2023). Non-Pareto optimal solutions as enablers for versatile heat exchanger networks. In A. Kokossis, M. Georgiadis, & E. Pistikopoulos (Eds.), Proceedings of the 33rd European Symposium on Computer Aided Process Engineering (ESCAPE33). Elsevier B.V.
  5. Huber, D., Werdinig, K., Birkelbach, F., & Hofmann, R. (2023). Highly efficient heat integration of a power-to-liquid process using MILP. In Proceedings of ECOS 2023
  6. Birkelbach, F., Kasper, L., Schwarzmayr, P., & Hofmann, R. (2023). Operation planning with thermal storage units using MILP: Comparison of heuristics for approximating non-linear operating behavior. In A. M. Blanco-Marigorta, B. Del Rio Gamero, N. Melian Martel, & N. El Kori (Eds.), Proceedings of ECOS 2023.
  7. Pratschner, S., Hammerschmid, M., Müller, S., & Winter, F. (2023). Evaluation of CO₂ sources for Power-to-Liquid plants producing Fischer-Tropsch products. Journal of CO2 Utilization, 72, Article 102508
  8. Huber, D., Birkelbach, F., & Hofmann, R. (2023). Unlocking the potential of synthetic fuel production: Coupled optimization of heat exchanger network and operating parameters of a 1 MW power-to-liquid plant. Chemical Engineering Science, Article 119506. Elsevier B.V.
  9. Huber, D., Birkelbach, F., & Hofmann, R. (2023). Assessing the impact of changing electricity and CO2 prices on synthetic fuel production: Multi-criteria heat exchanger network synthesis.