Polyphem – Small-Scale Solar Thermal Combined Cycle (Gas Turbine/ORC)

Duration: 04/2018 - 03/2022
Contracting Authority/ Sponsors: European Union, Horizon 2020 research and innovation programme
Project Partners: CNRS PROMES, CEA, CIEMAT, ARRAELA SL, KÄFER Isoliertechnik GmbH & Co.KG, Orcan Energy GmbH,   Euronovia, Aalborg CSP AS
Website: https://www.polyphem-project.eu
Project Focus:
Polyphem - Project Concept
© Fraunhofer ISE
Power plant concept.
THEMIS CNRS PROMES solar tower power plant
© Polyphem
THEMIS CNRS PROMES solar tower power plant in which the POLYPHEM prototype will be integrated.
Dispatchable production fulfilling a certain electricity demand profile
Dispatchable production fulfilling a certain electricity demand profile.

How can the efficiency and flexibility of small-scale solar thermal power plants be improved? The POLYPHEM project addresses this question with a pragmatic approach. With the aim of increasing flexibility and performance, the POLYPHEM project will build and validate an innovative power plant cycle in an industry-relevant environment. By using a solar driven micro gas turbine and integrating a thermal energy storage (TES), this project prepares the next generation of small solar power plants. Fraunhofer ISE supports the project especially in the following tasks:

  • System integration / overall system planning
  • System simulation and optimization
  • Experimental performance assessment
  • Life Cycle Analysis

The POLYPHEM concept comprises a solar-powered micro gas turbine coupled to an Organic Rankine Cycle (ORC) via an integrated heat storage unit. This coupling enables direct power generation by the micro gas turbine during periods of solar radiation as well as power supply using the heat storage and ORC, which are decoupled from the solar input. This innovative configuration increases the flexibility and capacity of solar power plants alike. This would make it possible, for example, to cover the power requirements of an island grid (microgrids) day and night. In addition, the water demand is significantly lower than that of comparable power plants due to the reduced cooling requirement.

A prototype of the POLYPHEM power plant cycle will be integrated into Themis' experimental solar tower plant in Targassonne (Eastern Pyrenees). In addition to finalizing the engineering diagrams for the entire demonstration plant, Fraunhofer ISE also contributes to the following POLYPHEM prototype components:

  • Design of the Recovery Heat Exchanger
  • Adaption and modification of the Micro-Gas Turbine and ORC cycle
  • Testing of the TES filler material with CNRS at their Microsol test facility
  • Development of a camera based measurement setup for circumsolar radiation and sunshape distribution

In parallel to the design of the overall system, Fraunhofer ISE further supports the project by performing system simulations for yield predictions. These simulations explore complex scenarios such as meeting demand profiles, location sensitivity analysis, and novel operating strategies. Furthermore, techno-economic optimization is also evaluated for these scenarios. Research findings of these simulations were presented at the international SolarPACES Conference in 2019, 2020, & 2021.


Further information on the tasks of »POLYPHEM«:

Taks: Simulation model for the POLYPHEM prototype – Digital Twin

Task: Development of a camera-based measurement system for circumsolar radiation