POLYPHEM project: A promising concept of co-generation technology of heat and electricity

Autumn 2022


After more than four years of collaborative research on Concentrated Solar Power (CSP), and particularly through the development of a solar-driven micro gas-turbine technology, the POLYPHEM project had come to an end in August 2022.

POLYPHEM: Small-Scale Solar
Thermal Combined Cycle POLYPHEM is a Horizon 2020 project funded under the Energy programme. Coordinated by CNRS-PROMES, this project was implemented by nine partners from four EU countries.

The particularity of this consortium, which is also its strength, is that it is a public and private partnership. Partners come from both the academic world such as CEALITEN, CIEMAT-PSA, and Fraunhofer ISE, but also business world such as ARRAELA, KAEFER SE, ORCAN ENERGY, AALBORG CSP, and EURONOVIA.

The main objectives of the POLYPHEM project were to improve on the one hand, the performance of smallscale Concentrated Solar Power (CSP) plants and, in the other hand, their flexibility to generate power on demand.

To this end, a new technology was proposed: a solar-driven combined cycle with integrated thermal energy storage. More detail information can be found on the project website.

Impact & applications
Initially, the main expected impact of this project was to enhance the competitiveness of low-carbon energy production systems through the technology developed. The expected progress is a better fitting of electricity generation to variable local needs, an overall conversion efficiency of solar energy into electricity of 18% for an investment cost of less than 5 €/W and a low environmental impact. By 2030, the cost of electricity production targeted by the POLYPHEM technology is 165 €/MWh for an annual direct normal irradiation of 2600 kWh/m2/year (North Africa and Middle East) and 209 €/MWh under 2050 kWh/m2/year (Southern Europe).

In addition to decentralized power generation, other applications are considered for the deployment of this technology used in poly-generation: solar heating and cooling of multifamily buildings, water desalination for small communities, industrial heat production, desalination of seawater or brackish water, etc.

Main results
POLYPHEM partners succeeded in having many specific results despite a major technical issue on the solar receiver. The main achievements are the selection of 2 alloys for the tailor made design of the air-solar receiver, the development and erection of an original TES (Thermal Energy Storage) made of concrete bricks and walls with oil as heat transfer fluid, the assessment of performance with creation of simulation models for each component such as the air/oil RHX (Recovery Heat exchanger) or the ORC (Organic Rankine Cycle), and the testing of the solarised microgas turbine. Finally, the project could bring the technology from TRL3 to TRL4 or TRL5!

As Andreas Poppinghaus from KAEFER SE, member of the Consortium, said "The multinational team of POLYPHEM faced many challenges, among not the least, the global pandemic COVID. However, key targets were reached, and the results are very promising."

POLYPHEM, a promising concept of co-generation technology of heat and electricity
Therefore, the deployment of the technology is strongly considered. Indeed, due to the simplicity of the concept and implementation, large parts of the plant can be produced and erected in the target country as local content. Also, maintenance can be done locally by trained personnel. So large parts of rural areas without proper energy infrastructure can gain power independence without harming the environment by transporting diesel over long distances.

Outcomes of the POLYPHEM project will allow in the short term to reinforce the competitiveness of this new low carbon energy technology, favour its integration in the medium term in the worldwide energy mix and contribute to the mitigation of climate change.

As a way of conclusion of this fruitful collaborative research, relevant reports, deliverables, webinars and scientific publications are available on the official website (https://www.polyphem-project.eu/). Join the POLYPHEM community by following us on social media LinkedIn (https://www.linkedin.com/company/ polyphem/) or Twitter (https://twitter. com/H2020CSP) to stay tuned!


This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement N° 764048.


This project has received funding from the European Union's Horizon 2020 research and innovation programme under Grant Agreement No. 766464.