VDemo-Fresnel II – Development of high-temperature stable absorbers and front surface mirrors for atmospheric conditions and experimental evaluation of Fresnel collector components

Participants:

• Fraunhofer ISE

• DLR

• PSE

Contact:

• Gabriel Morin, Fraunhofer Institute for Solar Energy Systems ISE

Funding:

• German Ministry for Environment, Nature Conservation and Nuclear Safety (BMU): 382 t€, PSE: 56 t€

Front surface reflecting mirror coated in sputtering machine (background).

The main aim of this project was the preparation of a linear Fresnel collector power plant module. This entailed a series of materials development tasks and experimental testing of collector com-ponents.
Fraunhofer ISE developed a sputtered air-stable absorber coating that resists up to 450°C with a solar absorptivity of 94% and emissivity of 18%.
The second goal of the project was the development of a front surface reflector to be used in solar tower receivers as well as in secondary concentrators in the linear Fresnel collector. DLR simulated the potential for higher reflectivities and free design parameters (2-axial instead of 1-axial bending of the glass sub-strate).
Furthermore, Fresnel collector components were also expe-rimentally qualified: A receiver erected by SPG was thermally qualified using an electric heater inside the tube. Component stability, temperature distribution and temperature-dependent heat loss were tested for temperatures up to 550°C. The accuracy of different types of slightly bent primary mirrors for Fresnel collectors was determined by flux density measurements.
This project will be followed by a linear Fresnel collector demonstration plant which is currently under construction by MAN Ferrostaal at the Plataforma Solar de Almería, with co-funding of the BMU.