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Small ceramic particles make the difference

The centrifugal receiver CentRec^® is designed to heat ceramic particles to temperatures up to 1,000°C. It is mounted on a tower and is irradiated by solar radiation concentrated by a heliostat field.

SOLAR RECEIVER OF THE NEXT GENERATION (Video)

Ceramic particles in the spin cyle: Where sunlight is turned into high temperature heat

The central part of the receiver is a rotating cylinder with an aperture opening where the concentrated radiation enters. Through its rotation and under the influence of gravitational and centrifugal forces the particles are pressed against the cylinder wall and move slowly downwards. The speed of the downwards movement varies according to the rotation speed of the chamber. During this movement the dark particles absorb the solar radiation directly and get heated. The hot particles exit the rotating cylinder near the aperture and are transported to a storage container.

During solar radiation, particles from the cold storage are lifted up the tower and are heated in the receiver to the desired temperature. The hot particles are then put into the hot storage.

Advantages of using ceramic particles (e. g. bauxite spheres of about 1 mm diameter):

• Particles can be heated up to 1,000°C
• Particles do not show freezing problems (as molten salts do)
• Particles are cheap: particles are used in process industry in huge quantities, and are mass produced
• Particles are dark: the particles can be used to absorb the solar radiation directly
• Particles are inert and environmentally friendly

Schematic representation of a solar tower plant with ceramic particle receiver. Pictures: DLR (CC-By 3.0)

When heat is required, i.e. for power production via a steam, a CO₂ cycle or for process heat, hot particles are transported to the heat exchanger and are cooled down while transferring the stored solar heat to the process. The particles are then stored in the cold storage.

The sizing of the system components can be adapted to the user demand. With an appropriately sized heliostat field and receiver, the process can be supplied around the clock with solar heat. Energy supply is also not affected by cloud passages. In addition, a fossil or electric particle heater can ensure full availability and/or storage charging with cheap excess electricity.

System successfully tested in DLR's Juelich Solar Tower

A 2.5 MW_th prototype of the receiver has been successfully developed by DLR and tested in 2018 under solar conditions at the Juelich Solar Power Tower, demonstrating receiver outlet temperatures of up to 965°C.