German engineers have developed an innovative concept of a solar tower power plant that improves efficiency and reduces cost.
The CentRec system developed by the German Aerospace Centre (DLR) uses minuscule ceramic particles to transfer heat from the power plant’s receiver to a steam turbine.
The ceramic particles can withstand considerably higher temperatures - up to 1,000 degrees Celsius - than liquid salts currently used as heat transfer agents in solar tower power plants.
"Ceramic particles enable power station operators to work at higher process temperatures of between 600 and 800 degrees Celsius and achieve a higher level of efficiency in the power generation process," said Reiner Buck, head of the Department of Point Focussing Systems at the DLR Institute of Solar Research, who led the project.
The ceramic particles form a part of the so called receiver – the part of a solar tower power plant where solar rays are focused using numerous moving mirrors.
Inside the receiver is a rotating drum filled with the ceramic particles, which are held inside by centrifugal force until they become hot enough to drive the plant’s steam turbine. After being heated up by the focused solar radiation, the particles fall out of the washing-machine-drum-shaped receiver, which is pointing downwards, into thermally insulated containers. There, the heated particles can be used either for immediate power generation or stored for later use for example after sunset, sealed inside the insulated containers.
"The rotation speed of the drum enables us to control the period of time that the particles spend in the receiver, and so their temperature when they leave it – regardless of the process the heat energy is to be used for," Buck said.
The researchers say low component costs of the system are one of its major strengths. The team believes the technology could also be used in industries working with high-temperature processes.
A prototype receiver with a capacity of 10kW has been tested in a high-flux solar furnace at DLR’s facilities in Cologne, Germany. The researchers plant to perform further tests of the technology using a solar tower in Jülich, increasing the receivers output to 500kW.