news / 2017-07-20

New heliostat concentrates the sun’s power

Mutual shading is less pronounced with pentagonal heliostats than with rectangular ones (Source: sbp sonne GmbH)

Heliostats are mirrors that bundle sunlight in solar tower power plants and direct it to the central receiver. This is situated at the top of the solar tower. Engineers have now developed a new geometric shape for heliostats with a pentagonal mirror. These are controlled by new software. Five of these new heliostats are currently undergoing practical testing on a test field in Jülich.

The heliostats reflect the sunlight onto the receiver at the top of the solar tower. (Source: DLR)

Pentagonal mirrors are closer to the geometrically ideal circular shape and, in particular, offer manufacturing advantages. For example, off-cuts are avoided, thus reducing the amount of production waste. In addition, pentagonal mirrors produce less mutual shading than the usual quadrangular ones. Two aspects are important in terms of the arrangement of the mirrors: the receivers need to be irradiated as uniformly as possible and should be erected as close to the tower as possible, but without mutually shading one other. Since the local topography has a considerable influence, the arrangement of the heliostats needs to be specifically calculated for each power plant project.


The new software controls the alignment of the mirrors more accurately than previous versions. The new control system can take into account the inclination of the axes, deformations caused by the weight of the mirrors and changes in the drive.


Five new “Stellio” heliostats are currently installed at the solar thermal power plant in Jülich. One of them is integrated into the “Helitep” test platform. The aim of the investigations is to determine the influence of wind, temperature and gravity on the heliostats as well as to measure the tracking accuracy and the optical quality.

The receiver: Focussed on by the mirrors

Solar tower power plants consist of a central, 50 170 m high tower construction with an irradiation absorber (receiver) at the top. A field of mirrors (heliostats) on an equal level are aligned towards this. These can track the sun and focus the light by 500 1000 fold on a target surface of the receiver. The heat generated there heats a heat transfer medium. Depending on the technology used, temperatures between 300 and 1,100 °C are generated.

Projects currently being funded

Project management

Heliostatdesign, Tower construction
sbp sonne gmbh
70197 Stuttgart