Catching the sun

Stellio 2.0

‘Achieving the 2050 goal’ from our previous edition, explained the pressing need to accelerate the development and deployment of advanced clean energy technologies to address the global challenges of energy and sustainable development. The possible contribution of thermo solar energy was featured.

stellio-2.0-1With the rising demand for cost efficient solar fields, many smart technologies are being researched and developed. The standard design of a parabolic trough collector or rectangular mirrors that rotate vertically to follow the sun‘s path, are now the focus of further development.

Stellio – Award winning Innovation

One research programme has resulted in the design of a new heliostat developed by sbp (schlaich bergermann partner) in Germany. This incorporates a pentagonal concentrator mirror combined with a low cost linear drive and new control software.

Four significant innovations were implemented with the Stellio Heliostat design: a stiff, symmetrical structure made of hot dip galvanized steel and “umbrella-like” galvanized support structure which is characterized by higher stiffness and smaller deformations and less vibration by wind loading reduced costs due to inclined drive axles and special control software five-fold concentrator shape excellent optical quality – the mirrors consist of silver plated 4 mm solar glass.

The developers used inclined drive axles for the new ‘Stellio’ heliostat.

“Thanks to the clever arrangement of the axes, a linear drive is sufficient for both the horizontal and vertical axis. This is more cost-effective than a rotary drive, which is often used in the vertical axis to enable a 360 degree pan,”

explains Dr Gerhard Weinrebe, a member of the senior management at sbp, the Stuttgart-based engineering office responsible for the project management. Combined with the intelligent control system, this makes it possible to save on steel and foundation costs.

The move away from the standard heliostat shapes also had an important impact on the efficiency of the new design. Weinrebe explains: “Actually, a circular shape is optimal. However, mirrors are manufactured in bands. This makes it very complex and costly to produce a circular heliostat, and there are a lot of waste offcuts. For this reason, a ‘quasi-circular’ shape provides the optimal solution.”

Other possible efficiency benefits of the new design are that the mutual shading caused by pentagonal heliostats is less than with the rectangular models. A lighter design also aids initial installation and adjustments that need to be made on site. Mirror arrangement needs to be recalculated for each power plant project due to topography and the mirrors must be arranged so that the receiver is uniformly irradiated and the heliostats need to be positioned as close as possible to the tower but not mutually shading one another.

Five Stellio models will be installed on site of the experimental solar thermal power plant in Jülich, one of them on the new ‘Helitep’ test platform. Here it will be possible to investigate, for example, the influence of external loads on the heliostats such as wind, temperature and gravity. In addition, the scientists will be able to test the optical quality and the tracking accuracy.

If implemented, Stellio system can reduce electricity production costs by more than 20%, 15% from the structual design and 5% by the reduction of the mirror surface due to the higher efficiency of the system. Stellio was awarded the SolarPaces Technology Innovation Award.

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Architect: sbp – schlaich bergermann partner

Image: sbp – schlaich bergermann partner

Posted on February 1, 2018 by Galvanizers Association

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