Stellio Heliostat – the state-of-the-art Concentrating Solar Power (CSP)

© Filmfabrik Schwaben
Solar 23.04.2015

Development History

schlaich bergermann partner´s sbp sonne gmbh are consulting engineers and technology developers in the field of Concentrating Solar Power (CSP). Stellio, the latest heliostat design developed by sbp, targets long-term cost-reduction and improved performance, especially for large power plants. Our team focuses on generating solar energy on a commercial scale and relies on the experience of having designed and built solar power plants and collector fields for more than 25 years, having pioneered technologies and operational frameworks globally.

Stellio was elaborated for and in collaboration with the South African company SASOL Technology for the South African market and site conditions. However, SASOL withdrew from the project and sbp formed a partnership with Masermic and Ingemetal Solar to advance the techno-economic concepts formulated to a prototype and a series design. The group has a combined extensive know-how based on over forty years of international experience in all existing CSP technologies and over 600 operating MW of CSP plants designed, manufactured, built or commissioned worldwide.

Stellio achieved technological innovations that surpassed expectations. The engineering design study aimed to minimize the Levelised Cost of Energy (LCoE), and the resulting design applied these innovations with the existing manufacturing technology to optimize optical quality close to the theoretical limit simultaneously   resulting in an optimized cost/performance ratio by a cost effective structural design. The drive and control systems revolutionize existing technologies resulting in unparalleled tracking quality at the lowest cost.

  • Image of the sun on a tower target
    Image of the sun on a tower target
  • Stellio heliostat aiming at target at 400 m distance
    Stellio heliostat aiming at target at 400 m distance

Three significant innovations are realized within the Stellio heliostat design

Reduced costs by sloped drive axis and dedicated control software
By changing tracking axes orientation to suit the yearly sun path using mathematical strategies, a sloped drive axis configuration was developed. This special arrangement in the drive system allows the use of cost-efficient off-the-shelf linear actuators. The drive system can self-calibrate using intelligent software to compensate tolerancesas well as self-weight deflections and foundation behavior. This control strategy enables reduction in size of structural components, thus significantly saving on steel and foundation costs without suffering performance losses.

Pentagon shaped Concentrator
The Stellio’s size (47.5 m²) and its compact round-like form are a balanced design to reduce cost and improve performance. The nearly circular concentrator minimizes shading and blocking, and can be manufactured very precisely through a high-precision jig. The design features off-the-shelf glass panels and an assembling process doing away with costly pre-manufactured facets. The pentagonal shape and the appropriate size offers very low astigmatism optics, and the central-symmetric structural system provides better optics by higher stiffness with less material, greater evenness of deflection and lower wind excitation.

Unprecedented optical quality
The advancement in heliostat technology by the introduction of the slope drive and intelligent control systems, together with the new central symmetrical concentrator design, all of which derived from detailed techno-economical studies, resulted in unprecedented optical precision for a heliostat of commercially significant size, as confirmed by independent international experts. An indication of cost savings obtained through this advanced technology is observed in the solar field costs which were reduced close to 100 Euro/m² meaning a LCoE reduction by over 20 percent (15 percent heliostat cost reduction and five percent required reflective area reduction due to higher efficiency) compared to today’s most competitive heliostat design.

The video shows a time lapse of the sun image on a tower target reflected by Stellio heliostat that demonstrates the accuracy with which the sharp image of the sun remains at the 12 m x 12 m target throughout the day.

The Stellio Group Partners

sbp sonne gmbh: Led the development of the technology from initial studies through series production design.
Ingemetal Solar: CSP steel experts supporting the design and cost control of the structural framework, responsible for the assembly and erection procedures.
Masermic: Experts in solar and automotive control development and manufacturing, responsible for developing the control and power supply strategy.

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