PI 124-13 2013-11-19

Rexroth technology in action: Let there be light in Norway

Thanks to these XXL mirrors, the Norwegian winter sun is also shining in Rjukan.

This winter, the residents of the Norwegian town of Rjukan will see sunlight in the winter months for the first time. The city is located in a valley which is so narrow that the approximately 3,500 residents have no direct sunlight from October to March. As of this year, three large movable mirrors on the opposite slope have been lighting up the central marketplace with reflected sunlight. The drive and control solution for the adjustment mechanism as well as the remote monitor have been supplied by Bosch Rexroth.

The city of Rjukan came into being in 1913 in Norway as Vermork, the largest hydroelectric power station in the world at the time, was constructed about 180 kilometers west of Oslo. The biggest challenge at the time was to provide as much protection as possible from the harsh mountain climate. In doing so, the city's founders accepted the fact that no sunlight would reach it over the entire winter season.

In time for the city’s 100th anniversary, the central square will now be illuminated in the dark season by sunlight for the first time. For this purpose, the Solar Tower Systems (STS) GmbH, Starnberg, constructed three movable mirrors on the mountain slope, about 500 feet above the city. Each of the 17 square meter, 500 kilogram heliostats follow the sun's path via computer control. A Rexroth control unit calculates the position of the sun and provides the optimum angle of the heliostats. Electric linear drives move the mirrors with a high degree of precision throughout the day in the appropriate position so that the sun rays illuminate the given area. The biggest challenge in this process is the harsh climate. In the mountains, there is often a wind force of 12, and gale-force winds of more than 140 kilometers per hour tug at the mirrors. The drives have to hold them in position reliably, even under these conditions.

Right next to the mirrors, the control unit and two webcams are housed securely in a small cabin. The autonomous power supply of the entire system occurs in a decentralized manner through solar panels, a small wind turbine and high-performance batteries in which the electricity is temporarily stored. Wind and temperature measurements ensure that the heliostats automatically move into a protective position in poor weather conditions.

The system on the mountain is linked via a wireless connection to a computer at City Hall. STS Starnberg and Bosch Rexroth of Lohr am Main can access this computer over the Internet for maintenance purposes and read all the necessary data of the control and drive system. The system manufacturer Solar Tower Systems (STS) is an innovative company for the construction of solar power plants with movable mirrors.

Economical, precise, safe, and energy efficient: drive and control technology from Bosch Rexroth moves machines and systems of any size. The company bundles global application experience in the market segments of Mobile Applications, Machinery Applications and Engineering, Factory Automation, and Renewable Energies to develop innovative components as well as tailored system solutions and services. Bosch Rexroth offers its customers hydraulics, electric drives and controls, pneumatics, gear technology, and linear motion and assembly technology all from one source. With locations in over 80 countries, more than 37,500 associates generated sales revenue of approximately 6.5 billion euros in 2012.

To learn more, please visit

The Bosch Group is a leading global supplier of technology and services. In fiscal 2012, its roughly 306,000 associates generated sales of 52.5 billion euros. Since the beginning of 2013, its operations have been divided into four business sectors: Automotive Technology, Industrial Technology, Consumer Goods, and Energy and Building Technology. The Bosch Group comprises Robert Bosch GmbH and its roughly 360 subsidiaries and regional companies in some 50 countries. If its sales and service partners are included, then Bosch is represented in roughly 150 countries. This worldwide development, manufacturing, and sales network is the foundation for further growth. Bosch spent some 4.8 billion euros for research and development in 2012, and applied for nearly 4,800 patents worldwide. The Bosch Group’s products and services are designed to fascinate, and to improve the quality of life by providing solutions which are both innovative and beneficial. In this way, the company offers technology worldwide that is “Invented for life.”

Additional information is available online at and


Search press releases


Jana Benzinger
Maria-Theresien-Straße 23
97816 Lohr am Main
Phone: +49 9352 18-1589