Surpassing Astronomical Challenges: FanGrid Wind Walls Ensure Stable Operation of Space Telescopes
09/01/2025
Signs of life outside the solar system, the mysteries of the first galaxies, the unexplored "dark side" of the universe... The Extremely Large Telescope (ELT) in Chile, with its massive 39-meter diameter mirror, will observe space, potentially revealing new discoveries about the evolution of all things, starting in 2028. The laser system plays a crucial role in this process, and highly specialized air handling equipment provided by OCRAM CLIMA provides cooling support for the laser system. Within these air handling units are 28 ebm-papst FanGrid wind wall systems.
Challenges Facing the Extremely Large Telescope
Cerro Armazones, located in northern Chile, rises above 3,000 meters and boasts over 300 cloudless nights each year, with clear skies and a dazzling starry sky. The air is cold and dry, and there is no light pollution from cities or other sources within a radius of over 100 kilometers, making it an ideal location for the Extremely Large Telescope (ELT). However, fine desert dust poses a potential threat to the telescope's delicate equipment, and the significant temperature swings between day and night also complicate operations. Furthermore, Chile is one of the most seismically active regions in the world, meaning the Extremely Large Telescope (ELT) must remain stable in a sometimes unstable geological environment.
Ensuring the stable operation of the Extremely Large Telescope is therefore a key priority. Even the slightest air turbulence within the telescope's dome could distort measurement data. Therefore, one safety measure involves adjusting the internal dome temperature to match the external ambient temperature in the hours before the dome's doors are opened, ensuring a stable observing environment.
AHU for the Laser Guide Star System
When the dome is open, a laser system directs its beam into the night sky to create up to eight artificial guide stars, which the adaptive optics system uses to measure atmospheric turbulence and apply necessary corrections. The images produced by the ELT will be 16 times sharper than those produced by the Hubble Space Telescope. For 25 years, this Portuguese company has specialized in customizing specialized air handling units (AHUs) for demanding applications, such as the ELT in Chile.
Behind the scenes, a total of 46 air handling units (AHUs) designed by Ocram continuously provide a constant supply of clean air. This air is conditioned to the ideal temperature for cooling the laser system—and although invisible to the naked eye, it is crucial. Even the slightest temperature fluctuation or traces of contaminants, such as dust particles, can significantly disrupt the ELT researchers' observations.
As a result, the telescope places extremely complex and stringent demands on the ventilation system and its components, such as fans. First and foremost is the instrument's location. Even at an altitude of 3,000 meters, these units must operate efficiently and reliably to ensure accurate output and the necessary air pressure. Furthermore, their performance cannot be compromised by earthquakes or desert dust clogging the filters.
Second is the ELT itself. These ventilation systems operate in an extreme environment and contain extremely sensitive electronics and sensors. Under all circumstances, they must provide absolutely stable performance to support the telescope's operations.
A Highly Specialized Plug-and-Play Solution
Designing such an unusual, high-end air handling unit (AHU) was fraught with challenges, including validation, simulations, numerous spreadsheets, and stakeholders from various countries. Developing the initial fan solution was equally complex. "The fan has additional components, such as external capacitors, which makes the wiring more complex," explained Marco Lopes, CEO of Ocram. "Each additional component in the system introduces new risks and challenges. We wanted to find a solution that would simplify our work, so we contacted ebm-papst Portugal."
Ocram outlined the requirements for the solution: primarily, technical requirements such as earthquake resistance, high-altitude adaptability, and absolute reliability, along with strict delivery schedules and a high cost-effectiveness. "This isn't a project you encounter every day," said Nuno Pires, Managing Director of ebm-papst Portugal. "But we were able to mobilize all our engineering capabilities, which is why we took on this challenge." ”
With support from its headquarters in Mülfingen, Germany, ebm-papst has assembled a small and flexible team. “Instead of providing a collection of parts for customers to assemble themselves, we offer a complete plug-and-play solution,” explained Nuno Pires. “This solution comes with all the necessary components, and the customer doesn't need to perform any additional installation work.” Active PFC and Automatic Resonance Detection
The solution involves integrating capacitors into the wind turbines. To ensure effective protection of ELT's technical instruments, all turbines are equipped with active PFC to meet stringent current harmonic limits (up to 10%). Simulations indicate actual values are significantly below this limit, reaching a maximum of 5%. To ensure system performance and operational reliability, the team designed a FanGrid wind wall consisting of six EC wind turbines. If one turbine fails, the remaining five can still provide the necessary output. "We also equipped these turbines with additional protection against possible resonance or seismic activity," said Nuno Pires.
The ELT is equipped with 28 similar FanGrid wind wall units. "The performance of ebm-papst is impressive," said Marco Lopes. "The excellent performance of this solution has enabled us to switch from our original large AC wind turbines to a smaller number of EC wind turbines."
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