AHUs Cool the Laser Systems of the World’s Largest Telescope

Extremely Large Telescope in Chile AHUs Cool the Laser Systems of the World’s Largest Telescope

2025-05-21 Source: ebm-papst 2 min Reading Time

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The Extremely Large Telescope (ELT) is currently being built in Chile’s Atacama Desert. The observatory’s goal is to study dark matter, Earthlike planets and extraterrestrial life forms. In the project, 28 FanGrids with 168 RadiPac EC fans are installed in the AHUs for the laser systems for cooling purposes.

Up to eight guiding star laser systems will help the ELT to take sharp images of space with the aid of its 39-meter primary mirror.(Image: ESO/L. Calcada) — Up to eight guiding star laser systems will help the ELT to take sharp images of space with the aid of its 39-meter primary mirror.
(Image: ESO/L. Calcada)

Up to eight guiding star laser systems will be used to ensure that the ELT can take precise images of space. To safeguard their operation, these systems must be supplied around the clock with pure and perfectly temperature-controlled air. OCRAM CLIMA was commissioned to design these highly specialized AHUs and turned to ebm-papst Portugal in search of a highly reliable and efficient solution.

Innovative Solutions for Complex Demands

The conditions of the Cerro Armazones mountain and the telescope itself placed very complex demands on the fan solution. They include the location at an altitude of around 3,000 meters in a region that is subject to frequent earthquakes, fine desert sand and dust, and variable weather conditions. Since the ELT itself is packed with highly sensitive technology, the fan systems must not cause any electronic interference.

A total of 28 FanGrids are installed in the highly specialized AHUs supplied for the ELT by OCRAM. All the RadiPac fans are equipped as standard with active PFC and automatic resonance detection.(Image: ebm-papst) — A total of 28 FanGrids are installed in the highly specialized AHUs supplied for the ELT by OCRAM. All the RadiPac fans are equipped as standard with active PFC and automatic resonance detection.
(Image: ebm-papst)

ebm-papst developed a tailored plug & play solution that integrates all components and minimizes OCRAM’s installation and validation effort. It proposed the use of FanGrids, with six individual EC fans stacked and assembled on top of each other. These redundancies ensure the systems’ greater operational reliability, efficiency and service life.

Technology for the Future

All the FanGrids are equipped with highly efficient RadiPac EC centrifugal fans. These impressed OCRAM with their economical motors and much lower carbon footprints than the AC fans that were originally planned. Due to the requirements, the ebm-papst team made technical modifications to the fans. To protect them from possible damaging vibration, the RadiPac fans are equipped with automatic resonance detection as standard. Thanks to active PFC (power factor correction), ebm-papst was also able to guarantee a maximum value of 5% to meet the ELT’s strict limit value of 10% for current harmonics.

Helping to Research the Universe

In May 2024, the first units were shipped to Chile and assembled by the OCRAM team. On-site measurements are now being performed to validate the plug & play solution. The successful collaboration between OCRAM and ebm-papst shows that we were working at the cutting edge of technology in this project.

Artistic rendering of the ELT: The Extremely Large Telescope is being constructed on Mount Cerro Armazones in the Chilean desert. (Image:ELT concept / ESO/L. Calçada / CC BY 4.0)

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