This is an excerpt from an article featured in ATMOsphere’s “Clean Cooling for Data Centers 2025” report, which can be downloaded here. ATMOsphere is the publisher of NaturalRefrigerants.com.
In September 2023 Penta Infra broke ground on a new 4.4MW colocation facility in Hamburg located near the city’s airport. The Hamburg colocation facility opened in the first half of 2025 and boasts 2,500m2 (26,909ft2) of IT space.
Six Secon air-cooled propane (R290) chillers were installed on the roof, each with a cooling capacity of 960kW (272TR) and a refrigerant charge of 38kg (84lbs) split across four separate refrigerant circuits. The water for the IT space is cooled to 20°C (68°F) and sent to computer room air-handlers, with the water returning to the chillers at a temperature of 32°C (89.6°F).
The data center has been dubbed “Penta Infra HAM01” by Penta, with Ruben Uijtermerk, Mechanical Engineer at the company, stating that propane was chosen as a refrigerant because “it combines excellent thermodynamic efficiency with a very low GWP, providing high energy performance while maintaining environmental responsibility.”
“Propane is particularly well-suited for medium-capacity applications like our Hamburg data center, offering reliable cooling performance with a proven safety record when installed with proper safety measures,” said Uijtermerk. “Secon’s extensive experience in implementing R290-based systems further ensures that safety and operational risks are minimized, adding confidence to this solution.”
Free cooling capabilities
The chillers at the Penta Infra Hamburg data center feature a master–slave network, with two fully redundant and self-monitoring master controllers. They also come equipped with automatic transfer switches and uninterruptible power supplies for the controllers. Secon’s chillers include free cooling, but due to size limitations they cannot cover as much cooling capacity as the two dry coolers (there are plans to install two more). While separate units, the dry coolers are integrated into the chillers in terms of hydraulics and controls.
Hamburg is located in northern Germany where summer temperatures range from 10 to 36°C (50 to 97°F), and winter temperatures range from −3 to 4°C (27 to 39°F). Thanks to the mild climate, the data center is able to use free cooling for a significant portion of the year. The power supply and control of the free coolers is managed by the chillers, which enables the full cooling capacity to be covered by free cooling. Pre-cooling mode starts at 27°C (80.6°F) and full free cooling is available from 16.5°C (61.7°F).
“Up to 80% of the annual hours can be covered purely by free cooling,” Schadt said. “It’s a decisive factor in achieving a very low PUE value for the data center.”
Pursuing a low PUE
The PUE value for the facility is dictated by the German Energy Efficiency Act (EnEfG), which went into effect in November 2023 and requires all data centers with a connected load of 300kW or more to meet energy efficiency and waste heat requirements. Data centers commissioned before July 1, 2026, must have a PUE of ≤1.5 and a PUE of ≤1.3 by 2030.
“We design according to the requirement in the EnEfG of an annual PUE of 1.2, meaning the hydrocarbon type chiller must be efficient enough to support this,” said Uijtermerk.
The EnEfG also carries requirements to reuse waste heat, but as of 2025 there is no district heating network to connect to. Penta Infra HAM01 has two heat exchangers in the basement that enable it to connect to a district heating network, with the city and Penta Infra engaged in early discussions about a future district heating project.
Uijtermerk said that in sites where district heating network connections are available, Penta sees “increased potential” in using reversible chillers, wherein heat is directly fed into the district heating network from the chiller; this would mitigate the need for dedicated heat pumps, increasing cost-effectiveness and maximizing the heat generating potential.
Neither the EnEfG nor the EU F-gas Regulation broach the issues of HFOs or PFAS. However, Uijtermerk said that Penta more frequently sees natural refrigerants mentioned in client requests for information and requests for proposals.
“There is increased awareness and appraisal by our clients for using natural refrigerants,” said Uijtermerk. “Penta believes that, if practically possible, hydrocarbons are the better choice over synthetic refrigerants.”
