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Together with HYDAC and ENGIRO — the electric drive specialist within the HYDAC Group — Eberspaecher has developed a comprehensive retrofit solution for Deutsche Bahn that modernizes the air‑conditioning systems of the existing diesel. At the heart of the project lies a decisive shift: replacing traditional refrigerants with environmentally friendly R290.

Since early 2025, Vanessa Fridrich has served as Product Manager at Eberspaecher. Her responsibilities include the series introduction of the new AC135 air‑conditioning units, planning and executing market launch activities, and identifying relevant target groups. By working closely with marketing, sales, and R&D, she ensures that the technical benefits of the product are translated into clear market and customer value. In an interview, she provided valuable insights from the perspective of a key project stakeholder.

Motivation and Project Initiator

Deutsche Bahn Nord actively sought an eco‑friendly alternative to conventional air‑conditioning solutions. As Vanessa Fridrich explains, the inquiry stemmed from the customer’s strong commitment to sustainability and the guiding principle: “We live in a world in which we constantly strive to live and act more sustainably.”

Together with HYDAC, Eberspaecher developed a generator‑based solution for an innovative air‑conditioning system using the natural refrigerant R290.

The project was driven primarily by:

• regulatory requirements such as the Kigali Amendment to the Montreal Protocol — an international agreement to phase down the consumption and production of hydrofluorocarbons (HFCs),
• the need for significant CO₂ reduction,
• and the high global warming potential and rising costs of conventional refrigerants.

In a comparative evaluation of various alternatives — including R744 and R290 — R290 emerged as the most suitable solution, particularly due to its excellent efficiency in air‑conditioning systems, even at higher ambient temperatures.

Market analyses also revealed that buses with combustion engines would remain in service longer than previously expected. The clear conclusion: any solution must be compatible with existing diesel vehicles. Thus, the drive technology-independent retrofit concept was born.

Deutsche Bahn Nord acted as a committed pilot customer, confirming market needs at an early stage. In parallel, the Busworld trade fair served as an important indicator of market potential. There, we were able to present a near-series functional prototype – while effectively showcasing that we already had a major client behind the solution. The clearly defined requirements concerning sustainability, refrigerant transition, and cost efficiency provided a strong basis for customer discussions and generated substantial interest — highlighting the urgency of rapidly developing a series‑ready solution.

From Initial Inquiry to Market Readiness in Record Time

The project began modestly: In early discussions between Deutsche Bahn and Eberspaecher, a system solution involving the R290 HVAC generator quickly began to take shape. After a few iterations and early feasibility assessments, it soon became evident to all parties that the concept was viable and worth pursuing. In this process, HYDAC took on the role of technology consultant and system integrator for Eberspaecher.

We relied deliberately on existing components and our expertise in thermal management to configure a tailored system solution — without having to develop everything from scratch. The proof of concept was completed in record time, followed by an intensive validation phase.

After extensive laboratory testing at HYDAC, the system was commissioned, performance data collected, and motor‑control logic optimized to reliably handle the dynamic load changes of an A/C compressor.

Application tests at the Eberspaecher plant further enabled assessment under realistic and extreme conditions using state‑of‑the‑art climate chambers (up to 45 °C) and bus simulators. The results were clear:

• Improved performance: The R290‑based system delivered noticeably stronger cooling compared to the previous solution.
• Measurable fuel savings: The electric drivetrain reduced fuel consumption.

A Platform Strategy Enables Efficient Global Rollout

What began as a customer‑specific project quickly evolved into a solution with global potential. The system kit addresses two key retrofit markets: buses without air‑conditioning and vehicles equipped with outdated or inefficient systems.

The presentation at Busworld led to a 2-digit number of international inquiries. The reasons behind this interest vary from region to region:

• Mexico: fuel savings are the primary motivation.
• Europe: regulatory requirements and the use of natural refrigerants are key.

Vanessa Fridrich highlights the versatility of the approach: “Every customer faces a unique challenge — and this one solution is flexible enough to address multiple problems at once.” 

To accommodate the wide variety of bus models, we pursue a platform strategy with currently no more than two kit variants. HYDAC’s core components — generator, control unit, and condenser box — remain standardized.

For HYDAC and ENGIRO, this project marks another step in the rollout of our fields application: versatile component and system partner in the field of electrification. With fast-to-implement engineering solutions and proven standard components, we create clear added value – especially for hybrid applications combining diesel and electric drives.