Ingénieur Thermal Principal (H/F)

As a Lead Thermal Engineer at Fluence, you will spearhead the design, testing, verification, and system integration of industrial liquid chillers and advanced thermal management subsystems for utility-scale Battery Energy Storage Systems (BESS). In this role, you will be the core technical owner ensuring our liquid cooling systems deliver optimal thermal performance, efficiency, reliability, and regulatory compliance.

Key Responsibilities

• Architect, specify, and integrate industrial liquid chillers, active refrigeration loops, pumps, and fluid distribution circuits into utility-scale BESS enclosures.
• Develop, review, and maintain Piping & Instrumentation Diagrams (P&IDs), fluid routing specifications, hydraulic balancing, and chiller specification sheets.
• Establish and validate chiller-to-system communications and control loops utilizing Modbus (TCP/RTU) protocols, including register mapping, telemetry, alarm thresholds, and safety handshakes.
• Design and execute comprehensive thermal validation plans, refrigeration performance protocols (AHRI 550/590), and plumbing/hydraulic pressure and leak tests (ASME B31.3 / B31.5).
• Ensure compliance of chiller subsystems and power electronics/drives with international safety, environmental, and EMC/EMI standards (UL 60335 2-40, IEC 61000 series, FCC Part 15, UL 9540, NFPA 855, ASHRAE 15/34).
• Lead Factory Acceptance Testing (FAT) at contract manufacturer (CM) and supplier sites, acting as the primary engineering authority for validation sign-offs and quality audits.
• Collaborate with cross-functional teams, including mechanical, electrical, firmware/software, safety, and field commissioning, to ensure seamless hardware and controls integration.
• Conduct root cause failure analyses (RCFA) on thermal components during prototyping, qualification, and field operation, driving design improvements and corrective actions.
• Support manufacturing and commissioning teams by troubleshooting thermal, hydraulic, and communication issues in test labs and field deployments.

Required Qualifications & Experience

• Bachelor's or master's degree in Mechanical Engineering, Thermal/Fluid Engineering, Aerospace Engineering, or a related discipline.
• 8+ years of professional engineering experience in liquid chiller design, refrigeration systems, HVAC development, or thermal management in the energy storage, industrial, or power sectors.
• Strong, demonstrated experience in chiller and subcomponent (compressor, condenser, evaporator, expansion valve, etc.) sizing.
• Hands-on experience with SOLKANE, XProps, CoilDesigner, VapCyc, thermodynamic calculation, and similar tools.
• Hands-on proficiency with industrial communication protocols, specifically Modbus (TCP/RTU) register mapping, testing, and troubleshooting.
• In-depth understanding of relevant industry safety, pressure, and testing standards: AHRI 550/590, ASHRAE 15, ASHRAE 34, ASME B31.3, ASME B31.5.
• Practical experience of instrumentation and testing chillers.
• Proven track record leading vendor evaluations, qualification testing, and supplier Factory Acceptance Testing (FAT).
• Excellent communication skills and ability to lead and collaborate effectively within international, multi-disciplinary teams.
• Fluent in English.

Additional Skills

• Experience with utility-scale Battery Energy Storage Systems (BESS) or renewable energy balance of plant (BOP).
• Familiarity with data analysis tools (Python/Visual Basics) and 1D simulation tools (Dymola/MATLAB).
• Demonstrated project management and technical vendor management capabilities.
• A passion for clean energy, decarbonization, and sustainable technologies.
• Fluency in additional languages is a plus.
• Ability and willingness to travel up to 20-30% to testing facilities, supplier sites, and contract manufacturing plants globally.

Our Culture

At Fluence, our culture is the foundation that drives our ambitious growth strategy and fuels our mission to transform the future of energy. Our core cultural pillars empower us to innovate, collaborate, and lead with purpose, ensuring we continue to deliver unparalleled value to our customers and the world.

Unleash Voices

We believe every voice matters. We encourage openness, active listening, and decisive action to create a culture where everyone has the opportunity to contribute to our success. We foster an environment where diverse perspectives are heard and valued, driving innovation and progress.

Customer Fluent

Our customers are at the heart of everything we do. We're committed to delivering exceptional value that exceeds expectations by understanding our customers' needs and adapting swiftly to meet them. Our deep focus on customer satisfaction drives us to continuously improve and innovate.

Infinite Impact

We are committed to creating the impossible. We push boundaries to deliver sustainable, game-changing solutions that shape a brighter, more energy-efficient future for all. Our team is passionate about making a lasting impact that will resonate for generations to come.

All In

We are all in for growth. Our teams are relentlessly focused on identifying and seizing opportunities that propel us forward. We embrace an ownership mindset, pushing ourselves and each other to accelerate progress and create lasting success.