Senior Thermal Engineer

Job Description

The Enphase Energy SST Product Innovation Team sits in the Office of the CTO and is responsible for defining, prototyping, and scaling the next generation of Enphase storage and power systems. We are a fast-moving, multi-disciplinary group on a mission to push the boundaries of energy density, reliability, and system efficiency.

You will be part of thermal solution team for cutting-edge medium-voltage power conversion systems, working side-by-side with power electronics, mechanical, and manufacturing engineers to bring world-class products to life. Your work will directly impact the reliability and performance of systems deployed at scale across the globe.

What You Will Do

• Apply rigorous first-principles thermal analysis: Approach every thermal problem with strong theoretical grounding - deriving analytical models from fundamental heat transfer (conduction, convection, radiation) before committing to simulation or hardware. Use theory to set expectations, bound the solution space, and critically evaluate simulation outputs.
• Decompose complex thermal problems into incremental steps: Break down system-level thermal challenges into discrete, testable sub-problems. Define a clear experiment or analysis for each sub-problem, resolve it completely, and build toward the full solution with confidence at each stage. Document the learning at every step so the team accumulates durable thermal knowledge.
• Design and harvest test results from thermal test vehicles (TTVs): Conceive and construct thermal test vehicles - purpose-built mock-up devices that simulate the thermal behavior of a system without testing the real device. Use TTVs to isolate specific thermal mechanisms (contact resistance, airflow uniformity, cold plate effectiveness, transient response) independent of full product complexity.
• Own end-to-end thermal solution: Lead thermal design from concept through validation for high-power-density power electronics and energy storage enclosures, ensuring junction temperatures, surface temperatures, and coolant conditions meet reliability targets across all operating and ambient environments.
• Design and optimize air-cooled systems: Develop forced-air and natural-convection cooling solutions, including heat sink geometry, fan selection, ducting, airflow channeling, and system-level pressure-drop budgets. Apply CFD tools (Ansys ICEPAK, FloTHERM, SolidWorks Flow Simulation, or Fluent) to model and optimize airflow and thermal resistance.
• Drive thermal analysis and simulation: Build detailed thermal resistance networks and CFD models to predict steady-state and transient temperature profiles. Correlate simulation results with hardware measurements and iterate models to maintain < 5??C prediction accuracy.
• Lead thermal testing and validation: Design and execute thermal characterization test plans using structured thermal test vehicles and incremental experimentation. Build bench setups with thermocouples, RTDs, IR cameras, and data acquisition systems. Analyze results against theoretical predictions, identify failure modes, and drive design improvements with data.
• Define thermal design rules and margins: Establish component-level and system-level thermal budgets, derating curves, and design guidelines. Drive thermal margin reviews as part of the product development process.

Who You Are and What You Bring

• BS, MS, or PhD in Mechanical Engineering, Aerospace Engineering, or closely related field
• Job title and level determined by candidate experience:
• Staff Engineer: BS + 8 yrs | MS + 6 yrs | PhD + 3 yrs: Sr. Staff Engineer: BS + 12 yrs | MS + 8 yrs | PhD + 5 yrs
• Candidates with greater experience are strongly encouraged to apply
• Strong theoretical thermal analysis - required: Demonstrated mastery of fundamental heat transfer: conduction (Fourier's law, spreading resistance, fin analysis), forced and natural convection (Nusselt/Reynolds correlations, boundary layer theory), radiation, and coupled transient analysis. Must be able to derive closed-form estimates before running any simulation and explain discrepancies between theory and measurement from first principles.
• Thermal test vehicle design and execution - required: Proven experience designing thermal test vehicles (TTVs) - mock-up devices that simulate the thermal behavior of a system without testing the real device. Ability to define heater placement, sensor layout, boundary conditions, and test matrix to generate clean, interpretable data. Experience correlating TV test results to analytical models and CFD.
• Structured problem decomposition - required: Ability to decompose a complex, multi-variable thermal problem into a logical sequence of incremental sub-problems, each with a defined hypothesis, experiment, and pass/fail criterion. Skilled at knowing which sub-problem to solve first and how to build toward a system-level solution efficiently.
• Deep expertise in air-cooled thermal design: Proven track record designing forced-air and natural-convection cooling systems for power electronics, including heat sink selection/optimization, fan-curve matching, system impedance curves, and CFD correlation.
• Proficiency with thermal simulation tools: SolidWorks Flow Simulation, Ansys Fluent, or equivalent. Ability to set up, run, and critically interpret CFD and thermal network results.
• Thermal testing and instrumentation: Experience designing thermal test plans, instrumenting hardware with thermocouples and resistance temperature detectors (RTDs), operating IR cameras, and processing thermal data.
• Product design for reliability: Experience designing thermal systems for long-term reliability under thermal cycling, humidity, altitude, and outdoor operating environments.
• Strong CAD proficiency: SolidWorks preferred; used for enclosure geometry, cooling geometry, and integration with the mechanical team.
• Excellent communication skills: Ability to clearly present thermal analyses, test results, and design trade-offs to multi-disciplinary teams and leadership.
• Solution-oriented thinking: Focus on identifying and implementing practical solutions rather than just identifying problems. Ability to quickly assess complex thermal challenges, generate multiple solution paths, and select the most effective approach based on constraints, timeline, and impact.

Additional Desired Skills

• Familiarity with IEC, UL, and IEEE standards for electrical equipment thermal ratings and energy storage systems
• Background in outdoor/field-deployed product thermal design (wide ambient range, solar load, weathering)
• Familiarity with power electronics loss modeling to generate accurate thermal source inputs

Work Location

Austin, TX - Full-time, On-site

The base pay range for this position is $110,000 to $167,000 per year. This salary range may be modified in the future. The successful candidate's starting pay will be determined based on job-related skills, experience, education or training, work location, and market conditions. This position is also eligible for bonus, equity, and benefits.