Mechanical Design Engineer III

Catalyzing a cleaner future.

ESS is a globally recognized leader in sustainable energy storage and is consistently identified as one of the most innovative and exciting technology players in energy storage. It is poised to be one of the fastest growing energy technology companies in the world, with projects already across 4 continents and an upcoming public offering. The ESS vision is about enabling the decarbonization of the grid by enabling us to achieve up to 100% of our electricity from clean, sustainable renewable energy.

These are ambitious goals, and we are pursuing them with passion. At ESS, we are leading the energy transition, creating the sustainable energy solutions of the future to help individuals, businesses and communities change energy into lasting value.

ESS is seeking a dynamic Mechanical Design Engineer with a strong background in mechanical design, thermodynamics, fluid flow and structural analysis. The role will focus on R&D of ESS's advanced battery power module technology to ensure performance, reliability and cost. The deliverables will require significant input into the mechanical design: structural and fluidic analysis, testing and validation, prototyping, specification creation and implementation, quality support, etc.

The ideal candidate will have a passion for sustainability and the environment, will thrive in a fast-paced entrepreneurial setting, be self-motivated, and have an interest in disruptive, cutting-edge technology.

What you'll do at ESS:

• Senior contributor to the mechanical design of stack and subsystem hardware (manifolds, flow fields, plates, frames, enclosures, seals) using 3D CAD and rigorous design control (models, drawings, specs, BOMs; GD&T).
• Analyze and optimize thermal/fluid performance and structural integrity (pressure/temperature/vibration/thermal cycling) using FEA/CFD. Translate insights into robust design updates.
• Engineer for manufacturability and reliability (DFM/DFA/DFR) across casting, machining, plastics (injection molding, extrusion, plastics welding), and sealing processes (welding, adhesives, gaskets).
• Select materials compatible with electrolytes and corrosive environments; address creep, fatigue, and stress-relaxation mechanisms with appropriate safety margins and life predictions.
• Correlate models to test: develop validation plans, define test articles/fixtures, analyze data, close the loop to simulation, and drive root-cause and corrective actions.
• Collaborate across all engineering and supply chain teams to convert performance targets into durable, cost-effective designs ready for production.
• Continuously improve cost, reliability, and serviceability while maintaining safety, compliance, and quality standards.

What you bring to the table:

Minimum Requirements

• B.S. in Mechanical Engineering (or related).
• 5+ years of experience in mechanical design and analysis of complex fluid or electrochemical systems (or equivalent combination of graduate and industry experience).
• Proficiency in 3D CAD (Inventor, Solid Works, or equivalent) for parametric design, detailed drawings, and BOMs.
• Strong foundation in thermodynamics, fluid mechanics, and solid mechanics, with hands-on FEA/CFD and tolerance stack-ups.
• Developed detailed engineering drawings using GD&T principles per ASME Y14.5, incorporating a strong understanding of quality inspection methods to accurately define and verify critical-to-function (CTF) and critical-to-quality (CTQ) features.
• Experience designing for corrosive or reactive fluids and hermetic sealing (welds, adhesives, gaskets).
• Track record of cross-functional execution from concept to validated hardware (proto → pilot → production).
• Clear, concise communicator; self-directed; able to juggle multiple design work streams.
• Ability to lift 50 lbs. unassisted
• Ability to follow job required Standards and Safety Protocols, per pre-defined processes
• Must be able to wear Personal Protection Equipment according to OSHA rules and regulations

We'd love to see

• M.S. in Mechanical, Materials Science, Energy Systems, or Chemical Engineering.
• Experience in battery, fuel cell, or power-generation system design.
• Demonstrated multiphysics experience…