Stack Testing Engineer

Twelve is pioneering a new industrial era with carbon transformation. We use electrochemistry to turn CO2 into critical products—fuels, chemicals, and materials—that today rely on fossil fuels. Our mission: to fundamentally change how the world makes its essential goods by transforming CO2 from a liability into a resource, building resilient, fossil-free supply chains, and advancing next-generation industry.

Overview

Twelve is a carbon transformation company developing proprietary electrochemical systems that convert carbon dioxide into high-value chemical feedstocks and fuels. The Stack Testing Engineer role sits at the critical juncture between R&D and pilot plant scale-up, supporting the integration and validation of stack-level innovations into operational platforms. This position is responsible for executing structured test protocols, driving data-driven system diagnostics and contributing to the technical roadmap required for commercial electrolyzer deployment.

What You Will Do

The Stack Testing Engineer is accountable for the safe commissioning, operation, and troubleshooting of subscale and full-scale electrolyzer stacks. The role involves detailed process monitoring, real-time data acquisition, and root-cause analysis to validate electrochemical performance and inform stack design iteration. The engineer is expected to work across disciplines—particularly with electrochemistry, reactor engineering, and controls teams—to ensure test integrity, capture failure modes, and enable continuous improvement. Execution of the Management of Change (MOC) process and adherence to safety engineering standards are essential responsibilities.

Key Roles and Responsibilities

• Commission and operate stack test stands, including integration of sensors, power electronics, gas and liquid handling systems, and data acquisition interfaces.

• Develop and execute experimental test matrices that quantify performance metrics such as polarization behavior, current efficiency, pressure drop, gas evolution, and degradation rates.

• Collaborate with materials science, process development, and controls engineering teams to characterize operating envelopes and define optimal steady-state and transient conditions.

• Analyze time-series and condition-based data to diagnose system inefficiencies and recommend modifications to hardware, controls, or operating procedures.

• Author and maintain detailed technical documentation including process flow diagrams (PFDs), piping and instrumentation diagrams (P&IDs), operating procedures, risk assessments, and test reports.

• Lead troubleshooting and design-of-experiments (DOE) efforts to de-risk scale-up and inform system-wide modifications.

• Support safety audits, pre-startup safety reviews (PSSRs), and execution of MOC packages to ensure testing aligns with Twelve’s process safety management framework

General Accountability

This role requires technical ownership of electrolyzer stack testing infrastructure and performance characterization. The Stack Testing Engineer will be accountable for maintaining experimental integrity, ensuring high uptime for testing equipment, and executing test runs that generate statistically significant datasets. The engineer will serve as the primary technical interface between development teams and testing operations, enabling the translation of lab-scale discoveries into scalable engineering solutions with verified operational readiness.

Review of Major Deliverables Required by Stack Testing Engineer Include, but are not Limited to the Following:

• Validated operating procedures for each stack configuration and test platform

• MOC documentation for hardware and control system changes

• Test summary reports capturing experimental conditions, key metrics (e.g., voltage/current profiles, Faradaic efficiency), and failure analyses

• Weekly KPI dashboards summarizing uptime, throughput, degradation rates, and anomaly trends

• Root cause investigation reports and recommended corrective actions

• Detailed feedback to inform mechanical, electrical, and process design modifications

Development of Stack Testing Engineering Deliverables

The Stack Testing Engineer will be responsible for developing comprehensive engineering documentation supporting system design validation and operational readiness. This includes process schematics, mass and energy balances, test protocols, validation plans, control narratives, and calibration procedures. Deliverables are expected to meet engineering quality standards required for auditability and traceability throughou