Junior Simulation Engineer

ON.energy is building the backbone of energy and AI infrastructure powering grid-safe data centers and mission-critical facilities. The company supplies and operates hyperscale power systems that solve the toughest resilience challenges, delivering custom solutions for AI data centers, mission-critical facilities, and front-of-the-meter assets. ON recently announced a 5GW partnership, with 3GW currently under construction across multiple hyperscale data center campuses. With patented technology and proprietary software, ON.energy develops projects worldwide that set new benchmarks for resilience.

At ON.energy, the Simulation Engineer for Battery Energy Storage Systems (BESS) is responsible for building, running, and validating simulation environments that ensure our energy management software performs correctly before it ever touches real hardware. This is a simulation-first role where the primary deliverables are high-fidelity Software-in-the-Loop (SIL) and Hardware-in-the-Loop (HIL) test environments that give our engineering teams confidence in every algorithm, control loop, and protection function we deploy. 

The ideal candidate is an early-career engineer with a solid foundation in dynamic systems, power electronics, or control theory, and a hands-on curiosity for building models that accurately reflect real BESS behavior. This role offers direct mentorship from senior R&D engineers and access to industry-leading real-time simulation hardware. 

SIL Simulation & Validation 

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• Develop and maintain Software-in-the-Loop (SIL) environments in MATLAB/Simulink to validate energy management algorithms, protection logic, and control strategies prior to hardware integration. 
  
• Build high-fidelity battery system models in Simulink — including cell electrochemistry, thermal dynamics, State of Charge (SoC), and State of Health (SoH) — and continuously improve model fidelity against measured data. 
  
• Design and execute automated regression test suites in MATLAB to verify algorithm correctness across operating modes, edge cases, and fault scenarios. 
  
• Analyze simulation outputs, document findings, and communicate results clearly to the broader engineering team. 
  

 HIL Testing & Integration 

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• Support the setup, configuration, and operation of Hardware-in-the-Loop (HIL) test environments, interfacing real EMS and BMS hardware with real-time simulation platforms. 
  
• Establish reliable communication between hardware controllers and simulation environments over industrial protocols such as CAN, Modbus, DNP3, or IEC 61850. 
  
• Execute functional, edge-case, and fault-injection test campaigns against EMS control logic, documenting pass/fail results and root-cause analyses. 
  
• Assist in debugging hardware-software communication issues and contribute to the continuous improvement of the HIL test infrastructure. 
  

 Model Development & Algorithm Support 

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• Collaborate with senior engineers to develop and refine Simulink models of battery behavior, inverter dynamics, and grid interaction for use across SIL and HIL environments. 
  
• Assist in prototyping energy management strategies including peak shaving, frequency regulation, and charge/discharge optimization — running simulation campaigns to evaluate performance. 
  
• Contribute to model-based design workflows in Simulink, supporting automatic code generation and deployment pipelines. 
  

 Documentation & Collaboration 

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• Maintain detailed technical documentation: test plans, test reports, model specifications, and simulation environment setup guides. 
  
• Participate in design reviews and contribute to internal knowledge-sharing and lessons-learned sessions. 
  
• Work cross-functionally with hardware, software, controls, and field engineering teams throughout the product development lifecycle. 
  

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• Entry-Level, 0–2 years of experience
  
• Hands-on experience with MATLAB and Simulink for model-based design and system simulation. Coursework, capstone, or internship experience is accepted.  
  
• Demonstrated understanding of Software-in-the-Loop and Hardware-in-the-Loop testing methodologies — what they validate, when to use each, and how they fit into a V-model development process.  
  
• Foundational knowledge of battery systems, power electronics, or energy storage technologies. Familiarity with SoC, SoH, and basic BMS functionality.  
  
• Coursework or project experience in control theory, embedded systems, or mechatronics. Ability to interpret and validate control logic behavior in simulation.  
  
• Ability to