Mechanical Engineering Intern

Fourth Power is commercializing the next generation of peak power: a utility-scale thermal energy storage system built to replace aging gas peaker plants with clean, dispatchable capacity across the multi-day durations that are increasingly defining grid stress. The system stores electricity as heat in carbon blocks at temperatures up to 2,400°C, then converts that heat directly into electricity using thermophotovoltaic (TPV) cells, dispatching power to the grid in under 10 seconds. Because the system carries no fuel to buy and no exposure to price volatility, it delivers a lower lifetime cost than building a new gas plant, with a power density high enough to fit 100 MW on a single acre. Spun out of MIT and backed by Breakthrough Energy Ventures, DCVC, and Munich Re Ventures, Fourth Power has raised $45 million and is building a commercial-scale facility in Bedford.

Fourth Power has a culture of teamwork, continuous innovation based on first principles, andrelentlessness in tackling challenging problems. Fourth Power is looking for highly skilled and motivated individuals who share our passion for mitigating climate change.

Job Description

We are seeking an Intern to join Fourth Power’s Engineering team to support testing and design optimization of key graphite components that comprise our high temperature energy storage system. If you are a student studying mechanical engineering, who enjoys hands-on work and are comfortable in a lab/test environment, we encourage you to apply!

This internship is for the Fall 2026 term and will run approximately Sep thru Dec 2026.

Job Type: Internship

Job Location: Bedford, MA and Middleton, MA

Your Role

• Assist with experimental setup, execution, and optimization

• Support joint design and mechanical testing apparatuses

Qualifications

• Basic experience with CAD (SolidWorks or similar)

• Familiarity with Microsoft Office (PowerPoint/Excel)

• Background in heat transfer, thermodynamics, or thermochemical systems

• Experience with or interest in vacuum and/or pressurized systems

• Exposure to simulation tools (e.g., ANSYS)

• Excellent organizational skills, attention to detail, and ability to work independently in a fast-paced environment.

• Strong communication skills to effectively collaborate with fellow engineers and technicians.