---
title: 'Senior Mechanical Engineer - Thermal & Fluids Systems at Critical Energy'
canonical: 'https://feeny.ai/job/senior-mechanical-engineer-thermal-fluids-systems-critical-energy-hawthorne-4192wgz9ham7'
type: 'job'
last_seen: '2026-11-09'
---

# Senior Mechanical Engineer - Thermal & Fluids Systems at Critical Energy

- **Company:** Critical Energy
- **Location:** Hawthorne, CA
- **Compensation:** $140k–$200k
- **Employment:** full-time
- **Work type:** onsite
- **Posted:** 2026-04-21
- **Last confirmed live:** 2026-11-09
- **Apply:** https://jobs.ashbyhq.com/critical-energy/3aec2249-e6b9-49e7-8c03-abec25039981

## Job description

Company Description: Critical Energy is an innovative, early-stage, venture-backed cleantech company on a mission to accelerate the global energy transition through abundant, low-cost clean energy. Founded by an ex-SpaceX engineer, Critical Energy designs and manufactures factory-built, modular power plants. These rapidly deployable systems convert heat into electricity using a closed-loop thermodynamic cycle and can be installed in just weeks. Critical Energy’s technology delivers high-efficiency, 24/7 power for geothermal applications and waste heat recovery (including from data center gas turbines), making clean energy practical and cost-effective for demanding sectors like AI hyperscalers and data centers. Backed by top climate and technology investors, Critical Energy is scaling rapidly.

Our Mission: To build an abundant, low-cost, 100% clean energy future through groundbreaking geothermal innovation. We are a team of passionate engineers, designers, and visionaries building cutting-edge solutions to meet the world’s energy needs with 100% clean energy. We are in the initial stages of development and building our team. This is your chance to join on the ground floor of something big! If you are ready to work at a fun, fast-paced, groundbreaking organization that is positioned to revolutionize geothermal energy, apply today!

About the Role: We are seeking a versatile Senior Mechanical Engineer with experience in thermal and fluid dynamics to support the design, development, testing, and optimization of clean energy power generation systems. Collaborating with engineers across the company, this Mechanical Engineer will take ownership from cradle to grave and help drive the project through completion. This role focuses on system-level modeling, thermal management, and fluid flow analysis, primarily at the 1D level, across components such as heat exchangers, turbines, pumps, cooling & lubrication loops, and other balance-of-plant subsystems. The ideal candidate will bridge system architecture, physics-based modeling, and product development, ensuring industry-leading performance, reliability, and integration of complex energy systems.

Responsibilities:

- Define system requirements, interfaces, and performance budgets for thermal and fluid subsystems
- Own system PFD and P&ID
- Develop sub-system and system-level models to calculate steady, transient, and off-design thermal and fluid behavior using commercial analysis tools or in-house tools (e.g., Python code)
- Support system trade studies evaluating performance, efficiency, and cost impacts
- Support the integration of components including heat exchangers, pumps, fluid management systems, piping networks, and other auxiliary and support systems
- Perform hand calculations using first principles to size components, determine flow rates, estimate component and system efficiency, etc.
- Perform CFD and thermal analysis to evaluate heat transfer, pressure losses, flow distribution, and efficiency
- Identify, outline, and support component-level and sub-system testing required for risk mitigation
- Assist in the development of test plans and instrumentation strategies to validate thermo-fluid performance
- Analyze experimental data to refine models and improve system design
- Support development of control strategies related to thermal and fluid system performance
- Generate technical documentation including system specifications, modeling reports, design trade studies, test analysis reports
- Develop and manage relationships with third-party vendors
- Support Field Ops teams with technical expertise and advice after product delivery and accept feedback on possible design improvements
- Other related tasks as defined by your supervisor that add value to the design needs

Required Qualifications:

- Bachelor's degree in mechanical engineering or related field, or equivalent experience
- 5+ years of proven experience designing and building complex systems from 0 ->1 with a strong portfolio of projects involving diverse and integrated machinery
- A solid understanding of and the ability to apply first principles of core mechanical engineering principles, including fluid mechanics, thermodynamics, and material science as it pertains to system sizing and modeling
- Experience with a modern CAD package and a willingness to immediately self-teach proficiency in Siemens NX
- Excellent analytical and critical thinking skills
- Working cross-functionally with Turbomachinery, Supply Chain, Manufacturing, Field Ops, and others.

Basic Experience:

- Experience with components and sub-systems common to power generation or process plants, like heat exchangers, pumps, turbines, valves, piping, fittings, sensors, and fluid management systems
- Understanding of thermodynamic cycles (e.g., Rankine, Brayton)
- Experience generating 3D models and managing assemblies in CAD while ensuring proper fit and function
- Building 1D models of thermo-fluid systems using commercial software (e.g., Aspen, Dymola)
- Proven experience using Python or another coding language to build thermal and/or fluid models
- In-depth knowledge of the design and operation of heat exchangers and how to select the appropriate type for a given application
- Understanding of the applicable codes, compliance, and regulations pertaining to development, deployment, and commissioning processing or power generation hardware
- Experience with computational fluid dynamics (CFD) using commercial software (e.g., ANSYS CFX, ANSYS Fluent, Numeca)
- You have worked with other engineering disciplines (such as Aerodynamics, Turbomachinery, Dev Test, Materials, and Manufacturing) to optimize designs for performance, reliability, and manufacturability
- You are effective and respectful in communicating with other engineers even when it is controversial or regarding errors that you have observed or have been observed in your work
- Experience creating and maintaining comprehensive design documentation including design reviews and component and system specifications

Bonus Experience:

- Experience specifically with power generation or process plant systems is not a requirement but is a significant bonus.
- Proven expertise in Siemens NX / Teamcenter environment
- Experience with finite element analysis (FEA) for static structural, vibration, and fatigue using commercial software (e.g., ANSYS Mechanical, NASTRAN, Catia)
- Hands-on experience with product development, such as resolving manufacturing issues and analyzing test data to inform design modifications

Compensation:

- Base salary ranges from $140-200k per annum
- Equity options
- 100% company-covered Platinum or HD/HSA (with company contribution) medical
- 100% company-covered dental and vision
- Daily catered lunch
- Several annual social and team building outings

Actual base salary offered will be determined by: experience, skills, and work location. This range is for base salary, our total compensation includes equity and benefits. We welcome you to apply even if your expectations are outside our listed range.

## Equal Opportunity

Critical Energy is committed to creating a diverse environment and is proud to be an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, gender, gender identity or expression, sexual orientation, national origin, genetics, disability, age, or veteran status. Critical Energy is committed to providing reasonable accommodations for qualified individuals with disabilities in our job application procedures and throughout employment. If you need assistance or any accommodation, please let us know.

Recruiting Agenices Critical Energy does not accept unsolicited resumes from recruiters or employment agencies without a fully executed recruitment agreement in place. In the absence of such agreement, Critical Energy reserves the right to pursue and hire any candidates without an obligation to pay fees. Agencies are requested not to contact Critical Energy hiring managers or employees regarding recruiting services.

## About Critical Energy

## Company Overview
- **One-liner**: Critical Energy builds factory-made, modular power plants that convert heat into electricity, starting with geothermal and waste heat recovery from data center gas turbines.
- **Entity Type**: Private (Seed VC – II)
- **Headquarters**: Hawthorne, California, USA
- **Founded**: 2024
- **Founders**: Spencer Jackson

## Core Business
- Primary industry: Clean energy, modular power generation, geothermal, waste heat recovery
- Target customers: B2B – energy developers, data center operators, utilities, industrial facilities seeking 24/7 dispatchable clean power
- Mission: “Building an abundant low‑cost clean energy future”

## Products & Services
- **Modular Power Plants**: Shipping‑container‑sized, factory‑built units that convert heat into electricity using a closed‑loop working fluid cycle. Initially deployed for geothermal and waste heat recovery from gas turbines. Custom turbomachinery enables adaptability to varying temperature and resource conditions.

## Market Standing
- **Valuation**: Not publicly available
- **Key Metric**: Total funding raised – $22M (Seed VC – II closed in June 2026, including $3M venture debt from Silicon Valley Bank)
- **Notable Investors/Partners**: Susa Ventures (lead), Upfront Ventures, Susquehanna, Silicon Valley Bank, MaC Venture Capital, Sustainable Investments, Humba Ventures, Scribble Ventures. Advisors include Mike Matson (BCG global geothermal lead), Greg Leveille (former CTO ConocoPhillips), Dave Welch (CEO AttoTude), John Kremer (former exec at Adobe and Chase)
- **Growth Signals**: Headcount of 20 employees (per Built In); team brings 50+ years combined SpaceX experience; recent $22M funding enables scaling from prototype to factory production; targeting weeks‑long installation vs. years for conventional plants

## Competitive Advantages
- **Modular & Factory‑Built**: Standardized hardware lowers construction costs and enables installation in as little as two weeks.
- **Adaptable Turbomachinery**: Custom design works across diverse heat sources and temperature ranges.
- **SpaceX‑Bred Engineering**: Founder Spencer Jackson spent seven years at SpaceX (Falcon Heavy, Starship, Raptor engine); team has deep aerospace and turbomachinery expertise.
- **Low‑Cost Dispatchable Power**: Provides 24/7 clean electricity without emissions or consumables, competing with natural gas peaker plants.

## Strategic Focus
- Current priorities: Deploying first geothermal projects, scaling manufacturing capacity for containerized plants, expanding waste heat recovery partnerships with data centers, and raising additional capital for commercial‑scale installations.

## Why Work Here
- **Culture & Team**: Engineering‑first environment with backgrounds from SpaceX, aerospace, and energy. Flat, fast‑moving startup tackling a hard technical challenge.
- **Location**: Hawthorne, CA (office near SpaceX HQ). Built In lists the workspace as in‑office with some remote options; the careers page supports on‑site collaboration.
- **Notable Perks**: Opportunity to work on physical hardware from concept to field deployment; exposure to cutting‑edge turbomachinery; early‑stage equity potential; direct mentorship from industry veterans.
- **Engineering Culture**: “We’re a group of engineers and innovators … having designed complex systems like rocket engines, turbomachinery, and large‑scale hardware.”

## Sources
1. [criticalenergy.com](https://criticalenergy.com)
2. [criticalenergy.com/who-we-are](https://criticalenergy.com/who-we-are)
3. [builtin.com](https://builtin.com/company/critical-energy)
4. [cbinsights.com](https://www.cbinsights.com/company/critical-energy)
5. [linkedin.com](https://www.linkedin.com/company/critical-energy-systems)

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