Stirling Engine - Lucent Technologies

Lucent Technologies requested a team of Stanford students develop new technologies harnessing Stirling engines for waste heat energy recovery in server cabinets. I was part of a four person team to addess the challenge to innovate.

Extensive research began while discussions with Lucent were initiated to discuss the scope of the project, which was decidedly heavy given the 7 weeks available for the investigation.

Mathematical models of Stirling engine generation and operation were created, with focus on evaluating both thermodynamic and mechanical systems. However it became clear that the engineers at Lucent who conceived the project did not understand the science involved in the creation of a heat-driven generator.

The proposed application required violating the 3rd Law of Thermodynamics, which was beyond our capabilities at the time.

We proposed driving Stirlings as heat pumps to remove waste heat and elminate fan noise. (Have you ever been in a server room? Fans are loud.) Data collected though modeling would later be used for optimizing design fundamentals such as displacement, regenerator dimensions, temperatures expected, and heat quantities rejected.

A proof-of-concept prototype was created to be delivered to Lucent in addition to the very extensive mathematical model. Budget and time constraints limited the design to one of utmost simplicity.

My responsibilities included CAD modeling, the creation of all machine prints, machining assorted parts for the prototype out of aluminum billet, and the selection and procurement of purchased parts.

Focus was placed on easily fabricated or off-the-shelf components wherever possible, promoting ease of replacement and a quick turnaround for debugging. For instance, the use of stock tie-rod air cylinders was ideal for the regular seal changes and modifications necessitated by the protoype’s heavy vibrational loads and high engine speeds.

Air was used as a pressurized system working gas to increase the themal efficeincy of the overall system as well as to test the seal integrity. Ideally a Stirling would be pressurized with hydrogen for maximum thermal efficiency and heat tranasfer. Nevertheless, our team opted to avoid possibilities of a catastrophic system failure (think HindenStirling) and used air at elevated temperatures instead.