Perhaps you’re aware of the free-piston Stirling engine that allows Stirling Ultracold ultra-low temperature (ULT) freezers to use less than a third the energy of legacy, compressor-based models. You may also know that this enabling technology, not only saves energy and associated operating costs, but uses 100% natural refrigerants that substantially reduce ozone-depleting and greenhouse gas emissions. However, you may not realize that the Stirling engine also advances the safety of biological samples with its inherent reliability advantages.
From the outset, Stirling Ultracold has believed that sustainable, energy-efficient ULT technology would present a very compelling choice for the research community, and we are pleased to see the recent efforts of some compressor-based ULT manufacturers to improve the efficiency of their cascade technologies.
However, it should be noted that energy efficiency was never our sole reason for bringing Stirling engine technology to laboratory cold storage. Improvements in ULT efficiency and sustainability, while important on their own merits, should always support or enhance the reliability of cooling systems that preserve valuable samples for research. The inherent reliability of the Stirling engine, while less understood, is vitally needed in our industry to further the safe preservation of biological specimens.
This innovation delivers several reliability advantages that address well-known failures associated with aging technologies used in most ULT freezers. To understand this, let’s first look at the basic differences between cascade-compressor and Stirling engine systems . . .
Unlike “cascade systems” with two compressors and cooling loops in a cascading arrangement, the Stirling engine uses a single reciprocating piston and a continuous, gravity driven thermosiphon to cool the cabinet interior. In contrast to standard cascade systems that regulate temperatures by switching compressors on and off, the Stirling engine’s linear motor system continuously modulates and adapts by controlling the motion of the free piston.
How Does the Stirling Engine Improve ULT System Reliability?
Below are several key design attributes and innovations that extend the operating life of the Stirling engine and address the common reasons why conventional ULT systems fail . . .
- The advanced integral linear motor system has only two moving parts.
- The moving parts never wear because gas bearings eliminate physical contact (friction) during motion
- There is no oil to clog up the system or lubrication levels to maintain.
- There are no valves to fail or maintain
- 100% adaptive, continuous modulation regulates temperatures without stop-start cycles.
- Electromechanical stress and amperage peaks from on-off surge currents have been eliminated.
- Minimal preventive maintenance is required for reliable cooling operation.
If you would like a more in-depth understanding of how advanced ULT technology can reduce your energy consumption, while also improving reliability and sample safety, please sign up to attend our Freezer Challenge Webinar, presented by Stirling Ultracold’s Director of Quality, Chuck Stout on Thursday, April 6th at 1 pm.