The concept of the Trilateral Cycle (TLC process) was first mentioned at the beginning of the 20th century.
At that time, however, there was no machine capable of implementing this process.
In the early 1990s, the TLC process was revisited by the British Professor Ian K. Smith. Prof. Smith identified a screw expander (a screw compressor for compressed air operated in reverse) as the ideal machine for the TLC process and conducted extensive research on the subject.
Prof. Smith already identified the utilization of low-temperature industrial waste heat, so-called low-grade heat, as the preferred field of application for the TLC process.
The upper limit of the term “low-temperature heat” varies between 150 and 300°C depending on the author.
Prof. Smith already highlighted the essential advantages of the TLC process compared to the well-known steam power or ORC processes:
– the very deep cooling of the heat source to just above the condensation temperature of the working fluid
– the absorption of almost all available thermal energy from the heat source (high exergetic efficiency)
– a simpler heat exchanger design due to heat transfer to a liquid working fluid
– the significantly larger amount of convertible energy despite a lower Carnot efficiency
Based on the research and publications of Prof. Smith, global research into the TLC process began with numerous theoretical studies confirming Prof. Smith’s findings.
Practical investigations focused on the search for the most suitable heat engine. In addition to various designs of screw expanders, scroll expanders, piston engines, and turbine solutions were also investigated.
These investigations mostly figured out that the requirements to a heat engine resulting from the TLC process are very difficult to meet. The tested heat engines were working but (for various reasons) lacked economic viability.
The absence of economically viable results has led to a decline in scientific interest in the TLC process in recent years.