History of a New Technology - Part 3

  • 2/5/2026
  • 4-minute read

From Prototype to Market – The Birth of Enex

Moving from theory to commercial practice required a phased strategy. At the end of the 1990s, the market wasn’t ready for a direct leap into pure transcritical systems; we had to “tame” the technology through intermediate steps, learning lessons that no refrigeration manual could have taught us.

1. The Transition Phase: Subcritical

In 1997, to accelerate the project’s maturity, we introduced the first subcritical systems wth CO2 as a refrigerant. The idea was to use CO2 only for low temperature (LT, evaporating from -35 to -40°C), while maintaintaining a conventional primary fluid for medium temperature brine chiller.

  • The Conegliano Success: At the “Bingo” supermarket in Conegliano (TV), we installed the world’s first subcritical low-temperature system in cascade with an indirect system (R134a chiller). This milestone drew interest from technicians across Europe. Other installations followed, including one in the UK that utilized Propane for the medium-temperature chiller.
  • The Technical Lesson: Despite the enthusiasm, limits emerged: the dual circuit, circulation pumps, and additional heat exchange reduced efficiency and increased complexity and cost. It was a compromise that only solved maybe 30% of the environmental problem—in a supermarket context, only the low-temperature portion

2. Year 2000: The World’s First Transcritical System

The first subritical systems in retail sector were the spark for the introduction of CO2 cascade also in industrial refrigeration, using ammonia for the brine chiller, for example.

The true “evolutionary leap” happened near Pordenone, always in Italy, in the year 2000. Here, we built the first transcritical system of a new type in the world: a single-stage, CO2-only, system.

We literally had to invent what was missing:

  • Control: We created a self-regulating mechanical system for high pressure control, as nothing existed on the market.
  • Mechanics: We designed coaxial air/water heat exchangers certified for 120 bar, building them by ourselves.
  • Chemistry: We field-tested which lubricating oils were actually suitable and compatible. We were writing the rules of the game while we were playing it.

3. The “Baptism of Fire” (and Ice)

The first “full-scale” plant arrived in 2002 in the province of Treviso, featuring three machines with compressors in parallel: single-stage for MT (medium temperature) and two-stage compressors for LT (low temperature).

However, radical innovation always collides with the unexpected. Two extreme events put the system to the test:

  1. The Oil Emergency (Winter 2002-2003): With temperatures dropping much below 0°C at night, we discovered that—since the machines were outdoors—the CO2 in idle compressors would condense, causing the oil and CO2 to separate. Upon restart, because the oil adopted was lighter than liquid CO2, the oil pump sucked up the latter instead of the lubricant, destroying compressors in minutes.
  2. The Record Summer (2003): One of the hottest since then, up to almost 40°C. The system held the pressure, but human factor “fragility” emerged. Maintenance errors led to the safety valves blowing at 160 bar. The noise was so loud that neighbors called the Fire Department.

The plant survived, but we realized that the technology demanded a new, much higher level of professionalism in maintenance and service. The results from that plant were presented at the IIR conference in Washington in 2003, sparking massive interest from technicians, particularly from Scandinavia.

4. 2004: Enex is Born

After twenty years as an employee—rising from being a laboratory technician to technical director—I felt that the structure of a large company was not suited to the risks and speed required for massively introducing CO2 in the market.

On March 1, 2004, I founded Enex. The name is a synthesis of Energy and Exergy (the part of energy that is actually usable). The concept of Exergy, a pillar of the second law of thermodynamics, embodied our mission: the highest possible efficiency.

Enex became fully operational by the end of 2004. It was the first company focused only on CO2 refrigeration. it was followed some years later by 2 other companies.