Competition is increasing between natural refrigerants, with NH3-CO2 cascade systems also gaining acceptance, said speakers at ATMOsphere Europe.
“CO2 is approaching ammonia” in the industrial refrigeration market, Giacomo Pisano, technical sales manager at Dorin, declared at ATMOsphere Europe 2017 last week in Berlin, Germany.
Pisano cited his company’s six-cylinder transcritical compressors that can run up to 60 m3/h – the largest transcritical CO2 compressors, according to Dorin – as a key technological development allowing CO2 to operate at higher capacities.
Pisano believes the industrial market is moving towards CO2 partly due to the safety and technical challenges of using ammonia – namely, that the commonly used industrial refrigerant is “toxic and flammable”. In addition, ammonia systems “call for special and more expensive components,” he said during the Industrial panel session at ATMOsphere Europe.
On the other hand, the combination of CO2 and ammonia in an NH3/CO2 cascade system appeals more to Nicolas Pondicq-Cassou, director, engineering mechanical systems, Profroid, a Carrier brand, and Paul Arrowsmith, refrigeration design manager, at British retailer Sainsbury's, who also participated in the panel discussion.
Before building its online fulfillment centre in London, Sainabury’s looked into the best solution using natural refrigerants. It thought about CO2 transcritical, an innovative ammonia/CO2 cascade and a standard ammonia/CO2 cascade.
The food retailer decided to go for a cascade with a high-side ammonia system contained within the plant room, external evaporative condensers and a secondary CO2 condenser with pumped CO2 to chilled cold stores and produce cabinets.
The frozen cold store and cabinets are cooled through a subcritical direct expansion CO2 system.
A key reason for opting for this type of system was the low-cost index (time and cost) of 0.7% and high coefficient of performance (COP) of 4.0. “The increased cost of this system was recovered within half a year on paper,” Arrowsmith said.
Similarly, in Profroid’s experience CO2 and ammonia together provide the best solution, according to Pondicq-Cassou. “Combining the best of ammonia and CO2 together,” he said.
Comparing an ammonia system and the ammonia-CO2 system, PROFROID found the latter offers the best combination of efficiency, safety and investment cost.
The manufacturer has tested a standard ammonia system and a cascade NH3/CO2 liquefier cascade system. There is “14% energy efficiency vs. a liquid ammonia system,” he said.
Profroid is now offering a packaged 2,000 kW compact-delivery NH3-CO2 system for industrial applications. It has also managed to reduce the ammonia charge by 80% compared to a standard ammonia solution with the same cooling capacity.
“We now believe there is a room for this solution, packaging systems from the factory,” Pondicq-Cassou said.
