Ultra-Low-Temperature Air-Cycle Machine Ready for COVID-19 Vaccine Storage and Tests

As the world gears up to produce and distribute vaccines for COVID-19, Mirai Intex, a five-year-old engineering and manufacturing company, is positioning its ultra-low-temperature (ULT) systems to serve as the refrigeration technology for COVID-19 vaccine storage and freeze-drying COVID-19 tests.

Mirai Intex’s ULT systems use air (R729) from the atmosphere as its refrigerant in what is called air-cycle refrigeration (defined by the reversed Brayton Cycle). Air-cycle technology is based on the heating capability of air during compression and its extreme cooling effect during the expansion process; no phase change occurs. Repetition of compression and expansion cycles brings temperatures down to -110°C (-166°F), according to the company. 

Expansion also generates energy, improving the efficiency of the system. In fact, an energy comparison study by an independent German engineering firm, Refolution, pointed out the efficiency advantages of Mirai Intex’s storage systems.

“Some COVID-19 vaccines require ultra-low temperatures like -70°C to -80°C (-94°F to -112°F),” said Vladyslav Tsyplakov, Development Director for Mirai Intex, which has a managing office in Vienna, Austria, and a production facility in Brno, Czech Republic. “Our refrigeration system for vaccine storage ranges from -40°C to -110°C (-40°F to -166°F)”

According to Tsyplakov, Mirai is expecting “a big demand for our products in the coming months,” as COVID-19 vaccines begin to emerge, though he declined to name customers due to nondisclosure agreements. “We are quite sure [of orders] this year.”

Mirai Intex is building a distribution and service network in Europe and around the world to handle installation and service of its machines, said Tsyplakov. 

Mirai Intex makes three “open-cycle” ULT machines, Mirai Cold 10, 15 and 22, with motor powers of 10kW, 15kW and 22kW, which can be used to support COVID-19 vaccine storage; they offer cooling capacities of up to 5.4kW/1.5TR, up to 9.5kW/2.7TR and up to 14.3kW/4.1TR, respectively. The machines use only air, without a secondary fluid. The Mirai Cold 10 unit, in particular, “is our most compact machine; therefore, it is an ideal solution for building medium-sized storage chambers to store COVID-19 vaccines,” Tsyplakov said. 

COVID-19 vaccines are gradually moving closer to becoming available. This week, the pharmaceutical giant Pfizer disclosed that early data indicated its COVID-19 vaccine – which requires temperatures as low as -80°C – is more than 90% effective in trials, according to media reports. 

New closed-cycle machine

Mirai Intex’s “closed-cycle” ULT machines can be employed for freeze-drying/lyophilization, such as freeze-drying PCR (polymerase chain reaction) tests used to detect the SARS-CoV-2 virus that causes COVID-19. “We are looking forward to [PCR] projects in 2021,” said Tsyplakov.

For both freeze drying and process cooling, Mirai Intex is releasing in the first or second quarter of 2021 a new close-cycle product, the Mirai Cold 15 T (T means it has an additional heat exchanger); it features a more powerful motor than its predecessor, Mirai Cold 10 T, yet is the same size.

The new model can maintain ultra-low temperatures from -40°C (-40°F) to -110°C (-166°F).  The new product is expected to have up to 10kW (2.8TR) of cooling capacity, said Tsyplakov.

Mirai Intex also offers a Mirai Cold 23 T machine and next year will release a Mirai Cold 80 T unit, its largest and most powerful machine.

Closed-cycle machines use air as the primary refrigerant in an indirect refrigeration system. (The air can be pressurized.) The system comes with a factory-equipped heat exchanger that is optimized to work with silicone oil as a working fluid (it is also compatible with other working fluids). 

All of Mirai Intex’s machine use water for system cooling, except for Mirai Cold 15 (open cycle), which is air-cooled. “We can make them more compact if they are water-cooled,” said Tsyplakov.

Following four years in development, Mirai Intex began installing its machines in the summer of 2019, and now has “multiple installations,” said Tsyplakov. One open-cycle installation is at German cryotherapy operator Coolinn, which uses it to serve a cryogenic sauna.  Several other closed-cycle machines are being used for freeze-drying applications. 

The company has stockpiled units and will be able to “ramp up” to meet projected demand for vaccine storage, he said.

Energy study

Though Mirai Intex’s machines cost more than comparable systems, operating costs (maintenance and energy) are substantially lower, said Tsyplakov, adding, “There’s no oil or lubrication in the system, no need to refill consumables, and no need for service by highly trained personnel.”

Mirai Intex offers energy savings from the extra energy derived from the air-expansion process. The system also employs a variable-speed drive to match energy consumption with cooling demand, and the open-cycle systems include a humidity-extraction device that prevents the build-up of ice in the chamber.

With regard to energy efficiency, Refolution last month completed a comparison of ULT refrigeration technologies, including the Mirai Intex machines, liquid nitrogen, and compressor HFC cascade systems. The temperature range of the systems is -40°C to -110°C.

Refolution found that even a small (under 5kW cooling capacity) open-cycle Mirai Intex system with the humidity extraction system has a higher full-load maximum COP than a big (over 100kW) optimized cascade system or a liquid nitrogen system, at temperatures below -70°C. (The COP values are nominated at a heat sink of 30°C/86°F ambient temperature.) 

For example, at -80°C, the Mira Intex system’s full-load maximum COP is 0.44, the cascade’s is 0.40, and the liquid nitrogen’s (directly from production) is 0.20. 

However, the big optimized cascade system has a higher full-load maximum COP than a medium-sized closed-cycle Mirai Intex system. At -80°C, the cascade system’s COP is 0.46, the Mira Intex’s is 0.36 and the liquid nitrogen’s is 0.20. (A “future-developed” closed-cycle Mira Intex system is expected to have a 0.50 maximum COP at -80°C, the study said.)

On the other hand, at partial loads, the Mirai Intex system can “adapt to change in process parameters with a more efficient operation” than conventional vapor compression systems “due to a single speed-controlled compressor,” Refolution’s report said.

Refolution has developed its own ULT storage room, which uses a Mirai Intex open-cycle machine.

We are quite sure [of orders] this year.

Vladyslav Tsyplakov, Mirai Intex