BELGIUM: As a possible solution for the viability of VRF air conditioning technology in a low-GWP future, Daikin will present a CO2 VRF system at the ISH exhibition in March.

Daikin Europe has not revealed further details about its CO2 VRV system, but this is not the first time the air conditioner maker has been linked to developing CO2 VRF systems.

The VRF (Variable Refrigerant Flow) air conditioning system was first developed by Daikin Industries in Japan in 1982 and introduced by Daikin Europe in 1987. Daikin later trademarked the VRV (Variable Refrigerant Volume) name, these energy efficient and flexible systems have used the high GWP refrigerant R410A for many years.

The European F-Gas Regulation, which requires the phase-out of high GWP refrigerants and is being applied worldwide under the Kigali Amendment, means that R410A is no longer environmentally friendly.

For large commercial applications, such as Daikin’s VRV systems, legislation allows for a longer transition time. Increasingly, HVAC manufacturers are launching VRF systems using R32 and providing customers with a solution for new installations until at least 2033. However, the flammability of R32, an A2L refrigerant, continues to limit its use in larger VRF systems and in applications in some European Member States.

Long term option

During presentations at the recent Chillventa exhibition, Daikin Europe acknowledged that upcoming phase-outs and quota restrictions require the development of lower GWP solutions.

The company highlighted CO2 as a “promising long-term option” for medium and large commercial systems and the “next logical step” for VRV systems. “It is a solution that deserves the full attention of all stakeholders in the HVAC market: component and HVAC manufacturers, as well as their design and installation partners, with the aim of launching the next generation of direct expansion systems,” Daikin said.

The CO2 VRV system was first unveiled at the Chillventa exhibition in Germany back in 2008 and was subsequently shown at a number of exhibitions in early 2009. This unit had a Daikin dual compression compressor, a two-stage intercooler circuit, a three-row heat exchanger and a four-way electronic expansion valve. It boasted a nominal cooling capacity of 28 kW and a heating capacity of 31.5 kW. It weighed 330 kg.

At the time, Daikin insisted that the new CO2 VRV system was more of a demonstration and research project for a new green technology, but this early development never went into production.

Four stage compressor

In 2016, Daikin presented a paper at a Purdue conference in the US, citing its work with a prototype VRF air conditioning system using CO2 refrigerant. This 14 kW unit used a four-stage compressor and expander, and an all-aluminum microchannel heat exchanger.

The Daikin four-stage compressor used in the 2016 tests mentioned

The heat exchanger size was increased by approximately 150% to match a similar R410A unit. This, combined with the additional components required, increased the calculated weight of the outdoor unit by approximately 250% compared to a unit running on R410A.

Additional components, including three internal heat exchangers, result in a 300mm increase in casing width and a 146% increase in internal volume compared to the R410A unit.

Daikin recognised that revolutionary technical advances were needed to further reduce product weight and size before CO2 VRF could be widely adopted in the commercial sector.

Comparison of internal components required for an earlier Daikin CO2 unit

The company is currently keeping mum on its latest version and hasn’t said when or if it will hit the market, but has promised to provide more information in the coming weeks.

https://www.coolingpost.com/world-news/has-daikin-finally-cracked-co2-vrf/