Low GWP refrigerants, an attractive choice for glass door merchandisers

Wednesday, 18 February, 2015

As high GWP refrigerants are increasingly phased out and leading industries go green, the need to find alternative, low GWP refrigerants for Glass Door Merchandisers and other food service equipment grows. But what happens to the performance of the GDMs when opting for low GWP? What about the safety of the natural refrigerants? And are the required components available at reasonable prices?

The questions are many when contemplating a switch from traditional refrigerants to low GWP including natural refrigerants such as propane and CO2. This article explores the opportunities for the low GWP refrigerants and seeks to answer some of the questions to help you find the right solution.

For the last 5-10 years, leading players in the beverage industry have been exploring different paths to a greener image through reduced carbon emissions. Replacing HFCs with low GWP refrigerants in the millions of Glass Door Merchandisers (GDM) is one of the most direct ways to achieve an improved carbon footprint. At the same time, use of low GWP refrigerants enables improved energy efficiency, the parameter that provides the largest positive impact on the carbon footprint.

Many substitute refrigerants have been tested in the development process, and two natural refrigerants – propane and CO2 – have emerged as the preferred alternatives in the industry, delivering performance and cost-effectiveness comparable to that of the well-known HFCs. A couple of new, synthetic refrigerants, e.g. R1234ze and R1234yf, have also shown potential, but at the moment they are not so widely used.

This article will focus on comparing the advantages and challenges of the natural refrigerants that are most used by the GDM industry at the moment, propane and CO2, to aid in choosing the optimal solution.

Propane (R290) offers good thermodynamic efficiency and with a GWP of only 31, propane also produces a very low climate impact through the entire life cycle. The refrigeration properties of propane, when considering pressure ratios and discharge temperatures, are quite similar to those of HFCs in many respects and therefore propane is a straightforward choice in many applications. Propane is highly energy efficient in daily use and helps bring down the electricity bills of the local stores, kiosks, sports facilities, offices, and many other venues where GDMs are popular fixtures. Furthermore, propane is non-toxic, and the relative cost of GDMs using propane is similar to that of HFC systems.

Despite its many advantages, propane and other hydrocarbons are often associated with serious concerns about flammability; concerns that may curb the use of the otherwise ideal refrigerant.

The use of propane, however, is strictly regulated. Assuming that all safety standards are followed, risks associated with the use of hydrocarbons have been eliminated from systems, for instance by reducing the system charge to very small levels. When hydrocarbon systems are designed , for example, to include refrigerant charge reduction to small levels, and when all safety standards are followed, GDMs have been found to be very safe.

In most countries today, standards and regulations that govern aspects of refrigeration safety allow solutions using propane. Safety issues have been curbed by development of components and systems that reduce the risk of flammability to a minimum during the entire life cycle, beginning with the industry producing the appliances, to the everyday use and disposal. For instance, some of the players in the beverage market have replaced 50% of their fleet with hydrocarbons which reduced their overall CO2 footprint to a large extent.

Since the amount of propane is minuscule in GDM applications, typically less than 150 g, in the unlikely event a leak should occur, the leakage will be so slow and with so little propane that the risk of fire is close to nil. In fact, the amount of propane in a modern Glass Door Merchandiser is lower than what you may find in the refillable gas lighter cans available on supermarket shelves.

Pros Cons
Low GWP Flammability
Wide range of components available Service technicians need specialized safety standard knowledge
Low Costs Different local regulations may apply
Good thermodynamic properties  
Good Capacity  

CO2 is one of the most environmentally friendly refrigerants with a GWP of one; it is widely available and a by-product in a number of industries, and the price of CO2 is low. Among industry experts, the viability of CO2 use in glass door merchandisers is becoming more and more accepted and even considered an attractive alternative to traditional HFCs.

In its efforts to reduce the carbon footprint by phasing out HFCs from GDMs globally, one of the major players in the beverage industry has established a goal that all new cold-drink equipment will use CO2 as its primary refrigerant by 20152. This ambitious endeavor has helped develop CO2 technology as a commercially viable option for the beverage industry worldwide.

This initiative has also highlighted some of the challenges with CO2 in Glass Door Merchandisers. First, the cost effectiveness of CO2 systems for small, hermetic systems like GDMs has become a frequently visited discussion topic. CO2 requires high operating pressures for efficient operation, up to 90 bar (1,323 psi), limiting the number of components available and potentially increasing the costs of the system.

For some years, it was believed that using CO2 as a refrigerant in GDMs would result in relatively poor energy efficiency because of its poor theoretical maximum efficiency. However, due to the high heat transfer coefficients and low sensitivity to pressure losses of CO2, it delivers very high performance in many applications.

It is important to remember that even though CO2 is a non flammable refrigerant, and therefore by some considered safer than propane, special competences are still required for the technician when servicing the equipment due to the higher pressure. 

At the moment, it seems that propane has taken the lead with its excellent properties, high energy efficiency and with the risks of flammability essentially eliminated in applications like glass door merchandisers. However, CO2 is close behind and subject to rapid product development that might bring the climate-friendly and cheap refrigerant on par with propane for GDM applications.

As we have seen, natural refrigerants are becoming increasingly popular as HFCs are phased out (e.g. the recent EU F-gas phase down directive) and companies are looking for ways to reduce their impact on the environment. Seen from a Danfoss point of view, propane and CO2 are good choices for glass door merchandisers when customers are keen to move on to natural refrigerants.

1 Regulation (EU) no 517/2014 of the European Parliament and of the Council of 16 April 2014 on fluorinated greenhouse gases and repealing Regulation (EC) No 842/2006

2 Coca-Cola Installs 1 Millionth HFC-Free Cooler Globally, Preventing 5.25MM Metrics Tons of CO2; by The Coca-Cola Company (2014, January 22). 
Retrieved from http://www.coca-colacompany.com/innovation/coca-cola-installs-1-millionth-hfc-free-cooler-globally-preventing-525mm-metrics-tons-of-co2 

Danfoss leads the development of solutions and components for natural refrigerants and offers a wide range of products specifically designed for handling propane and CO2. Furthermore, Danfoss provides training, design tools and consulting services to promote the use of low GWP refrigerants and to support the development of forward thinking solutions in all parts of the value chain.