Why are so many supermarkets now choosing CO₂ refrigeration?

Monday, 19 August 2019

Around the world, there is little doubt that CO2 is fast becoming food retailers’ refrigerant of choice.

At Danfoss alone, we’re currently seeing supermarkets switching to CO2 refrigeration systems at a rate of around 10,000 a year—and that number is growing fast. Meanwhile, alongside the traditional large applications, CO2 is being used in a broader range of settings than ever, including very small systems like remote condensing units.

There are several reasons for this. Partly, it’s being driven by the global push to move away from HFCs in favor of natural refrigerants. Many HFCs have a global warming potential (GWP) more than 1,000 times higher than CO2, and increasing regulation is creating refrigerant cost and availability issues.

But it’s also because many of the traditional obstacles that once prevented people choosing CO2 no longer apply—making it easier to use its unique properties to increase efficiency and cut heating costs.

CO2 was once considered expensive to use. As a high-pressure refrigerant, it requires more specialized components than other refrigerants. This additional installation cost was often unattractive.

However, that picture has changed.

Although CO2 still needs special components, the recent dramatic changes in refrigerant availability and cost mean the refrigerant itself is now much less expensive than most alternatives.

Meanwhile, the volumetric refrigeration capacity of CO2 is 5-10 times higher than conventional refrigerants. It therefore needs a far smaller charge—further reducing refrigerant cost—as well as smaller components and pipe dimensions, which saves money on copper and insulation materials.  

These savings often cancel out the cost of the additional components—so the initial installation cost for a CO2 system compares favorably with a conventional alternative. Installers tell us cost parity is very common.

And when you consider the potential energy savings—as well as the growing number of areas that tax refrigerant charge based on its GWP—the total cost of ownership is typically far lower with CO2.

Until recently, CO2 was best used in areas with cooler climates. But now, new technology makes it a realistic and efficient option everywhere—even in regions with high ambient temperatures.

We have successful trans-critical CO2 systems in stores all over the world—including Africa, Asia, and the Middle East. Recently, we worked to bring CO2 to Italy’s largest hypermarket, where ambient temperatures can reach 38˚C.

This is possible because technology like the Danfoss Multi Ejector Solution™ significantly increases energy efficiency during trans critical operation in hot ambient conditions. It offers a 10% energy savings annualized over the year and, at peak times, is around 30% more efficient than a traditional CO2 booster system.

Importantly, the Multi Ejector solutionTM improves efficiency in part-load conditions, which is where refrigeration systems do the vast majority of their work.

Similarly, our CO2 Adaptive Liquid Management (CALM) solution—which combines our new Liquid Ejector with our Adaptive Liquid Control algorithm—optimizes efficiency in all conditions. This solution allows super-heat to fall to zero, while the Liquid Ejector pumps any liquid leaving the evaporator back into the receiver. This maximizes efficiency, while safeguarding the compressors.

CO2 also brings the potential for cost savings outside the refrigeration system itself, because it’s perfect for heat recovery.

Used as a refrigerant, CO2 has a high discharge temperature and a non-condensing nature. This makes it relatively easy to reclaim and re-use this energy—even under sub-critical conditions—and use it to heat a store’s water and space with minimal additional equipment.

This is an extremely cost-effective way to heat the store, effectively reducing heating costs to zero. And there is often no need for a boiler, further reducing the initial installation costs across two systems.

In most countries, CO2 is still a growing technology. It therefore requires engineers to learn some new skills. However, once these are acquired, many refrigeration professionals find they prefer working with CO2.

Where CO2 is well established, it’s considered a core refrigeration skill—and its growing popularity elsewhere means other countries are catching up.

The skill base outside supermarket refrigeration is growing too. CO2 is increasingly used in other store formats, industrial refrigeration, heat pumps, rooftop chiller units, air conditioning, and even efficient data center cooling.

At Danfoss, we’re also working hard to help our customers give their skills a boost. Our CO2 Champions program enables experts to share best practices and advice, while our Mobile CO2 Training Unit has been on the road for the last three years, training refrigeration professionals all over the world.

At Danfoss, we’re delighted food retailers around the world have seen that CO2 is a winning refrigerant. We have spent more than ten years refining the technology to make it easy and efficient to use everywhere.

Russia now has its first transcritical CO2 hypermarket, while Al Salaam supermarket in Jordan recovers waste heat from its CO2 refrigeration system to heat its water supply.

That transition is excellent news for everyone. If all the world’s supermarkets switched to natural refrigerants like CO2 instead of HFCs, the impact on climate change would be equivalent to taking tens of millions of cars off the road.

We want to make that transition easier. That’s why we’re creating an ever-growing portfolio of CO2-ready valves, electronics, and line components—so installers, contractors, and engineers can bring this technology to more applications, and more retailers, than ever.

Supermarkets are choosing CO2 because it’s cost-effective, it’s good for the environment, and it’s efficient in any climate. If you’re making that same choice, we’ll make sure you have all the components, training, and support you need.