From a global perspective, there is a lot of interest in the wider use of R-744 (CO2), especially in supermarket refrigeration. Recently, a number of international studies and seminars have reported some of the latest developments regarding R-744.


The Spanish energy consulting firm Tewis Smart Systems organized a seminar on natural refrigerants. Attendees came from installation companies of the Iberian Peninsula.

The purpose of the seminar was to update installers about innovations regarding installation, start-up, operation, and maintenance of R-744 cooling systems. It focused on design, safety, efficiency, and environmental sustainability. During the seminar, Alfa Laval introduced its range of evaporators for use with R-744 that support pressures up to 80 bar. The company said the technology can be used in subcritical and transcritical applications Alfa Laval and Tewis are working together for the promotion of R-744 for commercial refrigeration applications. In the Spanish market, Alfa Laval has been in collaboration with the Ahorramas supermarket chain. Tewis participated in the design of the first installation of R-134a and CO2 cascade system at the Ahorramas “La Gavia” supermarket located in Madrid. The cascade system was a combination of HFC-134a for the central of positive compressors that feeds the wall-mounting and positive temperature rooms and R-744 for the central of negative compressors that feeds the floor mounting and rooms of negative temperatures.

According to Alfa Laval, Spain’s high ambient temperatures pose difficulties to the applications of transcritical CO2, but the company said that in the future it will be an option, especially for the Northern region of the country.


Australia’s Renewable Energy Regulator held a public consultation on the methodology used for calculating the financial incentive for solar and air-source heat pump water heaters. As part of the consultation, hot water service manufacturer Edson proposed a combination of direct solar and ambient heat harvested by heat pumps that use R-744 as the refrigerant.

The manufacturer is offering a solar boosted R-744 heat pump water heater. The hybrid system can cover up to 90 percent of annual hot water needs from the sun via solar collectors (65 percent contribution of hot water) and solar energy stored in the environment using a heat pump (25 percent contribution of hot water).

Developments in Australia also point to how regulatory issues are factoring in R-744. According to the web publication

“Natural refrigerant CO2 will not be subject to carbon equivalent pricing. … Owners of solar and heat pump water heater installations are entitled to [receive] Small-scale Technology Certificates (previously called Renewable Energy Certificates or RECs). The number of certificates is calculated based on the electricity in megawatt hours (MWh) that the system is estimated to displace over a 10-year period. The subsequent trade in these certificates provides a financial incentive for the installation of solar water heaters and heat pumps. For the case of solar hot water/heat pumps, the majority of owners choose to assign their certificates to an electricity retailer or an installer in exchange for a financial benefit such as a discount off their invoice.”

It was also noted that the Australian Office of the Renewable Energy Regulator (ORER) held a public consultation on the amendments to the Regulation 19B Legislative Instrument – Small-scale Technology Certificate (STC) methodology for solar water heaters and air-source heat pump water heaters. The Australian government also offers rebates for replacing electric hot water systems through its Renewable Energy Bonus Scheme, but this program will close June 30.


At ATMOsphere Europe 2011 in Brussels, Georges Khoury, chief engineer of eco activities at Sanden, described the R-744 heat pump water heater for the European market. Advocates said the development of high-efficiency R-744 heat pump water heaters for domestic hot water production is an example of using natural refrigerants in both high-capacity refrigeration and in smaller applications for residential use. The use of a natural refrigerant in a heat pump was partially in response to France introducing stricter thermal regulations to achieve the European Union targets of reducing emissions by 20 percent, increasing the share of renewable energies to 20 percent and achieving 20 percent more energy efficiency — all by 2020.

With the idea of reducing energy consumption in a building, it was noted during the event that domestic hot water production ranks first in terms of energy consumption, ahead of heating. But the cost of technology to significantly reduce energy consumption is considered too high even in Europe. “That could be the opportunity for European CO2 heat pumps,” said Khoury.

The model shown in Belgium by Sanden is based on the Japanese Eco Cute, which many consider the base model for the R-744 heat pump. It was contended that R-744 shows a good temperature glide to water and a high coefficient of performance (COP) in this application, and it allows having a heat pump without electric backup.

Sanden’s challenge was to adapt the Japanese model for use in Europe in terms of electricity, supply voltage, change from outdoor to indoor unit, and change to small-capacity water tanks. In addition, the heat pumps had to comply with European standards and change from constant heating capacity to variable heating capacity, as well as change from soft water to hard water.

“The aim is to achieve an annual COP of 3.0, which would correspond to an energy use of 25 percent of the energy consumption of an electric boiler,” according to the website According to Sanden, field tests were carried out in one of the colder regions in France near Paris in 10 family houses of different sizes. The company said the owners were satisfied with the availability of hot water and the very low noise levels.

“The heat pumps operated during a cold winter period with temperatures down to -19°C with neither failures nor scaling issue,” reported The main conclusion of the field tests is that the COP increases with high hot water consumption and that the COP depends actually more on the amount of hot water consumption than outdoor conditions.


In China, R-290 (propane) remains more preferred than R-744, but R-744 refrigeration has been used in two supermarkets.

Driving the interest in China is concern over the still high use of HCFCs. As a developing country, China is subject to a slower phasedown of such refrigerants than developed countries such as the United States. According to, “In 2009, the country was responsible for over 58 percent of HCFC consumption in developing countries. Its industrial and commercial refrigeration is one of the largest users of HCFC. China faces the challenge to freeze HCFC consumption by 2013 and reduce its use from this level by 10 percent by 2015.”

At the same time, the publication noted, “The R-744 refrigeration market in China is still in its infancy, lacks mature technology and market demand.”

But work is underway. The company Zhenjiang Gaoxiang began to produce R-744 refrigeration units in 2010, with the R-744 technology imported from Dorin, an Italian company.

Yantai Moon produced China’s first domestically made NH3/CO2 screw cascade refrigeration system in 2008. The system has been inspected and accepted by the Shandong Science and Technology Bureau.

Regarding heat pumps, China has released the R-744 heat pump standard GB/T26181-2010 for hermetic motor-compressors for household and similar use heat pump water heaters, although such technology has not yet been introduced to the market.

Publication date: 04/02/2012