Providing a brief history of natural refrigerants, going back to over 150 years ago when ice was used as the first refrigerant, Hafner opened his hour-long lecture by alluding to the recent landmark Paris agreement to address climate change globally.
“What next after Paris?” he asked ATMOsphere Asia participants. “Well, companies focusing on natural working fluids will face no risk of investing in technologies being on the phase-out agenda in the future,” he argued, while questioning the GWP levels of newly developed HFCs.
Integrated solutions and ejectors – future of CO2 technology
Europe has been at the forefront of developing the next generation of CO2 commercial refrigeration for years now, from parallel compression to ejectors for AC and multi-ejectors. Hafner was particularly keen to point out the benefits of using ejectors, which allow evaporators to be flooded completely – making them more energy efficient and consequently delivering higher energy savings.
“Compared to a baseline booster system – we can see on average 10% reductions in energy usage with parallel compression and an additional 10-20% with ejectors. If you can convince supermarket operators to include heating and other HVAC&R functions, then they can make additional savings with such an integrated system – the total cost will be lower and maintenance will be simpler.”
Hafner predicted that supermarkets would eventually end up using just one integrated system for all heating and cooling needs, while in the near future stores would start to export waste heat to local district heating networks.
“The adapted ejector technology offers high system performance and COPs even at high ambient temperatures – if natural refrigerant solutions are more efficient than HFCs, then we can eliminate the discussion about efficiency and they will introduce themselves. We need to have a solution: and the ejector is the solution.”
Future CO2 heat pumps to provide comprehensive heating, cooling solutions
Speaking to the audience, many of whom he assumed had EcoCute CO2 heat pumps installed in their homes, Hafner said: “CO2 has the perfect gliding temperature for heat rejection – this is the basic fundamental reason why heat pumps are the perfect match for CO2,” he said. “Other fluids have to go to very high condensing temperatures to reach the same water temperature.” He further noted that by adding ejector technology, CO2 heat pumps are able to far outperform the other technologies available on the market, even in high ambient temperature conditions.
“CO2 has very good properties, even in very high ambient temperatures, to reject heat to the ground or the air, and this is perfect for the chiller. Another 20% increase in COP can be achieved by adding an ejector .”
As a next step in technology development, Hafner suggests that the CO2 heat pumps should follow the trend for integrated technology in the commercial refrigeration sector, in that one unit should be able to satisfy all residential heating and cooling needs, including air conditioning and space heating.
CO2 can revolutionise mobile refrigeration, air conditioning
“Transport refrigeration is also very important, such as containers which are facing very high temperatures.” Hafner mentioned a Danish company using hydrocarbons (R290), which could feasibly enter the transport refrigeration market in Japan, while Carrier has developed CO2 units used all around the world.
For automotive and public transport there exist lingering challenges, but similarly huge opportunities. Back in 1990, the very first CO2 mobile air conditioning (MAC) system was proven to be a more energy efficient solution than R12. Yet the solution is not yet widespread, despite companies like Daimler announcing in 2015 that they are committed to CO2. “If MAC goes CO2, the buses will follow,” Hafner asserted.
As early as 1998, it was announced that CO2 would soon be ready for MAC, with Daimler supportive and DENSO announcing that R744 had achieved 25% better efficiency than R134a. “Even at very high ambient temperatures like in India, it was proven to be a good solution and fuel consumption was significantly lower with CO2 (30% less).”
However, the chemical industry convinced industry to go down the path of adopting R1234yf. “I don’t know how they did that, but they did. The safety and flammability issues are really serious. If these low-GWP fluids decompose, then they become highly flammable.” He warned that this becomes particularly serious in the services sector, where the consequences could potentially be fatal.
Heat pumps using CO2, Hafner argued, have the potential to revolutionise train air conditioning. “In Europe, 30% of a train’s entire energy consumption goes to HVAC&R – it’s a lot of energy. They are using electricity mainly for heating, but CO2 heat pumps could make a big difference here. With two evaporators and two gas coolers, you can utilise the high turnover of air left in the cabin, and with ejectors the systems can be even more efficient.”
“For transport refrigeration in Japan, technology to preserve food also means sustainable technology. Especially when talking about fishing vessels, there are still a lot of systems using [R22].”
“We should leapfrog straight to R744 – CO2 is more compact. On vessels where space is limited, CO2 is a good replacement when making refurbishments,” he said.
