The Dreosti Memorial Lecture presented by Andy Pearson, edited by Eamonn Ryan
This is an abbreviated version of the lecture delivered by SAIRAC centres in Johannesburg, Durban, Port Elizabeth and Cape Town. Due to its importance and length, the entire lecture will be run in four parts in the succeeding issues of RACA Journal.
The journey to a better world: a refrigeration perspective. All images by © RACA Journal
Introduction
Engineers have always balanced optimism with realism. They recognise the flaws in current systems but remain hopeful about their ability to drive progress. Over the past three decades, the refrigeration industry has actively pursued innovations to address environmental concerns associated with traditional systems. Despite notable advances, issues like climate change, energy security, political instability, resource depletion, and population growth continue to challenge the sector. This raises critical questions: “Have we done enough?” and, “What more needs to be done?”
Reflecting on four decades of technological and political developments, it is clear that significant investments in research and development have been made. Yet, progress often seems incremental rather than transformative. Innovations frequently involve substituting one refrigerant for another rather than rethinking the cooling process. While new technologies have emerged, they often address only parts of the cooling process and fall short of their promises.
Main challenges in refrigeration system design
Over the past thirty years, the refrigeration sector has faced three main challenges:
- Environmental impact: Addressing the ozone depletion and global warming potential of refrigerants has been a major focus, regulated by agreements such as the Montreal and Kyoto Protocols.
- Performance efficiency: Energy efficiency impacts both operational costs and environmental emissions. High energy costs drive the need for more efficient systems, but initial investments can be daunting.
- Safety and reliability: Compliance with national and international safety regulations is crucial to prevent accidents and ensure system reliability.
International agreements often progress slowly. The phase-out of ozone-depleting chlorofluorocarbons (CFCs) will stretch over 40 years, ending in 2030 with a complete ban on substances like R-22. Energy efficiency improvements are similarly affected by fluctuating energy prices and the upfront costs of new technologies. Safety measures, while essential, can be hard to justify financially despite their importance.
Achievements and innovations
Key achievements include the Montreal Protocol, adopted in 1987, which is hailed as one of the most successful international treaties. Initially focused on CFCs, the Protocol has been amended to address hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) through the Kigali Amendment of 2016. This amendment extends the Protocol’s scope to include high global warming potential substances, adapting its successful model to address climate change.
The transition in refrigerants has occurred in three phases:
- From CFCs to HCFCs: This shift aimed to reduce ozone depletion potential but was only a partial solution.
- From HCFCs to HFCs: HFCs like R-134a were introduced as chlorine-free alternatives. However, their high global warming potential exposed limitations in the Kyoto Protocol’s regulations.
- From HFCs to HFOs: Hydrofluoroolefins (HFOs) with shorter atmospheric lifetimes have emerged as the latest alternative, though they bring new environmental concerns about their breakdown products.
Each transition has introduced technical challenges, from adapting technologies to new refrigerants to addressing safety issues with substances like R-1234yf. While each step has been difficult, it has paved the way for more complex solutions in the ongoing quest for better refrigeration technologies.
Refining refrigeration: progress and compromises
The evolution of refrigeration technology has seen substantial achievements but also numerous setbacks. Early refrigerants like R-404A, a blend of R-125 and R-143a, were effective in addressing ozone depletion but had high global warming potentials.
Although R-404A was a suitable alternative to R-22 in the 1990s, it fell out of favor as the focus shifted to low GWP fluids.
Balancing ozone depletion and global warming has led to compromises. Simple metrics like GWP ratings do not capture the full spectrum of environmental impacts, making the transition an ongoing process. The GWP logarithmic scale helps set regulatory standards, guiding the shift toward more environmentally friendly options.
Advancements in natural refrigerants have gained traction. Hydrocarbons like propane (R-290) and isobutane (R-600a) are effective and safe alternatives, with R-600a becoming widely adopted. Carbon dioxide, though effective in commercial applications, remains costly and less efficient compared to HCFCs and HFCs. Ammonia has seen a resurgence in industrial applications, where modern systems have mitigated leakage risks.
The introduction of air cycle systems, though historically significant, remains niche due to its limited commercial use.
Left to right: SAIRAC national president Robert Fox, Dr Andy Pearson receiving a memento of the occasion, and SAIRAC Johannesburg chairman Gregory Grobbelaar.
Evaluating progress and future directions
As we approach 2025, it’s essential to assess refrigeration technologies in the context of broader climate agreements. The Vienna Convention and Montreal Protocol, along with regulations like the European F-gas regulations and the U.S. AIM Act, have successfully addressed ozone depletion. Ozone levels are expected to recover to 1980s levels by around 2060, a significant achievement.
However, addressing global warming has proved more challenging. The Paris Agreement aims to limit temperature rise to 1.5°C above pre-industrial levels, but current emission reduction forecasts fall short. Optimistic scenarios suggest only a 10% reduction in emissions by 2030, which is insufficient to meet the targets.
In refrigeration, progress must be evaluated based on environmental impact, efficiency, and safety. R-600a remains the dominant and safest option for domestic refrigerators, with minor efficiency improvements expected. Industrial systems have seen enhancements with low-charge ammonia plants, and carbon dioxide has proved effective in industrial freezers. Ongoing development is expected to address remaining gaps.
Future refrigeration technologies
Predictions about CO2 in refrigeration have largely proved accurate. While CO2 has seen success in freezers and heat pumps, its use in other industrial applications remains limited. Ammonia is typically more cost-effective and efficient compared to CO2 systems, which, despite low initial costs, have high maintenance expenses and shorter lifespans.
Commercial refrigeration has made notable strides. Various CO2 systems, including CO2 as a volatile secondary refrigerant and transcritical CO2 systems, have proved effective. Retailers have adopted propane in display cases and hydrocarbon systems in smaller appliances.
For large water chillers, refrigerants like R-134a, R-1234yf, R-1234ze(E), and R-1233zd(E) are prevalent, while ammonia and CO2 are less common. Water-based chillers, though efficient, have not surpassed the dominance of HFC and HFO chillers due to their size and cost.
Mobile air-conditioning has faced challenges with refrigerant transitions. R-134a replaced R-12 but raised leakage concerns, leading to the European MAC directive. R-152a was initially considered but rejected due to flammability. R-1234yf is now predominant despite flammability concerns. CO2 and propane were considered but did not gain widespread acceptance.
Heat pumps vary by application. Ammonia and HFO-1234ze(E) are competitive in district heating, with CO2 systems emerging but not yet widespread. HFCs are common in smaller heat pumps, with CO2 used in water heaters for heating mains water.
Over the past 30 years, efficiency improvements have been significant. In the US, residential air-conditioner efficiency increased by 30% from 1992 to 2015. Despite this, many systems still fall short of their efficiency potential, with some cold storage facilities consuming ten times more energy than best practices.
Next steps
Future progress will depend less on refrigerant choice and more on cleaner energy sources and transitioning processes to electricity. Cleaner electricity is essential for reducing CO2 emissions, and shifting processes from fossil fuels to electricity is equally crucial. Success in one area without the other will not prevent severe climate impacts. The relationship between grid decarbonisation and electrification is key.
In South Africa, the grid emission factor was 985 gCO2e/kWh in 2021 due to coal reliance. The South African Renewable Initiative (SARi) aims to add 19 GW of renewable capacity by 2030, covering 30% of the country’s electricity needs. However, challenges in energy transmission, storage, and supply reliability remain, and the cost of renewable energy must address these issues.
Future directions for electricity and refrigerant management
As we advance toward a cleaner electricity grid and transition from fossil fuels, electricity buying and selling methods will change significantly. Cleaner electricity, especially during high renewable generation periods, could see production costs approaching zero. However, the unpredictability of these times poses a challenge.
Efficiency remains crucial, even with low electricity costs. Efficient refrigeration systems will reduce grid strain, supporting other uses. Incentive schemes may be necessary to encourage efficient energy use, such as compensating users for consuming electricity during high renewable output periods. Future electricity pricing models might shift from simple unit rates to more complex structures. A higher standing charge could cover intermittency management costs, while variable rates might range from negative to positive values.
Efficiency incentives could involve a ‘free’ electricity threshold, with high charges beyond this point. Such systems would require sophisticated control strategies to balance user benefits with product quality and safety, though complex systems may face trust and comprehension issues.
Regulations and the future of fluorinated refrigerants
The regulatory landscape for fluorinated refrigerants is evolving, with potential bans or restrictions on these substances. Many fluorinated refrigerants are categorised as perfluorinated alkyl substances (PFAS), but not all fall under this definition. For example, R-32 is excluded. Ultra-low GWP substances like R-1234yf might face regulation sooner than moderate GWP substances like R-32.
The focus of environmental regulations has shifted from ozone depletion to global warming and persistent organic pollutants, leading to unintended consequences. Replacing R-22 with R-404A decreased ozone depletion but increased GWP, prompting a shift to lower-GWP alternatives like R-410A.
Breakdown products and environmental impact
Fluorinated refrigerants decompose into various breakdown products, such as trifluoroacetic acid (TFA). While TFA is present at low levels, its persistence in aquatic environments raises concerns. R-23, a degradation product, has a long atmospheric life and high GWP, necessitating caution in adopting short-lived fluorochemicals.
Alternatives like R-1234yf break down into TFA, while R-1234ze forms calcium fluoride, a less harmful substance. R-1234ze(E) might be a viable alternative, though it requires a larger compressor. R-1234ze(Z) has potential uses in high[1]temperature applications but is not widely used as a refrigerant.
If PFAS regulations tighten, fluorinated refrigerants may face increased restrictions. This could lead to a rise in hydrocarbon use, necessitating improved safety standards and practices. Updating safety standards to address new hazards and ensuring rigorous enforcement are crucial to prevent accidents and ensure safe use of flammable refrigerants.
| BIO:
Dr Andy Pearson graduated from the University of Strathclyde with a degree in Manufacturing Science and Engineering and joined Star Refrigeration in 1986, he working in their design office, as a site manager, a commissioning engineer and sales manager and then as head of the Contracts Group, He completed his PhD at University of Strathclyde with his thesis on “use of Carbon Dioxide as a refrigerant” in 2006”, he became the Group Managing Director of Star Refrigeration Ltd in 2016. |
 Dr Andy Pearson. |
