Sustainability in HVAC Design – Refrigerants

Refrigerant loss is a significant challenge in the maritime sector, with reports indicating an annual loss of 20 to 40%. This loss is exacerbated by the continuous motion of wind and waves, which causes wear and tear on equipment, leading to leaks. These refrigerant leaks contribute to the release of approximately 18.2 million tonnes of CO2 annually — more than the total emissions of a country like Croatia.

Today, natural refrigerants are becoming more common in onshore installations, but the maritime sector has been slower to adopt them. Older vessels, particularly those launched before 2000, still rely on refrigerants like R-22, while newer vessels typically use R134a for air conditioning and R404a for provision cooling. The hesitation to switch stems from the challenges posed by natural refrigerants. For example, CO2, ammonia, and propane—considered natural refrigerants—have issues like high pressure, toxicity, and flammability, which complicate their use on ships. With frequent leaks and the need for systems to withstand constant motion, these natural refrigerants present potential difficulties in onboard cooling systems.

The ideal refrigerant would have a Global Warming Potential (GWP) of 1, meaning it has the same impact on the environment as CO2. However, that's not the whole story. To be effective, the refrigerant should also be non-corrosive, non-flammable, and non-toxic. Its boiling point needs to be slightly below the desired cooling temperature to maintain efficiency, and its specific heat must be optimised to extract the maximum amount of energy during evaporation.

Finding the right refrigerant remains a challenge. Low-GWP refrigerants like R-1234ZE are not ideal, as they are classified as low-flammability (A2L), which makes them unsuitable for maritime use. Moreover, class bureaus such as DNV and Lloyd's are still developing regulations for these refrigerants, preventing widespread adoption on ships. Nonetheless, the gap between synthetic refrigerants with high GWP, like R134a (GWP 1430), and alternatives such as R515B (GWP 293), is significant. Although these alternatives are not without their limitations, they represent an important step forward in the search for sustainable refrigerants.

while onshore installations are increasingly transitioning to natural refrigerants with low GWP, the maritime sector faces unique challenges due to the dynamic and demanding environment of the sea. Natural refrigerants, though promising, present issues of toxicity and flammability, making them less ideal for use in the confined, moving spaces of ships. Despite these challenges, the maritime sector is making strides. New synthetic refrigerants with much lower GWP values than R134a and R404a are increasingly being used, providing hope for a more sustainable future in marine HVAC systems.

Refrigerants play a crucial role in the marine and offshore industries, where they are used in various cooling systems, air conditioning, and refrigeration units aboard vessels, rigs, and offshore platforms. However, the impact of refrigerants on the environment—especially regarding their contribution to global warming—is a concern that needs attention. Read on to understand how refrigerants used in these sectors can affect greenhouse gas emissions, the difference in their environmental impact, and ways to design and operate systems to minimize their contribution to climate change.

What are Greenhouse Gases (GHGs) and Carbon Dioxide "Equivalence"?

The major GHGs include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and several types of fluorinated gases, including hydrofluorocarbons (HFCs), per fluorocarbons (PFCs), sulfur hexafluoride (SF6), and nitrogen trifluoride (NF3). These gases, which contribute to global warming, have varying lifespans in the atmosphere, and their global warming potential (GWP) is often expressed in CO2-equivalent terms (CO2e).

For example, CO2, the most well-known GHG, has a GWP of 1, whereas methane has a much higher GWP, depending on the time frame considered. The concern is not only about carbon emissions but also about the collective impact of all GHGs, with their respective GWPs contributing to overall climate change.

The Role of Refrigerants in the Marine and Offshore Industries

In the marine and offshore sectors, refrigerants, particularly HFCs and other fluorinated gases, are widely used in cooling systems on ships, platforms, and rigs. These refrigerants are vital for air conditioning, refrigeration, and cooling applications on board, helping maintain safe temperatures and prevent equipment from overheating. However, they can also pose a significant environmental threat if not properly managed.

F-gases, including HFCs, are particularly concerning because they have high GWPs. For instance, R-410A, a common HFC refrigerant, has a GWP equivalent to 2,088 kg of CO2 for every kilogram of the gas released into the atmosphere. In the event of leaks or improper disposal, these refrigerants can contribute to the buildup of greenhouse gases in the atmosphere, exacerbating global warming.

Global Warming Potential and Refrigerants

F-gases like HFCs, PFCs, and SF6 are among the most potent GHGs, with GWPs much higher than CO2. The GWP of refrigerants depends on their chemical composition and how long they remain in the atmosphere. For example, HFCs can have a GWP of several thousand times that of CO2, making their leakage a critical issue.

The marine and offshore industries are especially vulnerable to this risk due to the nature of their operations. Refrigerants are often stored in large quantities on ships and offshore platforms, and if these systems are not maintained properly, significant amounts of these potent gases could be released into the atmosphere, contributing to climate change.

Reducing the Impact of Refrigerants

To minimise the environmental impact of refrigerants in the marine and offshore industries, several strategies can be employed:

1. Leak Prevention: The risk of refrigerant leakage is higher in mobile and offshore environments due to the harsh conditions and constant movement. Proper installation, regular maintenance, and leak testing are essential to ensuring that refrigerants do not escape into the atmosphere. For example, using more robust and well-maintained refrigerant piping systems can help reduce leakage rates.
2. Use of Low-GWP Refrigerants: One of the most effective strategies is to switch to refrigerants with a lower GWP. Alternatives like hydrocarbon-based or natural refrigerants are gaining popularity as they have much lower global warming potential. Additionally, new refrigerants like HFOs (Hydrofluoroolefins) are being developed to replace HFCs, offering a significant reduction in environmental impact.
3. Design Improvements: Optimising the design of refrigerant-based systems is crucial. This can include minimising the amount of refrigerant required in systems, reducing pipe lengths, and even replacing certain systems with water-based alternatives, where feasible. For example, using centralised cooling systems instead of distributed refrigerant systems like VRF (Variable Refrigerant Flow) can significantly reduce the amount of refrigerant required on offshore platforms or vessels.
4. End-of-Life Management: Proper recovery and disposal of refrigerants at the end of their life cycle can prevent large amounts of GHGs from being released. This requires the use of specialised equipment to capture and recycle refrigerants before equipment is decommissioned.

Conclusion

Reducing the environmental impact of refrigerants in the marine and offshore industries requires a multifaceted approach, involving better system design, the use of low-GWP refrigerants, regular maintenance, and effective end-of-life recovery strategies. By taking these steps, we can significantly reduce the contribution of refrigerants to global warming, while ensuring that cooling systems on vessels and offshore platforms remain functional and efficient.