The UK is experiencing a marked change in its summer climate, with increasingly warmer and more prolonged heatwaves becoming the new normal. This shift poses challenges to various sectors, especially those that rely heavily on refrigeration systems. A key question now facing the refrigeration industry is whether design parameters, typically set around a maximum ambient temperature of 32°C, need to be adjusted to accommodate this changing climate. Let’s explore the potential implications of such a change.
The Current State of Refrigeration Design
Traditionally, refrigeration systems in the UK are designed to cope with ambient temperatures of up to 32°C. This design parameter has been adequate given the UK’s historically moderate summers. However, recent trends indicate that summer temperatures are not only rising but are also lasting longer, suggesting the 32°C benchmark may no longer be sufficient.
When refrigeration systems operate above their design temperature, their efficiency drops, resulting in increased energy consumption and reduced cooling capacity. Eventually, the refrigerant pressure can exceed the system’s safety limits, triggering a high-pressure safety switch that shuts the equipment down entirely. This scenario is particularly problematic for industries such as food storage, supermarkets, and pharmaceuticals, where it is crucial to maintain a constant, low temperature.
This is an enhanced problem for environmentally-friendly CO2 systems which become inefficient when operating super-critically (typically when the ambient is above 21ºC) and reach extremely high pressures.
Why the 32°C Design Parameter?
The 32°C design point was selected based on decades of climate data in the UK. It represented a reasonable upper limit that systems could handle without placing excessive strain on their components or necessitating significant over-sizing, which would have resulted in unnecessary costs and energy inefficiency during cooler months.
Additionally, international refrigeration standards and practices have influenced this design choice. Countries with climates similar to the UK often follow this guideline, aiming to balance the need for robustness with economic and environmental considerations.
The Case for Increasing the Design Temperature
1. Climate Data Trends
Recent climate data indicates a trend of rising summer temperatures in the UK, with 2022 recording some of the highest temperatures on record, well exceeding 32°C in many areas. The UK’s Met Office has suggested that heatwaves are likely to become more frequent and intense in the coming years.
If this trend continues, the traditional 32°C design point may prove inadequate for maintaining optimal cooling performance during peak summer conditions. Systems that struggle to maintain their set temperatures during these periods could compromise food safety, pharmaceutical integrity, and overall system reliability.
2. System Longevity and Reliability
Refrigeration systems that regularly operate at temperatures at the top of the design point experience increased wear and tear, resulting in a higher risk of breakdowns and a shorter operational lifespan. By designing systems to handle higher ambient temperatures, such as 35°C or even 38°C, the risk of system failure during heatwaves could be reduced, potentially lowering maintenance costs and extending the equipment’s life.
3. Energy Efficiency Considerations
While increasing the design temperature might initially seem to imply a need for more powerful, energy-consuming systems, the opposite could be true. Systems designed for higher ambient temperatures can be optimised for energy efficiency under these new operating conditions. This might result in a refrigeration system that, while potentially larger or more robust, operates more efficiently during peak temperatures, reducing overall energy consumption during hotter periods.
Potential Drawbacks of Increasing the Design Temperature
1. Higher Initial Costs
Designing refrigeration systems to operate efficiently at temperatures above 32°C will entail higher initial capital costs. Larger compressors, more robust components, and improved insulation may be necessary to maintain operation at these increased temperatures. For businesses with tight budgets, these upfront costs could be a significant concern.
2. Oversizing Risks
Oversized systems are less efficient and more difficult to control during cooler months, leading to unnecessary energy consumption and increased operational costs. Although compressor technologies with widely variable operating ranges exist, they are mostly aligned with the air-conditioning market and generally not available for low temperature applications.
3. Environmental Considerations
Increasing system sizes and capacities usually means a greater environmental impact, both in terms of manufacturing and operation. Larger systems require more materials, potentially increasing the carbon footprint of refrigeration installations. Additionally, these systems may use more refrigerant, which, if not managed correctly, could result in higher greenhouse gas emissions.
Finding a Middle Ground: Adaptive Design Strategies
Rather than simply raising the design temperature across the board, a more nuanced approach could involve incorporating adaptive strategies into refrigeration system design. Examples include:
- Variable Capacity Compressors: Systems equipped with variable capacity compressors can adjust their output according to ambient conditions. This enables efficient operation across a broader range of temperatures without oversizing the system for typical conditions. In the future we may see more development in these compressor technologies to suit a wider range of applications.
- Enhanced Heat Exchanger Design: Improving the design of heat exchangers can help systems dissipate heat more effectively during hotter periods, thereby maintaining efficiency without necessarily increasing the overall system size. Using energy efficient EC fans helps to control motor capacity efficiently.
- Advanced Control Systems: Integrating intelligent control systems that monitor real-time climate data can allow refrigeration units to dynamically adjust their operational parameters, ensuring they remain efficient under varying conditions.
Conclusion: Adapting to a Warmer Climate
With climate change bringing increasingly warmer and unpredictable summers to the UK, the refrigeration industry must consider whether the traditional 32°C design parameter remains sufficient. While there are arguments both for and against increasing this benchmark, the evolving climate suggests that designing for higher temperatures may become necessary to ensure system reliability and efficiency.
However, a blanket increase in the design temperature might not be the most economical or environmentally friendly solution. Instead, adopting more flexible, adaptive design strategies could provide a balanced approach, enabling refrigeration systems to operate efficiently across a wider range of temperatures without significantly raising costs or environmental impact.
Ultimately, the decision will depend on various factors, including climate projections, industry requirements, and the specific needs of each application. By staying informed and adaptable, the refrigeration industry can continue to offer reliable and efficient solutions in the face of an ever-changing climate.
