Air movement: an overlooked key to more energy efficiency in refrigeration

In the evolution of commercial refrigeration systems, compressors have long been recognised as the "heart" of the system, commanding most attention and investment in efficiency improvements. Yet another critical component acts as the system's "lungs" – the air movement system – which has been systematically underestimated despite its profound impact on overall performance. As compressor technology has reached elevated efficiency levels, achieving further gains requires a holistic approach to system design, with air movement emerging as a key new frontier for optimisation.

The fundamental role of air movement in refrigeration is deceptively simple: to promote air circulation that enables efficient thermal exchange in both the condenser and evaporator. However, its implications extend far beyond this, influencing energy consumption, product preservation, system reliability, and the carbon footprint of the entire commercial refrigeration sector.

Historically, the refrigeration industry has focused primarily on the compressor, the component with the largest share in energy consumption and cost in most refrigeration systems. However, as compressor technology has advanced significantly, for forced convection systems, the performance bottleneck has shifted. Operating a highly efficient compressor with inadequate fans is analogous to fitting a powerful engine in a vehicle with a deficient cooling system – the full potential simply cannot be achieved. In other words, besides an efficient ventilation system directly contributing to the appliance energy consumption, the thermodynamic performance of the compressor itself can be significantly impaired by the low effectiveness of the heat exchangers. A system with optimized air movement can deliver up to 7% energy savings.

Imagine it in scale. The total electricity consumption of commercial refrigerators across the EU 27 countries in 2020 (the most recent period with precise data available) was estimated at 52 TWh per year¹. A 7% improvement in efficiency – achievable through optimized air movement – would translate into savings of approximately 3.64 TWh annually. To put this into perspective, such an amount of energy is sufficient to power more than one million households in the United Kingdom for an entire year, based on Ofgem’s reported average residential electricity use of around 3,000 kWh per household².

When it comes to the cold compartment, inadequate air distribution increases the temperature difference between the coldest and warmest zones, thus forcing the compressor to work more intensively in order to attend the temperature criteria defined by international regulatory standards. Notwithstanding, since all the evaporator fan's energy consumption is converted into thermal load during operation, achieving high component performance is critical for minimizing the application's overall energy use. Furthermore, regarding the heat rejection from the condenser to the environment, insufficient airflow also elevates condensing temperature and pressure, thus forcing the compressor to operate under less efficient conditions.

Technology and design working together

Creating efficient  air movement  in a refrigeration system comes from optimizing three fundamental elements and the synergistic interaction among them:  motor, blade, and shroud. Together, they form a fan pack,  which is usually coupled to the heat exchanger through a housing. Each part directly influences the airflow efficiency. The proper integration between them is what differentiates a premium solution from a conventional one, delivering maximum airflow whilst minimising energy consumption.

It is worth noting that acquiring the three components separately, even if they are optimised for efficiency, has the additional challenge of proper assembly, given the significant efficiency losses related to mounting gaps and blade positioning. In a fan pack, all components are designed to fit and work with each other to achieve the highest airflow rate for an imposed system impedance with minimum energy consumption.

Now, let’s break down the importance of each element and the critical aspects for their maximum efficiency:

• Motor technology: using EC (electronically commutated) technology represents a watershed, because it allows fan speed adjustment according to demand. Thanks to the embedded electronic control, it can reach output efficiency levels of 70%, whilst shaded pole technology reaches only 30%. This technological advancement alone can more than double the efficiency of the air movement subsystem.

• Blade design: It is an equally crucial and complex science that balances multiple parameters. The most critical aspects include aerodynamic profile, angle of attack, pitch,  hub-to-tip ratio (the relation between the diameters of the fan’s center and of the blade’s tips), and number of blades. Blades with optimised aerodynamic profiles reduce movement resistance, increasing efficiency. The blade’s angle determines how much force is applied to the air in each rotation – excessively aggressive angles move more air but require more power and generate turbulence; overly gentle angles are inefficient. The number of blades directly affects air-moving capacity and noise levels. There must always be a balance between flow rate and drag, with a sweet spot equilibrating these effects. Intelligent aerodynamic design can generate such substantial gains without simply increasing motor power. It is possible to achieve improvements of up to 40% in airflow with an optimum balance of all variables. The imperative is to consume less energy whilst delivering the same airflow rate, or to deliver a higher level of airflow whilst maintaining the same power consumption level.

• Shroud: The shroud completes the air movement system, directing airflow precisely and whilst minimising aerodynamic losses. This fan part must be designed to maximise air capture and direct flow through the heat exchanger with minimal energy loss. The physical integration between motor, blade, and shroud creates a solution that functions as a single system, not as independent parts. To achieve optimal design, extensive Computational Fluid Dynamics (CFD) simulations are employed to optimize every detail, alongside prototyping and experimental evaluation in wind tunnels. Considering the extreme operating conditions involved (high temperatures and humidity), material selection also matters, such as employing polymers with strength-to-weight ratios that maintain their properties in all situations. Finally, proper positioning and installation are fundamental since a well-designed fan pack, if poorly installed, will significantly compromise performance.

Collateral positive impacts

Proper air movement generates value across multiple dimensions that extend beyond direct energy savings. We can list a few:

• Product conservation: Uniform air movement eliminates hot spots within the refrigeration equipment, ensuring all products are maintained at the ideal temperature. In food retail, this means less waste due to deterioration, greater shelf life for sensitive products, and better consumer experience. For medical and pharmaceutical applications, it is a matter of regulatory compliance and safety.

• Frame breaking opportunities: Optimised air movement allows the use of more compact   heat exchangers without capacity loss, providing potential for 5-10% increase in useful internal volume of equipment. This is valuable for retailers wishing to maximise product display space without increasing equipment footprint.

• Durability and reliability: Adequate air movement reduces thermal stress on all system components. Compressors operating at lower condensing temperatures may have extended service life. Electronic products exposed to less heat tend to degrade more slowly. This translates into a lower total cost of ownership (TCO).

• User experience: Efficient air movement reduces fan speed and noise, creating a better shopping experience in retail and more comfort  in spaces where commercial refrigerators are close to people for long periods of time (mini-bars in hotels, display cases in offices).

Air movement and decarbonisation

Decarbonisation is one of the most important drivers in the refrigeration industry today, and air movement improvement is part of the path to get there, reducing energy  consumption. It  reinforces a fundamental principle: energy savings drive sustainability.

Since most global electricity still comes from fossil sources, each kilowatt-hour avoided means fewer CO₂ emissions. Even with renewable energy, reducing demand decreases infrastructure needs, optimises natural resources consumption, and increases system resilience.

The path to decarbonisation does not depend on revolutionary technologies, but on systematic optimisation of each component. Air movement related components, once overlooked, now also represent a significant opportunity for meaningful progress towards a more sustainable future.

1. "Commercial Refrigerators: Energy labelling and ecodesign requirements apply to this product.”

2. "Average gas and electricity usage: Information on average gas and electricity usage and how it is calculated".