For around 200 years, refrigeration technologies have progressively led to the provision of essential goods and services for humans, not least the preservation of food and medicine. Today, however, society is facing considerable challenges in light of climate change and population growth – it is estimated there will be an extra 2 billion people on the planet by 2050, while life expectancy will be notably longer.
With this in mind, the concept of efficient technology garners more significance when trying to accommodate the extra energy demand of the future. Already, the energy consumption of refrigeration equipment represents 15% of global electricity use (often over 20% in developed countries). As a result, the use of efficient motors and drives is vital.
Aside from society as a whole, among the commercial beneficiaries of greater efficiency in refrigeration processes will be cold storage equipment manufacturers, who will be able to gain ground on competitor offerings and attract more customers. Reduced energy consumption continues to be a primary market driver, regardless of whether the application concerns industrial cold storage, walk-in cold rooms, chilled water units, commercial refrigerators, blast freezers, air-cooled condensing units, air-cooled racks, water-cooled racks or wine cellars.
Of course, every application is different and solutions will vary. For industrial and commercial cold storage applications, it is likely that induction motors along with AC drives will offer optimum efficiency. However, as a point of note, always seek out motors with frames that are able to offer a high level of resistance to the corrosive, harsh environments encountered in this sector. In terms of the drive, it is clear that precise and reliable control is essential for applications involving frozen food, where any failures can be extremely costly.
Energy efficiency is also important to refrigeration chiller manufacturers, where permanent magnet (PM) motors and frequency converters can make a real difference in lowering electricity consumption.
Moreover, those OEMs in this segment prepared to invest accordingly can potentially increase the performance of their systems for less cost, which in turn is good news for end users.
PM motors are not asynchronous, but they have the advantage of high efficiency at low loads (at least IE4 efficiency). This is important as cooling systems are required to perform many hours of operation at low loads. Over time, a PM motor is the most energy efficient and economical motor.
Away from OEMs, the advantages of modern motors and drives can also be applied directly at end users. Take dairies, for example, where there is an obvious requirement for effective refrigeration. It is not implausible for dairies to achieve energy savings of circa 20% from their refrigeration process (for cooling milk after pasteurisation or sterilisation) as a result of switching to PM motor technology and AC drives. The same applies to those specialising in yoghurt, cream or butter.
Since refrigeration is a key element in the dairy product manufacturing process, optimum operation is paramount. With this in mind, when the time comes to invest in new commercial refrigeration systems, careful consideration should be given to the motors fitted to the reciprocating air compressors. Here, the difference in energy consumption between, say, a standard 90kW asynchronous AC motor and a 105kW PM motor, will be notable.
Refrigeration systems at dairies are used to cool water to 1°C typically, which in turns cools milk to around 4°C. Most installations operate almost continuously, but at variable load. This is where the benefits of PM motors come to the fore, as their performance retains almost constant partial load, unlike standard asynchronous motors. In turn, this should lead to a considerable reduction in energy consumption.
To put the theory to the test, a digital energy analyser can be used to assess competing solutions. However, any tests are almost certain to produce similar results across a range of different load profiles. Depending on the type of measure – perhaps number of pistons, speed, evaporation temperature or condensation temperature – the calculated energy savings when using a PM motor with AC drive are likely to be between 18-21% in comparison with an asynchronous motor, even when taking into account the losses of the drive and the motor.
Of course, compressors are just one example. Optimised motor and drive solutions for the refrigeration, cooling and cold-storage sector can also be applied to evaporators, condensers, pumps and cooling towers.
It is also worth mentioning that, alongside modern hardware technologies, apps now exist which are able to provide energy consumption calculation comparisons between different technologies. Such apps allow OEMs to estimate and quickly assess the value of energy savings that can be achieved with high-efficiency drive and motor solutions; data that can be conveniently presented to potential customers. After all, if customers are aware they can make energy savings and reduce their ROI, often to less than 12 months, they will be more likely to invest.