Magnetic bearings are playing an increasingly important role in the development of sophisticated and efficient compressors.
It could be argued that two key concerns for operators of compressors include enhancing their efficiency and reducing maintenance needs (and their ensuring costs). This is part of a global effort to make equipment more sustainable, including environmentally-friendly district cooling initiatives.
As such, magnetic bearings in centrifugal compressors offer a key solution, serving as an alternative to traditional bearings, which employ oil as a lubricant and often lead to problems.
Such is the fact that, and as we’ll see below in this article, magnetic bearings for centrifugal compressors have been recommended by professional and regulatory bodies, such as the U.S. Department of the Navy. Their studies found that oil-free magnetic bearing compressors operate more efficiently, particularly during partial load conditions.
What are magnetic bearings?
Magnetic bearings are a type of bearing that uses magnetic forces to support and stabilize the rotation of a shaft or other moving parts without the need for physical contact.
In order to function, magnetic bearings consist of two main components: the rotor (or the rotating part) that typically includes permanent magnets or electromagnets, and the stator (or stationary part), that contains electromagnets that generate magnetic fields. Through the combination of both, magnetic forces are able to maintain the desired position and stability of the rotor.
A magnetic-bearing chiller compressor can be installed as part of a new chiller installation or a retrofit on an existing chiller. Additionally, it has been prescribed for chillers that, as a rule, run at partial loads. This is particularly important as an advancement for compression equipment in the 50-500 TR range (Conry et al., 2002).
The benefits of magnetic bearings in a centrifugal compressor
As we’ve mentioned above, the fact that magnetic bearings operate without any physical contact between the rotating and stationary parts results in several advantages:
- Frictionless operation: the lack of physical contact between the moving parts means there is virtually no friction. This increases the heat transfer efficiency of the chiller, as no oil can enter the equipment; as well as reducing energy losses due to friction.
- Low maintenance: the absence of mechanical contact and an oil free functioning also means there are no parts that can wear out. As a result, there are reduced maintenance requirements and a longer service life.
- High-speed capability: magnetic bearings can support very high rotational speeds without the limitations imposed by friction.
- Great precision and control: they offer excellent control over the position and orientation of the rotating element, making them suitable for certain applications that require precise positioning and stability.
- Reduced noise and vibration: because of the absence of physical contact, noise and vibrational levels are minimized.
- Light weight: magnetic bearings are lightweight, allowing for faster and easier installations.
In fact, as part of their research, the U.S. Department of the Navy identified an average of 49% power savings and a 6.4-year return on investment, highlighting the economic and energy benefits of magnetic bearings. This unveiling how magnetic bearings can become a wise investment.
Oil-Free: The environmental benefit of magnetic bearings
A significant benefit of magnetic bearings is their oil-free operation. This design represents an alternative to traditional bearings that rely on mechanical contact to support the load and reduce friction.
Traditional bearings rely on oil for lubrication, which can lead to several issues such as oil leaks, contamination, and the need for regular oil changes. These problems not only increase maintenance costs but also pose environmental risks.
In contrast, magnetic bearings operate without any physical contact and eliminate the need for oil by using magnetic fields to create a contactless support system for the rotating shaft. This oil-free design reduces maintenance requirements, extends the service life of the equipment, and enhances overall system reliability.
Additionally, oil-free operation means there is no risk of oil-related failures, making the compressors more environmentally friendly. This advantage is particularly crucial in applications where maintaining cleanliness and reducing environmental impact are priorities, such as in medical facilities, food processing plants, and cleanrooms.
Chiller efficiency: the key for sustainable cooling
With the global climate crisis looming over, the development of increasingly efficient equipment stands out as a key achievement. This is precisely the context in which the importance of magnetic bearings and chiller efficiency can be understood.
As global concerns about climate change and energy consumption grow, improving the efficiency of cooling systems has become a priority in various sectors, including residential, commercial, and industrial applications. As more and more cities embrace district energy, the development of efficient and sustainable compressors remains a crucial aspect. As such, this guarantees that sustainable cities will also be able to provide comfortable temperatures for citizens.
District cooling represents a centralized system that provides cooling to multiple buildings or areas from a single energy source. It is considered more sustainable compared to conventional individual heating and cooling systems for several reasons, their energy efficiency being one of the most important. As such, the heat pumps are a type of cooling technology that can also be used for heating. They operate by transferring heat from one location to another, and when used in cooling mode, they can achieve high levels of efficiency compared to traditional heating and cooling systems.
Compression chillers are the heart of these district cooling systems, as they are responsible for the cooling process. Their primary function is to produce chilled water, which then turns into the cooling medium used to cool the buildings in the network. The chiller achieves this by absorbing heat from the water, typically through an evaporator, using a refrigeration cycle.
It’s precisely in this aspect where chiller efficiency through the use of magnetic bearings remains particularly crucial. In other words, achieving chiller efficiency through magnetic bearings will have a direct impact on how efficient and sustainable district cooling systems can be.
Additionally, as we’ve seen above, research has shown the magnetic bearings configuration to be particularly useful in partial load scenarios. This must be taken into consideration when designing district cooling systems, as compression chillers are in charge of efficiently handling varying cooling loads from different buildings in the district. In fact, their role in load management helps ensure that cooling resources are allocated optimally, minimizing waste and ensuring consistent cooling across the network.
When designing sustainable, optimized district cooling systems, efficiency must remain a top priority. This is also true of some additional aspects which relate to the installation’s environmental impact. This includes the use of sustainable refrigerants (moving away from those contributing to ozone depletion and global warming) and guaranteeing water savings, particularly in projects where water scarcity can become an issue.
At ARANER, we’re at the forefront of developing sustainable district cooling systems that adjust to the particular needs of each project. As such, our focus has been on implementing significant enhancements in our equipment, including the use of magnetic bearings whenever they stand out as an adequate response.
Get in touch with us and learn how we can supercharge your project with sustainability and efficiency at the front.
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