The MagLev chiller substitutes a magnetic field for ball bearings.
Most of us take air-conditioners for granted in the sweltering summer months, even though they gobble up electricity and contribute to global warming. MEP Middle East takes a closer look at the MagLev chiller, which offers significant benefits in terms of energy efficiency and running costs.
Towards the end of April 2009, the US Department of State’s Bureau of Overseas Building Operations (OBO) announced that the first large-tonnage magnetic levitation (MagLev) bearing chiller in Europe had come on-line at the US Mission to the United Nations in Geneva, Switzerland. However, this was not the first application of MagLev technology in the world – that occurred on Earth Day in 2007, at the US Embassy in Tokyo.
OBO mechanical engineer William Christensen commented that a patent for magnetic levitation had been granted as long ago as 1942, but technology then was unable to take advantage of its potential. Ten US patents were awarded on this technology between 1941 and 1978 alone. It is only recently that the emergence of nanosecond-fast semiconductors at last provided the fine-tuned electronic control needed to maintain a motor shaft within microscopic tolerances.
Compressors
Air-conditioners operate by compressing gas and then allowing it to expand, thereby producing the desired cooling effect. However, compressors are power hungry and generate heat. The ball bearings that support the compressor’s spinning driveshaft ultimately wear out.
By the end of its life, a compressor has often lost half its efficiency, and is burning twice the energy – all for the same effect.
Manufactured by Multistack LLC of Sparta, Wisconsin in the US, the MagLev chiller substitutes a magnetic field for the ball bearings. The drive shaft is suspended in the air by magnets, while it spins at about 40 000 revolutions a minute. This eliminates friction completely, along with normal wear-and-tear.
“In the past, the magnetic field could only be changed 60 times a minute. Today it can be adjusted 60 times a second. The chiller’s drive shaft is kept spinning at 40 000 revolutions a minute within a ‘wiggle room’ amounting to only 70 microns,” explained Christensen. The compressor uses 30% less electricity than a conventional compressor, generates much less heat, and it works at maximum efficiency throughout its life.
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MagLev technology eliminates metal-to-metal contact and does not need lubricating oil. This does away with virtually all compressor maintenance and increases energy efficiency, as oil degrades heat transfer. The chiller’s quiet, vibration-free operation and low starting-power requirements reduce electricity charges, and can allow for a smaller standby generator to be used in new office building construction. MagLev chillers are also very quiet due to a lack of reciprocating mass, in addition to the extremely fine balance achieved through digital control.
No cooling tower
The new chiller is also ‘green’, as it has no cooling tower, meaning it needs no water to cool the refrigerant.
This also eliminates the need for biocide and corrosion-control chemicals, which end up in the wastewater. The total water-use reduction at the US Embassy in Tokyo is in excess of four million gallons a year, while the Embassy has, in turn, gained more than 125 square metres of useable space.
Matthew Wallace from ETI Professionals Inc. commented on the technology’s return-on-investment: “Although MagLev chillers are about 20% more expensive, the lifecycle costs and maintenance cost are significantly lower. Current chillers must have oil analysis completed once per year at $2,500 average. Every five years they recommend the compressors be rebuilt, which costs $30,000.
“Since the MagLev chillers do not use oil and do not have the friction which would cause the compressor to be rebuilt, there is a total savings of $210,000 over the 25-year lifecycle ($150,000 for rebuilds and $62,500 for oil analysis). This does not include the labour costs for performing the maintenance. The Maglev chiller must have its capacitors changed every five years, at $500 in parts, equating to $2,500 over a 25-year lifecycle. This, again, does not include labour.”
In terms of the Geneva Mission, the MagLev chiller is part of a strategy to make US embassies worldwide the standard bearers for ‘green’ building HVAC services.
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What are the sizes of maglev bearings currently in production?