The RAC Cooling Industry Awards 2009

The RAC Cooling Industry Awards held on 30th September at the Hilton Hotel, Park Lane, London, saw Klima-Therm walk away as winners of two prestigious awards and a highly commended finalist for a third.

Together with Cool-Therm & Geoclima, Klima-Therm has demonstrated its dedication to achieving energy efficient solutions in the cooling industry and was awarded for their efforts with the following:

“Environmental Pioneer - Air Conditioning” Award - Winner
“Environmental Collaboration of the Year” Award - Winner
“Environmental Product of the Year: Air Conditioning” – Highly commended

Environmental Pioneer - Air Conditioning    

Klima-Therm, Cool-Therm & Geoclima

The three firms behind the Turbomiser chiller walked away with the title for their harnessing of distinct technologies to achieve dramatic energy savings.  Their description of the product as "ultra-efficient" is not marketing hype but an indication of the step change they have achieved by utilising floating head pressure, sophisticated control systems and reduced compressor run-time together in an integrated package.

The combination claims up to half the energy costs of a comparable screw-based machine, without compromising cooling performance, cutting payback time to less than a year.  And the superlatives don't end there - one high profile customer, the Dorchester Hotel, is claiming the installation of the Turbomiser is saving £10,000 every month in air conditioning energy costs.
When additional benefits of the system - such as reduced refrigerant leakage (thanks to reduced joints), oil-free design for reduced maintenance, variable-speed drive and a unit weight a quarter of conventional compressors - are added in, the package leaves the companies involved as worthy winners.

Judges said: "A compelling argument for energy efficiency and environmental pioneering."

Environmental Collaboration of the Year

This new category in the Awards was introduced to recognize the fact that if the industry is to push forward the frontier for environmentally-led technology that justifies its investment, there will need to be more partnerships and collaborations between companies and individuals.  We were inundated with entries, with every conceivable permutation of collaboration presented, from companies with complementary shills through to full supply chains and even rivals.

The team that was ultimately selected by the judges crossed disciplines and international boundaries to create a technological breakthrough that is more than the sum of its parts.  While the Turbomiser chiller owes a degree of its success to the cutting edge compressor at its heart, it has taken real design collaboration between UK specialists and an Italian manufacturer to create far more than just a Turbocor chiller, but a unique product with a whole suite of innovative energy saving enhancements.  Each partner has brought a distinctive perspective and skills to the collaboration, combining the intimate knowledge of the market and emerging technology on the part of the Brits, with manufacturing capability and willingness to adapt.

The collaboration continues, with a rolling program of enhancements which has seen the launch of the second generation Turbomiser II.  Independent tests of the technology in Italy found the 700kW machine achieved COPs of up to 15.5 at typical mid-season conditions, with an average performance of between 5 and 7.

Environmental Product of the Year: Air Conditioning

The team behind the Turbomiser have added to their clutch of accolades with a commendation from the judges in this category.  "In time, this could well become the standard for chillers," they said, citing the controllability as a major benefit.

The quiet revolution in chillers

Developments in centrifugal compressors over the last five years have produced packaged water chilling equipment with considerably higher operating efficiencies than comparable compressors. The chillers are marketed in the capacity range 300 to 1,500kW; and this CPD module presents the new technology of the compressor and the chiller, together with a recent case study to illustrate the application.

By way of introduction, centrifugal compressors have been used in refrigeration applications for many years at the large-capacity end of the market, beyond about 500kW cooling capacity. In the air conditioning field the refrigerant R134a is now generally used, although in industrial applications propane and ammonia are often selected. The centrifugal compressor is different in operation to reciprocating, screw, scroll or vane compressors, which are positive displacement machines and achieve the pressure rise by reducing the volume of the gas. In a centrifugal compressor, suction gas enters the eye of the spinning impeller and is thrown by centrifugal force to the periphery of the impellor. The blades of the impeller impart a high velocity to the gas and build up the pressure. From the impeller the gas flows either into diffuser blades or into a volute, where some of the kinetic energy is converted to pressure. The compressor may
contain one or more impellers, therefore single or multistage, depending on the pressure ratio required for the application.

Advantages of centrifugal compressors over other types include the following:

• The impeller is the only moving part;
• Noise and vibration are low;
• Lubrication is only required for the bearings; and
• They are compact in size.

Recent features that have been introduced or developed for centrifugal chillers, and which result in energy savings, are:

• Ma g n e t i c bearings within the compressor;
• Oil-free compressor;
• Floating head pressure;
• Micro-channel aluminium condensers, that reduce refrigerant charge while increasing the effectiveness of heat exchange;
• Flooded evaporators that ensure optimum energy transfer between refrigerant and water;

• Inverter-controlled compressors whose output can be precisely matched to the load; and

• Use of a liquid refrigerant pump system that significantly increases thermodynamic efficiency across the chiller’s operating range.

Magnetic bearings

This is a digitally controlled system consisting of both permanent magnets and electro magnets, which replace the conventional lubricated bearings. Figure 1 shows the main components of the system. The compressor shaft rotates on a levitated magnetic cushion and magnetic bearings (two radial and one axial) hold the shaft in position. Permanent magnetic bearings do the primary work, while digitally controlled electromagnets provide the fine positioning.  Four positioning sensors per bearing hold the levitated assembly within a tolerance of 0.0005 mm, so that when the shaft moves from the centre point the electromagnet’s intensity is adjusted to correct the position, six million times per minute. When the compressor is shut down the shaft rests on graphite lined, radially located bearings. The compressor uses capacitors to smooth ripples in the DC link to the motor drive and, in the event of a power failure, the motor becomes a generator, using its momentum to produce electricity, keeping the capacitors charged for the brief “stopping” period and providing enough power to maintain the shaft’s levitation. The use of magnetic bearings also incurs more than 500 times fewer frictional losses than conventional bearings. This results in a reduction in the starting current to just 2A, removing the transient starting spikes frequently associated with screw and reciprocating compressors and the need for expensive soft start arrangements, as well as eliminating the risk of penalty charges for exceeding maximum power demands. 

Oil free compressor

Until the development of the magnetic shaft bearing, all compressors required oil lubrication by varying degree, which meant the oil mixing with the refrigerant as it was compressed. In this scenario, some oil leaves the compressor and enters the refrigerant system. Highly efficient oil separating vessels can be fitted to the compressor discharge and return the oil to the compressor, but a small amount of oil will still enter the system and travel in or with the refrigerant, through the condenser and into the evaporator. Many air conditioning packaged chillers with D-X evaporators have no oil separator and rely on refrigerant velocity to carry oil back to the compressor. Oil adversely affects the heat transfer rate and pressure drop, particularly in the evaporator, so cooling capacity and efficiency is reduced. Magnetic bearings eliminate the need for oil lubrication and with it the need for oil pumps, sumps, heaters, coolers and oil separators, plus the associated maintenance requirements.

Floating head pressure

An important aspect of the control philosophy for the chiller is that the system is designed to operate with a floating head pressure, providing opportunities for savings not available to conventional designs, where head or condenser pressure is maintained at or near design condition to provide system and expansion valve stability during variable load periods. Floating head pressure allows the condensing pressure to fall during low ambient conditions, which increases the efficiency of the chiller. Matching the components of the chiller is important to maximise the potential of this new compressor. Integration of the controls and managing the floating head pressures is vital to optimise chiller performance, particularly when managing the liquid pressure amplification for free cooling (see later).

Flooded evaporators

A flooded shell and tube evaporator has the refrigerant in the shell covering the tubes through which the chilled water flows. It is a more efficient heat exchanger than the D-X type, but refrigerant level has to be controlled, often by critical refrigerant charge. Centrifugal chillers have always used flooded evaporators, but oil management was always a disadvantage. Oil-free centrifugal compressors eliminate this problem and result in further increased efficiency. Features of the flooded evaporator incorporated into these chillers include:
• Being designed and optimised specifically for R134A with specially finned tubes;
• A refrigerant level sensor, which makes it possible to take full advantage of the total heat exchange surface area. This helps to create higher saturated suction gas temperatures and higher EER values while lowering energy consumption; and
• An added heat exchanger further increasing the overall energy performance levels by interchanging heat between the saturated suction gas and condensed liquid refrigerant, raising the temperature of the suction gas while sub cooling the liquid, improving the cooling  efficiency and EER values.

Variable speed compressor

The centrifugal, oil-free compressor incorporates an inverter-driven, permanent magnet, brushless motor. Typically, traditional induction motors of this size are in the 92 per cent efficiency range, but the new compressor’s permanent magnet DC motor provides an efficiency of between 96 and 97 per cent. The variable speed drive provides a speed range from 18,000 to 48,000 rpm.

Micro-channel aluminium condensers

The micro-channel, parallel flow, air-cooled condenser coils are designed to increase performance by up to 45 per cent, making it possible to significantly reduce condenser dimensions for a given capacity. Constructed entirely of aluminium, the coils’ weight is also reduced by as much as 45 per cent while the manufacturing method reduces the potential for refrigerant leakage, which makes it easier for end-users to comply with the F-Gas regulation. Other benefits of micro-channel condenser coils include a reduction in coil depth, which lowers air pressure drop, reducing fan power required to create the design air flow rate. The smaller coils also result in a 30 per cent reduction in the refrigerant volume and a reduction in refrigerant pressure drop across the coil of 65 per cent, enhancing energy efficiency still further. The condenser fans feature low noise sickle blades that are arranged so that,when the compressor cycles off, they have the ability to reverse and blow out dust that has gathered on the coil surfaces. This feature helps to maintain coil efficiency and overall energy consumption. Figure 3 shows a water cooled centrifugal chiller incorporating the new compressor, available for applications using cooling towers or dry coolers.

Liquid pressure amplification system

Figure 4 shows the principle of a liquid pressure amplification system, which can circulate liquid refrigerant from the condenser to the evaporator at low ambient temperatures, without running the compressor. For example, if the ambient is 10 deg C db, the air cooled  condenser may cool refrigerant to 12/14 deg C, which could meet the cooling requirement. This has been incorporated into the new centrifugal chillers, where a 1kW liquid pump increases cooling capacity at all condensing temperatures, but has greatest effect at lower temperatures. This glycol-free alternative to conventional free-cooling is highly efficient, and dramatically reduces energy consumption while maintaining refrigeration performance. A secondary benefit of the reduced compressor run-time is extended plant life. With the low-power liquid pump taking the load, the compressor does not have to work so hard or for so long, reducing wear and the likelihood of breakdown.

Case study

A recent project has been the replacement of chillers and cooling towers at the Dorchester Hotel in London. The original R22 chillers were in the basement with a condensing water riser to the cooling towers on the roof. They were removed in stages as they were replaced by three of the new centrifugal chillers on the roof, each with a cooling capacity of 1MW and each containing three  compressors. Even though cooling towers generally deliver more efficient operation than air-cooled condensers, such is the efficiency of the new chillers that energy costs have been reduced by £10,000 a month compared with the previous system. These savings are expected to achieve a payback in the first year on the additional capital cost, compared with a conventional screw chiller. There are also savings in water treatment and chemical costs associated with the cooling towers. The analysis of the cooling load throughout the year suggests a £90,000-a-year saving compared with a screw compressor chiller – a 30 per cent saving. Two chillers were positioned on the roof of the 10th floor in space previously occupied by coolingtowers, and the condensing water riser was converted to carry chilled water. The third chiller was placed on the roof of the third rear floor, freeing up the basement plant room. There were strict planning conditions regarding noise, and it is intriguing that the new chillers are quieter than the previous cooling towers. It is claimed that this new breed of centrifugal chillers is “probably the most efficient HFCbased chiller in the world”, able to achieve energy efficiency ratios of 10 and above. The technology can reduce end users’ power bills by between 30 and 50 per cent, while at the same time dramatically  cutting carbon emissions. On some applications, the saving can cut pay-back time to less than a year. The performance claims have been independently verified by a leading consultant at a test facility in Italy. As a resultof its innovative design, the machine requires 30 per cent less refrigerant than comparable conventional chillers, reducing servicing costs and potential environmental damage from large-scale leakage.

© Terry Welch
Steve Chaplin (Klima-Therm)

Link to CIBSE article: http://www.cibsejournal.com/cpd/2009-07/

PDF Download: cibse journal - july 09 cpd.pdf

References

Engineerlive, www.engineerlive.com/Energy-Solutions/Heat_Recovery
ACR News, August 2008, www.acr-news.com
DatacentreManagement, 26 January 2009, Chillers come of age
Modern Building Services, “Geoclima develops new chiller range based on Turbocor compressor”, June 2009
HPAC Engineering, January 2004, “Frictionless Compressor Technology”

What is claimed to be the leanest and greenest of a new generation of super‐frugal chillers is being launched this month across Europe. RAC reports

AN ULTRA-EFFICIENT CHILLER BEING LAUNCHED BRINGS WITH it claims of unprecedented energy savings for end-users and takes carbon reduction into new territory for the industry. The Turbomiser II is the fruit of a twoyear development programme by Italian manufacturer Geoclima and UK company Klima-Therm. It has been heralded as probably the most efficient HFC-based air-cooled chiller in the world, thanks to EERs of 10 and above without the need for additional free-cooling circuits and associated glycol (which can prove expensive and is not favoured in many applications). This saves both on initial cost and ongoing pump energy. Building on the success of the first generation Turbomiser, which itself set a new standard for efficiency, the second generation Turbomiser II takes performance into new territory, its backers say. The new chiller can reduce end-users' power bills by 30-50 per cent, while at the same time dramatically cutting carbon emissions. On some applications, the saving can cut payback time to less than a year.

Thanks to innovative design, the machine requires 30 per cent less refrigerant than comparable conventional chillers, reducing servicing costs and potential environmental damage from large-scale leakage. Ken Strong, managing director of Bristolbased Cool-Therm says: "The energy performance is staggering. These kind of savings are unheard of with conventional technology, and it gives end-users a decisive advantage in terms of running costs. And the savings go on accumulating throughout the life of the plant." The chiller uses a combination of high efficiency components and technologies, combined with an adaptive control system that integrates and optimises performance. 

The heart of the system are invertercontrolled Turbocor compressors whose output can be precisely matched to load, while other features include: microchannel aluminium condensers, that reduce refrigerant charge while increasing the effectiveness of heat exchange; flooded evaporators that ensure optimum energy transfer between refrigerant and water; and a Liquid Pressure Amplification (LPA)system that significantly increases thermodynamic efficiency across the chillcr's range. Unlike standard chillers whose head pressure is fixed the system is designed to operate with a floating head pressure, providing opportunities for savings not available to conventional designs. Thus the Turbomiser II chiller constantly self- regulates and optimises its performance in response to ambient conditions and  load. This is achieved with the use of the 1 kW LPA system, under the electronic control. This effectively increases capacity at all condensing temperatures, but has greatest effect at lower temperatures. As a result, it can deliver refrigerant many times more efficiently than a compressor. Another key to the chiller's ultra-low energy consumption is the fact that the compressor does not have to run to  maintain a fixed head pressure. By using the LPA system at lower ambient temperatures, the compressor(s) can be switched off, while  the LPA pump circulates refrigerant around the system. This provides a highly efficient, glycol-free alternative to conventional free-cooling and dramatically reduces energy consumption. On many applications, this can cut payback time to less than one year.

The  Turbomiser II can halve the energy costs compared with a conventional screwbased machine, according to the companies behind it. A secondary benefit of the reduced compressor run-time is extended plant life. With the low-power LPA system taking the load, the compressor does not have to work so hard or for so long, reducing wear and the likelihood of breakdown. A first generation version of the Turbocor chiller recently installed at The Dorchester Hotel in London is saving the end-user £10,000 per month in energy costs. The developers believe the Turbomiser II takes this performance to a higher level still. The chiller is available in capacities from 250 kW to l .5 MW, and can be used in most commercial and industrial applications. It is ideal for application in data centres, retail developments and deep plan buildings that have a constant base load, as well as applications such as hospitals and hotels needing all-year-round cooling.