22 Energy Efficient Air Conditioning
New design changes the future for air conditioning
T
here are three key stages in the lifecycle of a building: construction, operation and decommissioning and of the total costs involved around 80% is accounted for in the operation stage.
This figure relates to what it costs to own, occupy and maintain a building and of that amount, around 80% is the cost of running the building services which include heating, ventilating and air conditioning.
Taking these figures into account, building owners and managers are putting greater emphasis on how much it costs to run their buildings – not simply the capital cost of new projects. Indeed, prominent figures in the operation and ownership sphere are now acutely aware that the equipment being installed plays the most significant part in a building’s energy performance.
At a recent industry conference, Michael Dick, director of operations and buildings for the Barbican, said he and his contemporaries “have to consider how our choices impact on buildings in the long-term.”
Chief amongst these considerations is the fact that today’s commercial buildings are increasingly air tight and filled with heat-generating office equipment and lighting.
It is here where careful, well-informed choices about designing, specifying and installing air conditioning plant must
be made to ensure that the most cost effective solution is in operation which will create the best possible environment for the occupants of the building. The requirement for a higher standard of air quality and increased energy efficiency in commercial buildings is leading the way when it comes to new product development in air conditioning. This demand comes from the owners and operators themselves, but is also being increasingly driven by legislation to greatly reduce the environmental impact of the leakage of air conditioning refrigerant and a heightened focus on assessing energy performance of buildings, both of which – in the form of the new F-Gas regulation and the introduction of the Energy Savings Opportunities Scheme (ESOS) – have become live issues for building managers to wrestle with in 2015.
Manufacturers are eager to develop products that respond to these challenges, and so the search for ever-lower energy consumption and greater savings must plough forward. One of the latest frontiers in this mission is in the material used in heat exchangers within air conditioning units.
For years, even in the most energy efficient models on the market, these components have been made of a combination of copper and aluminium. But, by switching to an all-aluminium construction the door has been opened
Mark Grayston, product manager at Mitsubishi Electric looks at the benefits of aluminium.
to significant savings on energy use, as well as a reduction in weight, better performance in terms of contact time with the refrigerant and less refrigerant volume.
Aluminium specialist Sapa commissioned tests to measure the performance characteristics of an air conditioning system using an all-aluminium micro-channel heat exchanger, compared to a baseline system with a traditional copper tube and aluminium fin heat exchanger. The results showed that almost 30% less space was required by the aluminium option, while weight was just over 60% of the copper solution. Crucially, the refrigerant volume required was 37% less than that needed by the copper heat exchanger. There is no reason why savings of this nature cannot be achieved in today’s commercial buildings. In appearance, the aluminium micro- channel heat exchanger is markedly different. A flat, rather than a cylindrical tube, is partitioned into narrow channels that increase the heat transfer through a higher surface per volume ratio. This type of tubing design is unique to aluminium and cannot be made in copper. The fact that the micro-channel heat exchanger is made entirely of aluminium also brings advantages in longevity. This one-metal construction removes the presence of galvanic currents
ACR News February 2015
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