N ov/ D e c 2 0 1 6
38
INFO L IN K - B PN
Air Conditioning & Ventilation
Specifying the right energy efficient air conditioner
[words] Nicholas Rider
C
reating a comfortable and thermally-stable interior environment for a home is a primary concern for the residential designer, and it can be achieved in a number of ways. On the one hand we have passive architectural design, which manipulates natural elements like sunlight and wind to achieve this stability and comfort, and on the other, there’s active, which relies on aid from mechanical space conditioning systems. And yet, despite a growing societal awareness about human-caused climate change, it appears that the uptake of mechanical space conditioning systems and active design in new homes and renovations appears to be increasing. According to a recent Federal government report, 40 per cent of Australian household energy usage comes from heating and cooling systems, making them the largest energy user in the average Australian home. New research from built environment expert Professor Mattheos Santamouris of the University of New South Wales, paints perhaps an even more troubling predicament. It finds that increased temperatures, population and economic growth, as well as the trend of smaller families living in larger homes could see worldwide cooling energy consumption rise by 750 per cent by 2050. This is all made more daunting when you consider that the vast majority of the world’s residential electricity use still comes from fossil fuel sources. At a local level, 86 per cent of Australia’s electricity is generated from fossil fuels, with 73 per cent from coal and 13 per cent from natural gas. So, what do we do? Other than offsetting your client’s energyuse through renewable sources, like solar energy, another potential solution is advocate a more energy efficient air conditioner—one that consumes less energy, but will keep them comfortable all year-round.
TYPES OF AIR CONDITIONERS There are two main types of air conditioners on the market – refrigerative and evaporative. It is important to consider which is suitable for your climate, be it a tropical or dry environment.
A refrigerative air conditioner cools the air via a method of heat extraction called refrigeration. This type of air conditioner is effective in tropical climates where high humidity is present.
Air conditioners can currently be rated up to 10 stars. If a product is rated at 6 stars or less, it will not show the extra star ‘super efficiency rating’ band.
On the other hand, evaporative air conditioners can drop the temperature of dry air significantly through the transition of water to vapour (evaporation), which can cool air using much less energy than refrigeration. This method of cooling is only effective in dry climates.
However, looking at the stars alone is not helpful, as the performance of a large appliance that is capable of heating and cooling a 200sqm house cannot be compared to a small product designed to condition a small bedroom. This means that the cooling and/or heating capacity required to heat or cool the room/house, which can be found on the power input label (measured in kilowatts (kW), needs to be determined before energy efficiency is considered.
Common products available include split system (non-ducted), window/wall units, ducted systems, multi-split system, double/ triple split system, and portable products.
THE E3 PROGRAM The Equipment Energy Efficiency (E3) Program is a collaboration between the Australian Government states and territories, and the New Zealand Government which aims to improve the energy efficiency of appliances used in Australia and New Zealand. Managed by the Greenhouse Energy Minimum Standards (GEMS) regulator in conjunction with the Energy Efficiency Advisory Team (EEAT), the E3 Program undertakes a range of activities including energy rating labelling, setting minimum energy performance standards (MEPS), and education and training.
ENERGY RATING LABELS The Energy Rating Label is the key initiative of the E3 Program. This label communicates the energy efficiency of an appliance through the use of stars, as well as displaying the annual energy consumption. Star ratings offer a simple and fair way of comparing the energy consumption of products that perform a similar task. The more stars a product has, the more energy efficient it is. An air conditioner’s efficiency is the amount of cooling (or heating) capacity (output) per unit of energy it consumes (input). Air conditioners have two different energy labels: one for air conditioners that provide cooling only, and another for air conditioners that provide heating as well as cooling. All domestic single phase, non-ducted air conditioners must carry an Energy Rating Label, but it is only voluntary for ducted systems.
SIZE DOES MATTER When purchasing a new air conditioner, it is important to ensure you’re selecting a suitably sized unit for your application. While air conditioners appear to look quite similar, they come with a diverse range of heating and/or cooling capacities. Sizing for air conditioners is provided as a kilowatt (kW) capacity output figure. Many elements within a home will impact the size of the air conditioner you require. These include whether you are looking to heat/cool a single room, a larger space or your entire home, size of the room/ home, external wall materials, insulation levels, and how many windows you have, their glazing, shading and orientation. Making sure you have selected an appropriate sized air conditioner will mean your clients are comfortable in their homes and using no more energy than is required.
RECENT INITIATIVES At a meeting in Kigali, Rwanda, on October 15, 197 parties agreed to an amendment in the Montreal Protocol, which would diminish the worldwide use of hydrofluorocarbons (HFCs), a group of greenhouse gases used predominantly in air conditioning and refrigeration. The Montreal Protocol is an international agreement designed to protect the stratospheric ozone layer, which was originally signed in 1987. It sets out a mandatory timetable for the phase out of ozone depleting substances. The World Bank says that the new amendment could “reduce the rise in the global mean temperature by 0.5 degrees Celsius by the end of the century.” Here are seven energy efficient air conditioners available on the Australian market: