Infrastructure Engineering - Research Publications
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ItemOpening the door on refrigerator energy consumption: quantifying the key drivers in the home(SPRINGER, 2018-08)There is little concrete understanding of the energy consumption of refrigerating appliances during normal use or the main influences on their energy consumption. To date, no widely accepted method to disaggregate measured energy consumption measured in the home into its key components has been demonstrated. This paper examines the main external factors that impact on the energy consumption of existing refrigerating appliances in the home and how they respond to changing conditions, namely: room air temperature, defrosting behaviour and user interactions. Analysis of field data from 235 homes in Australia demonstrates that room air temperature is by far the largest factor accounting for typically around 75% of total energy consumption. Where present, energy used for defrosting is relatively small at around 10%, but this does vary by household and the type of defrost controller. User interactions typically account for 15% of total energy consumed by main household refrigerating appliances, but this varies from a few percent to as much as 45% in large households. The method set out in this paper provides a basis for more in depth analysis and a better understanding of energy consumption of household refrigerators in different regions.
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ItemImpact of room temperature on energy consumption of household refrigerators: Lessons from analysis of field and laboratory data(Elsevier, 2018-02-01)Refrigerators are a common appliance in developed and emerging economies around the world. These appliances consume significant energy globally and improving their efficiency is an important aspect of future climate change mitigation. It is widely understood that the energy consumption of household refrigerating appliances is strongly influenced by room temperature and many analysts have identified ambient temperature as the most important factor in normal use. Room temperature has two main effects on the energy consumption of refrigerating appliances. Firstly, the temperature difference between the compartment and the room dictates the heat gain into the appliance through the wall insulation and door seals. A second effect is that a change in room temperature affects the condensing temperature. An increase in room temperature reduces overall refrigeration system efficiency by increasing the difference between the evaporating and condensing temperature. This paper examines laboratory data for 111 appliances where energy consumption is measured at four ambient temperatures from 10 °C to 40 °C. Field data for 235 appliances in homes is also examined. This is more complex to analyse, but it does provide useful information on underlying energy changes due to changes in room temperature during normal use. This paper determines the ratio of energy at 16–32 °C (energy conditions in IEC62552-3) and explores the shape of the energy curve at intermediate temperatures in order to develop a generalised energy curve as a function of temperature for the refrigerating appliances measured. The field data gave highly comparable shape data to that measured in the laboratory. The results provide a useful method to estimate the likely power consumption of different appliance types under a wide range of operating conditions, even where limited data is available.
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ItemEnergy impacts of defrosting in household refrigerators: Lessons from field and laboratory measurements(Elesevier, 2018-02-01)Many modern household refrigerating appliances have automatic defrost systems that keep the evaporator clear of frost and ice and obviate any user interaction to remove frost accumulation that occurs during normal use. The energy impact of defrosting has received little attention to date and there is little understanding on how these systems operate in homes. This paper uses laboratory measurements for 110 appliances over a period of weeks and field measurements for 195 appliances over periods of up to one year to observe the energy characteristics of defrosting systems. Field data covering some 55,000 individual defrost events has been analysed to obtain unprecedented insights into defrosting intervals during normal use. This data also provides useful information about the pattern of defrosting and a comparison between laboratory measurements and field measurements. A method to estimate incremental defrost and recovery energy in normal use is proposed.