Towards a Residential Air-Conditioner Usage Model for Australia

Mark Goldsworthy

doi:10.3390/en10091256

Abstract

Realistic models of occupant behaviour in relation to air-conditioner (a/c) use are fundamentally important for developing accurate building energy simulation tools. In Australia and elsewhere, such simulation tools are inextricably bound both in legislation and in the design of new technology, electricity infrastructure and regulatory schemes. An increasing number of studies in the literature confirm just how important occupants are in determining overall energy consumption, but obtaining the data on which to build behaviour models is a non-trivial task. Here data is presented on air-conditioner usage derived from three different types of case study analyses. These are: (i) use of aggregate energy consumption data coupled with weather, demographic and building statistics across Australia to estimate key predictors of energy use at the aggregate level; (ii) use of survey data to determine characteristic a/c switch on/off behaviours and usage frequencies; and (iii) use of detailed household level sub-circuit monitoring from 140 households to determine a/c switch on/off probabilities and their dependence on different building and occupant parameters. These case studies are used to assess the difficulties associated with translation of different forms of individual, aggregate and survey based information into a/c behaviour simulation models. Finally a method of linking the data gathering methodologies with the model development is suggested. This method would combine whole-of-house “smart”-meter data measurements with linked targeted occupant surveying.

Highlights

The ability to understand and predict when occupants will use air-conditioning, and the energy consumed when doing so, is important for design of electricity infrastructure, for developing regulations aimed at reducing household energy consumption, and for designing systems that provide occupants with better comfort outcomes at lower economic and environmental cost
In the first case study, aggregate level dwelling energy use data was linked with aggregate data on the dwelling characteristics, demographics and climate, and a statistical analysis was performed
This analysis used total household energy consumption and not a/c energy consumption, and is likely to underestimate the effect of climate and building thermal performance, a/c energy use is a substantial portion of total energy use for most households, even in relatively mild climates

Summary

Introduction

The ability to understand and predict when occupants will use air-conditioning, and the energy consumed when doing so, is important for design of electricity infrastructure, for developing regulations aimed at reducing household energy consumption, and for designing systems that provide occupants with better comfort outcomes at lower economic and environmental cost. In Australia, all new residential buildings constructed must meet a minimum building energy efficiency level that is assessed through annual thermal simulation of the proposed building, combined with representative weather data and assumptions around occupancy and air-conditioning (a/c) usage behaviour. Assumptions around how occupants will behave in relation to a/c use, and the simulation models themselves are effectively enshrined in Australian law, with far reaching implications for the building construction industry and for the design of the approximately 20,000 new dwellings built every month [5].

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