Volume 49, No. 4, November 2015

Volume 49, No. 4, November 2015

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Technical Articles

Characterising indoor air temperature and humidity in Australian homes.

Harrington, L. W., Aye, L. and Fuller, R. J.
Information about indoor air temperatures in residential buildings is of interest for a range of reasons, e.g. the health and comfort of occupants, energy demand for space heating and cooling. To date there have been few long term studies that measure and characterise indoor air temperatures in Australian homes. New primary research undertaken by the authors measured temperatures in 273 homes over the period 2011 to 2014 in seven climate zones, from Melbourne in the south to Cairns in the north of Australia. Humidity data was also collected in 20 homes. This paper is a description of the data collected and the subsequent analysis. Indoor temperatures were compared with outdoor temperatures and a mathematical model was fitted to the data. In general, monthly average indoor temperatures were found to be 2ÅãC higher than monthly average outdoor temperatures, apart from periods with consistently cold weather, where the monthly average outdoor temperature was less than 20ÅãC, which were found to have larger differences. The indoor temperature model developed has been compared with data measured by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in 438 homes in three Australian cities. The model developed using project measurements are highly consistent with the CSIRO data. Further data collection compared indoor and outdoor humidity in 20 houses in Sydney and Melbourne. The indoor humidity ratio was found to be, on average, slightly higher than outdoors, but indoor levels generally track outdoor levels quite closely. This is likely due to the high air exchange rate in most houses.

Australian reactive-gas emissions in a global chemistry-climate model and initial results.

Woodhouse, M. T., Luhar, A. K., Stevens, L., Galbally, I., Thatcher, M., Uhe, P., Wolff, H., Noonan, J., Molloy, S.
Earth system models (ESMs) simulate the complex interactions and feedbacks between the atmosphere, land, ocean, ice, and biosphere for climate and environmental applications. Atmospheric chemistry forms an important component of current ESMs by controlling the magnitudes, lifetimes and distributions of a large number of short-lived climate forcing agents, such as ozone, methane and aerosols. The Australian Community Climate and Earth-System Simulator (ACCESS) is currently used for climate and weather applications, and is being developed into an ESM with one component being reactive chemistry and aerosols based on the UK Chemistry and Aerosol (UKCA) model. We have compiled a multi-decadal, annually varying, emissions database for reactive gases and aerosols that includes both anthropogenic and natural components with important seasonal variations for use in ACCESS-UKCA. This paper examines Australian emissions of reactive gases, namely methane, oxides of nitrogen, carbon monoxide and sulphur dioxide, from this dataset and compares them with those available from the Australian National Greenhouse Gas Inventory (NGGI) for the years 1990– 2012. These emission data include various anthropogenic source sectors and also biomass burning. Generally, there is good agreement between the two datasets for the reference year 2000, but there are significant interannual variations in the NGGI data, especially for carbon monoxide from biomass burning, that are not accounted for in the gridded data. Australian anthropogenic emissions account for between 0.5–2.6% of global anthropogenic emissions, and between 3.6–23.9% of Southern Hemisphere anthropogenic emissions depending on the species. Early model results for carbon monoxide, ozone and aerosol optical depth are presented and compared with observations, which point to the need for a better understanding of atmospheric chemistry in the Southern Hemisphere.

Updated emissions estimation method for diesel non-road vehicles and equipment.

Cravigan, L. T., Smit, R.
Non-road emissions make up a substantial and increasing proportion of total emission loads in Australia, particularly in the absence of emissions standards, and have been poorly characterised to date. This paper discusses the recent update to the 2008 NPI combustion emission estimation method for non-road diesel engines (NPI 2008; NPI 2015), which applies the USEPA NONROAD model (USEPA 2010a). This method includes 3 important variables, which improve emissions estimation by better representing 1) the emissions standard to which the engine is compliant, 2) the transient use of the engine and 3) the deterioration of engine emissions over time. An assessment of emissions standards, engine emissions data and activity data identified the USEPA NONROAD method as the most appropriate for use in Australia in the absence of local data. The Australian non-road population is unique and characterised by a small proportion adopting modern emissions control technology. Australia also has a greater proportion of large engines (>560 kW) than the United States and Europe. In addition, nonroad engines in Australia are more intensively used compared to those in the United States or Europe. Using 2008 population and activity data (NSW 2012a) emissions are estimated to increase by an average of 50% for uncontrolled engines and decrease an average of 80% for Tier 4 engines using the updated emission estimation technique (NPI 2015). A minimum emission performance for Australian non-road engines will only be achieved when national efforts to introduce emission standards and other measures to reduce emissions (e.g. retrofitting) take effect.