Rotorua Domestic Heating Survey Prepared by Shane Iremonger and Bruce Graham
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Rotorua Domestic Heating Survey Prepared by Shane Iremonger and Bruce Graham Environment Bay of Plenty Environmental Publication 2006/14 September 2006 5 Quay Street P O Box 364 Whakatane NEW ZEALAND ISSN 1175 - 9372 Working with our communities for a better environment Environment Bay of Plenty Contents Chapter 1: Introduction ......................................................................................1 Chapter 2: Survey methodology .....................................................................3 Chapter 3: Results ...............................................................................................7 3.1 Heating methods ..............................................................................................7 3.2 Heating season and time of day .......................................................................7 3.3 Wood burning ...................................................................................................8 3.4 Source of wood.................................................................................................9 3.5 Wood burner age..............................................................................................9 3.6 Coal burning .....................................................................................................9 3.7 Gas usage ........................................................................................................9 3.8 Rubbish burning................................................................................................9 Chapter 4: Conclusion......................................................................................11 Appendices...........................................................................................................13 Appendix I – Rotorua Domestic Heating Survey .......................................................15 Appendix II – Questionnaire ......................................................................................21 Appendix III – Raw Data Codes ................................................................................29 Environmental Report 2006/14 Rotorua Domestic Heating Survey 1 Chapter 1: Introduction As part of the Rotorua LAMA emission inventory and airshed dispersion modelling investigations, Environment Bay of Plenty required a survey of home heating methods to be undertaken. This survey was designed to assess the methods of home heating, volume and types of fuel used, as well as the frequency of operating specific heating devices. This report gives a summary of the key results from the 2005 survey. Environmental Report 2006/14 Rotorua Domestic Heating Survey 3 Chapter 2: Survey methodology The survey was based on telephone interviews of 800 households in the Rotorua urban area. There are about 17,000 households altogether in Rotorua and the survey sample size was designed to give a margin of error of ±3.5%, at the 95% confidence level. The households were selected on the basis of the twenty five census area units (CAUs) (Figure 1) in the urban area, and the distribution was designed to ensure a proportional representation across all of these CAUs. Full details of the survey methodology and the questionnaire are given in the report by APR Consultants Ltd (see Appendix 1). Environmental Report 2006/14 Rotorua Domestic Heating Survey Environment Bay of Plenty 5 Figure 1: Rotorua Local Air Management Area Environmental Report 2006/14 Rotorua Domestic Heating Survey 7 Chapter 3: Results 3.1 Heating methods The distribution of heating methods used by each household for heating their main living area was as follows: • Open fire..........................5% • Wood (log) burner..........43% • Multi-fuel burner...............2% • Gas (reticulated)............19% • Gas (bottled)..................25% • Oil-fired............................0% • Geothermal......................5% • Electricity .......................33% The results for households using wood for heating compare well with the figure of 45% reported for Rotorua in the 2001 census. Similarly, the census figures for gas usage were 15% reticulated and 28% bottled. Geothermal heating was a low percentage of the total across the whole city, but in those areas where it is available the proportion of users was more typically 30 to 50%. 3.2 Heating season and time of day A very small proportion (<5%) of households reported heating their homes throughout the year, while the majority of homes were only heated between May and September. There was an additional shoulder period for April and October, during which 30 to 40% of homes were heated. People were asked about their heating practices during four different times of the day. The peak period for heating was between 1600 and 2200 hours, with up to 95% of households using some form of heating during this time. About 40% reported heating during 0600-1000h, 45% from 1000-1600h, and about 30% heated overnight (2200- 0600h). The only notable exception was overnight gas heating, which was only used by 4% of households with this heating method. Environmental Report 2006/14 Rotorua Domestic Heating Survey 8 Environment Bay of Plenty 3.3 Wood burning The survey respondents were asked to estimate their wood usage, either on a daily basis or the total amount used during winter. This data was problematic in that a significant number of assumptions had to be made in converting the householder units, such as cubic metres, trailer-loads or truck loads, into standardised measurements based on weight. In addition, fewer than 10% of wood users were able to give an estimate of their daily wood use, although 90% provided figures for the seasonal total. This latter data was combined with the information on heating season to give an estimate of the average daily wood use for each household. The distribution of daily wood use by those households using log burners is shown in Figure 2 below. The average wood usage1 per household was 6.5 kg/day, and 75% of households used less than 8.5 kg/day. However, it should be noted that these figures represent the average usage throughout the heating season—the usage on some days would be much higher than these, and on other days it would be lower. An average daily wood use of 6.5 kg/day is equivalent to a total wood consumption of about 1 tonne for the entire heating season, or about 1.2 truck loads (1 truck load is approximately 5 cubic meters, or 800 kg). The figure for average daily wood usage is quite similar to those reported for other cities and regions, especially those in the North Island. Average Daily Wood Use 14.0% 12.0% 10.0% 8.0% 6.0% % of households of % 4.0% 2.0% 0.0% 135791113151719212325272931 Daily Wood Use (kg/day) Figure 2: Daily wood use for households using log burners. The results for daily wood use on open fires and in multi-fuel burners was too limited to allow detailed analysis in the form shown above. However, the wood quantities reported by households using these methods were very similar (±20%) to those reported for log burners. The total wood use by all forms of wood burners is estimated to be 9,800 tonnes/year, for the whole of Rotorua. 1 All wood weight figures are based on well-seasoned wood, i.e. approximately 25% moisture. Rotorua Domestic Heating Survey Environmental Report 2006/14 Environment Bay of Plenty 9 3.4 Source of wood Respondents were asked to identify how they obtained their wood. Of the 400 respondents that used wood, 362 provided an answer, with a distribution of, 63% buy their wood, 37% collect it. 3.5 Wood burner age Respondents were also asked to estimate the age of their wood burners, and the resulting distribution of answers is shown below: Pre-1990: 42% 1990-1995: 17% 1996-2000: 13% 2000-05: 28% The irregularities in this distribution suggest that some respondents may have found it difficult to clearly remember dates for events that happened more than 5 to 10 years ago. 3.6 Coal burning Only 14 people reported using coal for heating, 10 in a multi-fuel burner and 4 on an open-fire, giving an overall usage rate of 1.75%. The average daily coal usage was 7.1 kg/day, or about 1.1 tonnes throughout the full heating season. Applying these figures to the entire population gives a total annual coal usage for Rotorua of about 300 tonnes. 3.7 Gas usage The average daily usage of reticulated gas was 11.35 kWh, while the consumption of bottled gas was 0.7 kg/day (or a 9kg bottle in 13 days). Interestingly, the usage rates for both forms of gas are equivalent to almost exactly the same heating rates on an energy basis. However, some of the reticulated gas may have been used for water heating and cooking, rather than just home heating. 3.8 Rubbish burning Eleven percent of all households reported that they used backyard rubbish burning to dispose of household rubbish or garden waste. While the individual quantities varied widely, the total amount of rubbish burned annually by all these respondents was estimated at 18.2 tonnes/yr, or an average of 220 kg per household. No information was obtained on the frequency of burning. Environmental Report 2006/14 Rotorua Domestic Heating Survey 11 Chapter 4: Conclusion This report is one of the modules of the scientific investigations for the Rotorua LAMA (Figure 3). Outputs from this investigation will be used to build a heating model for inclusion in the emission inventory and the dispersion model. Figure 3: Rotorua LAMA investigations. Environmental Report 2006/14 Rotorua Domestic Heating Survey 13 Appendices Appendix I...........................................................................