COMPARISON OF AGGREGATED DATA WITH DATA FROM OFFICIAL STATISTICS

In this section, the estimated total energy consumption and emissions to air from the Norwegian dwelling stock are compared to estimations from other sources.

4.3.1 Total energy consumption in the dwelling stock

Based on data from Rypdal (1993), the stationary energy consumption in private households in 1990 was estimated to be 40 TWh (see Table A.2 in Appendix A). In Ljones et al. (1992), the total energy consumption in the dwelling stock in the heating season 1989/1990 was estimated to be 38 TWh. This estimation was based on an average yearly energy consumption of 21 500 kWh per household and 1.77 million households. In the estimation model, the total energy consumption in the dwelling stock is estimated to be 45.4 TWh in 1990 for a total number of 1.75 million dwellings (see Table 4.4). This is significantly higher than the 40 TWh estimated on basis of Rypdal (1993), and the 38 TWh estimated in Ljones et al. (1992). Thus, it seems at first sight as if the total energy consumption in the dwelling stock has been over-estimated in the estimation model. However, the estimation of 45.4 TWh is based on weighted monthly mean temperatures for a standard year for the period from 1931 to 1960, while the estimations of 40 TWh and 38 TWh referred to 1989 and 1990 which were years with extraordinary mild winters.

Table 4.6 shows the weighted monthly mean temperatures used in the estimation model and the monthly mean temperatures for Blindern Meteorological Station in Oslo for a standard year (average for the period from 1931 to 1960), and for 1989 and 1990. The monthly mean temperatures at Blindern in Oslo are about the same as the weighted temperatures estimated to be average for the entire dwelling stock. A degree-day number of 3733 oC·days and a yearly mean temperature of 5.9oC are estimated for Blindern based on the monthly mean temperatures for a standard year. The corresponding values

estimated on the basis of the weighted monthly mean temperatures are a degree-day number of 3678 oC·days and yearly mean temperature of 5.8oC. This indicates that the temperatures at Blindern can be taken to be representative also for the entire dwelling stock.

Table 4.7 shows the total energy consumption and associated emissions to air of CO₂, SO₂, NO_x and PM from the dwelling stock according to the surveys and statistics conducted by Statistics Norway, and calculations made on the stereotypes of houses in the estimation model.

Table 4.6. Weighted monthly mean outdoor temperatures for the entire country (used in the estimation model). Monthly mean temperatures for Blindern Meteorological Station in Oslo, for a standard year (average for the period 1931 to 1960), and for the years 1989 and 1990. Sources: Statistical Yearbook 1990 and 1991 (NOS B921, 1990 and NOS B980, 1991).

Year Monthly mean temperatures (oC)

Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. Weighted -3.2 -2.9 -0.1 4.2 9.4 13.0 15.6 14.7 10.8 6.1 2.1 -0.7 5.8 Blindern Meteorological Station (Oslo)

Standard year -4.7 -4.0 -0.5 4.8 10.7 14.7 17.1 15.9 11.3 5.9 1.1 -2.0 5.9 1989 2.3 2.6 3.5 5.1 10.9 15.2 17.0 14.2 11.5 6.4 2.5 -2.7 7.4 1990 0.8 3.4 4.6 6.4 12.4 15.1 16.6 15.9 10.1 6.2 0.1 -1.1 7.5

Table 4.7. Total energy consumption and emissions to air of CO₂, SO₂, NO_x and PM from the dwelling stock based on three surveys conducted by Statistics Norway. Rypdal (1993) referring to 1990, Ljones et al. (1992) referring to the heating season 1989/1990, and SSB (1993) referring to 1990. Estimated total energy consumption and emissions to air from the dwelling stock based on the estimation model and different sets of

temperature data.

Reference Total energy consumption Total emissio

Total Electri-

city

Fuel oil Fire- wood

CO₂ SO₂ NO_x PM

Statistics Norway surveys

TWh TWh TWh TWh Million tons 1 000 tons 1 000 tons 1 000 tons 1990 (Rypdal, 1993)* 39.7 30.3 3.6 5.6 - - - - 1990 (SSB, 1993) - - - - 1.4 1.6 2.0 12.3 1989/90 (Ljones et al., 1992) 38.0 28.8 3.7 5.5 - - - -

The estimation model

Weighted temperatures 45.4 32.2 5.2 8.0 1.4 1.9 2.3 17.2

Blindern, standard year 45.8 32.5 5.3 8.1 1.4 1.9 2.3 17.5

Blindern, 1990 40.5 29.6 4.3 6.6 1.2 1.6 1.9 14.2

Blindern, 1989/1990 40.0 29.4 4.2 6.5 1.1 1.5 1.9 14.0

The total energy consumption in the dwelling stock is estimated to be 45.8 TWh when monthly mean temperatures in a standard year at Blindern are used in the estimation model. This estimation is 0.9% higher than the 45.4 TWh estimated when using the weighted monthly mean temperatures.

Calculations based on monthly mean temperatures for Blindern from 1990 and from the heating season 1989/1990, shows that the estimated total energy consumption in these years would be reduced to 40.5 TWh and 40.0 TWh, respectively. The estimation of 40 TWh for the entire dwelling stock is 5% higher than the estimation of 38 TWh in Ljones et al. (1992), and identical to the estimation of 40 TWh in Rypdal (1993). A high degree of accuracy therefore seems to be found when the total energy consumption in the

dwelling stock is estimated on basis of the stereotypes of houses in the estimation model, and corrections are made for temperature variations.

4.3.2 Total emissions to air from the dwelling stock

In the residential sector, only combustion of fossil fuels generates emissions of CO₂. Table 4.7 shows that the total CO₂ emission from stationary combustion in private households in 1990 was estimated to be 1.4 million tons in SSB (1993). The total consumption of fossil fuels in the dwelling stock was estimated to be 3.6 TWh and 3.7 TWh in the two other surveys referred to in Table 4.7. Using a CO₂ emission factor of 265 g/kWh (74 g/MJ)10, the associated emissions to air of CO₂ from the combustion of fossil fuels are calculated to be 0.95 million tons and 1.0 million tons, respectively. Using monthly 1990-temperatures from Blindern in the estimation model, the total CO₂ emissions are estimated to be 1.2 million tons. This value lies between the estimation of 1.4 million tons in SSB (1993), and the estimation of approximately 1.0 million ton based on Rypdal (1993) and Ljones et al. (1992). The emissions of SO₂ estimated on the basis of the estimation model correspond well with the numbers from SSB (1993), while the emissions of NO_x and PM differ slightly.

It should be noted that large uncertainties are involved in the estimations of the total energy consumption in the dwelling stock and the associated emissions to air. It should also be noted that varying climate (i.e. outdoor temperatures) significantly influence the total energy consumption in the dwelling stock as shown in Table 4.7.

4.3.3 Conclusions on estimated total energy consumption and emissions

to air from the dwelling stock

Based on the stereotypes of houses in the estimation model, the total energy consumption in the dwelling stock has been estimated to be 45.4 TWh. This is notably higher than the total energy consumption of 38 TWh and 40 TWh, respectively, estimated on basis of

two surveys conducted by Statistics Norway. These two surveys, however, referred to 1989 and 1990 which were unusually mild years, while average temperatures for the period 1931 to 1960 were used in the estimation model.

Temperature data for Blindern Meteorological Station are to a large extent representative for the entire dwelling stock. Using data from Blindern for a standard year (average for the period from 1931 to 1960) in the estimation model, the energy consumption in the dwelling stock is estimated to be 45.8 TWh. This is only 0.9% higher than when using weighted monthly mean temperatures for the entire country for the period from 1931 to 1961. If the mild climate in 1989 and 1990 is taken into account in the estimation model by using monthly mean temperatures from Blindern Meteorological Station from 1989 and 1990, the total energy consumption is estimated to be 40.5 TWh in 1990 and 40.0 TWh in the heating season 1989/1990.

It may therefore be concluded that a high degree of accuracy is found when the energy consumption in the entire dwelling stock is estimated on basis of the stereotypes of houses in the proposed estimation model. Also the estimated total emissions of CO₂, SO₂, NO_x and particulate matter from the estimation model correspond well with data from surveys and statistics performed by Statistics Norway.

4.4 SIGNIFICANCE OF SOME PARAMETERS DESCRIBING THE