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Appendix 1 SUMMARY OF DATA SOURCES AND METHODS

This 1990 vs. 2002 comparison

The Scottish Energy Study (2002) is the first major analysis of Scottish energy supply and demand for over a decade. The most recent full study was by AHS Emstar - published in 1993, but based on 1989/90 data.

One of the aims of the 2002 Scottish Energy Study is to analyse trends in fuel supply and energy demand since 1990. This entails comparing information developed under the current study with that presented in the AHS Emstar report.

The present Energy Study uses a wide range of data, from the DTI, utilities and other sources. We have drawn on the 1990 study final published report, which contains a Sankey energy flow diagram for Scotland, plus some headline summary information on electricity and other fuels. This diagram provides the main quantified results for Scotland in 1990.

It has proved difficult to obtain additional details of the data sources, analysis method or conventions used for this 1990 dataset. Even if this level of detail were known, it is unlikely that the methodology would match that used for the current study. This is because recent DTI statistics provide more detailed UK regional breakdowns than were available for 1990, and the amount of available statistical information, predominantly from the internet, is an order of magnitude larger than it was in the early 1990s.

Because the 1990 data and the 2002 data from this study are not directly comparable it has been necessary to develop a methodology to provide a comparison. Our methodology uses DTI data for UK energy in 1990 and 2002 to scale and cross-check the results of both Scottish studies.

This appendix provides full details of this methodology.

Methodology

This appendix describes the analysis method used and then presents the findings of the comparison. To provide these outputs the main steps have been:

1. Analysis of the AHS Emstar study findings:

• Converting data units from PJ to TWh and use of 'standard' kg CO ₂/kWh factors for fossil fuels to calculate the CO ₂ emissions.
• Analysis of energy supply and demand picture.
• Analysis of secondary fuels, in particular, electricity.
  Estimates overall generating efficiency (at power stations and including distribution/transmission/etc losses) to produce a figure based on findings from the AHS study.

2. Comparing the unadjusted AHS figures with the 2002 Energy Study:

• Identification of any substantial differences to total and fuel split that cannot be explained by known, Scottish-specific issues.

3. Analysis of the DTI Energy Statistics for the four 'demand' sectors ⁶ in 1990:

• Converting DTI energy data from ktoe to standard TWh.
• Calculating pro-rata energy statistics for Scottish population (1990 Scotland = 8.9% of UK population) ⁷.

3. Comparing and contrasting the two sets of 1990 data:

(i) AHS Emstar 1990 base year assessment of Scottish energy, with

(ii) DTI 1990 data pro-rata for Scottish statistics for the four main 'demand' sectors.

• Identifying any substantial differences to total and fuel split that cannot be explained by known, Scottish-specific issues.
• Commenting on these differences and, where applicable, suggesting alternative figures that could be used for 1990 total and fuel split.

4. Analysis of DTI Energy Statistics for the four 'demand' sectors in 2002:

• Converting DTI figures from ktoe to standard TWh then pro-rata statistics for Scottish population (2002 = 8.5% of UK)
• Comparing the DTIUK pro-rata figures for 2002 with those of 1990.
• Identifying and commenting on any general ( UK) trends that would be applicable to Scotland.

5. Analysis of energy and electricity data from the Scottish Energy Study 2002; comparing and contrasting the findings with:

• AHS Emstar 1990 base year assessment of Scottish Energy, after factoring in factors identified in 1-4 above.
• Identification of major changes in energy patterns.

Analysis of AHS Emstar Study findings

Analysis of 1990 Sankey figure

Data from the AHS Sankey flow diagram is repeated in Figure 5 below.

Figure 5: Energy flow diagram from 1993 AHS study (in PJ⁸)

Data from the figure have been converted into energy 'supply' and 'demand' tables, as shown in Table 2 and Table 3.

Table 2: AHS report: primary energy supply - 1990 (as TWh)

Assuming 'imports' simply mean fuels from outside Scotland ⁹, then according to the AHS study, Scotland consumed 229 TWh of primary energy in 1990, and by calculation was responsible for 45.2 Mt of CO ₂ emissions.

All of this energy was either consumed directly by Scottish end-users or converted into electricity, which in turn was consumed almost entirely by Scottish end-users. In 1990, only 0.14 TWh or 0.15% of Scottish electricity was exported, 99.85% was consumed within Scotland ¹⁰.

A cross-check with 'demand' sectors also gave 229 TWh of primary energy, as shown in Table 3 and Figure 6.

Table 3: AHS report: energy demand - 1990 (as TWh primary)

Figure 6: Scottish supply and demand - 1990 - based on AHS report

Peterhead was operating exclusively on oil from the late 1980s until 1992/3. ¹² The AHS study did not identify any gas for electricity generation in 1989/90. Further exploration suggests that this appears to be correct.

Secondly, the AHS report does not include the use of gas in CHP, which was also present in 1990, although this latter point could well be a presentational issue - this gas may be 'seen' as direct consumption within the industry or services sectors that operate these CHP schemes.

1990 electricity

As already commented, electricity has to be handled differently, as it is both a consumer of primary fuels and provider of secondary fuel to the other 'demand' sectors. As such, Scottish electricity and associated CO ₂ emissions can be considered virtually self-contained in 1990 (with a small amount of CO ₂ associated with the exports), making it much easier to handle than the 2002 picture.

There is little detail on electricity data in the AHS report. There are no specific data on generating efficiencies for the different primary fuels, nor was there any information on self-consumed electricity, distribution & transmission losses or electricity used to generate pumped hydro. For the purpose of this report, these have been estimated by back-calculating typical generating efficiencies for different generators in 1990 and estimating typical self-consumed, losses, etc in order to arrive at the above table and match both the primary 'in' and delivered 'out' figures. Assumptions and estimations are shown in Table 4.

Furthermore, no mention is made of CHP and small-scale generators (which did exist in 1990), nor electricity used for pumped hydro, which again existed in Scotland in 1990 (Cruachan, Oban opened 1965, and Foyers, Loch Ness). These have been factored in.

Table 4: Back-calculations for AHS electricity data - 1990

The 1990 picture for Scottish electricity is shown in Table 5 and Figure 7:

Table 5: AHS report: Scottish electricity - 1990 (as TWh)

Therefore:

Overall generating efficiency = 26.57 / 85.82

= 31.0%

Average emission factor = 0.348 kg CO ₂/kWh(d)

Figure 7: Scottish electricity generation and primary fuel consumption - 1990 ¹⁴

Note: The corresponding 2002 figure for saleable electricity was 40 TWh, i.e. over 50% higher. The absolute difference works out at 13 TWh, of which 8 TWh was exported. We estimate 2002 Scottish demand at 32 TWh (excluding CHP), which is 5.5 TWh higher than in 1990. Together, these account for the 13 TWh difference.

1990 delivered energy

Based on the AHS report, delivered energy consumption in Scotland in 1990 is shown in Table 6 and Figure 8:

Table 6: AHS report: demand sectors - 1990 (as TWh delivered)

In addition, approximately 10.0 TWh was consumed for oil refining, plus 3.6 TWh was used for coke making. These processes can be considered as either industries in their own right, or their energy use can be considered as losses through secondary fuel conversion. For consistency, refining oil and coking have been included as secondary fuels for both 1990 and 2002.

Thus, the analysis of the AHS report suggests that in 1990, Scotland consumed 157 TWh of delivered energy. Nearly 45% of this energy was oil-based fuel ¹⁵, with natural gas making up 25% and electricity and solid fuels the remainder. Industry was the largest demand sector, followed by transport and domestic, with services being the smallest.

Figure 8: Energy use in 1990 - based on AHS report

Direct comparison of AHS figures with 2002 Energy Study - no adjustments

The 1990 Scottish delivered energy consumption, based on Table 6 above but (for consistency) including energy losses from coke and oil processing, is given below in Table 7:

Table 7: AHS report: Scottish consumption based on 'demand' sectors - 1990

Findings from the 2002 Scottish Energy Study are shown in Table 8:

Table 8: Energy Study: Scottish consumption based on 'demand' sectors - 2002

Consumption in the domestic energy appears to have risen by 43%, which is a very large increase that is difficult to justify, particularly given that the Scottish population has fallen slightly.

One would expect some increase in domestic energy use, particularly for electricity consumed by domestic appliances and other electrical goods (see Figure 9 below). However, based on the above figures, the proportion of electricity use has fallen from 28% in 1990 to 22% in 2002, which contradicts known UK trends.

Further analysis is made in this appendix, which compares the AHS figures with DTI Energy Statistics for UK pro-rated for the Scottish population. This also suggests that the 1990 Scottish domestic energy total and fuel split are likely to be inaccurate and would need some attention before any meaningful comparison can be made.

Figure 9: Percentage of UK households that own domestic appliances

For Scottish industry, the total energy consumption appears to have fallen by some 30% between 1990 and 2002. This would not be entirely unexpected with an integrated steelworks plus several large engineering, chemicals and metal operations closing during the intervening 12 years. However, the total (and oil) figures are still slightly higher than one might expect.

Service sector consumption appears to have risen by about 10%. Again, this would not be unexpected. Furthermore, in the service sector the proportion of electricity rose from under 30% to over 40%, which again would be expected - resultant from increasing demands for PCs and other office equipment plus air-conditioning. In addition, natural gas consumption has risen (from under 30% to over 40%), at the expense of coal and oil.

Energy demand for transport has also risen, by 10%, which again agrees with known trends in increasing use of road and air transport. This sector was and remains dominated by oil-based fuels.

In conclusion, most of the trends resultant from the direct comparison of AHS's 1990 figures with the Scottish Energy Study 2002 data would appear reasonable, with the exception of domestic fuel total and fuel split. This area will need attention before any sensible comparison can be made. This is addressed in the following sections.

DTI Energy 'demand' sectors statistics: 1990

Given the observations made regarding the AHS data for 1990, this appendix uses DTI data for the entire UK in 1990 as a method of cross-checking.

This uses the fact that in 1990 the Scottish population was 8.9% of UK population, using this we scaled the DTI data for the UK to give the figures in Table 9:

Table 9: DTI statistics for Scotland as 8.9% of UK population - 1990 (as TWh)

Clearly, a pro-rata analysis is very simplistic. Comments on how these data are handled are discussed in the following pages.

Comparison of 1990 AHS figures with DTI figures

IMPORTANT NOTE:

The following comparison draws out the changes in consumption between 1990 and 2002. Because of the different data collection and analysis methods, this comparison must be treated with care - much of this is indicative rather than absolute fact. For example, where there are clear differences that are contradicted by other known facts we can try to adjust the data in the light of these facts. Where the comparison is 'in tune' with known facts it is impossible to know if the comparison is an accurate reflection of the actual level of changes or is only an approximate match.

Drawing a comparison between Table 7 (the AHS report findings) and Table 9 ( DTI statistics based on pro-rated for population):

Energy demand

Domestic

The 1990 DTI population pro-rata figure for Scotland is 42.2 TWh, made up from 63% gas, 20% electricity, 10% solid fuel and 6% oil-based fuel.

The AHS total of 39.2 TWh is lower than the unadjusted figure. Furthermore, its split is 53% gas, 28% electricity, 12% solid and 7% oil-based fuel. Three observations are made on this:

Firstly, as already commented, if anything, Scotland would be expected to have greater than UK pro-rata domestic consumption ¹⁶, having a colder climate, poorer housing stock ¹⁷ and fewer 'useful' daylight hours than the UK average.

Secondly, whilst one may expect lower than UK average accessibility to gas in Scotland, particularly in the Highlands and Islands, it is difficult to account for the very much lower proportion of gas in the AHS report (only 53%) compared with the UK average figure (63%). It would be reasonable to expect some differences and to expect larger than pro-rata consumption of other fossil fuels to compensate (which can be seen), but not to the extent indicated here.

Thirdly, the AHS electricity consumption figure is very difficult to explain. One may expect some additional use (due to less gas availability and extra lighting requirements) but conversely, taking different standards of living in Scotland compared with the UK in 1990, one would expect fewer domestic electrical appliances such as videos, washing machines, fridge-freezers, etc. Furthermore, as discussed earlier, one would expect the proportion of electricity consumption to rise rather than fall between 1990 and 2002.

Suggested modifications to the 1990 domestic energy total consumption and fuel split in each are discussed in the following pages.

Industry

The 1990 DTI population pro-rata figure for industrial energy use in Scotland is 40.0 TWh, comprising 33% gas, 22% electricity, 21% solid fuel, 21% oil-based fuels and 2% coke oven gas.

The AHS total of 50.3 TWh is some 25% more than the DTI pro-rata figure. It is split 25% gas, 17% electricity, 26% solid and 31% oil. Coke oven gas (from Ravenscraig) appears to have gone to waste; this would be unusual practice for an integrated steelworks, but investigating this level of data from 1990 is beyond the scope of the Energy Study.

It would not be unreasonable to assume that, at the time, Scotland would have been greater than pro-rata UK industry, with an integrated steelworks plus several other large, energy-intensive industries operating. This would also help to account for the higher than pro-rata solid fuel consumption. It is also difficult to know where the AHS study 'drew the line' between oil-refinery activities and secondary petrochemical processing, which could account for the apparently high percentage oil figure.

As commented already, the AHS figures suggest that Scottish industry in fact consumed 50.3 TWh in 1990. This may be a little high (and have disproportionately high oil use), but given the above commentary, there is insufficient evidence to contradict and adjust the AHS figures.

Services & other

The 1990 DTI figure for Scottish services is 19.9 TWh, comprising 38% gas, 33% electricity, 23% oil-based fuels, 5% solid fuel and 1% others.

The AHS total of 24.4 TWh is some 23% higher than the DTI-based figure. It is split 29.5% gas, 29.5% electricity, 35% oil-based fuels and 6% solid fuel.

It would be reasonable to expect Scotland to have had greater than pro-rata total consumption, for the same reasons as with the domestic sector. Increasing the DTI figure by 15% (similar to that of the domestic sector on the previous page) would raise its total to 23 TWh. The AHS total, 24.4 TWh, does not fit uncomfortably with this.

One may also expect a lower than UK pro-rata gas figure and correspondingly higher than pro-rata figures for other fossil fuels, for similar reasons as already discussed.

The AHS figures suggest Scottish services consumed 24.4 TWh in 1990. As with industry, this may be a little high (and have disproportional high oil use), but given the above commentary, there is insufficient evidence to contradict and adjust the figures.

Transport

The 1990 DTI-based figure for Scotland's consumption is 49.9 TWh, predominantly oil. AHS figures are somewhat lower, at 42.5 TWh, also predominantly oil. The difference, of 7.4 TWh (or 17%) is not insignificant.

One may expect Scotland's total to be less than UK pro-rata, particularly with less long-haul air transport. This is sensitive to how air transport fuel is measured - an issue that has been identified with the 2002 data, see Volume 1. Although this would not fully explain the difference, it would bring the difference down to approximately 4 TWh, i.e. less than 10%.

An additional possibility is that the AHS study may have attributed the energy associated with transporting industrial and service goods in Scotland to the industry and services sectors, whereas DTI statistics would have classified them as transport. There is no direct evidence to support this hypothesis, but it would help to further explain the apparent low AHS oil (and total) figures for Scottish transport in 1990. This could also explain the apparent high oil (and total) consumption figures for industry and services.

Electricity consumption

The AHS figure of 26.7 TWh Scottish consumption matches the DTI-based consumption figure of 24.4 TWh reasonably closely. The AHS total is 9% greater than the DTI pro-rata figure.

Much of the commentary for the demand sectors, domestic, industry and services, would suggest that Scotland's overall demand for electricity in 1990 would be slightly greater than its pro-rata population, which would fit comfortably with the AHS figure.

Energy supply

Given the limited information available on the AHS Emstar data and their analysis, it is difficult to make detailed comments on the robustness of the raw data regarding energy supply. However a few differences do stand out:

• Solid fuel: the AHS total for non-electricity consumption of solid fuel (23 TWh) is a lot more than the DTI pro-rata figure (14 TWh for all sectors).
  Most of the difference can be attributed to Ravenscraig, which was one of five UK integrated steelworks in 1990 and would have consumed large quantities of coal/coke in the blast furnace. The AHS report indicates 36 PJ (10 TWh).
  There is little reason to doubt the AHS figures.
• Gas: was consumed directly by industry, domestic and services but was not consumed in electricity generation until 1993.
• Oil: was the biggest primary supplied fuel, predominantly used for transport applications but also used heavily for industry, services and electricity generation (far more so than in 2002).

Adjustments to the AHS figures

Based on the sector-by-sector reviews above:

• Revising (increasing) the 1990 domestic energy demand to 48.5 TWh, which is pro-rata UK adjusted up by 15%.
• Adjusting the domestic fuel mix to be (what is thought with hindsight) to be a more realistic split (of 60% gas, 20% electricity, 12% solid and 8% oil ¹⁸).
• Keeping the other demand sectors as in the AHS report.

This would increase the total demand for 1990 to approximately 166 TWh.

Table 10 shows the results of making these modifications to the AHS, including the fuel split:

Table 10: AHS (revised): demand sectors - 1990 (as TWh delivered)

Re-estimating the CO ₂ emissions associated with these fuels (and ensuring we re-include the losses from coal transformation and oil refining) gives the results in Table 11 and Figure 10:

Table 11: AHS (revised): supplied energy and CO ₂ emissions - 1990

Figure 10: Revised 1990 energy picture

Thus, using the AHS report as the basis but adjusting domestic consumption up to what is believed (with hindsight) to be a more realistic total and fuel split suggests that, in 1990, Scotland:

• Consumed nearly 166 TWh of delivered energy across its main demand sectors, plus nearly 14 TWh for oil refining and coking.
• Consumed (by calculation) 236 TWh of primary energy²⁰.
• Was responsible for 46.5 Mt of CO ₂ emissions.

DTI Energy 'demand' sectors statistics: 2002

Table 12 shows the results from using population data to pro-rata the DTI all-sectors energy consumption figures for 2002:

Table 12: DTI statistics for Scotland as 8.5% of UK population - 2002 (as TWh)

General comments on DTI's UK 1990 v. 2002 figures and trends over the intervening 12 years:

• UK domestic consumption rose by 17% over 12 years. This growth is likely to reflect:
  (a) changes in demography, with larger number of single or dual occupancy dwellings, combined with
  (b) the relentless growth in electric-powered kitchen appliances/ PCs/leisure goods/etc
  …rather than poorer energy performance. The large (23%) increase in electricity consumption figure supports point (b).
  For heating, gas use has grown (25%), whereas solid fuel consumption has more than halved. Surprisingly, oil consumption has risen (albeit by a small amount).
• UK industry energy consumption has shrunk by some 12%. Much of this will be due to closures of some heavy, energy-intensive industries such as steel, bauxite refining, non-ferrous metal (largely outside Scotland) and others. This reflects an on-going UK trend away from heavy industry, to which Scotland is no exception.
  This trend is in part reflected by the fuel make up: solid fuel has fallen considerably ²¹, as have oil-based fuels, whereas gas and electricity have both risen despite the reduced total.
• Overall transport consumption has risen by approximately 22%. However, the figures behind this headline show large variations. DTI figures suggest only a modest (3%) increase in UK private-vehicle road transport, but a 20% increase in road freight. Road journey figures indicate larger increases, particularly in private vehicles. One may expect the impact from this to be partly counterbalanced by more efficient engine consumption, but not by as much as the statistics suggest. Other studies have reported higher figures.
  Air transport increased the most, by over 50%.
• Finally, services largely mirror domestic figures with respect to trends in total consumption and fuel mix.

Main findings from the 2002 Scottish Energy Study

Analysis of the 2002 'headline' figures

Findings from the 2002 Scottish Energy Study are shown in Table 13:

Table 13: Energy Study: Scottish consumption based on 'demand' sectors - 2002

It is not appropriate to compare Table 13 (above) with the DTI 2002 figures shown in Table 12. A great deal of information for Table 13 was drawn from DTI statistics but with numerous modifications to take into account Scottish-specific issues ²².

Scottish electricity - 2002

The primary fuels used to generate electricity are shown in Table 14 and Figure 11:

Table 14: Scottish Energy Study - electricity - 2002

Figure 11: Scottish electricity generation - 2002

The difference between the sum of the sectors and the total supplied is due to methodologies used for reporting electricity. DTI Energy Trends reports all electricity generation including CHP that is self-consumed by on-site processes, whereas the Scottish Energy Study would 'see' these as primary fossil fuels (predominantly gas and oil). Adding CHP and small-scale electricity generation to the total electricity would effectively be double-counting this fuel.

As commented earlier, the electricity picture in 2002 is likely to be more detailed and accurate, but as a consequence will be more complicated than the AHS study findings. Part of this is presentational, as the AHS report did not contain any split for generating efficiencies or storage/losses away from the generator, but part is real, in particular, the growth of exports (to England and more recently NI), which in 2002 represented approximately 20% of Scotland's saleable electricity.

From the above, Scotland's CO ₂/kWh (saleable electricity) = 16.28 Mt/40.12 TWh

= 0.4058 kg CO ₂/kWh

This represents a large increase in the Scottish electricity CO ₂/kWh factor between 1990 and 2002 of nearly 18%, explained by the decrease in nuclear and increase in fossil fuel generation (particularly coal). Renewable sources have grown, however, most of the large hydro MPPs were already built in 1990 and the new renewable energy capacity had only a small impact on the 2002 figures.

The generating efficiency can be calculated from:

Primary energy in (including renewable sources) = 109.40 TWh

Saleable electricity (including exports) = 40.12 TWh

Generating efficiency ²⁴ = 40.12 /109.40 = 36.7%

This, in fact, represents a big improvement since 1990, when the generating efficiency after G, T & D losses was estimated as only 31%. The improvement is predominantly because of the recent introduction of more efficient combined cycle gas turbine ( CCGT) generators at Peterhead plus the higher level of renewable sources.

Overall

Table 15 shows the results of feeding these into a 2002 picture for CO ₂ emissions, to enable a comparison with the results in Table 2:

Table 15: Scottish Energy Study: energy consumption and CO ₂ emissions - 2002

However, in 2002, 8.0 TWh (or 20%) of the 40.1 TWh of saleable electricity was exported to England and NI. Table 16 shows the results of extracting this primary energy on a pro-rata basis.

Table 16: Scottish Energy Study: energy consumption and CO ₂ emissions - 2002 - after exported electricity subtracted

It is worth noting that the above analysis for CO ₂ emissions is different to the main method used in the Scottish Energy 2002 Base Year report. For the 2002 report, electricity consumption is multiplied by a standard UK 'basket'" factor (of 0.432 kg CO ₂/kWh). This allows the 2002 Base Year report to accommodate the fact that Scotland's electricity is intimately linked with that of England and Northern Ireland. In 1989/90, Scotland exported only 0.15% of its electricity; by 2002 this had risen to 20%. The analysis in Table 13 allows one to make a comparison for primary fuels between 1990 and 2002, i.e. to enable a comparison with the results in Table 2.

In conclusion, and after extracting the primary electricity used to generate exported electricity, in 2002 Scotland:

• Consumed 165 TWh of delivered energy across its main demand sectors, plus nearly 11 TWh for oil refining. Hence, total consumption in 2002 was 176 TWh.
• To provide the 176 TWh of energy consumed, the primary energy ²⁹ required in Scotland was 230 TWh, as found in 1990, most of the losses were associated with electricity generation. Consumed nearly 165 TWh of delivered energy across its main demand sectors, plus nearly 11 TWh for oil refining.
• Was responsible for 44.0 Mt of CO ₂ emissions.

NAEICO ₂ emissions: 1990 & 2002

The NAEI³⁰ assessment of CO ₂ emissions for 1990 and 2002 is shown in Table 17. This is built up from a different basis, with:

• All electricity attributed to the point-of-generation rather than point-of-use (this would not matter unduly for 1990, but has a substantial impact on the 2002 data).
• International air and marine transport is largely ignored.
• The assumptions and calculations made for apportioning energy for domestic, industry and other sectors is built on a different basis.

Nonetheless, the figures provided an interesting comparison:

Table 17: NAEI comparison for Scotland CO ₂ emissions: 1990 v. 2002

Firstly, the NAEI total of fuel CO ₂ emissions for 1990 (50.29 Mt) is 3.8 Mt higher than the revised AHS figures of 46.5 Mt. This is within 7.5% of the NAEI total, which gives one some confidence in the revised figures ³¹.

The NAEI total of CO ₂ emissions for 2002, 47.61 Mt, closely matches the unadjusted CO ₂ emission figure from Table 15 (the 2002 Energy Study including the contribution from exported electricity). The adjusted figure of 44.0 MtCO ₂ in Table 16 differs by only 0.1 Mt compared with the 2002 Energy Study's actual findings of 44.1 Mt³². This gives good confidence in the 2002 figures.

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