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Scottish Energy Study: Volume 1: Energy in Scotland: Supply and Demand

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5 Energy Supply

This section considers the primary fuels used in Scotland, and estimates both how much fuel is supplied and also its use by demand sector. It discusses each fuel in turn:

  • Solid fuel - mostly coal.
  • Natural gas.
  • Oil-based fuels.
  • Nuclear fuel.
  • Renewable energy.

5.1 Solid fuel - predominantly coal

5.1.1 Coal 'big-picture': imports & exports

Scotland currently produces approximately 7 Mt/year of coal, approximately 4.5 Mt of which arise from the main producer, Scottish Coal, at eight open-cast sites, mainly in Ayrshire.

The majority of coal consumption in Scotland is for power generation, although much of this uses imported coal. Power generation, in particular, is carried out at Longannet and Cockenzie power stations, which consume approximately 6.2 Mt/year. Both power stations are subject to stringent limits on their SO x emissions under the National Emissions Ceiling Directive ( NECD), the Large Combustion Plant Directive and IPPC. NECD sets bubble limits on SO x for all EU member states. Scottish coal has a sulphur content of approximately 1% and so fits within England's 'bubble', but not Scotland's. Because of this, only a proportion ( e.g. for Longannet about 23%) of Scottish coal is used for generation within Scotland. The remainder is sent to power stations south of the border. At the same time, Scottish Power imports coal from as far afield as Russia, Colombia and South Africa.

There is some inconsistency between information on imports and exports from Scotland: many studies take a UK-wide view, which blurs substantial movements of coal between Scotland and England. Information on imports on the Scottish Executive website suggest a figure of 1 Mt/year (given with a cautionary warning). However, given the comments above concerning exports of coal to power stations in England, this is likely to be a substantial underestimate.

For consistency, the Scottish Energy Study considers movements of coal and other fuels to (and from) Scotland from (and to) elsewhere in the UK as 'exports' and 'imports'. Unfortunately, there is little data available on coal movements within the UK. Furthermore, recorded imports into Scotland from outside the UK may be transferred to England and beyond; again these data are not easy to track. As such, the 'big picture' for coal (oil and gas) is based on estimations and calculation 36.

The indigenous Scottish coal extraction figure is 7.27 Mt 37. Using DUKES 'standard' 7,444 kWh/tonne, this would represent 54.15 TWh of primary fuel. The vast majority of this (95%+) was from open-cast mines and the largest areas were East Ayrshire and South Lanarkshire. Non- UK imports are believed to be approximately 1 Mt (7.44 TWh), although some of these may be transferred on elsewhere in the UK.

Anecdotal evidence suggests that Scottish Coal supplies a little over 1 Mt of coal to Longannet. Using the same proportion for Cockenzie, total indigenous coal supplied for Scottish electricity generation would be approximately 1.5 Mt (10.6 TWh), i.e. about 25-30% of the primary energy requirement 38. Taking the details of solid fuel use for each demand sector (from section 3.1-3.4, non-electricity demand was estimated as 4.17 TWh (equivalent to 550 kt coal) 39. Assuming all 4.17 TWh of non-electricity demand is met by indigenous coal, this would mean that:

  • Indigenous coal consumed in Scotland: = 14.8 TWh (or 2.0 Mt).
  • Imports = 29.46 TWh (3.9 Mt) from rest of UK and overseas.
  • Exports = 39.5 TWh (or 5.3 Mt) to rest of UK and overseas.

Table 16: 'Big-picture' analysis for Scottish coal, 2002

As Mt coal

As TWh

Indigenous output

7.24

54.15

Indigenous coal consumed within Scotland

2.0

14.8

Estimated 'imports'

3.9

29.46

Estimated 'exports'

5.3

39.5

5.1.2 Coal consumption within Scotland

This sub-section estimates the total tonnage of coal consumed within Scotland:

  • Directly - predominantly for domestic use plus some industry (such as cement & paper).
  • Generating electricity (predominantly at Longannet and Cockenzie power stations).

For the Scottish Energy Study, the total consumption for Scotland has been calculated from the bottom-up total 40. Based on the figures from sections 3 and 4:

Table 17: 'Bottom up' consumption of coal in Scotland, 2002

Sector

Bottom-up figures ( TWh)

Electricity generation

39.94

Domestic

3.02

Industry

1.11

Services

0.04

Total

44.11

Coal is consumed by a small number of industrial users, including paper and cement, sugar, process heat and chemicals. Very little coal is used by the public sector. Domestically, much coal is imported: this has been estimated by Scottish Coal as 40-50,000 tonnes a year.

Figure 14: Coal consumption in Scotland

Figure 14: Coal consumption in Scotland

5.2 Natural gas

5.2.1 Gas 'big-picture': imports & exports

Gas is an important energy industry in Scotland. The vast majority of 'indigenous' gas is from the North Sea, landed in Scotland. Gas is also imported by piping from Norwegian and Danish fields into Scotland. Exports are predominantly to England or via England to Continental Europe, although some are transferred to Northern Ireland via ' SNIP' (Scotland - Northern Ireland pipeline): the gas market only recently opened up in NI.

Figures for Scotland, provided by the DTI41, gave a top-down picture of:

Table 18: 'Big-picture' analysis for Scottish natural gas, 2002

As TWh

As Mtoe

Indigenous gas

391.38

33.65

Estimated 'imports'

71.76

6.17

Estimated 'exports'

-378.2

-32.52

Therefore, calculated own use

84.94

7.30

It is believed that these figures are net CV of the landed fuel. There will be some accounting differences (such as to where leakage losses are attributed or defining precisely the Scottish-English border), but these are likely to be small compared with the overall magnitudes.

5.2.2 Gas consumption within Scotland

Gas is a major fuel source in Scotland, being consumed by the domestic, industry, and all service sectors. Over the past 10-20 years, gas consumption has tended to grow, generally at the expense of other fossil fuels, predominantly coal and fuel oil, because of its availability, low cost, versatility, no/low storage requirements and low atmospheric emissions of dust, SO x, etc. Despite gas being a major industry in Scotland, general availability of gas is less than the UK average, particularly in the remoter regions.

Direct sales of natural gas within Scotland for 2002, based on Transco reported figures, were 64.43 TWh total, split 30.62 TWh industry & services and 33.81 TWh domestic 42.

These figures matched fairly closely to the sum of the bottom-up figures for the demand sectors, of 63.44 TWh, as shown below:

Table 19: 'Top-down' v. 'bottom-up' gas consumption in Scotland, 2002 (as TWh)

Sector

Transco figures

Bottom-up figures

Difference

Domestic

33.805

34.48

-2.0%

Industry

30.619

17.59

5.4%

Services

11.37

Total

64.424

63.44

1.5%

The overall difference between the two sets of data is only 1.5%, which is considered quite good. In addition, the split between domestic and industry & services is broadly similar. There will be subtle differences to do with:

  • The bottom-up figures are based on best estimations.
  • How DTI apportion sales to Scotland and England: the Transco sales 'border' may not match exactly the England-Scotland border.
  • Gas sales to CHP generators are recorded as direct sales to a sector. However, if the CHP unit sells electricity directly or via the grid, this fuel could also be 'seen' by DTI's Energy Trends as gas consumed for electricity generation 43.
  • Distribution losses and leaks.
  • Some service sector consumption will be captured at the top-end of the domestic consumption figure; similarly, some heavy domestic consumers (or grouped consumers) may have been captured in the 'service' criterion.

All of these would help to account for the small difference between the two sets of data.

For the purpose of the Scottish Energy Study, the Transco figure of 64.42 TWh will be used. The bottom-up build figures will be used to (a) help confirm and (b) provide a split of consumption by the demand sectors.

Adding in the estimated gas used to generate electricity via electricity generation (conventional steam cycle and CCGT plants and exports from CHP - section 4.1) gives:

Table 20: 'Top down' consumption of gas in Scotland, 2002

Sector

Top-down figure ( TWh)

Domestic

33.81

Industry & Services

30.62

Electricity generation

21.11

Total

85.54

Figure 15: Gas consumption in Scotland

Figure 15: Gas consumption in Scotland

5.3 Oil-based products

5.3.1 Oil 'big-picture': imports & exports

Oil is a major energy industry in Scotland. Again, the vast majority of 'indigenous' oil is from the North Sea, landed in Scotland. Crude oil, piped from Norwegian and Danish fields into Scotland, accounts for most of the 'imports', although there may also be some crude oil shipped into Scotland for the refinery at Grangemouth in order to make the correct blend of final product. Exports will be piped to England (or via England to Continental Europe), or transported by tanker. Losses are likely to be very small compared with the overall size of the market.

Figures for Scotland, provided by the DTI44, gave a top-down picture of:

Table 21: 'Big-picture' analysis for Scottish crude oil, 2002

Million tonnes (Mtoe)

As TWh

Indigenous oil

98.768

1,148.67

Imports

0.434

5.05

Exports within UK

-22.265

-258.95

Exports outside UK

-68.073

-791.69

Therefore, total crude to be refined in Scotland

8.864

103.08

Note: some of these data are from 2002/3 or 2003, so figures will not match precisely with the estimated volume of oil refined within Scotland. However, they are reasonably close and the headline 'indigenous', 'import' & 'export' figures are useful in that they give perspective regarding the amount of oil passing through Scotland compared with oil consumption within Scotland.

5.3.2 Oil consumption within Scotland

The vast majority of oil-based products that are consumed in Scotland are for transport use, in particular, road transport which has grown over the past 10-20 years. Smaller amounts of oil are used for process heating in industry, and space/water heating for the industry, domestic and services sectors.

Details of how the DTI oil statistics for UK - split down into England & Scotland, Scotland and NI - have been handled are shown in Appendix 4.

  • The main problem identified in section 3.2, Transport, was the accounting methodology used to apportion fuel use to Scotland, NI and England & Wales. For road-fuel, this gave a heavy skew to England & Wales and away from Scotland. It is believed that the cause of the issue has been identified and correctly adjusted. Particular attention was needed for road transport because it was by far the largest. DTI and NAEI data were cross-referenced with other sources, including estimated km road journeys and 'typical' km/litre fuel figures.
  • Scotland's rail transport energy and CO 2 figures were calculated based on Scotland/England & Scotland pro-rata population.
  • Scotland's air transport use was calculated from the DTI statistics. It was believed that these figures did not suffer the same skew as fuel used for road transport. Fuel for air transport will be less than pro-rata Scotland/England & Scotland population.
  • Scotland's marine energy use was calculated as greater than pro-rata Scotland's population because there are numerous large ports in Scotland. A figure of double pro-rata population was used. Earlier studies on shipped goods support this.
  • Scotland's industry oil-based fuel consumption was estimated based on the Scottish proportion of UK industry energy demand. For 2002, this was approximately 8.2% of the UK total, i.e. similar to Scotland's pro-rata population.
  • Scotland's domestic and service oil-based fuel consumption was calculated based on the pro-rata Scotland/ UK population. Public services are likely to be slightly more (because Scotland receives greater than pro-rata population funding from Government sources), whereas commercial services are likely to be slightly less (as many commercial centres are in London).
  • The top-down figure for Scotland's (very small) oil for electricity generation figure was back-estimated from the DTI statistics for electricity 45.

Scotland's oil-based figures matched closely the bottom-up figures, both in total and split across the sectors, which gave confidence to their robustness. The bottom-up figure (from section 3) and top-down figure (from Appendix 4) were 61.12 and 61.02 respectively. These represent a difference of about 0.1%. Even ignoring transport energy, which was calculated via the same route and thus represents a large 'ballast', the totals and splits are reasonably close to each other.

Table 22: 'Top-down' vs. 'bottom up' oil consumption in Scotland, 2002

Sector

Top-down

Bottom-up

Transport

46.77

46.77

Industry

5.26

5.09

Domestic

5.25

5.82

Services

3.06

2.78

Electricity generation

0.78

0.56

Total

61.12

61.02

In addition, there is the 10.65 TWh self-consumed by oil refineries, calculated in section 4.2.2.

For the purpose of the Scottish Energy Study, a total of 61.1 TWh will be used, made up from 60.4 direct demand plus 0.78 for electricity, together with 10.65 TWh self-consumed by oil refineries. The bottom-up build figures will be used to (a) help confirm and (b) provide a split of consumption by the demand sectors.

Figure 16: Oil consumption in Scotland

Figure 16: Oil consumption in Scotland

5.4 Nuclear Fuel

In 2002 there were three nuclear power sites in Scotland: Torness, Hunterston and Chapelcross. British Energy plc had four Advanced Gas Cooled ( AGR) reactors running at Hunterston in Ayrshire and Torness in East Lothian. In addition, British Nuclear Fuels Ltd ( BNFL) operated a set of four small Magnox reactors at Chapelcross in Dumfries & Galloway, although Chapelcross ceased production in 2004.

The amount of nuclear fuel used has been estimated, based on known generation of electricity in 2002 from Torness, Hunterston and Chapelcross nuclear stations divided by a 'typical' nuclear generation figure of 37.6%, taken from DTI's 'Plant loads, demand & efficiencies' 46.

This gives a primary energy consumption figure of 42.19 TWh. There are no other energy-related uses for nuclear fuels.

The true primary energy input into nuclear generation was not evaluated for this report and the CO 2 emissions associated with its generation were set as 0.0 kg CO 2/kWh. This approach allows the results of the study to illustrate the fact that nuclear generation is also a potential source of low temperature waste heat, just as are conventional generators. In theory, up to 26.3 TWh of low-grade heat are available from nuclear generators.

5.5 Renewable sources

In 2002, Scotland generated 5.1 TWh of electricity from renewable energy sources:

Table 23: Electricity generation from renewable sources in Scotland, 2002

Renewable source

GWh

Natural hydro MPP

3,696

Natural hydro (small-scale)

762

Wind & other non-thermal renewable

406

Thermal renewable (bio-mass)

237

Total

5,101

In recent years, there has been about 10% year-on-year growth of electricity from renewable sources across the UK. The equivalent renewable figure for Scotland in 2001 was approximately 4,247 GWh47: 3,008 GWh from natural hydro MPP plus 1,239 GWh from small-scale hydro, wind and thermal sources (biomass).

It would be very difficult to provide a meaningful figure for the amount of primary energy consumed to generate this electricity. For thermal sources of renewable energy we have allowed for this, reflecting the fact that the heat as well as the electricity from these sources could be used. As with nuclear generation, CO 2 emissions associated with its generation were set as 0.0 kg CO 2/kWh 48.

Figure 17: Renewable electricity sources in Scotland

Figure 17: Renewable electricity sources in Scotland

Based on the sum of the demand sectors, it is understood that the direct consumption of renewable fuel by consumers in Scotland is of the order of 3,000 GWh/year. However, it is recognised that tracking direct consumption of renewable energy is very difficult:

  • Data are not collected on primary energy consumption of (say) domestic/public house consumers of wood-burning fires/boilers/stoves. Indeed, it is not easy to see how these data could be collected. The fuel is often scavenged from dead wood, ad-hoc tree felling, discarded furniture/pallets/wood or paper waste, etc. 49
    Secondly, it is our opinion that, because the fuel is considered 'free', less attention is paid to optimising efficiencies of the fires or boilers.
  • Similarly, small-scale waste-material burners, used to (say) fuel boilers, make use of a variety of waste streams. The prime motivator for these is often to reduce waste that would otherwise go to landfill; generating energy is a secondary concern. As such, little emphasis is given to assessing the primary fuel calorific value and/or the burning efficiency of the heater/boiler.