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

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6 Overall Energy and Associated CO 2

Having discussed energy demand and supply separately in earlier sections, this section builds a picture of how supply feeds through to meet demand. The sub-sections cover:

  • Representing energy flows diagrammatically via Sankey diagrams.
  • Summarising the balance of supply and demand.
  • Primary energy.
  • How Scotland compares with the UK.

6.1 Energy Flow in Scotland

One powerful method of representing complex energy flow patterns is by using Sankey diagrams. A series of Sankey figures are included overleaf to illustrate:

Figure 18: The big picture: Scottish energy inputs, production, consumption and exports.

Figure 19: Main overview of energy flows in Scotland 50.

Figure 20: Energy supply in Scotland: the top-down 'supply' detail.

Figure 21: Electricity sector energy flow in Scotland: electricity generation detail.

Figure 22: Final energy by sector in Scotland: the bottom-up "demand" detail.

Figure 18: Sankey diagram big picture

Figure 18: Sankey diagram big picture

Figure 19: Main overview of energy flows in Scotland

Figure 19: Main overview of energy flows in Scotland

Figure 20: Energy supply in Scotland

 Figure 20: Energy supply in Scotland

Figure 21: Electricity sector energy flow in Scotland

Figure 21: Electricity sector energy flow in Scotland

Figure 22: Final energy by sector in Scotland

Figure 22: Final energy by sector in Scotland

6.2 Scottish Summary for 2002

Based on the above, the overall energy figures based on the sum of 'demand' and 'supply' sectors (including refineries) are given in Table 24 , Table 25 and Figure 23 51:

Table 24: Energy consumption, based on sum of demand sectors in Scotland, 2002

Solid

Oil-based

Natural gas

Electricity

Renew & heat sold

Total

Units

Domestic

3.02

5.82

34.48

12.27

0.46

56.05

TWh

Industry

1.11

5.09

17.65

10.34

1.13

35.32

TWh

Services

0.04

2.78

11.37

11.28

1.36

26.83

TWh

Transport

46.77

0.30

47.07

TWh

Refineries

10.65

10.65

TWh

Total

4.17

71.11

63.5

34.19

2.95

175.92

TWh

Figure 23: Final energy by sector in Scotland

Figure 23: Final energy by sector in Scotland

Table 25: Energy consumption, based on sum of supply sectors in Scotland, 2002

Fuel

TWh (supply)

Comments

Solid

4.1

From bottom-up calculations

Oil-based

60.4

DTI adjusted figures

Oil-based - refineries

10.6

Identical to bottom-up calculations

Natural gas

64.4

Transco figures

Electricity

32.1

Taken from section 4.1

Renew & heat sold

2.9

Identical to bottom-up calculations

Total

174.5

The above supply figures will be used for the purpose of calculating and attributing CO 2 emissions to the Scottish energy picture. The difference between these 'supply' figures and the bottom-up 'demand' grand total is 0.6%. However, the 'bottom-up' figures are based more on assumptions and estimations and therefore are less likely to be robust.

For the Scottish Energy Study Model 1 analysis of electricity and its associated CO 2 emissions, a standard primary: delivered energy factor of 2.60 and a kg CO 2/kWh factor of 0.432 have been used 52. Clearly, it is possible to analyse the total CO 2 emissions from electricity generation within Scotland, then to either attribute all this generation to Scotland or apportion some to the exported electricity - either pro-rata or with some 'intelligence' as to which MPP generators will be providing the exported electricity. The pros and cons of different approaches have already been discussed in section 2.3.

6.3 Assessment of Primary energy

This section describes an assessment of primary energy consumption in Scotland.

The total is derived by summing direct consumption of primary fuels in demand sectors, with consumption of fuels as input to electricity generation.

If the effects of electricity exports are to be taken into account, it is then necessary to subtract the primary energy required to generate the 8 TWh of electricity that Scotland exported in 2002.

Table 26: Estimated primary energy consumption in Scotland, 2002

Direct

Electricity

Total

Comment

Solid

4.17

39.94

44.11

Mostly electricity. No top-down figure for 'direct'.

Oil-based

60.46

1.05

61.51

Oil refineries

10.65

0

10.65

Natural gas

63.5

21.11

84.61

Nuclear

0

42.2

42.2

Renew & heat sold

2.9(+) 53

5.46(+)

8.43(+)

Not possible to assess direct use of renewable assumed primary energy for electricity.

Total

138.78

104.3

243.08

Electricity exported to the rest of the UK

-21.6

-21.6

Primary energy required to generate 8.03 TWh of exported electricity, calculated using a UK average efficiency of 38.5%

Total, excluding electricity export

82.7

221.48

On this basis, Scotland consumes 243.1 TWh (874 PJ) of primary energy but is ultimately only responsible for 221.5 TWh (796 PJ) or 91% of the consumption figure, if exports are taken into account.

The CO 2 emissions associated with this energy use, together with non-energy CO 2 emissions, are discussed further in section 8.

6.4 Scotland compared with the Rest of the UK

Based on the above and extracting data from sections 3.1 to 3.4, one can make a top-down assessment of how Scotland compares with the entire UK for total energy and fuel split:

Table 27: Scottish v. UK energy, split by demand sectors, 2002

Solid

Oil

Gas

Elec

Others

Total

UK

Domestic

21.05

40.6

376.33

114.54

3.21

555.73

Industry

33.0

73.85

174.7

112.37

19.01

412.93

Services

0.31

21.63

100.88

97.78

10.68

231.28

Transport

-

635.4

-

2.8

-

638.2

Refineries

93.72

93.72

Total

54.36

865.2

651.91

327.49

32.9

1931.86

Scotland

Domestic

3.02

5.82

34.48

12.27

0.46

56.05

Industry

1.11

5.09

17.65

10.34

1.13

35.32

Services

0.04

2.78

11.37

11.28

1.36

26.83

Transport

-

46.77

-

0.3

-

47.07

Refineries

10.65

10.65

Total

4.17

71.11

63.50

34.19

2.95

175.92

% of UK

7.7

8.2

9.7

10.4

9.0

9.1

Overall, Scotland accounts for slightly greater energy consumption than pro-rata its population, 9.1% compared with 8.5% of the population. The main reasons for this are the requirement for extra heating in domestic and services, plus greater than pro-rata oil refining. These more than offset the slightly below pro-rata consumption by industry and transport.

The fuel split is not dissimilar to the UK average, with slightly lower demand for coal (predominantly because Scotland does not have any integrated steelworks and only one of the UK's 17 cement works). Gas and electricity are slightly higher than pro-rata, despite gas not being as widely available to remoter parts of Scotland; this factor is more than made up for by the increased demand for space/water heating requirements.