Future energy demand and supply
Future energy demand and supply

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Future energy demand and supply

2.2.1 The World Energy Council scenarios

Among numerous attempts to forecast the future of global energy systems, one of the most recent and comprehensive was produced in 1998 by the World Energy Council (WEC) and the International Institute for Applied Systems Analysis (IIASA), a leading 'think tank' based in Austria. There are six WEC scenarios, grouped into three main cases, which compare predicted primary energy use in 2050 with a base year, 1990 (IIASA and WEC, 1998). These scenarios are summarised in Table 1, and their predictions are compared in Figure 8a.

Table 1 World Energy Council global energy scenarios (1998)

Case (economic growth per year; efficiency improvement)Scenario descriptionBlend of primary energy sources in 2050/%
CoalOilGasNuclearRenewables
A: High Growth (2.7%; medium)

A1: ample oil/gas

A2: return to coal

A3: non-fossil future

15

32

9

32

19

18

19

22

32

12

4

11

22

23

30

B: Middle Course (2.2%;low)mixture of sources2120231422
C: Ecologically Driven (2.2%; high)

C1: new renewables

C2: renewables + new nuclear

11

10

19

18

27

23

4

12

39

37

Base year: 1990mainly fossil fuels243419518
Figure 8 (a) Global primary energy use: historical development (1850-1990), and projections to the end of the 21st century, based on the three WEC scenarios (Table 1). (b) Global population growth 1850-1990 and projections to 2100.

Case A scenarios involve high economic growth and a medium improvement in the efficiency of primary energy use. Scenarios in Case C involve lower economic growth, a steady de-emphasis of fossil fuels and high improvement in efficiency. Case B employs an intermediate strategy as regards the blend of energy sources, the same economic growth as C and low improvements in efficiency. As well as the differences in economic growth, the different improvements in the efficiency of energy usage result in the three future trends for primary energy use shown on Figure 8a. As you might imagine, there is a huge range of possible scenarios that involve varying rates of economic growth, different blends of targeted energy sources, and various achievements in improving efficiency, of which the WEC settled on six that seemed realistic.

The inclusion of energy efficiency measures in the different WEC scenarios, unsurprisingly strongest for the Ecologically Driven case, is critical. However, the High Growth scenarios display a stronger commitment to energy efficiency than the Middle Course scenario, acknowledging that sustainability may not be incompatible with growth.

  • Which of the scenarios from Cases A and B would you judge to be the most sustainable?

  • On the basis of the figures in Table 1, scenario A3 ('non-fossil future') should be the most sustainable, as it has the lowest proportion of fossil fuel use and the highest contribution by renewable alternatives. However, this would ultimately depend on the total energy consumption of each scenario.

The WEC went further with the three 'probably sustainable' scenarios (A3, C1 and C2) in terms of their decreasing demands on non-renewable sources, by assigning specific contributions to the different kinds of alternative energy sources. The details of their modelling are shown in Figure 9. Note that the models rely most heavily on solar (25 to 38% by 2100) and biomass (18 to 25%) resources, with geothermal, wind, wave and tidal (i.e. other) sources having only the same weight as hydro (3 to 5%). Hydropower has the least potential for further development. If appropriate technologies can be adopted sufficiently, the likelihood of solar energy becoming the single most important contributor by 2100 poses no problems except for the amount of the Earth's surface that needs to be used. This surface could be that which would otherwise be non-productive desert or part of it could be incorporated into buildings and even roads. There is, however, a far less tractable issue concerning the massive adoption of another alternative energy source — biomass.

Figure 9 Models of the relative contributions of different energy resources to global primary energy use according to WEC scenarios: (a) A3; (b) C1; (c) C2. (See Table 1.) Note: 'Other' refers to other renewable resources.

Activity 2

Even for Case C, Figure 8a predicts annual primary energy use at the end of the 21st century to be about twice that at the start. About 11% of all land would be needed to grow enough biomass totally to supplant global primary energy use at the start of the 21st century. If 25% is to be supplied by biomass, what proportion of the Earth's land surface would be needed to grow the vegetable matter needed?

Answer

By the end of the century 22% of all land would be needed to supply the global energy use. If biomass were to contribute 25% of global primary energy by 2100, 0.25 × 22% = 5.5% of all land would be needed to grow it, and most of that would have to be in biologically productive areas.

Figure 8b predicts a doubling of human population by 2100, which places at least twice the current demand on fertile land for food production. Any modelling that is constrained within arbitrary limits, inevitably conflicts with factors that lie outside its remit.

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