Electrification of the energy system has been a major driver of the his-torical energy transformation from an originally biomass-dominated energy system in the 19th century to a modern system with high reli-ance on coal and gas (two of the major sources of electricity genera-tion today). Many mitigagenera-tion scenario studies (Edmonds et al., 2006;
as well as the AR5 database; cf. Sections 6.3.4 and 6.8) have three generic components: (1) decarbonize power generation; (2) substitute electricity for direct use of fossil fuels in buildings and industry (see Sections 9.3 and 10.4), and in part for transportation fuels (Chapter 8); and (3) reduce aggregate energy demands through technology and other substitutions.
Most scenarios in the WGIII AR5 Scenario Database report a continu-ation of the global electrificcontinu-ation trend in the future (Figure 7.13). In the baseline scenarios (assuming no new climate policies) most of the demand for electricity continues to be in the residential, commercial, and industry sectors (see Chapters 9 and 10), while transport sectors rely predominantly on liquid fuels (Section 8.9). Biofuels and electricity both have the potential to provide transport services without fossil fuel emissions. The relative contribution of each depends at least in part on the character of technologies that evolve to provide transport services with each fuel.
Electricity production is the largest single sector emitting fossil fuel CO2 at present and in baseline scenarios of the future. A variety of mitiga-tion opmitiga-tions exist in the electricity sector, including renewables (wind, solar energy, biomass, hydro, geothermal), nuclear, and the possibility of fossil or biomass with CCS. The electricity sector plays a major role in mitigation scenarios with deep cuts of GHG emissions. Many
mitiga-7
tion scenario studies report an acceleration of the electrification trend in mitigation scenarios (Figure 7.13).
Mitigation scenario studies indicate that the decarbonization of the electricity sector may be achieved at a much higher pace than in the rest of the energy system (Figure 7.14). In the majority of stringent mitigation scenarios (430 – 480 ppm and 480 – 530 ppm), the share of low-carbon energy increases from presently about 30 % to more than 80 % by 2050. In the long term (2100), fossil-based electricity genera-tion without CCS is phased out entirely in these scenarios.
Figure 7.15 shows the evolution over time of transformation pathways for primary energy supply, electricity supply, and liquid fuels supply for reference scenarios and low-concentration scenarios (430 – 530 ppm CO2eq). The development of the full scenario ensemble is further com-pared to the three illustrative mitigation scenarios by the ReMIND, MESSAGE, and GCAM models discussed in Section 7.11.2 (see Figure 7.10). The effect of climate policy plays out differently in each of the three supply domains. In aggregate, mitigation leads to a reduction in primary energy demands. However, two distinctly different mitiga-tion portfolios emerge – one in which hydro-carbon fuels, including biomass, BECCS, and fossil CCS play a prominent role; and the other where, taken together, non-biomass renewables and nuclear power take center stage. In both instances, the share of fossil energy without CCS declines to less than 20 % of the total by 2100. Note that in the scenarios examined here, the major branch point occurs around the 2050 period, while the foundations are laid in the 2030 to 2050 period.
Electricity generation is a somewhat different story. While as previously noted, electricity generation decarbonizes rapidly and completely (in many scenarios emissions actually become negative), taken together, non-biomass renewables and nuclear power always play an impor-tant role. The role of CCS varies greatly, but even when CCS becomes extremely important to the overall mitigation strategy, it never exceeds half of power generation. By 2050, the contribution of fossil CCS tech-nologies is in most scenarios larger than BECCS (see Figure 7.11). In contrast to the overall scale of primary energy supply, which falls in cli-mate policy scenarios relative to baseline scenarios, the scale of power generation can be higher in the presence of climate policy depending on whether the pace of electrification proceeds more or less rapidly than the rate of end-use energy demand reductions. With regards to the deployment of individual non-biomass renewables or different CCS technologies, see also Figure 7.11 and Figure 7.12.
Liquid fuels are presently supplied by refining petroleum. Many sce-narios report increasing shares for liquids derived from other primary
Figure 7�14 | Share of low-carbon energy in total primary energy, electricity and liquid supply sectors for the year 2050. Colored bars show the interquartile range and white bars indicate the full range across the baseline and mitigation scenarios for different CO2eq ppm concentration levels in 2100 (Section 6.3.2). Dashed horizontal lines show the low-carbon share for the year 2010. Low-low-carbon energy includes nuclear, renewables, fossil fuels with CCS and bioenergy with CCS: WGIII AR5 Scenario Database (see Annex II.10).
Scenarios assuming technology restrictions are excluded.
0 20 40 60 80 100
2010
2010
Low Carbon Share of Primary Energy (2050) [%]
Primary Energy
0 20 40 60 80 100
Low Carbon Share of Electricity (2050) [%]
Electricity
n.a.2010
0 20 40 60 80 100
Low Carbon Share of Liquids Supply (2050) [%]
Liquid Fuels Supply
430-480 ppm CO2eq 480-530 ppm CO2eq 530-580 ppm CO2eq 580-650 ppm CO2eq Baselines 650-720 ppm CO2eq
Min 75th Max Percentile
Median 25th
Figure 7�13 | Share of electricity in total final energy for the year 2050 in baseline scenarios and five different levels of mitigation stringency (long-term concentration lev-els in ppm CO2eq by 2100). Colored bars show the interquartile range and white bars indicate the full range across the baseline and mitigation scenarios (See Section 6.3.2).
Dashed horizontal line shows the electricity share for the year 2010. Source: WGIII AR5 Scenario Database (see Annex II.10). Scenarios assuming technology restrictions are excluded.
0 20 40 60 80 100
2010
Electricity Share of Final Energy (2050) [%]
Min 75th Max
Median 25th Percentile
Baselines 430-480 ppm CO2eq 480-530 ppm CO2eq 530-580 ppm CO2eq 580-650 ppm CO2eq 650-720 ppm CO2eq
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430-530 ppm CO2eq (AR5 Scenarios) Baselines (AR5 Scenarios)
2030 2050 2100 Three Illustrative Scenarios Renewables and Nuclear
Biomass + BECCS + Fossil CCS Fossil Fuels (w/o CCS)
a) Primary Energy
430-530 ppm CO2eq (AR5 Scenarios) Baselines (AR5 Scenarios)
2030 2050 2100 Biomass + BECCS + Fossil CCS Fossil Fuels (w/o CCS)
7
energy feedstocks such as bioenergy, coal, and natural gas. This transi-tion is gradual, and becomes more pronounced in the second half of the century. Like aggregate primary energy supply, the supply of liquid fuels is reduced in climate policy scenarios compared with baseline scenarios. In addition, the primary feedstock shifts from petroleum and other fossil fuels to bioenergy.