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Chapter 3

Direct Solar Energy

Table 3.7 | Evolution of cumulative solar capacities based on different scenarios reported in EREC-Greenpeace (Teske et al., 2010) and IEA Roadmaps (IEA, 2010b,c).

Low-Temperature (GWth)

Solar Heat

2009 180

2015

2020

230

Cumulative installed capacity

Current value

EREC – Greenpeace (reference scenario)

180

2009 2015 2020

2009 2015 2020

22

0.7

Solar PV Electricity (GW)

CSP Electricity (GW)

44

80

5

12

EREC – Greenpeace ([r]evolution scenario)

EREC – Greenpeace (advanced scenario)

IEA Roadmaps

98

335

108

439

951

210

25

105

30

225

N/A

148

715

780

N/A

1,875

2,210

Note: 1. Extrapolated from average 2010 to 2020 growth rate.

direct solar to the world electricity supply by 2030 of 633 TWh (2.3 EJ/ yr) (Sims et al., 2007).

Chapter 10 provides a summary of the literature on the possible future contribution of RE supplies in meeting global energy needs under a range of GHG concentration stabilization scenarios. Focusing specifi- cally on solar energy, Figure 3.22(a) presents modelling results for the global supply of solar energy. Figure 3.22(b) shows solar thermal heat generation, and Figures 3.22(c) and (d) present solar PV and CSP electricity generation respectively, all at the global scale. Depending on the quantity shown, between 44 and about 156 different long- term scenarios underlie these figures derived from a diversity of modelling teams and spanning a wide range of assumptions about— among other variables—energy demand growth, cost and availability of competing low-carbon technologies, and cost and availability of RE technologies (including solar energy). Chapter 10 discusses how changes in some of these variables impact RE deployment outcomes, with Section 10.2.2 describing the literature from which the scenarios have been taken. Figures 3.22(a) to 3.22(d) present the solar energy deployment results under these scenarios for 2020, 2030 and 2050 for three GHG concentration stabilization ranges, based on the IPCC’s Fourth Assessment Report: >600 ppm CO2 (Baselines), 440 to 600 ppm (Categories III and IV) and <440 ppm (Categories I and II), all by 2100. Results are presented for the median scenario, the 25th to 75th percentile range among the scenarios, and the minimum and maximum scenario results.13

In the baseline scenarios, that is, without any climate policies assumed, the median deployment levels for solar energy remain very low, in the

range of today’s solar primary energy supply of below 1 EJ/yr, until 2050. It is worthwhile noting that the much smaller set of scenarios that reports solar thermal heat generation (44 compared to the full set of 156 that report solar primary energy) shows substantially higher median deployment levels of solar thermal heat of up to about 12 EJ/ yr by 2050 even in the baseline cases. In contrast, electricity genera- tion from solar PV and CSP is projected to stay at very low levels.

The picture changes with increasingly low GHG concentration stabi- lization levels that exhibit significantly higher median contributions from solar energy than the baseline scenarios. By 2030 and 2050, the median deployment levels of solar energy reach 1.6 and 12.2 EJ/yr, respectively, in the intermediate stabilization categories III and IV that result in atmospheric CO2 concentrations of 440-600 ppm by 2100. In the most ambitious stabilization scenario category, where CO2 con- centrations remain below 440 ppm by 2100, the median contribution of solar energy to primary energy supply reaches 5.9 and 39 EJ/yr by 2030 and 2050, respectively.

The scenario results suggest a strong dependence of the deployment of solar energy on the climate stabilization level, with significant growth expected in the median cases until 2030 and in particular until 2050 in the most ambitious climate stabilization scenarios. Breaking down the development by individual technology, it appears that solar PV deployment is most dependent on climate policies to reach significant deployment levels while CSP and even more so solar thermal heat deployment show a lower dependence on climate policies. However, this interpretation should be applied with care, because CSP electric- ity and solar thermal heat generation were reported by significantly fewer scenarios than solar PV electricity generation.

13 In scenario ensemble analyses such as the review underlying the figures, there is a constant tension between the fact that the scenarios are not truly a random sample and the sense that the variation in the scenarios does still provide real and often clear insights into collective knowledge or lack of knowledge about the future (see Section 10.2.1.2 for a more detailed discussion).

The ranges of solar energy deployment at the global level are extremely large, also compared to other RE sources (see Section 10.2.2.5), indicating

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