In the most ambitious climate stabilization scenarios, the 75th percen- tiles of the solar primary energy supply by 2030 reach up to 26 EJ/yr, a five-fold increase compared to the median of the same category and the highest estimates even reach up to 50 EJ/yr. For 2050 the equiva- lent numbers are 82 EJ/yr (75th percentile) and 130 EJ/yr (maximum level), which can be attributed to a large extent to solar PV electricity generation, which reaches deployment levels of more than 80 EJ/yr by 2050, but CSP electricity and solar thermal heat also contribute sig- nificantly under these very high solar deployment levels. The share of solar PV in global electricity generation in the most extreme scenarios reaches up to about 12% by 2030 and up to one-third by 2050, but in the vast majority of scenarios remains in the single digit percentage range.
To achieve the higher levels of deployment envisioned by some of these scenarios, policies to reduce GHG emissions and/or increase RE sup- plies are likely to be necessary, and those policies would need to be of adequate economic attractiveness and predictability to motivate sub- stantial private investment (see Chapter 11). A variety of other possible challenges to rapid solar energy growth also deserve discussion, as do factors that can contribute to it.
Resource potential. The solar resource is virtually inexhaustible, and it is available and able to be used in most countries and regions of the world.The worldwide technical potential of solar energy is considerably larger than the current primary energy consumption (IEA, 2008), and will not serve as a primary barrier to even the most ambitious deploy- ment paths included in the scenarios literature summarized above.
Regional deployment. Industry-driven scenarios with regional visions for up to 100% of RE supply by 2050 have been developed in various parts of the world, often with substantial levels of solar energy deployment.
The Semiconductor Equipment and Materials International Association developed PV roadmaps for China and India that go far beyond the targets of the national governments (SEMI, 2009b,c). These targets are about 20 GW by 2020 and 100 GW by 2050 for electricity generation in China and 20 GW and 200 GW in India (both PV and CSP) (Ministry of New and Renewable Energy, 2009; Zhang et al., 2010).
In Europe, the European Renewable Energy Council developed a 100% Renewable Energy vision based on the inputs of the various European industrial associations (Zervos et al., 2010). Assumptions for 2020 about final electricity, heating and cooling, as well as transport demand are based on the European Commission’s New Energy Policy (NEP) scenario with both a moderate and high price environment as outlined in the Second Strategic Energy Review (European Commission, 2008). The scenarios for 2030 and 2050 assume a massive improvement in energy efficiency to realize the 100% RE goals. For Europe, this scenario assumes that solar can contribute about 557 TWh (2,005 PJ) and 1415 TWh (5,094 PJ) heating and cooling in 2030 and 2050, respectively. For electricity generation, about 556 TWh (2,002 PJ) from PV and 141 TWh (508 PJ)
Direct Solar Energy
from CSP are anticipated for 2030 and 1,347 TWh (4,849 PJ) and 385 TWh (1,386 PJ) for 2050, respectively.
In Japan, the New Energy Development Organisation, the Ministry for Economy, Trade and Industry, the Photovoltaic Power Generation Technology Research Association and the Japan Photovoltaic Energy Association drafted the ‘PV Roadmap Towards 2030’ in 2004 (Kurokawa and Aratani, 2004). In 2009, the roadmap was revised: the target year was extended from 2030 to 2050, and a goal was set to cover between 5 and 10% of domestic primary energy demand with PV power genera- tion in 2050. The targets for electricity from PV systems range between 35 TWh (126 PJ) for the reference scenario and 89 TWh (320 PJ) for the advanced scenario in 2050 (Komiyama et al., 2009).
In the USA, the industry associations—the Solar Electric Power Association and the Solar Energy Industry Association—are working together with the USDOE and other stakeholders to develop scenarios for electricity from solar resources (PV and CSP) of 10 and 20% in 2030. The results of the Solar Vision Study (USDOE, 2011) are expected in 2011.
Achieving the higher global scenario results for solar energy would clearly require substantial solar deployment in every region of the world. The regional scenarios presented here suggest that regional deployment paths may exist to support such a global result. Nonetheless, enabling this growth in regions new to solar energy may present cost and insti- tutional challenges that would require active management; institutional and technical knowledge transfer from those regions that are already witnessing substantial solar energy activity may be required.
Supply chain issues. Passive solar energy markets and industries have largely developed locally to this point because the building market itself is local. Enabling high-penetration solar energy futures may require a globalization of at least knowledge on passive solar technologies to enable broader market penetration. Low-temperature solar thermal is implemented all over the world within local markets, with local suppli- ers, but a global market is starting to be developed. The PV industry is already global in scope, with a global supply chain, while CSP is start- ing to develop a global supply chain—in 2010, the CSP market was driven by Spain and the USA, but other countries such as Germany and India are also helping to expand the market. In general, supply chain and materials constraints may impact the speed and scope of solar energy deployment in certain regions and at certain times, but such factors are unlikely to restrict the ability of solar energy technologies to meet the higher penetrations envisioned by the more aggressive scenarios presented earlier. In fact, the modular nature of many of the solar technologies, both in manufacturing and use, as well as the diverse applications for solar energy suggest that supply chain issues are unlikely to constrain growth.
Technology and economics. The technical maturity and economic competitiveness of solar technologies vary. Passive solar consists of well-established technologies, though with room for improvement;