First the report tallies the current proportion of global energy supply from renewable sources (p. 5, compare my January 2011 estimate which was very similar):
On a global basis, it is estimated that RE accounted for 12.9% of the total 492 Exajoules (EJ)5 of primary energy supply in 2008 (Box SPM.2) (Figure SPM.2). The largest RE contributor was biomass (10.2%), with the majority (roughly 60%) being traditional biomass used in cooking and heating applications in developing countries but with rapidly increasing use of modern biomass as well.6 Hydropower represented 2.3%, whereas other RE sources accounted for 0.4%.The report discusses its 164 scenarios for the future (p. 18):
More than half of the scenarios show a contribution from RE in excess of a 17% share of primary energy supply in 2030 rising to more than 27% in 2050. The scenarios with the highest RE shares reach approximately 43% in 2030 and 77% in 2050.If renewable energy provides only 27% of energy supply in 2050 (the IPCC median scenario value), then this would imply that to meet a low stabilization target something like 60% or more of global energy supply would have to be produced by some other carbon-free energy source, such as coal or gas with CCS or nuclear power, neither of which seems to be possible without major technological innovation.
The IPCC does note that there are obstacles -- both social and technological -- that must be overcome, and appears to make some key assumptions about how this might occur (p. 12 -- exact details will have to await the full report, but track records for forecasting technological innovation and social acceptance are not so good):
A variety of technology-specific challenges (in addition to cost) may need to be addressed to enable RE to significantly upscale its contribution to reducing GHG emissions.Even to reach the scenarios envisioned the report assumes a massive investment in energy technologies, from well over $100 billion per year to $500 billion per year starting yesterday (p. 23):
The four illustrative scenarios analyzed in detail in this Special Report estimate global cumulative RE investments (in the power generation sector only) ranging from USD2005 1,360 to 5,100 billion for the decade 2011 to 2020, and from USD2005 1,490 to 7,180 billion for the decade 2021 to 2030.The bottom line is that the IPCC has provided a rather sobering outlook for the deployment of renewable technologies. Perhaps most surprising of all is that despite the sobering outlook, the word "innovation" appears only once and the notion of "research" into energy technologies appears only twice. The IPCC continues to show blinders when it comes to energy technology innovation (see, e.g., PDF).