• 690 TWh from natural-gas-fired power plants

• 320 TWh from renewable-energy sources, mostly hydropower (250 TWh), wind (34 TWh), geothermal (15 TWh), and biopower (8.7 TWh)

• 180 TWh from combined-heat-and-power plants, fed primarily by natural gas and coal

• 57 TWh from oil-fired power plants.

Through the deployment of new technologies and the repowering of current assets, the United States has many promising options both for increasing its electricity supply and for changing its electricity-supply mix. These estimates of new electricity supplies using different energy sources and technologies were derived independently and should not be added to obtain a total new supply estimate. As noted in Chapter 1, the AEF Committee has not conducted an integrated assessment of how these energy-supply technologies would compete in the marketplace or of how that competition and other external factors would affect deployment success.

Renewable-energy sources (Figure 2.7) could provide about an additional 500 TWh of electricity per year by 2020 and about an additional 1100 TWh per year by 2035 through new deployments in favorable locations. These levels exceed the amounts of new electricity supplies that are likely to be available from new nuclear-power generation or new coal-power generation with CCS in 2020 or from new nuclear power generation in 2035. However, expansion of transmission capabilities would be required to transport new electricity supplies from renewable resources to demand centers and regional energy markets. Backup supplies of electricity, or the capability to store energy during times when electricity production exceeds demand, would be needed when renewable sources were unavailable. Given current cost structures for renewable energy (discussed later in this chapter), policies such as renewable portfolio standards and tax credits would likely need to be continued, and possibly expanded, to obtain these new supplies.

Coal-fired plants with CCS (Figure 2.8) could provide as much as 1200 TWh from repowering and retrofit of existing plants and as much as 1800 TWh from new plants. In combination, the entire existing coal power fleet (which currently delivers about 2000 TWh of electricity per year) could be replaced by CCS coal power by 2035. However, successful commercial-scale demonstrations of CCS technologies would be required during the coming decade to realize this potential. (A brief discussion of CCS demonstration needs and constraints is provided under Finding 6; additional information is