streamlined permitting, and/or renewable portfolio standards are essential to support significant growth of the market for renewable electricity. With such policies and economic incentives in place, up to 20 percent of additional domestic electricity generation could come from non-hydropower renewable technologies within approximately the next 25 years.

In turn, significant technological and scientific barriers must be surmounted if renewables are to provide upward of 50 percent or more of domestic electricity generation in a reliable, controllable system that also has a low-carbon-emissions footprint. The barriers include those related to transmission as well as system integration and flexibility, including storage and other enabling technologies. Specifically, large-scale and distributed electrical energy storage, and/or large capacities for rapidly controllable low-carbon-emission generation, would be required to reach such a goal. Further, a systemwide intelligent, digitally controlled grid could reduce the need for backup power and storage and further facilitate the penetration of renewable electricity into the marketplace. Significant R&D is required now if such technologies are to be available in time to facilitate deployment of renewable electricity at a level of 50 percent or higher. Research is also needed to ensure that large-scale deployment of renewable electricity will not lead inadvertently to undesirable environmental consequences.

CRITICAL UNKNOWNS

The panel notes that many major unknowns will affect the future of electricity from renewable resources. Several are highlighted below.

  • Technologies—The prospects for reducing manufacturing costs and improving the efficiencies of renewable electricity technologies, including the potential for solar photovoltaics to bring the installed system cost down to less than $1 per watt with at least 10 percent module and system efficiency to enable widespread deployment without subsidies;

  • Economics—The price of electricity in the future, how prices will be structured, and the explicit or implicit price of CO2 imposed by any future climate policy;

  • Policy—The structure of renewables portfolio standards, tax policies (production and/or investment tax credits), and other policy initiatives directed at renewable electricity;



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