ing a predominant (i.e., greater than 50 percent) level of renewable-electricity penetration, especially if the sources are predominately intermittent, will require scientific advances and dramatic changes in the ways we receive and use electricity. Beyond the continuing needs for improvements in cost, scalability, and performance of renewable electricity-generation technologies, some combination of intelligent two-way electric grids, cost-effective methods for large-scale and distributed storage (either direct electricity energy storage or generation of chemical fuels), widespread implementation of rapidly dispatchable fossil electricity technologies (for backup), and greatly improved technologies for cost-effective long-distance electricity transmission will also be required.
Given the long time periods covered in this report, it is conceivable that other technological approaches, in addition to those just discussed, will evolve. They include the possibility of high-altitude kites tethered to generators for producing wind-derived electricity, or satellites in space that would collect sunlight, convert the energy into a laser or microwave beam, and aim the beam at a terrestrial plant for generating electricity or producing hydrogen. Other approaches may be based on new processes developed from basic advances in fields such as bioengineering and nanotechnology. Additionally, new approaches may ensue from the application of systems engineering in a world that is highly constrained not only by energy supplies but also by water availability and waste-disposal options. For example, it is conceivable that neighborhood combined-energy-waste-and-water plants may be attractive for reducing pressures on the infrastructure and limiting the amounts of consumables entering the system. Such approaches could be of great benefit as the world’s population becomes increasingly urbanized.
Wind, solar photovoltaics, concentrating solar power, conventional hydropower, hydrothermal, and biopower technologies are technically ready for accelerated deployment; both individually and collectively, these technologies could make significantly greater contributions to the U.S. electricity supply than they do today. Advances in the currently developed renewable electricity-generating technologies will be driven by incremental improvements in individual components, “learning curve” technology maturation, and achievement of economies of scale in commercial production.