energy resource for the East and West Coasts at more than 0.5 million GWh/yr (EPRI, 2005). This study also estimates the wave energy base in Alaska to be 1.3 million GWh/yr, though it is unclear whether such a resource could be fully exploited. EPRI (2005) put the capacity of the tidal energy resource at a 152 MW annual average, which corresponds to an annualized electrical energy production of 1300 GWh/yr. The biomass resource base is discussed in Chapter 5.
Solar and wind renewable resources offer significantly larger total energy and power potential than do other domestic renewable resources. Solar energy is capable, in principle, of providing many times the total U.S. electricity consumption, even assuming low conversion efficiency. The land-based wind resource also is capable of making a substantial contribution to meeting current U.S. electricity demand without stressing the resource base. For these reasons, solar and wind resources are emphasized, but other non-hydroelectric renewables can make significant contributions to the electrical energy mix as well, at least in certain regions of the country. However, renewable resources are not distributed uniformly. Resources such as solar, wind, geothermal, tidal, wave, and biomass vary widely in space and time. Thus, the potential to derive a given percentage of electricity from renewable resources will vary from location to location. Awareness of such factors is important in developing effective policies at the state and federal level to promote the use of renewable resources for generation of electricity.
A renewable electricity-generation technology harnesses a naturally existing energy flux, such as wind, sun, or tides, and converts that flux into electricity. Such technologies range from well-established wind turbines to pilot-plant hydrokinetic systems to methods, such as those that exploit salinity and thermal ocean gradients, that are in the conceptualization or demonstration stages. Some of these technologies produce power intermittently (technologies that rely on wind and solar resources), whereas others are capable of producing baseload power (technologies that rely on hydropower, biomass, and geothermal resources). Though renewable-electricity technologies show much variability, they do have several shared characteristics: (1) the largest proportions of costs, external energy needs, and material