Electric power from renewable energy: Realities for policy-makers

Current wind and photovoltaic technologies are incapable of providing the all-renewable electric power future that many have envisioned, because of the inherent mismatch between their unpredictable, intermittent nature and society's demands for electric power on demand. Paths for using these technologies are in combination with electric power storage or as fuel-savers with fossil-fueled power plants. In a cloudless world, photovoltaic costs double if power is needed at night, and when there are clouds, costs escalate dramatically. Electric power from wind turbines varies as the cube of the wind velocity, which can fluctuate from zero to high values over short periods. To make competent national energy policy, the public and policymakers need an unbiased, authoritative analysis of the maximum possible, long-term contributions of renewables to U.S. electric power needs.