Solar Energy Resources in the United StatesSolar energy resources suitable for utility-scale or distributed generation are found in many parts of the United States. Where Are Solar Resources Found?As the sun shines everywhere on Earth, some level of solar energy resources exist everywhere. However, that does not mean that solar energy resources can be developed economically at any location. For example, a utility-scale solar energy project requires:
Where Are Solar Resources in the United States Strong Enough to Be Economical for Energy Production? Concentrating Collector Solar Potential on Tribal Lands Click to enlarge  Concentrating Collector Solar Potential on Tribal Lands (2.5 MB)  Photovoltaic Solar Potential on Tribal Lands Click to enlarge Photovoltaic Solar Potential on Tribal Lands (2.5 MB) Areas suitable for solar energy production require high direct normal insolation (DNI) and a large area of nearly level topography. Under clear sky conditions, about 85% of the sunlight is DNI and 15% is scattered light that comes in at all different angles. DNI can be used by all solar energy systems, whereas the scattered light can only be used by photovoltaic systems. The size of a solar field for a given power plant generating capacity is, in general, directly proportional to the DNI level. The solar resources in the southwestern United States (Arizona, California, Colorado, Nevada, New Mexico, and Utah) are among the best in the world for large-scale solar power plants, having suitably high DNI (see maps at right). Most commercial-scale solar energy projects of 10 megawatts (MW) or more that are currently operational or under development are located in Arizona, California, Nevada, and Florida. An atlas of solar radiation data from 1961 to 1990 is available from the National Renewable Energy Laboratory (NREL). NREL also provides various solar maps on its Web site. In addition, NREL provides concentrating solar power resource maps for the southwestern United States, including separate maps for Arizona, California, Colorado, New Mexico, Nevada, Texas, and Utah. Access to Transmission FacilitiesIf existing suitable transmission facilities are not available for a proposed solar energy development, new transmission lines and associated facilities must be constructed. In some cases, existing transmission facilities might require upgrading. The costs associated with construction or upgrading activities may determine whether or not a project is economically feasible. Electric transmission systems are discussed separately in the Energy Transmission section.  |
